Patent Publication Number: US-2023141867-A1

Title: Valve priming and depriming

Description:
CLAIM OF PRIORITY 
     This patent application claims the benefit of priority of [Lead Inventor Name] U.S. Provisional Patent Application Ser. No. 63/276,144, entitled “VALVE PRIMING AND DEPRIMING,” filed on Nov. 5, 2021 (Attorney Docket No. 2754.307PRV), which is hereby incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     This document pertains generally, but not by way of limitation, to agricultural equipment. 
     BACKGROUND 
     In an example, an agricultural product (e.g., fertilizer, water, pesticides, or the like) is applied to a field (e.g., croplands, farmland, or the like). For instance, a sprayer includes one or more nozzles, and the nozzles discharge the agricultural product from the sprayer. Optionally, the sprayer includes one or more valves that facilitate flow through the nozzles. In one example, the control valve includes a solenoid-operated valve that is a normally-closed-valve (e.g., an NCV, or the like). For example, the solenoid-operated valve is biased closed, and thereby inhibits flow through the valve. Application of current to the solenoid-operated valves energizes the solenoid, and accordingly overcomes the bias of the valve to open the valve. For instance, current is selectively supplied to the solenoid-operated valves, and the valves are modulated according to a specified duty cycle. In another example, the valves are primed with an agricultural product, for instance to displace air from the valves. For example, the valves are opened until agricultural product is discharged from at least one of the nozzles. 
     SUMMARY 
     In an example, an agricultural sprayer applies an agricultural product to plants (e.g., vegetables, fruits, crops, weeds or the like). In an example, the agricultural product is delivered to one or more control valves of the sprayer. For instance, the control valves are included in the agricultural sprayer, such as a sprayer coupled with a prime mover (e.g., a tractor, truck, or the like). In some examples, the one or more valves are normally-closed (e.g., an NCV, or the like) solenoid-operated valves, and the valves are biased closed. For instance, a first valve includes a solenoid having a coil, and the solenoid generates a magnetic flux when powered. The magnetic flux moves a valve operator of the valve with respect to the coil. Movement of the valve operator selectively permits (or inhibits) flow of fluid (e.g., water including agricultural product, air, or the like) through the control valve. 
     In another example, the valves are in communication with a valve controller. The valve controller facilitates opening and closing of the valve according to a specified duty cycle. For instance, the valve controller includes an actuator, and the actuator cooperates with the one or more valves to move the valve operator. Accordingly, the actuator helps open (or close) the one or more of the valves, and thereby permit (or inhibit) flow of fluid through the valves. 
     In yet another example, the system determines whether the valve operator has moved with respect to the coil. For instance, the system monitors variations of control valve characteristics of the one or more valves to determine whether the valve operator has moved. In an example, movement of the valve operator alters electrical characteristics of the control valve. Optionally, the actuator helps supply a current to the coil, and the current flowing through the coil generates a magnetic flux with the coil. The magnetic flux helps move the valve operator with respect to the coil (e.g., to open the valve). In some examples, movement of the valve operator with respect to the coil varies electrical characteristics of the control valve, such as by changing the magnitude of current flowing through the coil. 
     In still yet another example, the valve controller monitors control valve characteristics to determine a status, configuration or the like of the one or more valves, for instance whether the valves are in an unprimed state or a primed state. For example, the control valve is in an unprimed state with a quantity of gas in a fluid chamber of the control valve. In another example, the valve is in a primed state with a quantity of liquid in the fluid chamber of the control valve (e.g., with incidental gas therein). Accordingly, in an example the control valve characteristics includes fluid mechanical characteristics of the valve or fluid (e.g., including, but not limited to, properties of the fluids, related mechanical characteristics of the valve, or the like) delivered through the valve. For instance, the fluid mechanical characteristics include, but not are not limited to fluid characteristics and associated changes in valve operation. For instance, the fluid mechanical characteristics include one or more of density of fluid, viscosity of fluid, compressibility (including incompressibility) of fluid, surface tension of fluid, state (e.g., liquid, gas, mixture), channeling or porting of the valve (e.g., with one or more flutes included in the valve operator, or the like), changes in these characteristics or the like. 
     In a further example, the system monitors control valve characteristics including performance of the valve operator in response to operation by the actuator of the valve controller. In an example, performance of the valve operator varies based on whether the valves are in the unprimed state, or in the primed state. For instance, the controller monitors at least one operator transition time corresponding to a time span for the valve operator to translate between the closed position and the open position. In some examples, the operator transition time varies according to whether the control valve is in the unprimed state, or in the primed state. 
     For example, variations in a ratio between liquid and gas in the fluid chamber induces variations in the control valve characteristics, such as the operator transition time. In an example, as the valve operator moves through the fluid in the fluid chamber, the fluid induces forces (e.g., drag, friction, or the like) on the valve operator as it moves through the fluid. For instance, the fluid in the fluid chamber includes one or more of a gas (e.g., air) or a liquid (e.g., water, agricultural product, or the like). In an example, force applied to the valve operator by a gas are less than forces applied to the valve operator by a liquid. For instance, the liquid (e.g., water including agricultural product) has a greater density than the gas (e.g., air) and accordingly liquid resists motion of the valve operator more than a gas. Accordingly, in the unprimed state, the forces applied on the valve operator are less than the forces applied in the primed state (e.g., according to the change in density of fluid in the fluid chamber, viscosity, surface tension, compressibility, incompressibility, or the like.). As described herein, opening the valve operator (e.g., with a driving current) is opposed by the forces applied by liquid or gas to the valve operator, and accordingly monitoring associated electrical characteristics affected by the opposed forces facilitates determination of characteristics of the valve including, but not limited to, primed and unprimed states. 
     As described herein, the system monitors the control valve characteristics, for example to determine whether the control valve is in one or more of the unprimed state or the primed state. For instance, the controller monitors the control valve characteristics to determine differences in the control valve characteristics, such as differences in control valve characteristics with respect to time. One or more of the control valve characteristics (e.g., current through the coil, operator transition time, or the like) vary based on the control valve being in the unprimed state or the unprimed state. Accordingly, the system monitors the variations in control valve characteristics to determine whether the control valve is in the unprimed state or the primed state. With monitoring of the prime configuration of control valves performance of the system is enhanced. For example, automated priming (or depriming) of the control valves is conducted to enhance agricultural product application and minimize waste of the agricultural product. 
     In an example, the system minimizes waste of agricultural product by determining whether the plurality of control valves are in the unprimed state or the primed state. For instance, the controller primes individual ones of the plurality of control valves and arrests priming operation upon detect of the primed state thereby minimizing waste of agricultural product. In some approaches, agricultural product is delivered to the plurality of control valves with the control valves while each of the control valves are open (thereby permitting flow through each of the control valves). The agricultural product optionally flows through each of the control valves until each of the control valves along a sprayer boom are primed. In this approach, the control valves are closed as each control valve indicates (e.g., through monitored electrical characteristics) it has reached the primed state. In practice in one example the sprayer nozzles nearest the sprayer vehicle begin spraying with a priming operation as the system pressurizes. Spraying cascades along the boom as the distal control valves receive agricultural product and begin priming. As the control valves near to the sprayer vehicle prime, and priming is detected, the valves close and those associated spray nozzles cease spraying. Accordingly, in this example priming appears as a cascade of spraying beginning near to the vehicle and ending at the sprayer boom end followed by arresting of spraying near to the vehicle and continuing to the sprayer boom end. 
     In an example, the system primes individual ones of the plurality of control valves to minimize waste of the agricultural product, such as by closing individual ones of the control valves while the control valves are in the primed state (thereby inhibiting flow through the primed control valves). The system continues delivery of agricultural product to control valves in the unprimed state, and monitors the control valve characteristics to determine whether remaining control valves in the unprimed state transition to the primed state. Accordingly, the system minimizes flow of agricultural product through control valves in the primed state. Thus, the system facilitates priming of the plurality of control valves while minimizing waste of agricultural product. In yet another example, the system monitors valve characteristics to determine whether the control valves transition from the primed state to the unprimed state (e.g., to evacuate agricultural product from the control valves). Thus, monitoring of the unprimed or primed states helps ensure agricultural product is evacuated from the sprayer. For instance, an operator evacuates agricultural product from the sprayer prior to traversing a public roadway (or other area where avoiding application of the agricultural product is desired). Accordingly, monitoring of the unprimed and primed states of the control valves enhances performance of the agricultural sprayer. 
     As described herein the system includes one or more smart nozzles. In some approaches, flow of fluid through the nozzle is restricted by an obstruction. For instance, debris blocks (including partially blocks) the flow of fluid through the nozzle, and flow of fluid through the nozzle is thereby diminished. Accordingly, the nozzle is in a restricted state (as opposed to an unrestricted state). 
     In an example, the system determines whether the nozzle is in the restricted state or the unrestricted state. For instance, the controller monitors valve characteristics, such as pressure, between valve operator cycles to determine whether the nozzle is in the restricted state or the unrestricted state. In another example, the rate of pressure decay in the valve outlet changes in correspondence with whether the nozzle is in the restricted or unrestricted state. In an example, pressure at the valve outlet decays at a first rate with the nozzle in the unrestricted state. The pressure at the valve outlet decays at a second rate with the nozzle in the restricted state. The second rate is less than the first rate. The system determines the nozzle is in the restricted state or the unrestricted state based on the comparison of the pressure decay corresponding to a valve operator cycle relative to a restricted nozzle threshold. In an example, the controller determines the nozzle is in the restricted state when the pressure decay of a valve operator cycle exceeds the restricted nozzle threshold. For instance, the controller monitors pressure decay using one or more electrical characteristics of the system (e.g., current, voltage, or the like) 
     This overview is intended to provide an overview of subject matter of the present patent application. It is not intended to provide an exclusive or exhaustive explanation of the invention. The detailed description is included to provide further information about the present patent application. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, which are not necessarily drawn to scale, like numerals may describe similar components in different views. Like numerals having different letter suffixes may represent different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document. 
         FIG.  1    illustrates a perspective view of an example of an agricultural sprayer. 
         FIG.  2    illustrates a schematic of an exemplary nozzle control system. 
         FIG.  3    illustrates a detailed schematic view of an exemplary nozzle control system. 
         FIG.  4    illustrates a cross-sectional view an example of a valve, according to an embodiment of the present subject matter. 
         FIG.  5    illustrates another cross-sectional view of the valve of  FIG.  4   , according to an embodiment of the present subject matter. 
         FIG.  6    illustrates an example of a system for applying an agricultural fluid including a controller, according to an embodiment of the present subject matter. 
         FIG.  7    illustrates a representation of one or more drive signals used to apply a specified duty cycle to a valve and the resultant waveform shapes that are monitored by the controller, according to an embodiment of the present subject matter. 
         FIG.  8 A  illustrates a cross-sectional view of the valve of  FIG.  4    in a fully unprimed state. 
         FIG.  8 B  illustrates a cross-sectional view of the valve of  FIG.  4    in a partially unprimed state. 
         FIG.  8 C  illustrates a cross-sectional view of the valve of  FIG.  4    in a primed state with a valve operator in an open position. 
         FIG.  8 D  illustrates a cross-sectional view of the valve of  FIG.  4    in a primed state with a valve operator in a closed position. 
         FIG.  9    illustrates a block diagram of a system for applying an agricultural product. 
         FIG.  10    illustrates a representation of characteristics of valve operation that are monitored (or determined) by the controller in combination with sensors described herein. 
         FIG.  11    illustrates a schematic view of another example of the agricultural sprayer. 
         FIG.  12    illustrates an example of a smart nozzle including the valve of  FIG.  4   . 
         FIG.  13    illustrates one example of a method for monitoring restriction of flow of a fluid through a nozzle. 
         FIG.  14    illustrates a schematic view of an example system for applying agricultural product. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    illustrates a perspective view of an example of an agricultural sprayer  100 . In an example, the agricultural sprayer  100  includes a reservoir tank  102  and one or more sprayer booms  104 . The sprayer booms  104  optionally include one or more nozzles  106 . In some examples, the agricultural sprayer  100  includes one or more electronic control units (ECU)  108  (e.g., a microprocessor based system), and for instance a master node  110 . (e.g., a microprocessor based system) 
     In an example, the reservoir tank  102  is integral with a prime mover  112  (e.g., a tractor, truck, combine, vehicle, or the like). In some examples, the reservoir tank  102  is a towed behind the prime mover  112  (e.g., the reservoir tank  102  is included with a trailer, or the like). The reservoir tank  102 , in an example, includes an agricultural product mixed with a carrier fluid, such as water. In some examples, the carrier fluid and the agricultural product are mixed in-line prior to or at the sprayer boom  104 . The nozzles  106  are positioned along the sprayer boom  104  to deliver the agricultural product (and the carrier fluid) to a crop (e.g., vegetables, fruit feed, or the like) according to the operation of one or more control valves associated with the nozzles  106 . Crops include, but are not limited to, any product grown in an agricultural field, such as row and non-row based crops as well as targets associated with crops including, but not limited to, weeds, pests, soil or the like. Agricultural products include, but are not limited to, fertilizers, water, pesticides, fungicides, herbicides, or the like. 
     The agricultural sprayer  100  includes one or more controllers  116 , for example the ECU  108  and the master node  110 . In an example, the master node  110  operates in conjunction with the one or more ECUs  108  to control delivery of the agricultural product from the reservoir tank  102 , to the sprayer boom  104  and the associated nozzles  106  for delivery to the agricultural field or crop. 
       FIG.  2    illustrates a schematic of an exemplary nozzle control system  200 , wherein the one or more nozzles  106  located on the boom  104  control a respective nozzle flow rate of an agricultural product dispensed from the nozzle  106 , shown in  FIG.  2    as smart nozzles  106  discussed herein. As shown in  FIG.  2   , the master node  110  is communicatively coupled to one or more valves (e.g., the PWM valve  206 ) of the boom  104 , such that system pressure within the boom  104  can be controlled by the master node  110 . In some examples, the master node  110  of the current system is not configured to control the flow rate within the system  200 , boom  104 , or at the smart nozzles  106 . Instead, the master node  110  controls the pressure within the system  200 , boom  104 , or at the smart nozzles  106 , and the pressure control provides control of the flow rate (e.g., control to a lower pressure decreases flow while control to a higher pressure increases flow). The master node  110  is in communication with a master flow meter  202 , a master pressure transducer  204 , and a master pulse width modulation (PWM) valve  206 . The master node  110  controls the master PWM valve  206  to provide a targeted system pressure (through modulated operation of a system pump associated with the master PWM valve  206 ), such that a desired droplet size of the agricultural product is generated at the nozzles  106 . For example, environmental conditions, such as wind, humidity, rain, temperature, field characteristics, or user preference determine whether a smaller or larger droplet size of the agricultural product is preferred. By controlling a targeted system pressure (e.g., maintaining, changing with variations in flow rate or the like), the preferred droplet size is maintained with the system  200 . 
     In the exemplary embodiment, each of the nozzles  106  is a smart nozzle that includes an electronic control unit (ECU) (e.g., ECU  108 , shown in  FIG.  1    or the like) that regulates, determines, and/or controls the nozzle flow rate of the agricultural product dispensed from the nozzle  106  with an associated control valve, as discussed in reference to  FIG.  3   . In other embodiments, a group of the nozzles  106  are associated with a common ECU and is collectively considered a single smart nozzle. The smart nozzles  106  are connected to, for example, the boom  104  and communicatively coupled to a controller area network (e.g., nozzle CAN bus  208 , wireless network or the like) of the overall control system  200 . As discussed herein, the CAN bus  208  is configured to distribute overall system information from the master node  110  (e.g., master node). The ECU at each smart nozzle  106  uses data from the overall system information to regulate, determine, and/or control the nozzle flow rate of each corresponding smart nozzle  106 . 
     The master node  110  controls one or more of a system pressure or system flow rate using, for example, the master pressure transducer  204  (or in other examples the flow meter, flow meter and pressure transducer together or the like) and the master pulse width modulation (PWM) valve  206 . Although  FIG.  2    illustrates a PWM valve as a master valve  206 , embodiments are not so limited. For example, the master valve  206  includes any valve capable of controlling pressure or flow rate of a system, such as a ball valve, PWM valve, butterfly valve or the like. For instance, the master node  110  maintains the system pressure or flow rate at a target system value (e.g., a target system pressure or target system flow rate). In another example, each smart nozzle  106  having an associated control valve (or valves) controls the component flow rate to the constituent nozzles associated with each smart nozzle. In another example, the master node controls the system pressure or system flow rate to one or more target values and the smart nozzles  106  control the flow rate for each of the constituent nozzles (e.g., one or more) associated with each smart nozzle. Collectively, the smart nozzles  106  may control the overall agricultural product flow rate of the system. 
     In an example, the target system pressure is provided by a user, such as at the user interface  210  connected to the master node  110  by the nozzle CAN bus  208 . In an additional example, the user also provides a target system flow rate (e.g., volume/area) at the user interface  210 . In an example, the master node  110  provides one or more of the target system flow rate or the target system pressure to each of the one or more smart nozzles  106 , such that each smart nozzle  106  (or each ECU, as discussed herein) determines an individual agricultural product flow rate (or pressure) for the smart nozzle  106 . For example, the system target flow rate is divided by the number of nozzles  106  to provide a target agricultural product flow rate for each of the one or more nozzles  106 . In an example, the master node  110  measures the flow rate (e.g., volume per time) with a master flow meter  202  and compares it with the overall target flow rate (e.g., designated by one or more of the user, crop type, soil characteristic, agricultural product type, historical data, or the like). The master node  110  is configured to determine a difference or error, if present, between the measured system flow rate and the target system flow rate. In such an example, the master node  110  provides the determined difference, by the nozzle CAN bus  208 , to the individual nozzles  106  (or ECUs, as discussed herein). The one or more nozzles  106  receive the difference on the CAN bus  208  and adjust their pressure/flow/duty cycle curve using the difference (e.g., compensating for errors in the system) to reduce the error between the measured and target system flow rates (or reduce the error between the measured and target system pressures). 
     Additionally, in at least some examples, the master node  110  reports the actual pressure, measured by the master pressure transducer  204 , as well as boom  104  information, including, but not limited to, one or more of yaw rate, speed, number of smart nozzles of the boom, distance between smart nozzles on the boom, to the smart nozzles  106  (or ECUs, as described herein) for individual flow rate control (or pressure control) of each of the smart nozzles  106 . For example, the information provided from the master node  110  is used in addition to nozzle characteristics to control the individual flow rate control of each smart nozzle  106 . Nozzle characteristics include, but are not limited to nozzle position on a boom, length of the boom, nozzle spacing, target flow rate for the system, yaw rate of the boom, yaw rate of the agricultural sprayer, speed of the agricultural sprayer, the overall system pressure or flow rate, agricultural product characteristics, valve performance such as a moveable valve operator transition time (including differences between specified and actual duty cycles), or the like. 
     The system  200  is configured for installation on an agricultural sprayer (e.g., the agricultural sprayer  100 , shown in  FIG.  1   ). In operation, because the sprayer moves during operation (translates and rotates, accelerates or the like), the one or more nozzle characteristics, in an example, are dynamic and flow rates through nozzles associated with a smart nozzle  106  dynamically change in some examples relative to other smart nozzles  106  of the system. 
       FIG.  3    illustrates a detailed schematic view of an exemplary nozzle control system  300 . The control system  300  includes the master node  110  communicatively coupled to one or more valves  301  of the boom  104 , such that system pressure within the boom  104  can be controlled by the master node  110 . Further, the master node  110  includes inputs from one or more of the master flow meter  202 , the master pressure transducer  204 , and the master pulse width modulation (PWM) valve  206 . Further, as described herein, the master node  110  is coupled to the user interface  210  and, in an example, a battery  302 , so as to provide power to one or more of the master node  110  and user interface  210 . 
     As shown in the embodiment of  FIG.  3   , a smart nozzle  106  optionally includes an ECU  108  coupled to a valve  304  (e.g., a PWM valve, ball valve, butterfly valve, or the like). That is,  FIG.  3    illustrates 36 ECUs relating directly to 36 nozzles of the nozzle control system  300 , but embodiments are not so limited. The master node  110  is communicatively coupled, by nozzle CAN bus  208  to ECU-18 and ECU-19, wherein ECU-18  108  and ECU-19  108  define a center region of the boom. From the center region of the boom, the ECUs  108  are communicatively coupled to the most proximate ECU  108  in the direction toward each terminal end  306  of the boom. That is, ECU-18 is communicatively couple to ECU-17, which is communicatively coupled to ECU-16, and so forth until the terminator after ECU-1 is reached. The same pattern holds for the other half of the boom. Although 36 ECUs  72  are illustrated, embodiments are not so limited. 
     Further, as shown in  FIG.  3   , each ECU  108  is coupled to one PWM valve  304 , however, embodiments are not so limited. In another example, a single ECU  108  is communicatively coupled to more than one PWM valve  304 . For instance, a single ECU  108  is communicatively coupled to more than one valve, such as every other valve, arrays of valves along portions of booms or the like. In an example, 12 ECUs split control of the 36 nozzles of the boom. In an example, a plurality of nozzles are partitioned into nozzle groups, such that each nozzle group includes an ECU  108  configured to control a nozzle group flow rate (or nozzle pressure that in turn controls flow) of the agricultural product dispensed from each nozzle of the nozzle group (by way of associated control valves  301 ) based on the nozzle characteristics, as described herein, of the respective nozzles. Thus, a smart nozzle includes, but is not limited to, a single nozzle, an associated valve and an associated ECU. In another example, a smart nozzle includes a group of nozzles (having associated valves) that are associated with a common ECU. 
     In still another example, the system  300  includes one or more location fiducials associated with the system  300 , the one or more location fiducials are configured to mark the location of one or more nozzles (or ECUs) of the plurality of nozzles on a field map (e.g., indexed with product flow rates, moisture content, crop type, agricultural product type, or the like). Optionally, each of the nozzles, nozzle groups, or ECUs  108  of the system is configured to control the agricultural product at individual rates according to the location of the one or more nozzles (or ECUs  108 ), the movement of the one or more nozzles relative to the field, another frame of reference or the like (and optionally in addition to the nozzle characteristics described herein). Further, each of the plurality of nozzles (or ECUs  108 ) is optionally cycled, such as on/off, according to the location of the nozzle (or location of a nozzle group or ECU  108 ) relative to a frame of reference, such as a field. 
     In an example, each nozzle ECU  108  is programmable to receive, track, or manipulate designated nozzle control factors (e.g., the specified duty cycle, the actual duty cycle, or the like) and monitor characteristics associated with each smart nozzle  106  (including one or more associated control valves). For example, each ECU  108  monitors one or more of nozzle spacing, target flow rate for the system, target pressure for the system, speed of the agricultural sprayer, yaw rate, nozzle location on the field, or the like. In yet another example, the ECUs  108  associated with each nozzle are instead consolidated into one or more centralized nodes that determine the individual flow rates of each of the respective nozzles in a similar manner to the previously described ECUs  108  associated with each of the nozzles. 
     In other examples, each ECU  108  (or the master node  110 ) monitors characteristics of the associated smart nozzle  106  including, but not limited to, operation of the control valve, electrical characteristics of the control valve (e.g., indicative of valve operation or performance) or the like. Such examples provide the benefit of comporting the system to user specifications, providing greater control of the system, and providing cost effective nozzle specific solutions including, but not limited to, efficient priming and depriming of the smart nozzles  106  as well as detection of maintenance issues such as tip blockage (e.g., fouling, plugging, sticking, seizing or the like). 
     The controllers  116  (e.g., the ECU  108 , the master node  110 , or the like) control the nozzle flow rate (or the timing of flow through the nozzle) based on a number of parameters, including, but not limited to: speed of the sprayer or boom, yaw rate, target system flow rate (e.g. volume/area), and on/off command at runtime. Such parameters permit the controllers  116  to calibrate the duty cycle curve (e.g., by adjusting the actual duty cycle of a valve) of each smart nozzle needed to achieve the target nozzle flow rate (or a target nozzle timing) of each of the smart nozzles. For instance, calibrating the duty cycle curve includes guiding an actual duty cycle of the nozzles (and their associated valves  301 ) to a specified duty cycle of the nozzles. Each smart nozzle is further configured according to nozzle spacing on the boom, location on the boom, and nozzle type. Further, in some examples, each smart nozzle regulates or controls the nozzle flow rate (or pressure) based on the location of the nozzle in the field (as described above). 
     As described herein, the agricultural sprayer  100  (shown in  FIG.  1   ) includes a nozzle control system including a plurality of smart nozzles  106  having one or more associated valves  301  (e.g., such as a PWM solenoid valve  304  as shown in  FIG.  3   , or the like) that regulate flow in order to provide a specified target application of an agricultural product from the nozzles  106 . In an example, the one or more associated valves  301  include the PWM solenoid valve  304 . As a plurality of nozzles  106  are used across the boom  104  (shown in  FIG.  1   ), achieving specified flow performance for each of the nozzles  106  enhances application precision and accuracy while minimizing application errors (e.g., misapplication, underapplication, overapplication, or the like). In some examples, one or more factors cause inconsistency in nozzle flow and droplet size (e.g., the size of droplets of agricultural product dispensed by the nozzle  106 ) of the sprayed agricultural product. Examples of these factors include, but are not limited to voltage drop of a solenoid drive voltage due to chassis wiring resistance, manufacturing tolerances of the mechanical elements in a valve itself (e.g., the valve  304 , shown in  FIG.  3   ), valve wear, valve contamination from the agricultural product, blocking (e.g., fouling or obstructions) of the nozzles or associated control valves, pressure variations across the boom or boom sections, variation due to an installed tip on the outlet of the nozzle, or open-stroke and close-stroke transition times for a moveable valve operator within the valve  304  controlling flow to the nozzle  106 . 
     In an example, and as described in greater detail herein, the system includes (or utilizes) an algorithm for tracking a position of a moveable valve operator (e.g., a poppet, or the like) of the valve  304  based on, for example, monitoring of back-emf (BEMF) generated in a solenoid coil by the moving valve operator as it transitions between its open and closed positions in the valve  304 . In another example, monitoring (e.g., capturing, recording, observing, cataloging, compiling, collecting, or the like) of the performance of the valve  304  optionally provides insight into valve health or nozzle faults and, for instance alerts a system user to a specific problem (e.g., with the user interface  210 , shown in  FIG.  2   ). 
       FIG.  4    and  FIG.  5    illustrate cross-sectional views of an example of the valve  304  in an open position and a closed position, respectively. The valve  304  is optionally a solenoid valve, for instance an electro-mechanical device that opens and closes an orifice by moving a moveable valve operator  400  (e.g., a poppet, gate, or the like) in a valve body  402  (e.g., a pressure vessel, frame, or the like). In an example, the valve body  402  of the valve  304  contains a lug  404  (e.g., a ferromagnetic material) and a housing  406  (e.g., a non-ferromagnetic material) that is coupled to the lug  404 . The valve operator  400  is movable in the housing  406 , for instance with a range of motion  407  to open and close the valve. The valve operator  400  includes a seal  408  (e.g., a gasket, membrane or the like) coupled with a first end  410  of the valve operator  400 . In an example, movement of the valve operator  400  within the housing  406  selectively opens and closes a channel  412  between a valve inlet  414  and a valve outlet  416 . For example, the seal  408  engages with a valve seat  409  (shown in the closed configuration in  FIG.  5   ) thereby inhibiting flow through the channel  412 . In the open position, the seal  408  is disengaged from the seat  409  (as shown in  FIG.  4   ) thereby allowing flow through the channel  412  (e.g., because the valve operator  400  is moved away from the seat  409 ).  FIG.  4    includes arrows indicating flow within the valve inlet  414  and the valve outlet  416 . 
     In an example, the valve  304  (the operator  400 ) is biased toward the closed position, for instance with a biasing element  418 , such as a coil spring, leaf spring, elastomer, magnet, or the like. In an example, the moveable valve operator  400  includes an operator flange  401  and the housing  406  includes a flare  411 . The biasing element  418  (a spring in this example) is coupled between the operator flange  401  and the flare  411 . In this example, the biasing element  418  provides a force between the housing  406  and the valve operator  400  to bias the valve operator  400  toward the closed position. 
     In some examples, the valve  304  operates by applying a voltage potential to a coil  420  (e.g., a winding of wire, or the like) that generates current in the coil  420 . The coil  420  generates magnetic flux when current flows through the coil  420 . In an example, the moveable valve operator  400  translates with respect to the coil  420  based on the magnetic flux generated by the coil  420 . The current flowing through the coil  420  optionally magnetizes the lug  404  (and the valve operator  400 ) of the valve  304 . For instance, the lug  404  is ferromagnetic, and a magnetic pole is established that attracts (e.g., draws, pulls, pushes, drives, or the like) the valve operator  400  toward the lug  404 . Accordingly, the valve  304  optionally includes a solenoid  421 , and the solenoid  421  includes (but is not limited to) the valve operator  400 , the lug  404 , and the coil  420 . 
     The valve  304  optionally includes a magnetic flux frame  422  surrounding one or more of the lug  404  or the valve operator  400 . The magnetic flux frame  422  encapsulates the magnetic field between the lug  404  and valve operator  400  and accordingly concentrates the magnetic field. For instance, the magnetic flux frame  422  enhances bounding of flux generated by the coil  420  to concentrate the magnetic field between the lug  404  and the valve operator  400 . 
     Referring again to  FIG.  4   , as the amount of current flowing through the coil  420  increases, the magnetic field generated by the coil  420  increases as does the resulting force applied to the valve operator  400 . For instance, an attractive force increases between the valve operator  400  and the lug  404 . As the attractive force generated (e.g., induced, developed, provided, or the like) by the magnetized lug  404  overcomes forces such as fluid pressure within the housing  406 , bias from the biasing element  418  or the like—the valve operator  400  begins moving from the closed position ( FIG.  5   ) to the open position ( FIG.  4   ). As described herein, the movement of the valve operator  400  is affected by one or more valve characteristics including fluid mechanical characteristics that affect valve characteristics (operation), such as the previously described fluid pressure, density of fluid (e.g., gas, liquid or the like), position of the fluid between the valve operator  400  and the lug  404 , bias from the biasing element  418 , pressure in the valve outlet  416 , plugging or fouling of the valve or the like, and these characteristics alter the movement and accordingly vary the operation of the valve (e.g., length of opening and closing, initiation of opening and closing, sticking or plugging of the valve, an actual duty cycle of the valve  304  or the like) relative to specified (e.g., predicted) behavior or values for the valve  304 . 
     A generated counter current (e.g., back electromotive force or back EMF) and corresponding magnetic field are examples of characteristics that alter the performance of the valve  304  relative to a specified duty cycle. For example, as the valve operator  400  moves toward the open position a counter current is generated in the coil  420  as the flux linkage changes because of a change of magnetically permeable material within the magnetic field (e.g., more of the valve operator having a higher magnetic permeability moves into the magnetic field and displaces fluid having a lower permeability). As the valve opens the flux linkage of the valve  304  changes due to the valve operator  400  occupying the previously fluid filled fluid gap  500 . Conversely, when the valve operator  400  is in the closed position ( FIG.  4   ) the fluid gap  500  is filled with the fluid having a lower magnetic permeability and the flux linkage again changes and generates counter current. The changes in flux linkage generate correspond counter currents (e.g., back EMF) that resist otherwise specified operation of the valve including opening and closing movements and thereby slow opening and slow closing as flux linkage changes and back EMF is generated. 
     The direction of the current generated in the coil  420  and its magnetic field caused by the moving valve operator  400  opposes the initial magnetic field of the coil  420  (e.g., the magnetic field generated by a current flowing through the coil  420 ). In an example, opposition of the initial magnetic field decreases the initial magnetic field generated by the coil  420  (e.g., according to Lenz&#39;s Law, or the like). Thus, in some examples, as the valve operator  400  moves nearer the coil  420  (or within the housing  406 ), the magnitude of current in the coil is reduced to oppose the originally created field caused by the current applied to the coil  420  (e.g., a ramping current, or the like). 
     In an example, as liquid (e.g., during priming of the valve, or the like) enters portions of the valve, the ratio of liquid to gas of the fluidic mixture changes. The fluid mechanical resistance to movement of the valve operator  400  changes in correspondence with the composition of the fluidic mixture in the fluid chamber  800  (shown in  FIG.  8   ) and in contact with the operator  400 . Accordingly, in an example the control valve characteristics include or are based on fluid mechanical characteristics of the valve  304  (or fluid in the valve  304 ). For instance, the fluid mechanical characteristics prompt changes in valve operation due to changes in composition of the fluid within the valve  304 . For instance, the fluid mechanical characteristics include one or more of density of fluid, viscosity of fluid, compressibility (including incompressibility) of fluid, surface tension of fluid, state (e.g., liquid, gas, mixture), channeling or porting of the valve  304 , changes in the same or the like. Differing densities, viscosities or the like affect valve operation and accordingly generate detectable changes in control valve characteristics. 
     For instance, the resistance to motion of the valve operator  400  increases based on the quantity of liquid in the fluid chamber  800  relative to gas. The denser a liquid (or greater proportion of liquid to gas) the greater the resistance to motion of the valve operator  400 . As discussed herein, resistance to motion of the valve operator  400  (including lack thereof) is detected and monitored to determine the primed and unprimed states of control valves and other states, such as tip blockage. For instance, an increase in density of the fluidic mixture (or associate ratio of liquid to gas) slows movement of the valve operator  400 , and accordingly increases a valve operator transition time. The controller  606  monitors the valve operator transition time (or changes in the valve operator transition time between cycles of the valve operator  400 ) to determine whether the valve is in the primed state or the unprimed state. 
     In another example, the valve operator  400  moves from the closed position to the open position. The valve operator  400  displaces fluid in the fluid chamber  800  (e.g., fluid between the housing  406  and the valve operator  400 ), from, in one example, the fluid gap  500  toward the valve outlet  416 . A compressible fluid (e.g., a more gaseous fluid) is easier to compress (in comparison to an incompressible fluid, such as water or the like) and move toward the valve outlet  416 . Accordingly, the fluid resistance to motion for a compressible fluid is less than an incompressible fluid. Thus, the force to open the poppet (and the associated current) is less with a compressible fluid. In another example, the valve operator transition time for a compressible fluid is less than the valve operator transition time for an incompressible fluid. Each of these control valve characteristics is measurable (e.g., with current monitoring, timing or the like) to assess the state of the valve including primed, unprimed, blocked or the like. 
       FIG.  6    illustrates a schematic diagram of a nozzle control system  600 . The agricultural sprayer  100  (shown in  FIG.  1   ) includes the nozzle control system  600 . For instance, the nozzle control system  600  is used in combination with one or more components (or functions) of the nozzle control system  200  (shown in  FIG.  2   ) or the nozzle control system  300  (shown in  FIG.  3   ). In an example, the nozzle control system  600  includes the plurality of nozzles  106  (shown in  FIG.  1   ) and one or more associated valves  301 . For instance, the valves  301  include one or more of the PWM solenoid valve  304  (shown in  FIGS.  3 - 5   ). Optionally, the nozzle control system  600  is a component of a controller for one or more valves (e.g.,  304 , smart nozzle  106  or the like) such as the associated ECUs  108  (see  FIG.  3   ). The valves  301  (shown in  FIG.  3   ) regulate flow to provide a specified target application rate of an agricultural product from respective nozzles of the agricultural sprayer  100 . 
     The nozzle control system  600  includes one or more sensors  602  that facilitate monitoring of one or more electrical characteristics (e.g., current, voltage, resistance, inductance or the like) of components of the system  600 . For example, the nozzle control system  600  includes a coil characteristic sensor  604  included in series with the coil  420 . In an example, the coil characteristic sensor  604  determines (e.g., measures, monitors, obtains, provides, evaluates, observes, or the like) the magnitude of current through the coil  420  (or voltage across the coil  420 ). In another example, a dissipation characteristic sensor  624  determines one or more electrical characteristics of the dissipation elements  616 . 
     In an example, the system  600  includes a nozzle controller  606  that monitors the electrical characteristics of the system  600 . The controller  606  is in communication with the sensors  602  as described herein. For example, the controller  606  monitors the magnitude of the current through the coil  420  with the characteristic sensor  604 . In another example, the controller  606  monitors other electrical characteristics, such as voltage with the sensor  602  provided on an opposed side of the solenoid coil  420 . The sensor  602  detects the voltage at the dissipation voltage node  626  (and across the second dissipation element  620 ). In some examples, the controller  606  performs one or more mathematical operations upon the monitored electrical characteristics. For instance, the controller  606  monitors one or more rates of change of the current through the coil  420 , rate of change of voltage (e.g., dissipation of voltage) or the like. 
     As discussed herein, movement of the valve operator  400  facilitates flow through the valve  304 . In an example, movement of the valve operator  400  (e.g., with respect to the housing  406 , shown in  FIG.  3   ) generates a change in current through the coil  420 . The controller  606  monitors the change in current through the coil  420  by way of the sensor  604 . By monitoring an electrical characteristic, such as current through the coil  420 , the controller  606  determines when the valve operator  400  actually moves (in contrast to when it should move based on a specified duty cycle). For instance, a decrease in current indicates actual movement of the valve operator  400 . Thus, the control system  600  (e.g., the controller  606  and sensor  604 ) detects actual movement of the valve operator  400  including one or more of initial (e.g., beginning, starting, or the like) movement of the operator, full transition of the valve operator  400  (e.g., to open or closed positions) and movement therebetween. As discussed herein, by comparing opening or closing movement (including associated electrical characteristics) with previous examples of opening or closing one or more states are detected including, but not limited to, primed, unprimed states, or tip blockage (e.g., fouling or plugging) of the valves and associated nozzles. 
     In an example, the valve control system  600  includes a power conditioning system  608 . The power conditioning system  608  provides a drive voltage potential to operate the system  600  (including the valve  304  having the coil  420 ). The coil  420  behaves as an inductor, and the current flowing through the coil  420  does not change instantaneously. The rate of adding energy into the coil  420  is optionally increased, for example by increasing the drive voltage potential (e.g., a voltage applied across the coil  420  with the power conditioning system  608 ) to overcome the inductance of the coil  420 . 
     In an example, the system  600  includes a coil drive voltage regulator  610 , for instance to facilitate operating the power conditioning system  608  at a fixed, or nearly fixed voltage. The controller  606  optionally modulates one or more of a high side switch  612  and a low side switch  614 , for instance to provide energy to the coil  420 . The high side switch  612  and the low side switch  614  are optionally located on either side of the coil  420 . For example, the high side switch  612  is included in the system  600  on a first side of the coil  420 . In an example, the low side switch  614  is included in the system  600  on a second side of the coil  420 . In an example, current flows through the coil  420  (and energizes the coil  420 ) when the switches  612 ,  614  are closed. In some examples, one or more of the switches  612 ,  614  are normally open, and modulation of the switch closes a circuit and allows current to flow through the switches  612 ,  614 . For instance, the switches  612 ,  614  are normally open to facilitate conservation of power in the system  600  (e.g., by selectively supplying power to the system  600  as needed). 
     In some examples, the coil  420  has a defined resistance, and when a potential is applied across the coil  420 , a first amount of energy will be dissipated by the coil  420  to build the magnetic field. A second amount of energy is dissipated due to the resistance of the coil  420  (e.g., as heat). Once the magnetic field builds to a sufficient level to overcome the fluid pressure at the valve inlet  414  and the bias provided by the biasing element  418 , the valve operator  400  moves toward the open position. Once the valve  304  transitions from the closed position to the open position, the amount of magnetic field needed to maintain the open position of the valve operator  400  is reduced because the initial additional force to separate the seal  408  from the seat  409  against the fluid pressure built-up upstream from the valve  304  is reduced (e.g., in comparison to when the valve operator is in the closed position). The amount of current running through the valve  304  is optionally reduced to maintain the valve  304  (e.g., the valve operator  400 ) in the open position, for example to save power (e.g., hitting and holding the valve operator  400  in the open position). In an example, a full voltage potential is applied to the coil  420  until the valve operator  400  transitions to the open position from the closed position. Once the valve  304  has opened, a reduced voltage potential (or current), or a modulated current (shown in  FIG.  7    as the rapid saw tooth portion of the current plot), is applied to the coil  420  to facilitate maintaining the valve operator  400  in the open position while reducing the power consumption due to the wiring resistance in the coil  420 . 
     In some examples, the system  600  includes one or more dissipation elements  616 , for instance a first dissipation element  618  and a second dissipation element  620 . The dissipation elements  616  include (but are not limited to) a flyback diode, freewheeling diode, clamp diode, transient voltage suppression diode, resistor, capacitor, or the like. In an example, the first dissipation element  618  includes a freewheeling diode, and the dissipation element  618  facilitates recirculation of current through the coil  420  to facilitate the maintenance of the magnetic field with less energy. The dissipation element  616  optionally has a dissipation characteristic and dissipates energy within the system  600 , for instance from the coil  420 . In some examples, the dissipation element  616  facilitates recirculation of energy within the system  600  (e.g., by recirculating current through the freewheel path  632 , or the like). For example, the dissipation element  618  facilitates recirculation of current through the coil  420  (with corresponding maintenance of the magnetic field) when the high side switch  612  is open (e.g., to inhibit current flow through the switch  612 ) and the low side switch  614  is closed (e.g., to allow recirculating current to flow between the switch  614  and the dissipation element  616  with the intervening circuit having the coil  420  and ground). 
     The second dissipation element  620 , for example, facilitates deenergizing of the coil  420 . For instance, the dissipation element  620  includes a clamping diode, and the dissipation element  620  quickly dissipates recirculating energy in the system  600  (e.g., removes, reduces, diminishes, dumps, minimizes or the like) from the coil  420  (or the system  600 ) when both switches  612 ,  614  are opened. Accordingly, current flowing through the coil  420  is forced to divert to a flyback path (e.g., the flyback path  634 , or the like) for dissipation across the dissipation element  620  (e.g., a clamping diode). 
     The valve  304  is optionally closed (e.g., to arrest flow in the channel  412  between the valve inlet  414  and the valve outlet  416 ) by dissipating the magnetic field between the lug  404  and the valve operator  400 . For example, the magnetic field between the lug  404  and the valve operator  400  is dissipated and the biasing element  418  biases the valve operator  400  away from the lug  404  and toward the closed position. In an example, the current flowing through the coil  420  is reduced to dissipate the magnetic field generated by the coil  420 . For example, the voltage potential applied to the coil  420  is removed from the coil  420 . When the voltage potential is removed, the current flowing through the coil  420  decreases and the magnetic field generated by the coil  420  also begins to dissipate (e.g., decay, reduce, decrease, diminish or the like). When the magnetic field has sufficiently dissipated, the biasing element  418  biases the valve operator  400  back towards the valve seat  409  and the closed position. 
     As the valve operator  400  begins to transition from the open position (shown in  FIG.  4   ) toward the closed position (shown in  FIG.  5   ), the amount of flux linkage in the magnetic circuit (e.g., between the lug  404  and the valve operator  400 ) decreases. For instance, fluid having a lower magnetic permeability fills the fluid gap  500  as the valve operator  400  (with a relatively higher magnetic permeability) moves out of the gap and toward the closed position. A counter current is generated in the coil  420  as the valve operator  400  begins to move, and the counter current opposes the change in flux linkage (e.g., according to Lenz&#39;s law, or the like). The direction of the current generated in the coil  420  by the transitioning valve operator  400  is such that the generated current generates a counter magnetic field opposed to the dissipating magnetic field in the coil  420 . In an example, the generated current is monitored (e.g., by the controller  606  in communication with the one or more sensors  602 ) to determine when the valve operator  400  transitions from the open position toward the closed position. 
     In some examples, the open time (initiation of opening, length of time to open or the like) for the valve  304  is improved by enhancing the addition of energy to the coil  420  with the power conditioning system  608  to rapidly overcome the bias provided by the biasing element  418 . 
     In other examples, the closing time (initiation of closing, length of time to close or the like) of the valve  304  is enhanced by dissipating energy in the coil  420  rapidly and thereby initiating movement of the valve operator  400  earlier with the biasing element  418 . For example, a dissipation element  620  allows for rapid dissipation of energy from the coil  420 . Increasing the rate that energy is dissipated from the coil  420  (and corresponding dissipation of the magnetic field) optionally reduces the close time of the valve  304  (e.g., a time duration for the valve operator  400  to transition from the open position to the closed position). Further, reducing the amount of energy to be dissipated from the valve  304  (e.g., the coil  420 ) optionally reduces the close time of the valve  304  because there is relatively less energy to dissipate before closing is initiated. 
     As described herein, the controller  606  monitors the sensors  602  (e.g., the coil characteristic sensor  604 , dissipation characteristic sensor  624 , tip pressure sensor  1204 , or the like). For instance, the controller  606  determines when the valve operator  400  moves based on the monitoring of electrical characteristics with the sensor  604  (e.g., a decrease in current corresponding to movement of the valve operator  400  with respect to the housing  406 ). 
     The controller  606  monitors the sensors  602  to correspondingly monitor the mechanical response of the valve operator  400  (e.g., movement of the valve operator  400  between the closed position and the open position). Monitoring of the mechanical response of the valve operator  400  facilitates, in one example, determining whether the valve is in a primed state or an unprimed state. 
     In some examples, the coil characteristic sensor  604  includes the sense resistor  622 . For instance, the sense resistor  622  facilitates monitoring of electrical characteristics of the system  600  (e.g., current through the coil  420 ), for example with the controller  606 . For example, the sense resistor  622  facilitates determining electrical characteristics of the coil  420 . Monitoring of the electrical characteristics of the coil  420  facilitates monitoring of movement of the valve operator  400 , for instance to determine when the valve operator  400  begins to transition from the closed position to the open position. In an example, the sense resistor  622  (in cooperation with the controller  606 ) facilitates determining when the valve operator  400  has fully transitioned to the open position (from the closed position). In some examples, the sense resistor  622  is located in series with the coil  420 . In an example, the sense resistor  622  is located in the system  600  between the coil  420  and the switch  612 . The sense resistor  622  is optionally located in series with the power conditioning system  608  and the coil  420 . Thus, the coil characteristic sensor  604  determines electrical characteristics of the coil  420  and facilitates monitoring of the electrical characteristic of the coil  420  with the controller  606 . Accordingly, monitoring of the electrical characteristics of the coil  420  facilitates determining when the valve operator  400  actually moves (e.g., because the mechanical response of the valve  304  differs from the electrical signals operating the valve  304 ). 
     In an example, the sensors  602  include a dissipation characteristic sensor  624 . For instance, the dissipation characteristic sensor  624  determines one or more electrical characteristics of the dissipation elements  616 . For example, the dissipation characteristic sensor  624  determines a voltage across the second dissipation element  620 , for instance by determining a voltage at a dissipation voltage node  626  between the coil  420  and the second dissipation element  620 . 
     In an example, the dissipation characteristic sensor  624  facilitates monitoring of movement of the valve operator  400 . For instance, the controller  606  optionally monitors the dissipation characteristic sensor  624  to monitor the mechanical response of the valve operator  400  (e.g., movement of the valve operator  400  between the open position and the closed position). The controller  606  monitors the sensor  624  to determine when the valve operator  400  begins to transition from the open position to the closed position. In another example, the sense resistor  622  (in cooperation with the controller  606 ) facilitates determining when the valve operator  400  has fully transitioned to the closed position (from the open position). 
     The system  600  optionally includes one or more signal processors  628 . For instance, the signal processors  628  provide signal conditioning, amplification, or the like for components of the system  600 . In an example, the signal processors  628  facilitate monitoring of electrical characteristics by the controller  606 . For example, the signal processors  628  condition electrical characteristics of the system  600  for monitoring by the controller  606 . For instance, the signal processors  628  allow the controller  606  to monitor the voltage at the dissipation voltage node  626 . The signal processors  628  allow the controller  606  to monitor current flowing through the coil  420 , for example by monitoring the voltage across the sense resistor  622 . 
       FIG.  6    shows arrows indicating flow of current through the system  600  in the various configurations described herein (e.g., during energizing of the coil  420 , maintenance of the energized coil, and dissipation of energy from the coil  420 ). The system  600  shown in  FIG.  6    includes an energizing path  630  (dot-dash stippled lines) that energies the coil  420  to generate the magnetic field (e.g., to open the valve). In an example, current flows through the energizing path  630  when the high side switch  612  and the low side switch  614  are closed. In another example, the system  600  includes the freewheel path  632  (dot-dash-dash stippled lines) that allows current to recirculate through the coil  420  (e.g., to maintain the magnetic field and hold the valve operator  400  in the open position). For instance, current flows in the freewheel path  632  including ground and the coil  420  when the high side switch  612  is open and the low side switch  614  is closed. In yet another example, the system  600  includes a flyback path  634  (dot-dot-dash stippled lines) that dissipates energy from the coil  420 . In an example, current flows through the flyback path  634  when the high side switch  612  and the low side switch  614  are open. Accordingly, the system  600  operates the switches  612 ,  614  to direct current flow through one or more of the energizing path  630 , the freewheel path  632 , or the flyback path  634  to accomplish energizing of the coil  420  and generation of the magnetic field, maintenance of the magnetic field or dissipation of energy (and the magnetic field), respectively. 
       FIG.  7    illustrates a representation of one or more drive signals used to apply a specified duty cycle to a valve (e.g., the valve  304 , shown in  FIG.  3   ) and the resultant waveforms (e.g., valve characteristics, such as one or more electrical characteristics, valve operator positions, specified and actual duty cycles, or the like) that are monitored (or determined) by the controller  606  in combination with the sensors described herein.  FIG.  7    shows one iteration (sequence) of an example specified duty cycle, the resulting actual duty cycle and the monitored or sensed characteristics described herein. 
       FIG.  7    shows time intervals T0, T1, T1′, T2, T3, T4, T5, T6, T7, T8, and TC along a common X-axis for each of differing plots that follow characteristics of the nozzle control system  600  during operation. The Y axes of the respective plots are graduated by corresponding characteristics including, but not limited to, voltage, current, open or closed states (and intermediate positions) or the like. In an example, the high side switch  612  and the low side switch  614  (shown in in the upper most plots of  FIG.  6   ) are modulated between on off states. The first (upper most) plot of  FIG.  7    shows a low side switch state  700  and the second plot shows a high side switch state  702 . For instance, the high side switch state  702  is in the on state at TO, and the low side switch state  700  is in the off state at T4. In some examples, a specified duty cycle  701  of the valve corresponds to the low side switch state  700  having a corresponding specified time length  703 , in this example of T0 to T4 of one full cycle (e.g., for a complete cycle including on and off of time T0 to TC). In other examples, the specified duty cycle  701  is represented as a percentage (e.g., 30, 40, 50, 60 percent or so on) of one full cycle (time T0 to TC). 
     The controller  606  (in cooperation with the sensor  604 , shown in  FIG.  6   ) monitors a coil electrical characteristic  704  (e.g., current) of the coil  420  as shown in the third plot of  FIG.  7   . In another example, the controller  606  (in cooperation with the sensor  624 , shown in  FIG.  6   ) monitors a dissipation element electrical characteristic  706  (e.g., one or more of voltage, current, or the like) of the dissipation element  620  shown in the fourth plot of  FIG.  7   . Additionally,  FIG.  7    shows a fifth plot of a valve operator position  708  indicating the position of the valve operator  400  within the valve  304  with the bottom of the curve corresponding to the closed position and the peak of the curve corresponding to the open position. In an example, the actual duty cycle of the valve corresponds to the valve operator position  708 . 
     Further, flow  709  agricultural product or the like through the valve of the valve system  600  is shown in the sixth plot (lower most) in  FIG.  7    and varies between a value of 0 (e.g., no flow) and  1  (e.g., 100 percent flow indicating the valve is open and steady state flow is provided). As discussed herein, movement of the valve operator  400  permits (or inhibits) flow  709  through the valve. 
     As shown in  FIG.  7    with the specified duty cycle  701  corresponding to the low side switch state  700  and the actual duty cycle  713  corresponding to the valve operator position  708  the valve operator movement (opening and closing) lags in comparison to the specified duty cycle  701 . For instance, the actual duty cycle  713  is clearly positioned behind (e.g., lagging, retarded, delayed, or the like) the specified duty cycle  701 . This variation or lag between the actual and specified duty cycles  713 ,  701  causes errant application of agricultural product (e.g., quantity of product applied, location of application, or the like) relative to the specified duty cycle  701 . 
     In one example, at time T0, the valve operator  400  is a closed position as shown with the valve operator position plot  708 . At time T0 both of the high side switch  612  and low side switch  614  (shown in  FIG.  6   ) are closed, a circuit is completed, and current begins to flow through the current sense resistor  622  and the coil  420  (shown in  FIG.  6   ). The coil  420  initially behaves as an inductor (resisting the increased current), and the coil electrical characteristic  704  (e.g., current) does not change instantaneously, but instead increases over time from T0 onward. For example, the coil electrical characteristic  704  increases with time as shown in  FIG.  7    after closure of the low side switch state  700  at TO. The resulting magnetic field generated from the coil  420  builds as current increases. The building magnetic field applies a corresponding increasing force to the moveable valve operator  400 . As the magnetic field builds in the coil  420  and the lug  404  the force produced by the field overcomes the combination of forces holding the valve operator  400  in the closed position (e.g., pressure holding the valve  304  closed, the bias force holding the valve closed, and any other forces on the valve operator  400  holding it closed position such as gravity) and the operator  400  begins moving toward the open position. 
     The plotted coil electrical characteristic  704  shows a plurality of inflection points  710 . As previously described, as the valve operator  400  begins to move (e.g., from closed to open) at approximately T1 a counter current is generated, and the counter current is graphically shown in  FIG.  7    with a first inflection point  710 A at T1 along the coil characteristic  704  plot. In contrast, if there was no moveable valve operator  400 , the current would follow the upward trending path indicated by the first dashed line  712 . In some examples, monitoring of this electrical characteristic is utilized to diagnose a service issue with the valve  304 , such as the absence of a valve operator  400  (e.g., after servicing). If the valve operator  400  is missing from the valve  304  (e.g., errantly not replace after service) the electrical characteristic  704  will behave in a manner consistent with first dashed line  712  and thereby facilitate diagnosis of a missing operator  400 . 
     The fifth plot of  FIG.  7    shows the valve operator position  708 , and the valve operator position  708  corresponds to a position of the valve operator  400  within the valve  304  with the bottom of the curve corresponding to the closed position and the peak of the curve corresponding to the open position. In an example,  FIG.  7    shows the valve operator  400  beginning to translate at time T1 (e.g., a translation start time, corresponding to when the measured current signature starts to depart from the dashed line  712 ). In an example, Faraday&#39;s law indicates that movement of the valve operator  400  generates a field in the coil  420 . Lenz&#39;s law indicates that the current generated by the valve operator  400  must oppose the direction of the building magnetic field caused by the driver of the coil  420  (e.g., the characteristic  704 , current, provided with the power conditioning system  608 , or the like). Accordingly, in an example, a change (e.g., decrease with respect to time) in the coil electrical characteristic  704  (the third plot), current, indicates one or more valve operator translation signatures  714 , specifically indicating when the valve operator  400  begins opening movement (from closed) toward the lug  404  of the valve  304 . 
     In some examples, the controller  606  (shown in  FIG.  6   ) compares the monitored electrical characteristics of the system  600  to the one or more valve operator translation signatures  714  (shown in the third plot and the fourth plot of  FIG.  7   ). For instance, a first valve operator translation signature  714 A corresponds to at least one inflection point  710  of the coil electric characteristic  704  for example at T1′. In an example, the inflection points  710  include one or more of a change in magnitude of a derivative of the characteristic  704 , such as an increase in the rate that the slope is decreasing; a change in sign of the slope of the characteristic  704 ; a change in sign of the derivative of characteristic  704 ; peaks and valleys; or the like. The controller  606  monitors the coil electric characteristic  704  (the third plot) and indexes at least a component of movement of the valve operator  400  (shown in the fifth plot) based on features of one or more of the coil electrical characteristic  704  or the dissipation element characteristic  706  (the fourth plot). The controller  606  compares the indexed the electrical characteristics to the valve operator translation signature  714 , for example by locating one or more of the inflection points in one or more of the coil electric characteristic  704  or the dissipation element characteristic  706 . 
     Referring to  FIG.  7   , as the valve operator  400  moves (indicated with the valve operator position  708 ), the inductance of the coil  420  begins to change as more of the volume inside the solenoid  421  is converted from fluid with a low magnetic permeability to include the valve operator  400  material with a relatively higher magnetic permeability. When the valve operator  400  reaches the top of the valve  304  (fully open, shown in  FIG.  4   ) and shown at T2 in the fifth plot of  FIG.  7    the valve operator  400  stops moving and no longer generates a counter current in the coil  420 . As shown with the coil electric characteristic  704  (third plot), the current ceases decreasing at a second inflection point  710 B and begins to rise again. The current in the coil  420  continues to build as it did before due to the potential through the coil  420  (applied by the power conditioning system  608 ) without the counter current provided by the previously moving valve operator  400 . Accordingly, the second inflection point  710 B corresponds to a second valve operator translation signature  714 B indicating the valve operator  400  is fully open. Thus, the controller  606  monitors the coil electric characteristic  704  and determines that the valve operator  400  has fully moved to the open position based on the valve operator translation signature  714 B at time T2. 
     At time T2, the valve operator  400  is at the open position, and at time T3 the controller  606  optionally reduces the current and associated magnetic field in the solenoid  421  for instance to save energy. For instance, the controller  606  maintains the current at a lower level recognized to retain (e.g., maintain) the valve operator  400  in the open position. In an example, the current is modulated as shown with the sawtooth wave at T3 (e.g., with selective opening and closing of the high side switch  612  while the low side switch  614  is closed). For example, the electrical resistance in the coil  420  and loss in one or more of the dissipation elements  616  and switches  612 ,  614  causes the coil electrical characteristic  704  to decay. In order to maintain the field generated by the coil  420 , the high side switch  612  is modulated to add energy to the solenoid  421  (e.g., the coil  420 , or the like) as needed to maintain the valve operator  400  open while minimizing power usage. 
     The modulated current maintains the magnetic field in the solenoid  421  with a slight imbalance (e.g., relative to gravity, fluid pressure, bias from the bias element or the like) to ensure retention of the valve operator  400  in the open position. In an approach, the inductance of the coil  420  is higher and the coil electrical characteristic  704  would follow the path indicated by a second dotted line  716  in the coil electrical characteristic  704  until it had saturated near a maximum value (e.g., approaches a limit, or the like) if the high side switch  612  was maintained in the on state. 
     Modulating (e.g., selectively opening and closing) the high side switch  612  circulates current in the system  600  at a level to generate a magnetic flux between the lug  404  and the valve operator  400  so as to maintain the position of the valve operator  400  (e.g., in the open position). Accordingly, the system  600  modulates the switch  612  to provide a force imbalance incident upon the valve operator  400  and ensure retention of the valve operator  400  in the open position while reducing the power needed to maintain the position of the valve operator  400 . 
     In some examples, the high side switch  612  is modulated between the on state and the off state (e.g., by selectively closing and opening the switch  612 ) while maintaining the low side switch  614  in the on (e.g., closed) state. Modulating the high side switch  612  while the low side switch  614  is in the on state causes current to flow through the freewheel path  632  that, in some examples, includes the low side switch  614 , the first dissipation element  618 , the sense resistor  622 , and the coil  420  (shown in  FIG.  6   ). Accordingly, modulating the high side switch  614  reduces the power usage for the system  600  to maintain the position of the valve operator  400  (e.g., in the open position). Thus, the performance of the system  600  is enhanced because of the reduced power consumption to maintain the position of the valve operator  400 . In some examples, modulating the high side switch  612  between closed and open (with the low side switch  614  closed) ensures retention of the valve operator  400  in the open position is referred to as a hit-and-hold algorithm. 
     In an example, during a rising edge of the low side switch control, a hit state is initiated in the high side switch  612  and the controller  606  starts recording electrical characteristics, for example by monitoring the current flowing through the coil  420 . The controller  606  analyzes the current data collected to determine if the valve operator  400  has translated between the open position and the closed position. In some examples, the controller  606  waits for a specified delay and repeats the analysis if a translation is not detected. In another example, the monitored valve characteristics change during operation based on the composition of fluid (liquid, gas, or mixture of liquid and gas) present in the valve  304  (e.g., the valve is primed with agricultural product, or the like). For instance, the monitored valve characteristics change when the valve  304  transitions from the unprimed state to the primed state. In yet another example, the controller  606  monitor either or both of current or voltage to assess variations in opening and closing behavior of the valve  304  that indicates whether the valve  304  is in an unprimed state or a primed state. 
     In an example, when the controller  606  determines the valve operator  400  has translated, the controller  606  optionally stops monitoring the electrical characteristics of the coil  420  and maintains the position of the valve operator  400  (e.g., by modulating the switch  612 , or the like). Optionally, the controller  606  waits for a specified duration for a compare event in the low side switch  614  timer. When a compare event occurs, the low side switch  614  and the high side switches  612  are turned to an off state. Accordingly, current is forced to recirculate in the flyback path  634  to be dissipated across the second dissipation element  620  (e.g., a clamping diode, or the like). At this point, the controller  606  monitors the dissipation characteristic  706  (e.g., a flyback voltage, or the like). At the end of a wait period (e.g., either 10 ms or the until the next update event), the controller  606  analyzes the dissipation characteristic for transition signature  714 . 
     The valve operator  400  is optionally moved to the closed position, for instance at time T4. In an example, both the high side switch  612  and the low side switch  614  are transitioned to the off state (e.g., to inhibit current flow through the switches  612 ,  614 ). With the switches  612 ,  614  in the off state, current is inhibited from flowing through the freewheel path  632 . Accordingly, the current recirculating in the coil  420  flows through the flyback path  634  (see  FIG.  6   ), optionally including the dissipation element  620  (e.g., a clamping diode), and begins to dissipate to free the valve operator  400  to move to the closed position. 
       FIG.  7    shows the monitored dissipation element electrical characteristic  706  (e.g., one or more of voltage, current, or the like) of the dissipation element  620  in the fourth plot. In an example, the dissipation element electrical characteristic  706  (“dissipation characteristic  706 ”) includes a monitored voltage at the dissipation voltage node  626  (shown in  FIG.  6   ). Since the dissipation characteristic  706  is greater than the voltage potential across the coil  420  with the switches  612 ,  614  in the off state, the energy of the magnetic field is quickly collapsed into a high electrical potential at the dissipation voltage node  626 . Conversely, as the voltage across the coil  420  rapidly rises the coil characteristic  704  (e.g., current) shown in the fourth plot flowing through the coil  420  quickly collapses to 0, for instance as shown by time T5 proximate to time T4. As previously discussed, current generates the magnetic field that retains the valve operator  400  in the open position, and the rapid decrease of current (and corresponding magnetic field) accordingly permits the movement of the operator toward the closed position. 
     In between T5 and T6, the dissipation characteristic (voltage)  706  is saturated, current decreases as shown in the third plot, and the magnetic field generated by the coil  420  decreases quickly. As the field decreases, the corresponding force retaining the open position of valve operator  400  against the fixed lug  404  dissipates—and the force provided by the biasing element  418  (shown in  FIG.  4   ) overcomes the retaining force and closing movement of the valve operator  400  is initiated. In some examples, the dissipation characteristic  706  includes one or more voltage inflection points  718 . For instance, a first voltage inflection point  718 A (shown at T5) correlates to the time when the current is directed to the second dissipation element  620  (and the voltage at the node  626  rises). In an example, a second voltage inflection point  718 B (shown at T6) corresponds to when the dissipation element  620  is no longer saturated.  FIG.  7    shows the valve operator position  708  (fifth plot) begins movement from the open position to the closed position at approximately T7 (e.g., a translation start time) corresponding to a third voltage inflection point  718 C. Closing movement finishes at approximately T8 (e.g., a translation stop time) corresponding to a fourth voltage inflection point  718 D. In an example, as the valve operator  400  moves away from the collapsing magnetic field, the valve operator  400  induces a current in the coil  420 , and accordingly provides a corresponding change in the otherwise dissipating voltage of characteristic  706  having a third valve operator translation signature  714 C. For example, the valve operator translation signature  714 C includes a change (e.g., an increase with respect to time, or the like) in the dissipation element electrical characteristic  706 , voltage in the example shown. In an example, the third voltage inflection point  718 C corresponds to movement of the valve operator  400  (e.g., translation signature  714 C). Completion of movement corresponds to, for instance, the fourth inflection point  718 D and a fourth translation signature  714 D when the valve operator  400  comes to a rest (and the valve  304  is closed). 
     In one example, Lenz&#39;s law indicates that the current generated by the valve operator  400  transitioning to the closed position opposes the change in the characteristic  706  as a result of the collapsing magnetic field. Thus, in an example, instead of seeing the voltage decay of the coil  420  (e.g., an inductor, or the like) that is discharging (represented by a third dotted line  720 ), the dissipation characteristic  706  will rise and then fall relative to the previous decay until the valve operator  400  has completed its movement (e.g., translation, transition, stroke, displacement, change, shift, or the like) from the open position (e.g., at T7) to the closed position (e.g., at T8). In an example where the field generated by the solenoid  421  is insufficient to maintain the valve operator  400  in the open position, the valve operator  400  will transition to the closed position prior to turning off the switches  612 ,  614 . At time T8, the valve operator  400  has fully completed movement to the closed position, and any remainder of the field generated by the coil  420  decays based on the lower inductance in the coil  420  since the fluid gap  500  has been reintroduced. In some examples, the valve  304  remains in this de-energized state until time TC which is the duration of a cycle. 
       FIGS.  8 A,  8 B,  8 C, and  8 D  illustrate cross-sectional views of the control valve  304  in one or more of a primed state, an unprimed state and intermediate states. For example,  FIG.  8 A  and  FIG.  8 B  show the valve  304  in a fully unprimed state and partially unprimed state (collectively referred to as unprimed).  FIG.  8 C  and  FIG.  8 D  show the valve  304  in the primed state with the valve operator open and closed, respectively (also shown in  FIGS.  4  and  5   ). In an example, the fluid chamber  800  of the valve  304  receives a fluidic mixture including one or more of a gas (e.g., air) or a liquid (e.g., water, agricultural product such as fertilizer, or the like). The fluid chamber  800  includes one or more of the valve inlet  414 , the valve outlet  416 , the channel  412  between the inlet  414  and the outlet  416 , and a space between the valve operator  400  and the housing  406 , such as a fluid gap  500 . The valve  304  receives fluid (e.g., agricultural product, water, air, or the like) through the valve inlet  414 . Movement of the valve operator  400  selectively opens and closes the channel  412  and allows fluid flow through the valve  304  to the outlet  416 . For example, the seal  408  of the valve operator  400  engages with a valve seat  409  (shown in the closed configuration in  FIG.  5   ,  FIG.  8 A , and  FIG.  8 D ) thereby arresting flow of fluid through the channel  412 . In the open position, the seal  408  is disengaged from the seat  409  (as shown in  FIG.  4   ,  FIG.  8 B , and  FIG.  8 C ) thereby allowing fluid flow through the channel  412  (e.g., because the valve operator  400  having the seal  408  is moved away from the seat  409 ). 
       FIG.  8 A  shows the fluidic mixture in the fluid chamber  800  having a first fluidic composition ( FIG.  8 A  is shown without liquid to illustrate the presence of a gas). For example, the fluid mechanical characteristics of the valve  304  change in correspondence with the composition of the fluidic mixture in the fluid chamber  800 . In an example, the first fluidic composition has a first density when the fluid chamber  800  primarily includes a gas (e.g., air, or the like). Accordingly, in this example the valve  304  is in the unprimed state when the first fluidic composition in the fluid chamber  800  has the first density.  FIG.  8 B  shows a second fluidic composition in the fluid chamber  800 . In another example, the second fluidic composition has a second density (shown by the presence of liquid  802  in comparison to  FIG.  8 A ). In one example, the fluid chamber  800  includes the liquid  802  at a first proportion or ratio (with respect to gas in the fluid chamber  800 ) and accordingly the fluidic mixture has the second fluidic composition (shown with proportion of liquid  802  in the fluid chamber  800 ). The liquid  802  is supplied to the control valve  304  (e.g., by the master PWM valve  206 ) and selectively flows through the valve  304  according to movement of the valve operator  400 . 
     In an example, the flow of liquid  802  through the valve  304  displaces the gas included in the fluid chamber  800  and corresponds to the valve  304  transitioning from the unprimed state to the primed state (e.g., ready to apply the fluid agricultural product). For example, the valve  304  is in the unprimed state when the fluidic mixture in the chamber  800  has the first fluidic composition or the second fluidic composition indicating initiation of priming of the valve  304 . In another example, the fluidic mixture in the chamber  800  has a third fluidic composition where the fluid chamber  800  has a greater percentage of liquid (with respect to gas in the fluid chamber  800 ) in comparison to the percentage of liquid in the second fluidic composition.  FIG.  8 C  and  FIG.  8 D  show the fluidic mixture in the fluid chamber  800  having the third fluidic composition (shown by the increased concentration of liquid  802  in comparison to  FIG.  8 A  and  FIG.  8 B ). In an example, the valve  304  is in the primed state when fluidic mixture in the fluid chamber  800  fills the fluid chamber (e.g., at least the valve inlet  414 ), for instance illustrated with the third fluidic composition in  FIGS.  8 C- 8 D . Accordingly, in an example, filling of the valve  304  (e.g., the valve inlet) with the agricultural product and minimizing of gases is illustrative of priming of the valve  304 , and is shown in  FIGS.  8 A-D  by the illustrated changes in composition of the fluidic mixture in the fluid chamber  800 . 
       FIG.  9    illustrates a block diagram of an agricultural product application system  900 . The system  900  includes the controller  606  and the one or more control valves  301  (e.g., one or more of the valve  304  shown in  FIGS.  3 - 5  and  8 A- 8 D ). The controller  606  monitors the operation of the valve operator  400  (shown in  FIGS.  3 - 5  and  8 A- 8 D ). As discussed herein, monitoring the operation of the valve operator  400  facilitates, in one example, determining if one or more of the valves  301  are in the primed state, the unprimed state, or blocked (e.g., fully blocked, fouled or the like). 
     In an example, the one or more control valves  301  include a first control valve  304 A, a second control valve  304 B, and a third control valve  304 C. The controller  606  includes an actuator interface  902  that facilitates opening and closing of the valves  301 . For instance, the actuator interface  902  is in communication with the first control valve  304 A to energize a first coil  420 A and cause movement of the valve operator (e.g., the valve operator  400 , shown in  FIGS.  4 - 5  and  8 A- 8 D ) from the closed position toward the open position. In another example, the actuator interface  902  cooperates with the valve  304 B to energize a second coil  420 B (and accordingly move a valve operator of the valve  304 B). In yet another example, the actuator interface  902  cooperates with the valve  304 C to energize a third coil  420 C (and accordingly move a valve operator of the valve  304 C). 
     The controller  606  monitors one or more valve characteristics of the one or more control valves  301 . In an example, the first control valve  304 A includes at least a first sensor  602 A that facilitates monitoring of valve characteristics of the control valve  304 A. The first sensor  602 A measures an amount of electrical current across the first coil  420 A and the controller  606  monitors the first sensor  602 A. Accordingly the controller  606  monitors the current across the first coil  420 A with the first sensor  602 A. In a similar example, the second control valve  304 B and third control valves  304 C include respective second and third sensors  602 B,  602 C that facilitate monitoring of valve characteristics of the control valves  304 B,  304 C. The controller  606  optionally monitors other valve characteristics of the valves  301 , such as electrical characteristics (e.g., voltage, or the like), valve operator positions (e.g., by way of monitoring associated electrical characteristics), specified and actual duty cycles, or the like. 
     Referring to  FIGS.  8 A- 8 D  and as described herein, movement of the valve operator  400  facilitates flow (or no flow) through the valve  304 . As the liquid  802  enters the fluid chamber  800 , the ratio of liquid to gas (corresponding to composition) of the fluidic mixture changes. For example, the ratio of the fluidic mixture in the fluid chamber  800  increases as liquid  802  (e.g., agricultural product, or the like) displaces the gas (e.g., air) in the valve  304 . Accordingly, in one example the density of the fluidic mixture within the fluid chamber  800  increases. The fluid mechanical resistance to movement of the valve operator  400  changes in correspondence with the fluid mechanical characteristics of the valve  304 , for instance density of the fluidic mixture in the fluid chamber  800  and in contact with the operator  400 . For example,  FIG.  8 A  shows the fluidic mixture having the first fluidic composition in the fluid chamber  800 , a relatively high ratio of gas to liquid. As shown in  FIG.  8 B , the liquid  802  is received in the fluid chamber  800 , and the liquid  802  fills the fluid chamber  800  changing the ratio of liquid relative to gas. The liquid  802  is denser than the gas in the fluid chamber  800 , and accordingly the liquid  802  increases resistance to movement of the valve operator  400  (e.g., increases drag, inertia or the like). In another example, the liquid  802  is less compressible than the gas in the fluid chamber  800 , and accordingly the fluid mechanical resistance to movement increases with the presence of liquid  802  in the fluid chamber  800 . In an example, the ratio of liquid to gas of the fluidic mixture in  FIG.  8 B  is greater than the ratio of the fluidic mixture in  FIG.  8 A  since the fluid chamber  800  includes the liquid  802  at the first concentration in  FIG.  8 B  (and the liquid  802  is absent or an incidental quantity in the fluid chamber  800  in  FIG.  8 A ). 
     In another example, the liquid  802  is received between the valve operator  400  and the housing  406 . For instance,  FIG.  8 D  shows the liquid  802  (shown as small dot stippling) is received in the fluid gap  500 . Accordingly, the fluidic mixture is interposed between the operator and the remainder of the valve  304  and flows around the valve operator  400  as the valve operator  400  moves with respect to the housing  406 . As described herein, a change in the ratio of liquid to gas of the fluidic mixture (and corresponding change in density) in the fluid chamber  800  induces a corresponding change in resistance to movement of the valve operator  400 . For example, the fluidic mixture having the first fluidic composition (e.g., shown in  FIG.  8 A ) imparts a first amount of drag, inertia or the like on the valve operator  400  as the valve operator  400  moves with respect to the housing  406 . In another example, the fluidic mixture having the second ratio of liquid to gas (shown with the liquid  802  at a first concentration in  FIG.  8 B ) imparts a second greater resistance to movement (e.g., drag, inertia or the like) on the valve operator  400  as the valve operator  400  moves with respect to the housing  406 . In yet another example, the fluidic mixture having the third greater ratio of liquid to gas (and corresponding increased density) in  FIGS.  8 C , D imparts a greater third resistance to movement to the valve operator  400 . The resistance to motion of the valve operator  400  increases based on the quantity of liquid  802  in the fluid chamber  800  relative to the quantity of gas in the fluid chamber  800 . The denser liquid resists motion of the valve operator  400 . As discussed herein, resistance to motion of the valve operator  400  (including lack thereof) is detected and monitored to determine the primed and unprimed states of control valves and other states, such as tip blockage. 
     Referring to  FIG.  4    and  FIG.  5    (and as described herein), the coil  420  generates a magnetic flux, and the valve operator  400  moves according to the magnetic flux generated by the coil  420 . For instance, the coil  420  induces a force on the valve operator to move the valve operator from the closed position (shown in  FIG.  5   ) and the open position (shown in  FIG.  4   ). In an example, the resistance to movement of the valve operator  400  varies in correspondence with the fluid mechanical characteristics of the valve  304 , for instance the ratio of the liquid to gas in the fluid mixture (and the attendant density) in the fluid chamber  800  (shown in  FIGS.  8 A- 8 D ). Accordingly, the force to move the valve operator  400  with respect to the housing  406  varies in correspondence with the resistance to motion imparted to the valve operator  400  by the fluidic mixture. In an example, the fluidic mixture in the chamber  800  has a greater ratio of gas to liquid (e.g., the first fluidic composition shown in  FIG.  8 A ), and the coil  420  receives a current value and generates a corresponding first magnetic flux to cause movement of the valve operator  400 . Because of the gas, the current and associated first magnetic flux are minimal in comparison to other example states (e.g.,  FIGS.  8 B-D ). The first state shown in  FIG.  8 A  and associated current to cause movement of the valve operator  400  are indicative of the valve  304  having an unprimed state. 
     In yet another example, the fluidic mixture in the chamber  800  has the second ratio of liquid to gas (and, in one example, corresponding greater density) as shown in  FIG.  8 B , and the fluidic mixture accordingly imparts a greater resistance to movement to the valve operator  400 . The coil  420  receives a second greater current that generates a second (also greater) magnetic flux to cause movement of the valve operator  400 . The second greater magnetic flux overcomes greater resistance to movement provided by the fluidic mixture. In the third configuration shown in  FIGS.  8 C,  8 D  the fluidic mixture in the chamber  800  has the third ratio of liquid to gas and corresponding fluidic composition. The coil  420  receives a third current (greater than the second current) and generates a corresponding third magnetic flux to overcome the greater resistance to motion provided by the fluid fixture to the valve operator  400 . The third magnetic flux and associated current are greater than the second magnetic flux and associated current. The second and third states shown in  FIGS.  8 B-D  and associated current to cause movement of the valve operator  400  are indicative of the valve  304  approaching and achieving a primed state. As discussed herein, the monitoring of current, voltage or the like associated with the valve  304  and variations in those characteristics facilitates identification of the state of the valve  304  including, but not limited to primed or unprimed states, intermediate states therebetween, as well as tip blockage (including full blockage, partial blockage, fouling or the like). Thus, one or more valve characteristics of the valves  301  vary in correspondence with the priming of the valves  301  (e.g., whether the valves  301  are in the primed state or unprimed state) and monitoring of the valve characteristics facilitates identification of the status of the valves  304 . 
     The agricultural product application system  900  (shown in  FIG.  9   ), including the controller  606  monitors valve characteristics such as current through the coil  420 . For example, the controller  606  determines whether individual ones of the valves  301  are in the primed state or unprimed state, blocked (e.g., fully, partially, fouled) or the like based on the monitored valve characteristics. In an example, the controller  606  monitors current through the coil  420  to determine whether individual ones of the valves  301  are in the primed state or the unprimed state. For instance, the controller  606  monitors variations in current applied to coils to determine whether individual ones of the valves  301  are in the primed state or the unprimed state. In another example, the controller  606  monitors a valve operator transition time to determine whether each of the valves  301  are in the primed state or the unprimed state. 
     As shown in  FIG.  9   , the system  900  includes a comparator  904  with the controller  606 , and the comparator  904  facilitates assessment of the status of the valves  301  (e.g., primed, unprimed, blocked or the like). For instance, the comparator  904  compares the monitored valve characteristics to a primed valve characteristic threshold to determine whether the valves  301  are in the primed state or the unprimed state. In an example, the controller  606  determines the valve  304 A (shown in  FIG.  9   ) is in the primed state when the monitored valve characteristics (in one example current to develop magnetic flux) exceed the primed characteristic threshold, such as a current threshold indicative of a lower magnetic flux that opens a valve filled or partially filled with a gas. In an example, the primed valve characteristic threshold includes a specified current value (e.g., a known current for an unprimed valve). In another example, the primed valve characteristic threshold includes a preceding current value when the valve  304  is known to be in an unprimed state (e.g., at start up of the system or after flushing of the system). In yet another example, the primed valve characteristic threshold includes identification of trend in current values with opening or closing of the valve  304 . For instance, the primed valve characteristic threshold includes differences between current values during a priming operation. The controller  606  operates the valve  304  with multiple instances of opening, and the current values approach a consistent current value after the valve  304  is primed (e.g., the current approaches an asymptote, or the like). The controller  606  optionally monitors differences between current values during valve movement (e.g., opening) and determines the valve operator threshold is exceeded when the differences between current are minimized, for instance the current used to open in successive opening operations is similar (e.g., identical, or with minimal change between operations). 
     For instance, the actuator interface  902  (shown in  FIG.  9   ) cooperates with the valves  301  to repeatedly open and close individual ones of the valves  301  (e.g., valve  304 A). In an example, the actuator interface  902  cooperates with a switch (e.g., the low-side switch  614 , shown in  FIG.  6   ) to provide energy to the coil  420 A (and induce a force on the valve operator of the first control valve  304 A). The controller  606  monitors the valve characteristics of the valves  301  while opening and closing the valves  301 . Opening and closing the valves while the controller  606  monitors the valve operation (e.g., current to open the valve) identifies whether the valve is in the primed state or the unprimed state (as well as intermediate states, the valve is blocked or the like) based on variations in valve characteristics. 
     In one example, the controller  606  cooperates with the first sensor  602 A to monitor the valve characteristics of the valve  304 A. In an example, the controller  606  monitors the current through the coil  420 A with the sensor  602 A while opening and closing the valve  403 A with the actuator interface  902 . The comparator  904  compares the monitored current through the coil  420 A to the valve characteristic threshold (e.g., a current threshold, previous current value or behavior or the like). The controller  606  determines whether the valve  403 A is in the primed state based on the comparison of the monitored valve characteristics (e.g., current) to the valve characteristic threshold. For instance, the controller  606  determines the valve  304 A is in the primed state when the current through the coil  420 A exceeds the valve characteristic threshold. 
       FIG.  10    illustrates a representation of characteristics of valve operation (e.g., electrical characteristics, valve operator positions, or the like) that are monitored (or determined) by the controller  606  in combination with the sensors described herein.  FIG.  10    shows two types of monitored or determined valve characteristics. For instance,  FIG.  10    shows the coil electrical characteristic  704 . In this example, the coil characteristic  704  is a first coil characteristic, such as current through a coil (e.g., the coil  420 A, shown in  FIG.  9   ) during a first valve operator cycle. Additionally, FIG.  10  shows a second coil characteristic  1000 . Further,  FIG.  10    shows the valve operator position  708  as a second example characteristic of valve operation representative of the position of the valve operator (e.g., the valve operator  400 ) during the first valve operator cycle. For example, the bottom of the curve for the valve operator position  708  corresponds to the closed position and the peak of the curve corresponds to the open position, while the sloped portions are representative of the operator moving between the open and closed positions. 
     The second coil characteristic  1000  corresponds to the current through the coil during a second valve operator cycle indicative of the valve in a primed state. Still further,  FIG.  10    shows the valve operator position  1001  indicating the position of the valve operator (e.g., the valve operator  400 ) during the second valve operator cycle. For instance, the bottom of the curve for the valve operator position  1001  corresponds to the closed position and the peak of the curve corresponds to the open position. 
     As described herein, one or more valve characteristics of the valves  301  vary in correspondence with the priming of the valves  301  (e.g., whether the valves  301  are in the primed state or unprimed state). The valves  301  include a fluid chamber (e.g., the fluid chamber  800 , shown in  FIG.  8   , or the like), and the valve characteristics vary in correspondence with the presence of a fluidic mixture (and ratio of gas and liquid) in the fluid chamber.  FIG.  10    shows variations in valve characteristics between the first valve operator cycle (e.g., having coil characteristic  704 ) and the second valve operator cycle (e.g., having coil characteristic  1000 ). For instance, the first coil characteristic  704  is representative of valve operation with the fluid chamber of the valve  304  having a first ratio of fluids (e.g., the fluid chamber primarily includes a gas, such as air or the like). The second coil characteristic  1000  is representative of the fluid chamber having the third fluidic composition (e.g., the fluid chamber  800  includes a greater ratio of liquid to gas, including liquid predominantly or entirely). Accordingly, the current value to move the valve operator  400  in the first valve operator cycle is less than the current to move the valve operator  400  in the second valve operator cycle (e.g., because of the greater resistance to motion in the second cycle).  FIG.  10    shows the first coil characteristic  704  with a first inflection point  710 A (in this example a peak). The second coil characteristic  1000  has a second inflection point  710 B (also a peak in this example). In this example, the second inflection point  710 B has a greater magnitude than the first inflection point  710 A. Thus,  FIG.  10    shows the current flowing through the coil during the first valve operator cycle (e.g., coil characteristic  704 ) is less than the current flowing through the coil in the second valve operator cycle (e.g., coil characteristic  1000 ). 
     The controller  606  (shown in  FIG.  9   ) monitors the valve characteristics to determine whether the valves  301  are in the primed state or the unprimed state. For example, the comparator  904  (shown in  FIG.  9   ) of the controller  606  compares valve characteristics between valve operator cycles. In an example, the controller  606  helps compare the control valve characteristics of the second valve operator cycle (represented with the characteristics  1000 ) with the control valve characteristics of the first valve operator cycle (represented with the characteristics  704 ). For instance, the comparator  606  helps determine a difference between the control valve characteristics with respect to the first and second valve operator cycles to facilitate identification of the status of the associated valve (e.g., primed, unprimed, an intermediate state or the like). 
     In an example, the controller  606  actuates the valves  301  (shown in  FIG.  9   ) to open and close (as described herein). The comparator  904  of the controller  606  compares the valve characteristics to a first valve characteristic threshold  1002  (e.g., a current threshold, previous current value, or the like). The first valve characteristic threshold  1002  corresponds to a current value indicative of the valve being in the unprimed state. For instance, the comparator  904  compares one or more of the first coil electrical characteristic  704  or the second coil characteristic  1000  to the first valve characteristic threshold  1002 . In an example, the controller  606  determines the valve is in the unprimed state when one or more of the coil characteristics  704 ,  1000  is equal to or less than the first valve characteristic threshold  1002 . As shown in  FIG.  10    the magnitude of the valve operator translation signature  714 A (corresponding to a peak current load during the first cycle) is less than the magnitude of the first valve characteristic threshold  1002 . Accordingly, the controller  606  determines the valve is in the unprimed state in the first valve operator cycle because the valve operator translation signature  714 A is less than the first valve characteristic threshold  1002 . 
     In another example, the comparator  904  of the controller  606  compares the valve characteristics to a second valve characteristic threshold  1004 . For instance, the second valve characteristic threshold  1004  corresponds to a current value indicative of the valve in the primed state. In an example, the comparator  904  compares one or more of the first coil electrical characteristic  704  or the second coil characteristic  1000  to the second valve characteristic threshold  1004 . In another example, the controller  606  determines the valve is in the primed state when one or more of the coil characteristics  704 ,  1000  (e.g., their peaks, inflection points or the like) exceed the second valve characteristic threshold  1004 . For example,  FIG.  10    shows the magnitude of the valve operator translation signature  714 B is greater than the second valve characteristic threshold  1004 . Accordingly, the controller  606  determines the valve is in the primed state because the valve operator translation signature  714   j B exceeds the second valve characteristic threshold  1004 . 
     In an example, the agricultural product application system  900  uses the valve operator translation signatures  714  to determine one or more valve operator transition times corresponding to a time duration for movement of the valve operator  400  between open and closed positions. In another example, the first valve operator translation signature  714 A corresponds to the inflection point  710 A of the coil electric characteristic  704  (at T1′). The first inflection point  710 A corresponds to the valve operator (e.g., valve operator  400 , shown in  FIG.  4   ) initiating movement from the closed position to the open position (shown with the valve operator position  708  in  FIG.  10   ) during the first valve operator cycle. The second inflection point  710 B corresponds to a second valve operator translation signature  714 B indicating the valve operator is fully in the open position. Thus, the controller  606  monitors the coil electric characteristic  704  and determines that the valve operator has fully moved to the open position based on the valve operator translation signature  714 B at time T2. For example, the controller  606  uses the valve operator translation signatures  714 A,  714 B to determine valve operator transition times. For instance, the controller  606  determines a time duration between valve signature  714 A and valve signature  714 B. In another example, the controller  606  determines a time duration between times T1′ and T2. The valve operator transition times change in correspondence with priming (or depriming) of the valve  304 . 
     In yet another example, a fifth valve operator translation signature  714 E corresponds to the inflection point  710 B of the coil electric characteristic  1000  (at T3). The inflection point  710 B corresponds to the valve operator (e.g., valve operator  400 , shown in  FIG.  4   ) initiating movement from the closed position to the open position (shown with the valve operator position  1001  in  FIG.  10   ) during the second valve operator cycle. The fourth inflection point  710 D corresponds to a sixth valve operator translation signature  714 F indicating the valve operator is fully in the open position. Thus, the controller  606  monitors the coil electric characteristic  1000  and determines that the valve operator has fully moved to the open position based on the valve operator translation signature  714 F at time T4. 
     In yet another example, the valve characteristics include a valve operator transition time. The controller  606  determines one or more valve operator transition times for a valve operator cycle. For instance, the controller  606  determines one or more valve operator transition times using the coil electrical characteristics  704 ,  1000 . As described herein, as a valve operator moves (indicated with the valve operator position  708 ), the inductance of the coil begins to change as more of the volume inside the solenoid is converted from fluid with a low magnetic permeability to the valve operator material with a relatively higher magnetic permeability. When the valve operator reaches the top of the valve  304  (fully open, shown in  FIG.  4   ) and shown at T2 for coil electrical characteristic  704  in  FIG.  10   —the valve operator  400  stops moving and no longer generates a counter current in the coil  420 . As shown with the coil electric characteristic  704 , the current ceases decreasing at a third inflection point  710 C and begins to rise again (indicating the valve operator has moved to the fully open position). In an example, the controller  606  determines the valve operator transition time with the comparator  904 . For instance, the comparator  904  determines the difference between T1′ and T2 in  FIG.  10   . The valve operator transition time in the first valve operator cycle corresponds to the difference between times T1′ and T2. 
     Further,  FIG.  10    shows the valve operator position  1001  indicating the position of the valve operator (e.g., the valve operator  400 ) during the second valve operator cycle (corresponding to the second coil electrical characteristic  1000 ). Similar to the first valve operator cycle, the controller  606  determines the valve operator transition time for the second valve operator cycle. For instance, the comparator  904  determines the difference between times between T3 (corresponding to valve operator translation signature  714 E) and T4 (corresponding to valve operator translation signature  714 F) in  FIG.  10   . The valve operator transition time to move from closed to open in the second valve operator cycle corresponds to the difference between times T3 and T4. 
     In still yet another example, the controller  606  monitors a valve operator transition time to determine whether each of the valves  301  are in the primed state or the unprimed state. As described herein, changes in the fluidic mixture within the valve affect the performance of the valve operator of the valve. For instance, liquid  802  in the fluid chamber  800  (shown in  FIGS.  8 A- 8 D ) induces greater drag on the valve operator. Accordingly, the fluidic mixture including the liquid  802  increases the valve operator transition time due to the increased drag on the valve operator. Accordingly, the controller  606  monitors the valve operator transition time between valve operator cycles to determine whether the valves  301  are in the primed state or the unprimed state. In an example, the first transition time corresponds to a time difference between signatures  714 A and  714 C. In another example, a second transition time corresponds to a time difference between signatures  714 E and  714 F. The second (longer) transition time is indicative of priming in the valve  301  because the valve operator takes longer to move through the surrounding liquid in comparison to gas. 
     For instance, the comparator  904  of the controller  606  compares the determined valve operator transition times to a valve characteristic threshold (e.g., a specified time duration, previous time duration of a prior opening movement, or the like). In an example, a third valve characteristic threshold  1006  includes a first transition time threshold corresponding to the unprimed state. In yet another example, a fourth valve characteristic threshold  1008  includes a second transition time threshold corresponding to the primed state. The comparator  904  of the controller  606  compares the determined valve operator transition time (e.g., time span between T1′ and T2 or time span between T3 and T4) to the third valve characteristic threshold  1006  and the fourth valve characteristic threshold  1008 . For instance, the controller  606  determines the valve is in the unprimed state during the first valve operator cycle when the determined valve operator transition time is less than or equal to the third valve characteristic threshold  1006 . In another example, the controller  606  determines the valve is in the primed state when the determined valve operator transition time exceeds the fourth valve characteristic threshold  1008 . For instance, the controller  606  determines the valve is in the primed state when the valve operator transition time (e.g., the time span between T3 and T4) is greater than the second transition time threshold  1008 . In yet another example, the controller  606  determines the valve is in the unprimed state when the valve operator transition time (e.g., the time span between T1′ and T4) is less than or equal to the first transition time threshold. Accordingly, the controller  606  determines the valve is in the primed state or the unprimed state according to the comparison of valve characteristics to one or more valve characteristic thresholds. 
       FIG.  11    illustrates a rear perspective view of another example of the agricultural sprayer  100 . The sprayer  100  includes a prime mover  112  and a boom  104  extending from the prime mover  112 . The one or more controllers  116  operate the sprayer  100  or components of the sprayer  100 . For example, the controller  116  controls the supply of fluid (e.g., agricultural fluid, or the like) to the smart nozzles  106 . In an example, the reservoir tank  102  is in communication with the smart nozzles  106 , and the reservoir tank  102  supplies agricultural fluid to the smart nozzles  106 . The smart nozzles  106  include a control valve (e.g.,  304 A, B, C) and one or more associated nozzles that receive flow according to operation of the control valve. 
     In an example, the controller  116  (e.g., the controller  606  shown in  FIG.  6    and  FIG.  9   , or the like) communicates with the valves  304 A- 304 D to open and close the valves  304 A- 304 D (and regulate the flow of fluid therethrough). In another example, the controller  116  primes the valves  304 A- 304 D. For example, the controller  116  determine each of the valves  304 A- 304 D are in the primed state or the unprimed state (as described herein). The controller  116  optionally cascades priming of the valves  304 A- 304 D along the boom  104 . In an example, the controller  116  cascades priming of the valves  304 A- 304 D along the boom  104  while determining whether individual ones of the control valves  304 A- 304 D are in the primed state or the unprimed state. For instance, the controllers  116  prime each of the control valves in sequence from a proximal end  1100  to a distal end  1102  of the boom  104 . In another example, the controllers  116  prime each of the control valves in sequence from the distal end  1102  to the proximal end  1100  of the boom  104 . As priming of the respective valves  304 A, B, C, D is confirmed (e.g., with the system and analysis discussed herein) the valves are shut while unprimed valves continue with the priming procedure. Unnecessary delivery of additional agricultural fluid through primed valves is thereby arrested while unprimed valves continue with priming. 
     For instance, the controller  116  repeatedly opens and closes the first control valve  304 A. The controllers  116  determine the control valve  304 A is in the primed state from characteristics as discussed herein. After determination of the primed state at the valve  304 A the controller  116  maintains the valve operator of the control valve  304 A in the closed position. Other valves  304 B, C, D that are not yet primed continue with opening and closing operations until each is primed, and at that priming operation of the now primed valve ends and the valve remains closed and ready for application operations (e.g., use in the field). The controllers  116  optionally prime the valves  304 A- 304 D in sequence, for instance by priming the second control valve  304 B after the first control valve  304 A is in a primed state. For example, the controllers  116  optionally maintain the valve operator for the first valve  304 A in the closed position while repeatedly opening and closing the valve operator for the second valve  304 B. Accordingly, the controllers  116  maintain the first valve  304 A in the primed state while priming the second valve  304 B. Thus, the valves  304 A- 304 D are transitioned between the primed state and the unprimed state on an individual basis. In other examples, a priming operation is conducted with all or a subset of the valves  304 A-D at the same time, and as a primed state is detected in one or more of the valves  304 A-D that primed valve is closed and the priming operation stopped, while priming continues with the other valves until also primed. 
     In another example, the controller  116  directs and controls priming of the valves  304 A- 304 D from the proximal end  1100  of the boom  104  to the distal end  1102  of the boom  104 . In still yet another example, the controller  116  primes the valves  304 A- 304 D from the distal end  1102  of the boom  104  to the proximal end  1100  of the boom  104 . In a further example, the controller  116  simultaneously primes the valves  304 A- 304 D, and closes each of the valves  304 A- 304 D as the individual valves  304 A- 304 D transition between the unprimed state and the primed state. Thus, the controller  116  in at least one example primes and assesses priming of each of the valves  304 A- 304 D on an individual basis. 
     Still yet further, the controller  116  optionally deprimes the valves  304 A- 304 D, for example by depriming the valves  304 A- 304 D in sequence from the distal end  1102  toward the proximal end  1100  of the boom  104 . In this example, air is delivered through the sprayer boom to the valves  304 A- 304 D and the controller  116  analyses the valves to identify the unprimed state, and thereafter closes valves that are unprimed (e.g., agricultural liquid is evacuated). Thus, the controller  116  optionally deprimes and identifies depriming of the valves  304 A- 304 D on an individual basis. 
       FIG.  12    illustrates an example of the smart nozzle  106  including the valve  304 . The smart nozzle  106  is in communication with the boom  104 , and the boom  104  supplies fluid to the valve  304 . The valve  304  regulates flow of the fluid through a nozzle  1200 , for instance to apply an agricultural product with the sprayer  100  (shown in  FIG.  1   ). In an example, the nozzle  1200  includes an application tip  1201 . The application tip  1201  facilitates dispersion of the fluid from the smart nozzle  106 . For instance, the application tip  1201  controls the spray pattern (e.g., fan-shaped, cone-shaped, or the like) of fluid from the nozzle  106 . In another example, the application tip  1201  controls the droplet size (e.g., super fine, fine, coarse, super coarse or the like) of fluid flowing from the nozzle  1200 . In some approaches, flow of fluid through the nozzle  1200  is restricted by an obstruction (e.g., debris, gelled agricultural product, product residue or the like) fully or partially. Accordingly, the nozzle  1200  includes a restricted state (where nozzle flow is restricted full or partially relative to a specified flow rate range) or an unrestricted state (where nozzle flow is unrestricted, and approaches or equals a specified flow rate range) collectively referred to as blocked. 
     In some examples, the smart nozzle  106  includes one or more of a boom pressure sensor  1202  or a tip pressure sensor  1204  in communication with one or more of the valve inlet  414  or the valve outlet  416 . For instance, the boom pressure sensor  1202  optionally measures pressure in the boom  104 , and accordingly measures fluid pressure supplied to the valve inlet  414 . Optionally, the smart nozzle  106  includes the tip pressure sensor  1204  in communication with the valve outlet  416 . In another example, the tip pressure sensor  1204  facilitates monitoring of pressure proximate to the valve outlet  416  (however the present subject matter is not so limited). In yet another example, instead of (or in addition to) one or more pressure sensors  1202 ,  1204  the controller  606  monitors characteristics indicative of blocking of valve  304  or nozzle  1200  using monitored valve characteristics (e.g., current, voltage, or the like). 
     As described herein, opening of the valve  304  supplies fluid to the valve outlet  416  and the associated nozzle  1200 . The fluid flows through the application tip  1201  and is discharged to the environment. For example, fluid is discharged from the application tip  1201  while the valve operator  400  is in the open position. While the valve  304  is open the pressure at the valve outlet  416  corresponds to the pressure in the boom  104 , and the pressure drives fluid through the application tip  1201 . With the valve operator  400  in the closed position, pressure in the valve outlet  416  decays toward ambient atmospheric pressure as the valve outlet  416  is isolated from the boom  104  and the higher pressure therein. 
     The rate of pressure decay in the valve outlet  416  changes in correspondence with restriction of the nozzle  1200 . In an example, pressure at the valve outlet  416  decays at a first rate with the nozzle  1200  in the unrestricted state. Fluid remaining in the valve outlet  416  immediately after valve  304  closure is applied and the outlet  416  equalizes with ambient pressure. In contrast, the pressure at the valve outlet  416  decays at a second lesser rate with the nozzle  1200  in the restricted state, for instance partially or fully obstructed or blocked. For instance, blockage of the application tip  1201  inhibits fluid flow through the application tip  1201 . Accordingly, after closure of the valve  304  the pressure of the fluid in the valve outlet  416  decays at a slower rate (in comparison to the unrestricted state) due to inhibited fluid flow caused by the blockage. In another example, a total blockage of the application tip  1201  (or the valve outlet  416 ) maintains the fluid pressure at the valve outlet  416  proximate to the pressure of the boom  104  because the fluid in the smart nozzle  1200  is trapped in the valve outlet  416 . In this circumstance decay of pressure in the valve outlet is minimal (e.g. remains proximate to the boom pressure even after valve  304  closure). 
     In an example, valve characteristics, monitored with the systems described herein, change in correspondence with the pressure decay (or lack thereof) at the valve outlet  416 . During normal operation (e.g., with the nozzle  1200  in an unrestricted state) with the valve operator  400  in the closed position, pressure upstream (e.g., at the valve inlet  414 ) of the valve operator  400  measured with the pressure sensor  1202  is higher than pressure downstream (e.g., at the valve outlet  416 ) of the valve operator  400  measured with the pressure sensor  1204 . Accordingly, a pressure differential exists at the valve operator  400  during normal operation. The pressure differential biases the valve operator  400  to remain closed. When opening of the valve  304  is desired, a current is applied to the coil  420  to move the valve operator  400 . The current applied to the coil  420  varies in correspondence with one or more valve characteristics including the pressure differential. With a greater pressure differential, for instance the differential between a boom pressure (upstream) and ambient (downstream) the valve operator is robustly biased in the closed position. With a smaller pressure differential, for example with a blockage that decreases or slows pressure decay the valve operator is biased in the closed position but less affirmatively because of the smaller pressure differential. In one example, measurement of the pressure differential with the pressure sensors  1202  and  1204  (upstream or downstream) or with the downstream sensor  1204  (along with a boom pressure set point) facilitates identification of a blockage. Large pressure differentials (at valve closure) approaching the predicted differential between boom pressure and ambient air pressure indicate the smart nozzle  106  including the valve  304  and the nozzle  1200  are unrestricted (e.g., not blocked). In contrast, pressure differentials less than the predicted differential at valve closure indicate a slower pressure decay downstream from the valve  304  and blockage of one or more of the valve or nozzle  1200 . In an example, the controller  606  monitors one or both pressure measurements from one or both of the pressure sensors  1202 ,  1204  to determine unrestricted and restricted states of the smart nozzle  106  and thereby identify if the smart nozzle  106  (e.g., the valve  304  or nozzle  1200 ) is blocked. 
     In an example, the controller  606  includes the comparator  904  (shown in  FIG.  9   ). For instance, the comparator  904  compares measured valve characteristics (e.g., pressure, current, or the like) between valve operator cycles to determine whether the smart nozzle  106  is in the unrestricted or restricted states. For example, the comparator  904  determines differences between valve characteristics of valve operator cycles to determine whether the nozzle  106  is in the unrestricted or restricted states. For instance, the comparator  904  compares a first pressure measurement corresponding to a first valve operator cycle to a second pressure measurement corresponding to a second valve operator cycle to determine a pressure differential between valve operator cycles. In another example, the comparator  904  compares current supplied to the coil  420  (shown in  FIG.  4   ) in the first valve operator cycle to current supplied to the coil  420  in the second valve operator cycle to determine differences in pressure between the first valve operator cycle and the second valve operator cycle. 
     As discussed herein, the amount of current to move the valve operator  400  from the closed position to the open position changes in correspondence with the pressure differential across the valve operator  400 . In the unrestricted state (no or minimal blockage) the downstream pressure rapidly decays toward ambient and the greater upstream (boom) pressure affirmatively biases the valve operator  400  to the closed position. Conversely, a blockage (full or partial) of the valve  304 , nozzle  1200  or the like lengthens pressure decay after valve closure and the pressure differential between the upstream and downstream sides the valve is slower. With the greater pressure differential of an unrestricted smart nozzle  106  (having the valve  304  and the nozzle  1200 ) more current is required to overcome the pressure differential bias that robustly seats the valve operator  400  in the closed position. In contrast, with a smaller pressure differential (e.g., with a partial or full blockage) the current to overcome the bias provided by the (smaller) differential is measurably less. 
     In one example the comparator  904  compares the monitored current to open the valve  304  (move the valve operator  400 ) with a predicted or threshold current value to determine if the smart nozzle  106  having the valve  304  is blocked in the valve  304  or the nozzle  1200  (or both). For instance, in an unrestricted state (no or minimal blockage) the monitored current should approach or exceed the threshold current. In contrast, in the restricted state (full or partial blockage), the pressure differential noted here is less because pressure decay is slower when the valve is closed. Accordingly the current to move the valve operator  400  is less. The comparator  904  determines the applied current is below the threshold current and the controller  606  provides an indication the smart nozzle  106  is blocked. 
     In some examples, the agricultural product application system  900  provides a notification (e.g., to a user, technician, or the like) of the status of the nozzle  1200 . For example, the agricultural product application system  900  displays on a screen whether the nozzle  1200  is in the restricted state or the unrestricted state. In another example, the system  900  applies remedial action (e.g., flushing of the valve  304 , flushing of the nozzle  1200 , rapid opening or closing of the valve operator  400  to break up residue or the like) based on the determination of whether the nozzle  1200  is in the restricted state or the unrestricted state. 
       FIG.  13    shows one example of a method  1300  for monitoring restriction of flow of a fluid through a nozzle, including one or more of the nozzle  1200  described herein. In describing the method  1300 , reference is made to one or more components, features, functions and operations previously described herein. Where convenient, reference is made to the components, features, operations and the like with reference numerals. The reference numerals provided are exemplary and are not exclusive. For instance, components, features, functions, operations and the like described in the method  1300  include, but are not limited to, the corresponding numbered elements provided herein and other corresponding elements described herein (both numbered and unnumbered) as well as their equivalents. 
     The method  1300  includes monitoring restriction of flow of a fluid through a nozzle  1200 , for instance of a smart nozzle  106  (shown in  FIG.  12   ). Restriction of the nozzle includes one or more of partial or total blockage of fluid flow (e.g., including fouling) through the nozzle  106 , failure of the application tip  1201 , damage of the application tip  1201 , or the like. Accordingly, the nozzle  1200  includes a restricted state (where nozzle flow is restricted relative to a specified flow rate range) or an unrestricted state (where nozzle flow is unrestricted, and approaches or equals a specified flow rate range). In an example, debris (e.g., dirt, gelled or residue agricultural product, or the like) clogs the application tip  1201  and inhibits flow of fluid through the application tip  1201 . In an approach, restriction of the nozzle inhibits flow through the nozzle  1200 , and leads to a misapplication or failure of application of agricultural product by the smart nozzle  106 . Thus, the system  900  monitors whether the nozzle  1200  is in the restricted state or the unrestricted state (and provided notification or remedial action) to enhance performance of the sprayer  100 . For instance, the system  200  minimizes misapplication of agricultural product because of (previously) unidentified restrictions of the nozzles, associated valves  304  or the like. 
     As described herein, the actuator interface  902  operates the valve  304  to regulate flow of fluid through the valve  304 . In an example, at  1302 , the method  1300  includes actuating the valve  304  to supply fluid to the nozzle  106 . For instance, the actuator interface  902  operates the valve  304  to translate the valve operator  400  between open and closed positions. Accordingly, in some examples, the actuator interface  902  cycles the valve  304  by opening and closing the valve operator  400 , with a cycle in one example including the valve closed, transitioning to open, arriving at the opened position, transitioning to closed and arriving at the closed position to complete the cycle. In another example, the actuator interface  902  operates the valve  304  to cycle the valve in a first valve operator cycle and a second valve operator cycle. The system  200  monitors valve characteristics, such as pressure decay of the nozzle  1200  (shown in  FIG.  12   ), current applied to open the valve or the like corresponding to the valve operator cycles. 
     In an example, the controller  606  (shown in  FIG.  6   ) monitors valve characteristics, for instance to determine health of the valve  304 . In another example, the controller  606  monitors valve characteristics during at least the first valve operator cycle and the second valve operator cycle. In yet another example, the controller  606  monitors pressure decay at the nozzle  1200 . For example, the controller  606  monitors pressure decay corresponding to a cycle of the nozzle  1200 . 
     In a further example, the controller  606  monitors the pressure decay at the nozzle  1200  after moving the valve operator  400  to the closed position during the first valve operator cycle. At  1304 , the method  1300  includes monitoring a first pressure decay at the nozzle  1200  corresponding to the first valve operator cycle. The controller  606  operates the valve  304  for the second valve operator cycle, and the controller  606  monitors the valve characteristics of the nozzle  1200 . For instance, the method  1300  optionally includes monitoring a second pressure decay at the nozzle  1200  corresponding to the second valve operator cycle. In some examples, the controller  606  monitors valve characteristics, such as pressure, between valve operator cycles (e.g., while the valve is closed). For instance, the controller  606  monitors valve characteristics between moving the valve operator  400  to the closed position in the first valve operator cycle, and moving the valve operator  400  to the open position in the second valve operator cycle. 
     At  1306 , the method  1300  includes comparing the pressure decay at the nozzle between the first valve operator cycle and the second valve operator cycle. In an example, comparing the pressure decay between valve operator cycles facilitates determining whether the nozzle  1200  is in the restricted state or the unrestricted state. For instance, in the first valve operator cycle the actuator interface  902  moves the valve operator  400  to the closed position according to a specified duty cycle (e.g., the specified duty cycle  713 , shown in  FIG.  7   ). In the second valve operator cycle, the actuator interface  902  optionally moves the valve operator  400  outside the specified duty cycle (applied during the first valve operator cycle). In a third valve operator cycle, the actuator interface  902  moves the valve operator  400  to the open position according to the specified duty cycle. 
     In an example, the specified duty cycle includes a specified delay period (e.g., a diagnostic period) between moving the valve operator  400  to the closed position in the first valve operator cycle, and moving the valve operator  400  to the next open position in the third valve operator cycle. The second valve operator cycle is in one example different than the specified duty cycle, and the actuator interface  902  moves the valve operator  400  to the open position outside of the specified delay period of the specified duty cycle. For example, in the second valve operator cycle, the actuator interface  902  moves the valve operator  400  within a pressure detection time period. The pressure detection time period is less than the specified delay period, and accordingly the valve operator  400  is moved to the open position outside the specified duty cycle in the second valve operator cycle. 
     Opening of the valve operator  400  outside of the specified duty cycle facilitates pressure monitoring of the nozzle  1200 . As described herein, the rate of pressure decay in the valve outlet  416  changes in correspondence with restriction of the nozzle  1200 . The valve operator  400  is opened outside the specified duty cycle to monitor the pressure at the valve outlet  416 . For example, the controller  606  monitors current supplied to the coil while the pressure is decaying at the valve outlet  416  (e.g., at a time within the pressure detection time period, or the like). The current supplied to the coil changes in correspondence with restriction of the nozzle  1200  (due to changes in the force balance acting upon the valve operator  400 ). Accordingly, opening the valve operator  400  outside the specified duty cycle allows for monitoring of the pressure decay at the valve outlet using changes in current needed to open move the valve operator  400 . 
     In one example, determining the pressure at the nozzle  1200  facilitates determining the flow coefficient (e.g., C v , or the like) for components of the smart nozzle  106 , including one or more of a flow coefficient for the valve  304  or flow coefficient for the application tip  1201 . Determining the flow coefficient for the smart nozzle  106  facilitates monitoring the performance of the smart nozzle  106 , for instance to determine a size of the application tip  1201  (shown in  FIG.  12   ). For example, the flow coefficient of the valve  304  includes pressure drop across the valve  304  based on the flow rate of fluid through the valve  304 . In a further example, determining the pressure at the nozzle  1200  facilitates determining the pressure difference across the valve  304  (e.g., a pressure differential between the valve inlet  414  and the nozzle  1200 ). The system  900  determines the flow coefficient using the determined pressure at the nozzle  1200  and one or more flow rates of the system  900 , for instance one or more of a nozzle flow rate, system flow rate, or the like. In another example, determining the pressure at the nozzle  1200  facilitates determining the flow coefficient for the application tip  1201 . For example, monitoring the pressure at the nozzle  1200  facilitates determining a pressure differential across the application tip  1201 . In an example, the system  900  determines the flow coefficient of the application tip  1201  using the pressure differential across the application tip  1201  and one or more flow rates of the system  900 . 
     In yet another example, the system  900  (shown in  FIG.  9   ) uses the determined flow coefficient of the valve  304  or the application tip  1201  to monitor performance of the smart nozzle  106 . For instance, the system  900  determines the size of the application tip  1201  (e.g., a size of an orifice of the application tip  1201 , or the like) using the determined flow coefficient of the valve  304  and the application tip  1201 . For example, a user exchanges a first application tip (e.g., application tip  1201 ) with a first flow coefficient for a second application tip having a second flow coefficient. The system  900  monitors the flow coefficient of the smart nozzle  106  to determine whether the first application tip or the second application tip is attached to the smart nozzle  106 . For example, the system  900  determines the first application tip is attached to the smart nozzle  106  when the flow coefficient for the application tip  1201  has the first flow coefficient. In another example, the system  900  determines the second application tip is attached to the smart nozzle  106  when the flow coefficient for the application tip  1201  has the second flow coefficient. Accordingly, the system  900  determines the size of the application tip  1201 , for instance to monitor a flow rate through the application tip  1201 . Further, the system monitors the flow coefficient (or changes in the flow coefficient) to determine whether the nozzle  1200  is damaged, blocked, fowled, or the like. In an example, damage to the application tip  1201  changes the flow coefficient of the application tip  1201 , and the system monitors the flow coefficient (or changes in the flow coefficient) to determine the application tip  1201  is damaged. For instance, the controller compares the determined flow coefficient to a flow coefficient threshold and makes valve health determinations based on the comparison. 
       FIG.  13    shows at  1308  the method  1300  includes determining the nozzle  1200  is in the restricted state or the unrestricted state based on the comparison of the pressure decay corresponding to a valve operator cycle relative to a restricted nozzle threshold. For example, the comparator  904  compares the monitored pressure decay to the restricted nozzle threshold. The controller  606  determines the nozzle  1200  is in the restricted state when the pressure decay of a valve operator cycle exceeds the restricted nozzle threshold. For example, the controller  606  determines the nozzle  1200  is in the restricted state when a first pressure decay rate corresponding to a first valve operator cycle is greater than a pressure decay rate corresponding to a (later) second valve operator cycle. For instance, blockage of the nozzle  1200  inhibits flow out of the nozzle, and reduces the rate of pressure decay at the valve outlet  416 . The comparator  904  compares the rate of pressure decay to the restricted nozzle threshold, and determines the nozzle  1200  is in the restricted state when the restricted nozzle threshold is exceeded (e.g., when the second pressure decay rate is reduced below a specified value, or the like. 
     Several options for the method  1300  follow. In an example, the method  1300  optionally includes issuing a notification if the nozzle  1200  transitions from the unrestricted state to the restricted state. For example, issuing a notification includes displaying the notification on a screen in a cab of a prime mover, such as the agricultural sprayer  100 . In another example, the method  1300  includes applying remedial action based on the determination of whether the nozzle  1200  is in the restricted state or the unrestricted state. For example, flushing of the valve  304  (or nozzle  1200 ) using one or more of a change in duty cycle, increase in pressure supplied to the valve  304  (e.g., pressure at the valve inlet  414 ), or cycling of the valve operator  400 . 
       FIG.  14    illustrates a schematic view of an example system  1400  for applying agricultural product. In an example, the system  1400  facilitates flushing of components of the agricultural sprayer  100  (shown in  FIG.  1   ). For example, the system  1400  applies remedial action (e.g., flushing of the valve  304 , flushing of the nozzle  1200 , rapid opening or closing of the valve operator  400  to break up residue or the like) based on a determination that the nozzle  1200  is in the restricted state or the unrestricted state. 
     In another example, the system  1400  flushes components of the agricultural sprayer  100  to remove agricultural product from the agricultural sprayer  100 . For instance, the system  1400  delivers a flushing fluid (e.g., water without agricultural product) to the booms  104  (shown in  FIG.  1   ), and the flushing fluid flows through the boom  104  to the smart nozzles  106  having the valves  304  and associated nozzles  1200 . In yet another example, the flushing fluid flows through the smart nozzles  106 . For instance, the flushing fluid flows through the fluid chamber  800  of the valve  304  (shown in  FIGS.  8 A- 8 D ) to reduce the amount of agricultural product present in the fluid chamber  800 . In a further example, the flushing fluid flows through one or more of the nozzle  1200  having the application tip  1201  (shown in  FIG.  12   ). 
     Referring to  FIG.  14   , the system  1400  for applying agricultural product includes a flushing fluid source  1402  (e.g., a tank, container, reservoir, or the like) in communication with the boom  104  and the valve  304  (shown with solid lines in  FIG.  14   ). The flushing fluid source  1402  includes a flushing fluid (e.g., water, air, or the like) and optionally is the carrier fluid without an agricultural product (fertilizer, herbicide or the like) injected to the carrier fluid. Thus, flow of the flushing fluid through components of the sprayer  100  (shown in  FIG.  1   ) reduces the concentration of agricultural product in the components of the sprayer  100 . For example, the system  1400  flushes the agricultural sprayer  100  prior to the sprayer  100  crossing a public roadway. In another example, the system  1400  flushes the agricultural sprayer  100  to remove a first agricultural product from the sprayer  100 . The flushing fluid removes the first agricultural product (e.g., an herbicide, or the like) from the sprayer  100 . Accordingly, system  1400  facilitates application of a second agricultural product (e.g., fertilizer, or the like) without (errantly) applying the first agricultural product or mixing the first agricultural product with the second agricultural product. 
     For instance, the system  1400  includes a flushing fluid valve  1404  in communication with the flushing fluid source  1402  and one or more of the boom  104  or the valve  304 . The controller  606  communicates with the flushing fluid valve  1404  to deliver flushing fluid from the flushing fluid source  1402  to the components of the sprayer  100 . For instance, the actuator interface  902  operates the flushing fluid valve  1404  to permit delivery of flushing fluid to the boom  104 . The flushing fluid flows through the boom  104  to the valve  304 . In some examples, the actuator interface  902  opens and closes the valve  304  while the flushing fluid valve  1404  is open. For example, the controller  606  monitors one or more valve characteristics of the valve  304  to determine whether flushing fluid flows through the valve  304 . In one example, the flushing fluid includes air, and the system  600  monitors valve characteristics to determine whether the air displaces liquid in the valve  304  (and accordingly changes the fluid mechanical characteristics in the valve  304 ) in a detectable manner corresponding to an unprimed state as discussed herein. 
     Various Notes &amp; Examples 
     Example 1 is a system for applying an agricultural product, the system comprising: a control valve including: a moveable valve operator configured to translate between a closed position and an open position; one or more sensors configured to monitor one or more control valve characteristics; and a valve controller in communication with the one or more sensors, wherein the valve controller includes: an actuator configured to repeatedly open and close the valve operator with agricultural product delivered to the control valve; a comparator configured to compare the monitored one or more control valve characteristics to a primed valve characteristic threshold; and wherein the valve controller is configured to determine the control valve is in one or more of a primed state or an unprimed state based on the comparison of the one or more control valve characteristics to the primed valve characteristic threshold. 
     In Example 2, the subject matter of Example 1 optionally includes wherein the one or more characteristics of the control valve includes at least one operator transition time corresponding to a time span for the valve operator to translate between the closed position and the open position. 
     In Example 3, the subject matter of Example 2 optionally includes wherein the operator transition time includes the time span for the valve operator to transition from the closed position to the open position. 
     In Example 4, the subject matter of any one or more of Examples 2-3 optionally include wherein the at least one operator transition time includes: a first operator transition time corresponding to the unprimed state; and a second operator transition time corresponding to the primed state. 
     In Example 5, the subject matter of Example 4 optionally includes wherein the second operator transition time is greater than the first operator transition time. 
     In Example 6, the subject matter of any one or more of Examples 4-5 optionally include wherein the primed valve characteristic threshold includes the first operator transition time. 
     In Example 7, the subject matter of any one or more of Examples 2-6 optionally include wherein: the primed valve characteristic threshold includes a transition time threshold; and the comparator is configured to compare the at least one operator transition time to the transition time threshold. 
     In Example 8, the subject matter of Example 7 optionally includes wherein the valve controller determines the control valve is in the primed state with the operator transition time exceeding the transition time threshold 
     In Example 9, the subject matter of any one or more of Examples 1-8 optionally include wherein a valve operator cycle includes movement of the valve operator between the closed and open positions, and wherein: the actuator is configured to open the valve operator in a first valve operator cycle; the actuator is configured to open the valve operator in a second valve operator cycle; the comparator is configured to compare the control valve characteristics of the first and second valve operator cycles; the valve characteristic threshold includes the control valve characteristics of the first valve operator cycle; and wherein the valve controller is configured to determine the control valve is in one or more of the primed state or the unprimed state based on the comparison of the control valve characteristics of the second valve operator cycle to the control valve characteristics of the first valve operator cycle and a difference therebetween. 
     In Example 10, the subject matter of Example 9 optionally includes wherein the control valve characteristics of the control valve include one or more electrical characteristics of the control valve. 
     In Example 11, the subject matter of Example 10 optionally includes wherein: the control valve includes a coil configured to generate a magnetic flux, the valve operator is configured to translate with respect to the coil based on the magnetic flux; and the one or more sensors are configured to measure one or more of current through the coil or voltage across the coil as the control valve characteristics. 
     In Example 12, the subject matter of Example 11 optionally includes wherein the valve controller is configured to determine the control valve is in one or more of the primed state or the unprimed state based on a comparison of the current through the coil in the second valve operator cycle to the current through the coil in the first valve operator cycle and a different therebetween. 
     In Example 13, the subject matter of Example 12 optionally includes wherein the valve controller determines the control valve is in the primed state if the current through the coil in the second valve operator cycle is greater than the current through the coil in the first valve operator cycle. 
     In Example 14, the subject matter of any one or more of Examples 11-13 optionally include wherein: the one or more characteristics of the control valve includes at least one operator transition time corresponding to a time span for the valve operator to translate between the closed position and the open position; and the controller is configured to determine the operator transition time based on one or more of the current through the coil or the voltage across the coil. 
     In Example 15, the subject matter of Example 14 optionally includes wherein the valve controller determines the control valve is in the primed state if the transition time for the valve operator in the second valve operator cycle is greater than the operator transition time in the first valve operator cycle. 
     In Example 16, the subject matter of any one or more of Examples 10-15 optionally include wherein: the valve controller is configured to determine at least one operator transition time based on the electrical characteristics of the control valve; and the at least one operator transition time corresponds to a time span for the valve operator to translate between the closed position and the open position. 
     In Example 17, the subject matter of Example 16 optionally includes wherein the valve operator transition time in the second valve operator cycle is greater than the valve operator transition time in the first valve operator cycle. 
     In Example 18, the subject matter of any one or more of Examples 1-17 optionally include wherein the actuator is configured to maintain the valve operator in the closed position if the valve controller determines the control valve is in the primed state. 
     In Example 19, the subject matter of any one or more of Examples 1-18 optionally include wherein: the control valve includes a fluid chamber configured to receive a fluidic mixture of one or more of a gas or a liquid including the agricultural product; in the unprimed state, a volume of the gas in the fluid chamber is greater than a volume of the liquid in the fluid chamber; and in the primed state, the volume of liquid in the fluid chamber is greater than the volume of gas in the fluid chamber. 
     In Example 20, the subject matter of any one or more of Examples 1-19 optionally include wherein: the control valve includes a fluid chamber configured to receive a fluidic mixture of one or more of a gas or a liquid including the agricultural product; in the unprimed state, the fluidic mixture in the fluid chamber has a first fluidic composition; in the primed state, the fluidic mixture in the fluid chamber has a second fluidic composition; and the second fluidic composition is different than the first fluidic composition. 
     In Example 21, the subject matter of any one or more of Examples 1-20 optionally include a flushing fluid source in communication with the control valve, wherein: the flushing fluid source includes a flushing fluid, the flushing fluid is different than the agricultural product; and the valve controller is configured to supply the flushing fluid to the control valve while repeatedly opening and closing the valve operator to flush the agricultural product from the control valve. 
     Example 22 is a method of priming a control valve, comprising: delivering an agricultural product to the control valve, the control valve in an unprimed state; detecting whether the control valve is in a primed state, detecting including: repeatedly opening and closing of the control valve while delivering flow of the agricultural product to the control valve, wherein repeatedly opening and closing of the control valve includes moving a valve operator between closed and open positions; monitoring one or more control valve characteristics while repeatedly opening and closing the control valve; comparing the monitored control valve characteristics of the valve operator with a primed valve characteristic threshold; and determining that the control valve is in one or more of the unprimed state or the primed state based on the comparison of the monitored control valve characteristics to the primed valve characteristic threshold. 
     In Example 23, the subject matter of Example 22 optionally includes wherein the one or more characteristics of the control valve includes at least one operator transition time corresponding to a time span for the valve operator to translate between the closed position and the open position. 
     In Example 24, the subject matter of Example 23 optionally includes wherein the operator transition time includes the time span for the valve operator to transition from the closed position to the open position. 
     In Example 25, the subject matter of any one or more of Examples 23-24 optionally include wherein the at least one operator transition time includes: a first operator transition time corresponding to the unprimed state; and a second operator transition time corresponding to the primed state. 
     In Example 26, the subject matter of Example 25 optionally includes wherein the second operator transition time is greater than the first operator transition time. 
     In Example 27, the subject matter of any one or more of Examples 25-26 optionally include wherein the primed valve characteristic threshold includes the first operator transition time. 
     In Example 28, the subject matter of any one or more of Examples 23-27 optionally include wherein the primed valve characteristic threshold includes a transition time threshold, and the method further comprising: comparing the at least one operator transition time to the transition time threshold. 
     In Example 29, the subject matter of Example 28 optionally includes determining the control valve is in the primed state with the operator transition time exceeding the transition time threshold. 
     In Example 30, the subject matter of any one or more of Examples 22-29 optionally include wherein a valve operator cycle includes movement of the valve operator between the closed and open positions, the method further comprising: opening the valve operator in a first valve operator cycle, wherein the valve characteristic threshold includes the control valve characteristics of the first valve operator cycle; opening the valve operator in a second valve operator cycle; comparing the control valve characteristics of the first and second valve operator cycles; and determining the control valve is in one or more of the primed state or the unprimed state based on the comparison of the control valve characteristics of the second valve operator cycle to the control valve characteristics of the first valve operator cycle and a difference therebetween. 
     In Example 31, the subject matter of Example 30 optionally includes wherein the control valve characteristics of the control valve include one or more electrical characteristics of the control valve. 
     In Example 32, the subject matter of Example 31 optionally includes wherein the control valve includes a coil configured to generate a magnetic flux, and the valve operator is configured to translate with respect to the coil based on the magnetic flux, and the method further comprising: measuring one or more of current through the coil or voltage across the coil as the control valve characteristics. 
     In Example 33, the subject matter of Example 32 optionally includes determining the control valve is in one or more of the primed state or the unprimed state, including: comparing the current through the coil in the second valve operator cycle to the current through the coil in the first valve operator cycle; and determining a difference between the current through the coil in the second valve operator cycle to the current through the coil in the first valve operator cycle. 
     In Example 34, the subject matter of Example 33 optionally includes determining the control valve is in the primed state, including: determining if the current through the coil in the second valve operator cycle is greater than the current through the coil in the first valve operator cycle. 
     In Example 35, the subject matter of Example 34 optionally includes wherein the one or more characteristics of the control valve includes at least one operator transition time corresponding to a time span for the valve operator to translate between the closed position and the open position, and the method further includes: determining the operator transition time based on one or more of the current through the coil or the voltage across the coil. 
     In Example 36, the subject matter of Example 35 optionally includes determining the control valve is in the primed state, including: comparing the transition time for the valve operator in the second valve operator cycle to the operator transition time in the second valve operator cycle; and determining if the transition time for the valve operator in the second valve is greater than the operator transition time in the first valve operator cycle. 
     In Example 37, the subject matter of any one or more of Examples 31-36 optionally include determining at least one operator transition time based on the electrical characteristics of the control valve; and wherein the at least one operator transition time corresponds to a time span for the valve operator to translate between the closed position and the open position. 
     In Example 38, the subject matter of Example 37 optionally includes wherein the valve operator transition time in the second valve operator cycle is greater than the valve operator transition time in the first valve operator cycle. 
     In Example 39, the subject matter of any one or more of Examples 22-38 optionally include maintaining the valve operator in the closed position if the valve controller determines the control valve is in the primed state. 
     In Example 40, the subject matter of any one or more of Examples 22-39 optionally include wherein the control valve is repeatedly opened and closed according to one or more duty cycles, and the method includes: repeatedly opening and closing the control valve according to a first duty with the control valve in the unprimed state; and repeatedly opening and closing the control valve according to a second duty cycle with the control valve in the primed state. 
     In Example 41, the subject matter of any one or more of Examples 22-40 optionally include wherein the control valve is repeatedly opened and closed according to one or more duty cycles, and the method includes: transitioning the control valve between the unprimed state and the primed state; varying the duty cycle of the control valve while transitioning between the unprimed state and the primed state, wherein: the control valve is repeatedly opened and closed according to a first duty cycle while transitioning from the unprimed state to the primed state; and the control valve is repeatedly opened and closed according to a second duty cycle while transitioning from the primed state to the unprimed state. 
     Example 42 is a system for applying an agricultural product, the system comprising: a plurality of control valves including a first control valve and a second control valve, each of the plurality of control valves including: a moveable valve operator configured to translate between a closed position and an open position; one or more sensors configured to monitor one or more control valve characteristics of individual ones of the plurality of control valves; and a valve controller in communication with the one or more sensors, wherein the valve controller includes: an actuator configured to repeatedly open and close the movable valve operator for the plurality of control valves, wherein agricultural product is delivered to the control valve with the actuator opening and closing the moveable valve operator; a comparator configured to compare of the monitored one or more control valve characteristics to a primed valve characteristic threshold; and wherein the valve controller is configured to determine each of the control valves is in one or more of a primed state or an unprimed state based on the comparison of the one or more control valve characteristics to the primed valve characteristic threshold. 
     In Example 43, the subject matter of Example 42 optionally includes wherein the valve controller is configured to cascade priming of the plurality of control valves as the valve controller determines control valves of the plurality of control valves are in the primed state. 
     In Example 44, the subject matter of Example 43 optionally includes wherein: the plurality of control valves are located along a boom of an agricultural sprayer, and the boom extends between a proximal boom end and a distal boom end; and cascading priming of the control valves includes priming each of the control valves in sequence from the proximal boom end to the distal boom end. 
     In Example 45, the subject matter of Example 44 optionally includes wherein: the first control valve is adjacent to the second valve along the boom; the first control valve is proximal with respect to the second control valve; priming each of the control valves in sequence includes: priming the first control valve; priming the second control valve with the first control valve in the primed state. 
     In Example 46, the subject matter of any one or more of Examples 43-45 optionally include wherein the valve controller is configured to cascade depriming of the plurality of control valves as the valve controller determines control valves of the plurality of control valves are in the unprimed state. 
     In Example 47, the subject matter of any one or more of Examples 42-46 optionally include wherein the valve controller is configured to cascade depriming of the plurality of control valves as the valve controller determines control valves of the plurality of control valves are in the unprimed state. 
     In Example 48, the subject matter of Example 47 optionally includes wherein: the plurality of control valves are located along a boom of an agricultural sprayer, and the boom extends between a proximal boom end and a distal boom end; and cascading depriming of the control valves includes depriming each of the control valves in sequence from the proximal boom end to the distal boom end. 
     In Example 49, the subject matter of Example 48 optionally includes wherein: the first control valve is adjacent to the second valve along the boom; the first control valve is proximal with respect to the second control valve; depriming each of the control valves in sequence includes: transitioning the first control valve from the primed state to the unprimed state; transitioning the second control valve from the primed state to the unprimed state. 
     In Example 50, the subject matter of any one or more of Examples 42-49 optionally include wherein: the plurality of control valves includes a first set of control valves and a second set of control valves; the first set of control valves includes the first control valve; the second set of control valves includes the second control valve; the first set of control valves are located along a first boom section of an agricultural sprayer, and the first boom section extends between a first proximal boom end and a first distal boom end; the second set of control valves are located along a second boom section of the agricultural sprayer, and the second boom section extends between a second proximal boom end and a second distal boom end. 
     In Example 51, the subject matter of Example 50 optionally includes wherein the valve controller is configured to operate the first set of control valves independent of the second set of control valves. 
     In Example 52, the subject matter of Example 51 optionally includes wherein: the valve controller is configured to maintain the moveable valve operator of one of more of the first set of control valves in the closed position while repeatedly opening and closing the valve operator of one or more of the second set of control valves. 
     In Example 53, the subject matter of any one or more of Examples 51-52 optionally include wherein: the valve controller is configured to maintain the moveable valve operator of one of more of the first set of control valves in the open position while repeatedly opening and closing the valve operator of one or more of the second set of control valves. 
     Example 54 is a method of monitoring restriction of flow of a fluid through a nozzle, the method comprising: actuating a control valve to supply fluid to the nozzle, wherein the control valve includes a moveable valve operator configured to translate between a closed position and an open position in a valve operator cycle including at least first and second valve operator cycles; monitoring a first pressure decay at the nozzle corresponding to a first valve operator cycle; comparing the pressure decay at the nozzle between the first valve operator cycle and a blockage detection threshold; and determining the nozzle is in a restricted state or an unrestricted state based on the comparison of the pressure decay relative to the blockage detection threshold. 
     In Example 55, the subject matter of Example 54 optionally includes issuing a notification if the nozzle transitions from the unrestricted state to the restricted state. 
     In Example 56, the subject matter of Example 55 optionally includes wherein issuing a notification includes displaying the notification on a screen in a cab of a prime mover. 
     In Example 57, the subject matter of any one or more of Examples 54-56 optionally include wherein determining the nozzle is in the restricted state or the unrestricted state includes: closing a valve operator of the valve in the first valve operator cycle according to a specified duty cycle; opening the valve operator in a second valve operator cycle, wherein the valve operator in the second valve operator cycle is opened outside the specified duty cycle of valve operator. 
     In Example 58, the subject matter of Example 57 optionally includes opening the valve operator in a third valve operator cycle according to the specified duty cycle. 
     In Example 59, the subject matter of any one or more of Examples 54-58 optionally include wherein determining the nozzle is in the restricted state or the unrestricted state includes: closing a valve operator of the valve in the first valve operator cycle; opening the valve operator in the second valve operator cycle, wherein the valve operator is opened within a specified time period after closing the valve operator in the first valve operator cycle. 
     In Example 60, the subject matter of any one or more of Examples 54-59 optionally include wherein a pressure sensor is in communication with the nozzle and configured to measure pressure at the nozzle, and monitoring the pressure the first pressure decay includes receiving measured pressure at the nozzle. 
     In Example 61, the subject matter of any one or more of Examples 54-60 optionally include wherein monitoring the first pressure decay includes monitoring one or more valve characteristics. 
     In Example 62, the subject matter of Example 61 optionally includes wherein the actuating the control valve includes energizing a coil of a solenoid, and the valve characteristics include an electrical characteristic of the coil. 
     Example 63 may include or use, or may optionally be combined with any portion or combination of any portions of any one or more of Examples 1 through 62 to include or use, subject matter that may include means for performing any one or more of the functions of Examples 1 through 62, or a machine-readable medium including instructions that, when performed by a machine, cause the machine to perform any one or more of the functions of Examples 1 through 62. 
     Each of these non-limiting examples can stand on its own, or can be combined in various permutations or combinations with one or more of the other examples. 
     The above description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention can be practiced. These embodiments are also referred to herein as “examples.” Such examples can include elements in addition to those shown or described. However, the present inventors also contemplate examples in which only those elements shown or described are provided. Moreover, the present inventors also contemplate examples using any combination or permutation of those elements shown or described (or one or more aspects thereof), either with respect to a particular example (or one or more aspects thereof), or with respect to other examples (or one or more aspects thereof) shown or described herein. 
     In the event of inconsistent usages between this document and any documents so incorporated by reference, the usage in this document controls. 
     In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of “at least one” or “one or more.” In this document, the term “or” is used to refer to a nonexclusive or, such that “A or B” includes “A but not B,” “B but not A,” and “A and B,” unless otherwise indicated. In this document, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Also, in the following claims, the terms “including” and “comprising” are open-ended, that is, a system, device, article, composition, formulation, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. 
     Geometric terms, such as “parallel”, “perpendicular”, “round”, or “square”, are not intended to require absolute mathematical precision, unless the context indicates otherwise. Instead, such geometric terms allow for variations due to manufacturing or equivalent functions. For example, if an element is described as “round” or “generally round,” a component that is not precisely circular (e.g., one that is slightly oblong or is a many-sided polygon) is still encompassed by this description. 
     Method examples described herein can be machine or computer-implemented at least in part. Some examples can include a computer-readable medium or machine-readable medium encoded with instructions operable to configure an electronic device to perform methods as described in the above examples. An implementation of such methods can include code, such as microcode, assembly language code, a higher-level language code, or the like. Such code can include computer readable instructions for performing various methods. The code may form portions of computer program products. Further, in an example, the code can be tangibly stored on one or more volatile, non-transitory, or non-volatile tangible computer-readable media, such as during execution or at other times. Examples of these tangible computer-readable media can include, but are not limited to, hard disks, removable magnetic disks, removable optical disks (e.g., compact disks and digital video disks), magnetic cassettes, memory cards or sticks, random access memories (RAMs), read only memories (ROMs), and the like. 
     The above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more aspects thereof) may be used in combination with each other. Other embodiments can be used, such as by one of ordinary skill in the art upon reviewing the above description. The Abstract is provided to comply with 37 C.F.R. § 1.72(b), to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description as examples or embodiments, with each claim standing on its own as a separate embodiment, and it is contemplated that such embodiments can be combined with each other in various combinations or permutations. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.