Chromatographic pumping system

To provide smooth constant flow from a pump, a chromatographic system comprises: a chromatographic column having an inlet; a pump for supplying fluid to the inlet of the chromatographic column; a power means for the pump motor; positive and negative feedback loop means for controlling said power means; means for energizing and said positive and negative feedback control means; said negative feedback control means receiving a signal from said means for measuring flow rate and including means for comparing said signal with said corrected flow rate reference signal while said second feedback loop is energized to generate an error signal controlling said power means; and said positive feedback control means applying an acceleration voltage to said motor from a time a preset period after the initiation of a return stroke of said piston until after a timed duration.

BACKGROUND OF THE INVENTION 
This invention relates to reciprocation pumps and control circuits for 
them. 
In one class of reciprocating pump, a piston continuously reciprocates in a 
cylinder to directly force a liquid from the cylinder, alternately pulling 
liquid into the cylinder through an inlet port from a reservoir and 
pushing it from the cylinder through an outlet port to the destination of 
the liquid. 
In some uses of this class of pump, the pumps are designed to reduce 
pulsation in the flow of fluid. One such use is liquid chromatography. It 
is desirable in liquid chromatography that liquid which is pumped through 
a chromatographic column flow at a constant flow rate through the column 
so that different molecular species in the effluent from the column are 
eluted at times that are reproducible from run to run. Pulses in which the 
liquid flows at unpredictable rates reduce this reproduciblity. 
In one type of prior art pump of this class, the pressure at the outlet 
port of the pump is measured by a pressure sensor. A feedback signal from 
the pressure sensor controls the speed of the pump motor to cause the pump 
motor to react to changes in pressure in the chromatographic column and 
thus maintain a more constant rate of flow of the fluid. One pump of this 
type is described in U.S. Pat. No. 3,985,467, issued Oct. 12, 1976 to 
Peter Lefferson. 
This type of pump has a disadvantage when used in liquid chromatography in 
that it maintains pressure constant against varying pressure loads but may 
cause the rate of flow of fluid through the chromatographic column to 
vary, even in applications where is is desirable to maintain the rate of 
flow of liquid constant. 
In another type of prior art pump of this class, the piston is driven at a 
constant rate while expelling liquid from the pump into the 
chromatographic column, but when returning on a fill stroke to draw fluid 
into the pump from the reservoir, the motor is driven at an increased and 
substantially constant speed to draw the fluid into the pump more rapidly. 
During the forward stroke of piston in this type of prior art pump, the 
piston moves at a higher than normal rate until the pressure in the pump 
cylinder equals the pressure that existed near the end of the liquid 
expelling forward stroke of the piston and just before the piston began a 
refill stroke. After the pressure in the cylinder reaches the pressure 
during constant flow rate pumping before the start of the refill stroke, 
the outlet valve is opened and the piston continues forward at a constant 
rate. This type of pump is described in U.S. Pat. No. 4,131,393 issued 
Dec. 26, 1978, to Haaken T. Magnussen Jr. and 4,180,375 issued Dec. 25, 
1979 to Haaken T. Magnussen Jr. 
This type of pump has several disadvantages such as for example: (1) the 
opening of the valve at the pressure of the last part of the previous 
cycle results in an increased time during which no liquid leaves the 
outlet port over that time needed to fill the cylinder; and (2) the 
constant speed of the motor during refill and pump up does not reduce the 
time before fluid leaves the pump as soon as it could. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of this invention to provide a novel pump. 
It is a further object of the invention to provide a novel method for 
pumping fluid in a manner that maintains a constant rate of flow of fluid 
through a chromatographic column spaced from the outlet of the pump. 
It is a still further object of this invention to provide a pumping 
technique in which the speed of the motor is constant during a second 
portion of a pumping stroke until a refill portion of a cycle is initiated 
and then continuously increasing in speed during refill and until after a 
first portion of the pumping stroke controlled in time duration. 
It is a still further object of this invention to drive a pump motor for a 
reciprocating pump at a constant rate during a first portion of a cycle 
with a feedback circuit and at an accelerating rate during a second 
portion controlled by a timer and an open loop control circuit. 
It is a further object of the invention to maintain average rate of flow 
constant. 
It is a still further object of this invention to provide a reciprocating 
pump for a chromatographic system in which the pump refill time is 
maintained as short as possible and liquid is pumped in such a manner as 
to prevent cavitation but increase the rate of flow of fluid temporarily 
to maintain as constant as possible from cycle to cycle the average amount 
of liquid pumped through the liquid chromatographic column. 
It is a still further object of the invention to cause a smooth 
acceleration of pumping for a time after a refill stroke to reduce the 
danger of cavitation but maintain the flow rate at the column as constant 
as possible. 
In accordance with the above and further objects of the invention, the 
speed of a motor which drives a direct displacement reciprocating pump is 
controlled by first and second related signals. These signals are related 
so that a high constant rate of pumping controlled by the first signal 
results in a long time of acceleration of the pumping action later under 
the control of the second signal to more quickly average the flow rate to 
the preset flow rate of the liquid after a refill portion of a pump cycle. 
The first signal provides a linear feedback control on the pumping motion 
of a piston during a time period in which the rate of flow of liquid from 
the pump is equal to a present rate of flow and the piston moves at a 
preset velocity. The second signal is a nonlinear positive feedback signal 
which accelerates the motor linearly through an open loop to pull liquid 
from the liquid reservoir as fast as possible without cavitation and to 
provide liquid without cavitation to the outlet port of the pump at a rate 
to replace, in the conduit to the chromatographic column, the liquid 
necessary to bring the average rate of flow back to the preset value with 
little interruption to fill the cylinder. Thus, the piston is driven in a 
continuously varying rate except for a portion of a pump cycle. 
A second feedback loop, within which the first and second signals operate, 
measures the flow rate from the pump and corrects the preset rate of flow 
current source to maintain the average flow rate over a pump cycle 
constant. 
From the above description, it can be understood that the pump of this 
invention has several advantages such as: (1) the time during which no 
liquid is pumped through the outlet port is low; (2) it is relatively 
uncomplicated because the acceleration time of the motor is time limited 
rather than distance limited; (3) it is able to accommodate a wide range 
of flow rates without cavitation; (4) it maintains an accelerating 
velocity during a first part of each pumping stroke related to the 
required liquid to be replaced; and (5) it repeatedly monitors rate of 
flow and corrects the input signal outside of the feedback loop to aid in 
maintaining average flow constant.

DETAILED DESCRIPTION 
In FIG. 1, there is shown a block diagram of a chromatographic system 10, 
having a low pressure system 12, a high pressure pumping system 14, a high 
pressure pump control system 16, a chromatographic column, and injector 
system 18 and a detector and collector system 20. The high pressure 
pumping system 14 communicates with the low pressure system 12 to receive 
solvents therefrom and with the chromatographic column and injector 18 to 
supply the influent thereto for detection and at times collection by the 
detector and collector system 20. 
To control the high pressure pumping system 14, the high pressure pump 
control system 16 is electrically connected to the low pressure system 12 
from which it receives signals relating to flow rate of the influent to 
the chromatographic column and injector system 18 and is electrically 
connected to the high pressure pumping system 14 to maintain that flow 
rate as constant as possible. 
The low pressure system 12, the chromatographic column and injector system 
18 and the detector and collector system 20 are not part of this invention 
except insofar as they cooperate with the high pressure pumping system 14 
and the high pressure pump control system 16 to provide a constant flow 
rate of solvents through the chromatographic column and injector system 
18. 
The low pressure system 12 includes a low pressure pumping and mixing 
system 24 and a general system controller 22. The general system 
controller 22 contains flow rate information and, in some configurations, 
gradient information as well as information for injecting samples into the 
chromatographis column or providing data acquisition and processing 
functions in conjunction with the detector and collector system 20. The 
general system controller 22 is not part of the invention except insofar 
as it provides signals to the high pressure pump control system 16 to 
control the flow rate from the high pressure pumping system 14. 
In FIG. 2, there is shown a block diagram of the high pressure control 
system 16 having a motor circuit 30, a flow rate circuit 32, a first flow 
rate control system 34, a second flow rate control system 36 and an 
average flow rate control loop circuit 47. The first flow rate control 
system and the second flow rate control system each apply signals to the 
flow rate control circuit through conductors 62 and 64, one of them 
applying generally linear signals during at least a portion of each cycle 
of operation of the motor circuit and the other applying nonlinear signals 
through conductor 64. 
The linear and nonlinear signals control a pulse-width-modulator within the 
flow rate circuit 32 which ultimately controls the speed of the motor 
circuit 30 to maintain the flow rate of the fluid through the 
chromatographic column and injector system 18 (FIG. 1) as nearly constant 
as possible. The linear and nonlinear signals are related, with the 
nonlinear signals being larger or smaller in relation to the linear signal 
and for this purpose the first flow rate control system and second flow 
rate control system are electrically connected through a conductor 556 in 
a manner to be described hereinafter. The average flow rate control loop 
circuit 47 periodically measures output liquid flow during each cycle of 
the pump and changes the signal on conductor 46 representing the preset 
flow rate to maintain an average flow rate equal to the preset flow rate. 
To provide a substantially linear signal during at least a portion of the 
motor circuit 30, the first flow rate control system 34 includes a linear 
flow rate control circuit 38 and a first compensation circuit 40. The 
first compensation circuit 40 receives signals from the motor circuit 30 
to provide certain correction signals to the linear flow rate control 
circuit 38 to which it is connected. The linear flow rate control circuit 
38 receives signals from the system controller 22 (FIG. 1) on a conductor 
46 indicating the desired rate of flow and supplies a resulting signals to 
the flow rate circuit 32 which includes corrections made in response to 
the motor circuit 30 and from the first compensation circuit 40. 
To provide a signal to the flow rate control circuit 32 to accelerate the 
pump motor, the nonlinear flow rate control system 36 includes a nonlinear 
flow rate control circuit 42 and a second and positive feedback 
compensation circuit 44 (hereinafter second compensation circuit). The 
nonlinear flow rate control circuit 42 receives signals from the motor 
circuit 30 to which it is electrically connected and applies signals 
through an electrical connection to the flow rate circuit 32 as modified 
by signals from the second compensation circuit 44. 
With this arrangement, the high pressure pump system 16 maintains the flow 
rate through the column relatively constant at the programmed rate to 
cause the time at which peaks are detected to be reproducible because of 
pulses of fluid of different rates occurring at different times in the 
column rather than constantly eluting the molecular species from the 
column. Generally, the high pressure pump control system 16 controls the 
pump motor through the motor circuit 30 in such a way as to maintain the 
average flow of fluid at the preset rate and minimize rapid fluctuations 
in flow rate such as might be caused by a refill stroke of a piston pump 
or the like. 
In FIG. 3, there is shown a block diagram of the flow rate circuit 32 and 
the motor circuit 30. The flow rate control circuit 32: (1) receives a 
signal on conductor 62 during a portion of a pump cycle which is the 
output of a servo loop and has a substantially linear relationship with 
the desired pumping rate; and (2) a signal on conductor 64 which is a ramp 
nonlinearly corrected in slope to relate to the preset average flow rate. 
Both signals contain some corrections which are directed to establishing a 
rate of pumping which permits a single piston reciprocating pump to 
approach constant flow through a chromatographic column across a period of 
time. 
The flow rate circuit 32 is electrically connected to the motor circuit 30 
through a conductor 66 to apply to the motor circuit 30 periodic 
pulse-width-modulated signals in which the pulse width (duty cycle) is 
related to the speed at which the piston is intended to move to: (1) 
reduce flow rate pulsations in the chromatographic column by maintaining 
the average rate of flow of influent to the column is as constant as 
possible; and (2) change the piston speed to reduce the time that the pump 
is not forcing fluid through its outlet port. The speed of the piston is 
controlled to avoid cavitation or changes in the flow rate that are so 
sudden as to disrupt the rate of flow through the chromatographic column 
and injector system 18 (FIG. 1). 
To provide a speed of piston movement for constant flow rate of the 
influent to the chromatographic column and injector system 18 (FIG. 1), 
the motor circuit 30 includes a motor 50, a brake circuit 52, a refill 
inception detector circuit 54, a tachometer disc and sensors system 58, 
and an overcurrent sensor circuit 60. The motor 50 is driven by power 
applied through the conductor 66 from the flow rate control circuit 32 and 
drives the piston of the pump (not shown in FIG. 3) through its outlet 
shaft 56. 
To slow the pump, dynamic braking is under some circumstances applied to 
the motor through the brake circuit 52 in response to control signals on a 
conductor 70 indicating the time of application of the brake. The brake 
circuit 52 transmits signals through a conductor 72 to the first 
compensation circuit 40 (FIG. 2) which is used to adjust the motor speed 
at the end of a motor acceleration portion of a cycle to reduce drive 
power to the motor. 
To aid in coordinating the pump motor control circuit within the second 
compensation circuit 44 (FIG. 2), the refill inception detector circuit 54 
transmits a signal on conductor 76 for application to the first 
compensation circuit 40 (FIG. 2) at the end of a liquid delivery stroke to 
initiate a refill portion of a cycle. This signal aids in timing the start 
and termination of motor acceleration. 
To generate signals indicating the volume of fluid pumped and motor speed, 
the tachometer disc and sensors system 58 generates signals for 
application through conductor 78 to the linear flow rate control circuit 
38 (FIG. 2) and the average flow rate control loop circuit 47 (FIG. 2). 
The overcurrent sensor circuit 60 detects currents which exceed a preset 
value in the motor circuit, usually indicating binding or a bearing fault, 
so as to avoid damage to the pump. 
In FIG. 4, there is shown a schematic circuit diagram of the flow rate 
circuit 32 having a comparator circuit shown generally at 80 and a driver 
circuit shown generally at 82, with the comparator circuit 80 receiving a 
ramp signal on conductor 64 from the second flow rate control system 36 
(FIG. 2), a linear signal on conductor 62 from the first flow rate control 
circuit 34 (FIG. 2) and an overcurrent protection signal on conductor 84 
from the second flow rate control system 36 (FIG. 2). 
These signals result in an positive-going variable width 13 KHz (kilohertz) 
pulse train being applied by the comparator through a conductor to the 
drive circuit 82 inversely related to how steep the ramp circuit applied 
to conductor 64 is, and directly related to the amplitude of the signal 
applied to 62, which determines the duty factor of the pulse train. 
The motor driver circuit 82, during the time duration it receives the pulse 
train from the comparator 80, applies a variable voltage across conductor 
66A and 66B, resulting in power being applied to the motor 50 (FIG. 3) 
during a time controlled by the pulse-width-modulator 32 and consistent 
with the pulse train applied by the comparator 80. 
To compare the ramp signal on conductor 64 with the servo input signal on 
conductor 62, the comparator circuit 80, is a LM 311 voltage comparator 
sold by National Semiconductor, 2900 Semiconductor Drive, Santa Clara, 
Calif. 25051, and described in its 1985 catalogue "Linear Integrated 
Circuits", having pin 1 electrically connected to the driver circuit 82, 
pin 2 electrically connected to conductor 62 through a 10K resistor 92 to 
receive the servo input signals, pin 3 electrically connected to conductor 
64 to receive the ramp, a pin 4 electrically connected to a source 94 of a 
negative 12 volts and to the electrical common through a 1 uf (microfarad) 
capacitor 96, pin 6 electrically connected to conductor 84 to receive an 
overcurrent signal from the second flow rate control system 36 (FIG. 2) 
and pin 8 electrically connected to a source 98 of a positive 12 volts. An 
equivalent circuit would be a simple comparator having an inverter on its 
output connected to one input of a two input AND gate and conductor 84 
connected to the other input. 
The comparator 86 has its noninverting input terminal electrically 
connected to conductor 62 through the resistor 92 and its inverting input 
terminal electrically connected to conductor 64. A first rail is 
electrically connected to the source 94 of a minus 12 volts and to 
electrical common through the capacitor 96 and its other rail electrically 
connected to the source 98 of a positive 12 volts. The output of the 
comparator from pin 1 is electrically connected to the driver circuit 82 
to apply a signal thereto corresponding to the time in which the ramp 
voltage applied on conductor 64 is less than the level on conductor 62. 
The driver circuit 82, includes a MTP12N05 MOSFET transistor 102, a MR2400F 
diode 104 (all manufactured by Motorola Corporation), and a source 106 of 
a positive 32 volts. The gate of the transistor 102 is electrically 
connected: (1) to the output of the comparator 86 through a 33 ohm 
resistor 108; (2) to a source 112 of a negative 8 volts through a 820 ohm 
resistor 110; (3) to the overcurrent sensor circuit 60 (FIG. 3) through 
the reverse resistance of a 1N5245B Zener diode 114; and (4) to a source 
98 of a positive 12 volts through the resistor 110. 
The source of the transistor 102 is electrically connected to the 
overcurrent sensor circuit 60 (FIG. 3) through a conductor 118. To provide 
noise filtering for the comparator 86, the source 98 of a positive 12 
volts is electrically connected to electrical common through two 1 uf 
capacitors 120 and 122 in parallel with each other and to the source 112 
of a negative 8 volts through a 1 uf capacitor 116, with a source of 
negative volts 112 also being electrically connected to the gate through 
the resistor 110 to provide biasing directly to the gate. A 0.2 uf 
capacitor 174 is connected across conductors 66A and 66B to filter lower 
frequencies. 
Conductor 118 is essentially grounded for power supply purposes and the 
drain is electrically connected through the forward resistance of the 
diode 104 to the source 106 of a positive 32 volts and to conductor 66A so 
that, the positive 32 volts is connected at all times to one end of the 
armature of the motor 50, (FIG. 3) conductor 66B on the other armature and 
being electrically connected through a current limiting inductor 124 to 
the anode of the diode 104 and the drain of the transistor 102. The 
capacitance across the motor is essentially 2 uf. The motor is a Pitman 
13000 series DC motor and the inductor is substantially 200 uh 
(microhenries). 
With this circuit arrangement, when the transistor 102 is conducting as a 
result of the positive pulse at its gate, current flows from the source 
106 of a positive 6 volts through the motor, the inductor 124 and the 
transistor 102 to ground through conductor 118, and when the positive 
pulse is not applied, the current is maintained by inductor 124 through 
diode 104 and, the motor and back through the inductor unless the motor is 
operating to generate current for dissipation in the brake circuit 52 
(FIG. 3) to be described hereinafter. 
With this arrangement, when the linear feedback circuit indicates that the 
motor speed falls below its preset speed, the pulse width is increased 
linearly and when the nonlinear feedback circuit indicates the need for 
acceleration to equalize the flow, the width of the pulse is increased 
provide a correction of motor speed in a velocity feedback loop during a 
portion of a pump cycle prior to refill. The nonlinear feedback circuit 
provides an acceleration signal prior to the constant flow portion of the 
deliver for a longer time as the flow rate during the last portion of 
delivery increases and a shorter time as it decreases. 
In FIG. 5, there is shown a schematic circuit diagram of the brake circuit 
52 (FIG. 3) having an input logic circuit 130, a drive circuit 132, and a 
shunt circuit 134. The input logic circuit 130 receives a signal on 
conductor 70 from the second flow rate correction circuit 36 (FIG. 2) and 
causes the drive circuit 132 to form a conducting path in the shunt 
circuit 134 across the armature of the motor to provide dynamic braking. 
The input logic circuit 130 also applies output signals through conductor 
72 to the second compensation circuit 44 (FIG. 2) and to conductor 62 to 
the flow rate control circuit 32 (FIG. 3). 
To provide a signal causing dynamic braking, the input logic circuit 130 
includes a NAND gate 136, input conductor 70 and output conductor 72 and 
62. The NAND gate 136 has one of its inputs electrically connected to a 
source 138 of a positive 8 volts and its other input electrically 
connected to the input 70 through a 10K resistor 140 to receive signals 
from the second flow rate correction system 36 (FIG. 2) indicating braking 
action. The output of the NAND gate 136 is electrically connected to 
conductor 72 to provide a positive output signal when braking action is to 
occur and to conductor 62 through the 1N5060 diode 142 to turn off drive 
pulses from the flow rate control circuit 32. 
To energize the dynamic brake, the drive circuit 132 includes first and 
second NPN transistors 150 and 152 and a diode 154. The anode of the diode 
154 is electrically connected to the output of the NAND gate 136 and its 
cathode is electrically connected to the base of the transistor 150 
through a 4.7K (kilohm) resistor 156 and to electrical common through a 
4.7K resistor 158. The emitter of transistor 150 is electrically connected 
to the base of transistor 152 and to electrical common through a 470 ohm 
resistor 160 and the emitter of transister 152 is directly connected to 
electrical common. The collector of the transistors 150 and 152 are each 
electrically connected to the input to the shunt circuit 134 through two 
39 ohm resistors 162 and 164 electrically connected in series. The 
transistors 150 and 152 are 2N3704 and D44C8 transistors manufactured by 
G.E. Corporation and described in the catalogue and the diode 154 is a 
type 1N914 diode. 
To form a conducting path for current generated by the pump motor when it 
is being driven by inertia and thus to provide dynamic braking, the shunt 
circuit 134 includes a D45H8 PNP transistor 170, and a 1N5060 diode 172. 
The transistor 170 has its base electrically connected to the output of 
the drive circuit 132, its emitter electrically connected to its base 
through a 220 ohm pull-down resistor 173 and its collector electrically 
connected through the diode 172 to its emitter and to conductor 74B 
through a resistor 176. 
The emitter of the transistor 170 is electrically connected to conductor 
66A so that, when the motor operates as a generator for dynamic braking, a 
path is formed between conductors 66A and 66B through the motor and 
transistor 170 when transistor 170 is saturated and provides an open 
circuit when the motor is driven as a motor. 
In FIG. 6, there is shown a schematic circuit diagram of the refill 
inception detection circuit 54 (FIG. 3), having an optical sensor 180, a 
rotatable flag 182 on the cam shaft, and a comparator 184. The flag 182 
shown in fragmentary schematic form, rotates with the cam shaft on it in a 
location to be detected by the optical sensor 180, which transmits a 
positive going pulse in response to a signal indicating the start of the 
refill cycle to the noninverting input terminal of the comparator 184. The 
comparator 184 signals the second flow rate control system 36 (FIG. 2) 
indicating the start of the refill cycle in response to the detected 
signal. 
For this purpose, the comparator 184 has its noninverting input terminal 
electrically connected to electrical common through a 2.2K resistor 186 
and to the output of the optical sensor 180. The inverting input terminal 
of the comparator 184 is electrically connected to conductor 76B, to 
electrical common through a 100 ohm resistor 188 and to a source 112 of a 
negative 8 volts through a 1.5K resistor 190 so that a reference potential 
is established, above which a signal is provided through conductor 76A 
indicating a refill cycle. The comparator 184 has positive and negative 8 
volt rails at 138 and 112. 
The optical sensor 180 has a light emitting diode, with its anode 
electrically connected to electrical common and its cathode electrically 
connected to a source of negative 8 volts through a 1.5K resistor 192 and 
has a light sensitive transistor therein with its collector electrically 
connected to the noninverting input terminal of the comparator 184 and its 
NPN emitter junction electrically connected to the source 112 of a 
negative 8 volts. 
In FIG. 7, there is shown a schematic circuit diagram of the overcurrent 
sensor circuit 60 (FIG. 3) having a current sensing network 202, a 
reference network 204 and a comparator circuit 206. The sensing network 
202 senses the motor current and the reference network 204 provides part 
of the reference with both values being compared in the comparator circuit 
206 to provide an output signal disabling the flow rate control circuit 32 
(FIG. 3 and FIG. 4) when the motor current is too high indicating a jammed 
condition of the pump or the like. 
To sense the current through the pump, the current sensing network 202 
includes three 0.1 ohm resistors 210, 212, and 214 respectively connected 
in parallel between a conductor 216 and a conductor 218. Conductor 216 is 
electrically connected to conductor 118 to receive motor current and 
conductor 218 is electrically connected to the electrical common so that 
the current flow through the motor on conductor 118 causes a voltage drop 
in the sensing network 202, which voltage drop occurs between conductors 
216 and 218. 
To provide a reference potential, the reference network 204 is electrically 
connected: (1) through 86.6K resistor 240 to 4.7K resistor 234 and thence 
to the source of a positive 8 volts; (2) to conductors 216 and 218; and 
(3) to the comparator circuit 206 through conductors 220 and 222. 
Conductor 216 is electrically connected through a conductor 200 to the 
anode of the Zener diode 114 (FIG. 4) of the flow rate control circuit 32 
(FIG. 2, 3, and 4) to receive current therethrough and to conductor 220 
through a 1K resistor 224. Conductor 218 is electrically connected to 
conductor 222 through a 4.75K resistor 226 and to a source 112 of a 
negative 8 volts potential through a 309K resistor 228. With this circuit 
arrangement, conductor 222 is maintained at a potential above the 
electrical common by the sources of potential 138 and resistors 234 and 
240. 
To compare the potential on conductors 220 and 222 for the purpose of 
indicating an overcurrent, the comparator circuit 206 includes the 
comparator 230 which is manufactured and sold by National Semiconductor 
Corporation (2900 Semiconductor Drive, Santa Clara, Calif. 95051) type 311 
having its inverting input terminal at pin 3 electrically connected to 
conductor 220 and its noninverting input terminal at pin 2 electrically 
connected to conductor 222 to provide a comparison of the voltages 
therein. 
During an overcurrent, the output at pin 7 of the comparator goes from 8 to 
common potential. The removes positive potential from resistor 240 and 
negative potential from sources 112 through resistor 278 causes the 
comparator to latch up and disable the motor drive circuit. 
At the end of the pulse cycle, a reset pulse on pin 6 at 296 resets the 
comparator from a clock in the second positive feedback and compensation 
circuit 44 to enable the comparator and drive circuit 32. 
The output of the comparator 230 at pin 7 is electrically connected to: (1) 
the source 138 through the resitor 234; (2) a conductor 84 through 680 ohm 
resistor 239; (3) the reverse resistance of the 8.2 IN5237 volt Zener 
diode 237 and the foreward resistance of diode 238; and (4) input 
conductor 222 through a 86.6K resistor 240. The conductor 84 (FIG. 4) is 
electrically connected to the pulse width modulator 86 (FIG. 4) so that 
conductor 84 provides signals to disable the flow rate circuit 32 (FIGS. 
2, 3 and 4) by de-energizing the comparator 86 upon a current overload 
condition. 
In FIG. 8, there is shown a schematic circuit diagram of the tachometer 
disc and sensor system 58 (FIG. 3) having a first and a second optical 
sensor 250 and 252 respectively, rotatable disc 254 and first and second 
270 ohm resistors 258 and 260 respectively. The first and second optical 
sensors sense indicia indicating the rotation of the pump on disc 254 
which is mounted to the output shaft of the pump motor. The optical 
sensors 250 and 252 are located in quadrature with respect to the indicia 
so as to indicate the amount of rotation of the motor and its direction in 
a manner in the art. 
With this arrangement, the optical sensors provide signals indicating the 
amount of rotation and direction of the motor by rotation of the disc in 
one direction as well as position of the piston in part of a delivery 
stroke by sensing indicia at equispaced distances along the disc 254. This 
type of circuit is described in U.S. copending application No. 713,328 to 
Robert W. Allington et al, assigned to the same assignee as this 
application and filed Mar. 18, 1985. 
To sense indicia on disc 254 the first optical sensor 250 includes a light 
emitting diode having its anode electrically connected to the electrical 
common and its cathode electrcially connected to the source 112 of a 
negative 8 volts through the resistor 258. To provide electrical signals 
indicating the amount of electrical rotation of the disc 254, the first 
optical sensor 250 includes a light sensitive element separated from the 
light emitting diode by the disc 254 to have light blocked or transmitted 
to it as the disc 254 rotates. 
The light sensitive element has its collector electrically connected to the 
linear flow rate control circuit 38 (FIG. 2) and nonlinear flow rate 
control circuit 42 (FIG. 2) and average flow rate control loop circuit 47 
(FIG. 2) circuit 47 through a conductor 262 and has its emitter 
electrically connected to the source 112 of a negative 8 volts to provide 
electrical signals to a conductor 262 indicating the amount of rotation of 
the pump. 
The second light sensor 252 has a light emitting diode in it with its anode 
electrically connected to the electrical common and its cathode 
electrically connected to the source 112 of a negative 8 volts through the 
270 ohm resistor 260. It has a light sensitive element separated from the 
light emitting diode 252 by the rotatable disc 254 so as to sense indicia 
upon it. 
The light sensitive element has its collector electrically connected to the 
linear and nonlinear flow rate control circuit 38 and 42 (FIG. 2) through 
a conductor 264 and average flow rate control loop circuit 47 (FIG. 2) and 
has its emitter electrically connected to the source 112 of a negative 8 
volts so as to provide electrical signals to conductor 264 indicating the 
amount of rotation of the disc 254 with the signals on conductors 262 and 
264 indicating the amount of rotation and the direction of rotation. 
In FIG. 9, there is shown a block diagram of the nonlinear flow rate 
control circuit 42 (FIG. 2) having a quadrature detector 270, a frequency 
to voltage converter 272, a multivibrator circuit 274, an exponential 
amplifier circuit 276 and a ramp generator 278. The quadrature detector 
270 is electrically connected to conductors 262 and 264 to receive signals 
from the tachometer disc and sensor system 58 (FIGS. 3 and 8) and apply a 
signal indicating the amount of rotation in one direction to a conductor 
290/frequency to voltage converter 272 which generates a signal 
representing in amplitude the rate of rotation of the motor for 
application to a conductor 280. 
Conductor 280 is electrically connected to the exponential amplifier 
circuit 276 and the output from the exponential amplifier circuit 276 and 
from the multivibrator circuit 274 are connected to the ramp generator 278 
to generate a ramp which varies in slope in a manner related to the motor 
speed. 
To receive correcting signals, the second compensation circuit 44 (FIG. 2) 
is connected to the ramp generator 278 through a conductor 282 and to 
select the flow rate operating range of the frequency to voltage converter 
control signal is applied to the frequency to voltage converter 272 from 
the linear flow rate control circuit 38 (FIG. 2) through a conductor 284 
to select a flow rate range. 
In FIG. 10, there is shown a block diagram of the quadrature detector 270 
(FIG. 9) having a pulse output conductor 290, a direction circuit 292 and 
a tachometer sensor input circuit 294. The tachometer sensor input circuit 
294 is electrically connected to conductors 262 and 264 to receive signals 
from the first and second optical sensors 250 and 252 (FIG. 8) 
respectively, which sensors generate pulses at the same frequency as the 
motor rotates but 90 degrees out of phase. The output of the tachometer 
sensor input circuit 294 applies both sets of pulses to the direction 
circuit 292 which selects oly those pulses which indicate a forward 
movement of the pump piston or plunger for application to the output at 
conductor 290. This circuit is explained in the aforementioned patent 
application. 
The tachometer sensor input circuit 294 includes a first channel 296 and a 
second channel 298 with the first channel 296 being electrically connected 
to the first optical sensor 250 through conductor 262 to recieve signals 
therefrom and electrically connected to the direction circuit 292 through 
a conductor 300 and the second channel 298 being electrically connected to 
the second sensor 252 (FIG. 9) through the conductor 264 to receive 
signals therefrom and to the direction circuit 292 through a conductor 302 
to supply signals thereto. The first channel 296 is identical to the first 
channel 298 except that they receive signals from different sources and 
supply to the direction circuit 292 through different conductors. 
In FIG. 11, there is shown a schematic circuit diagram of the first channel 
296 (FIG. 10) within the tachometer sensor input circuit 294 (FIG. 10) 
having a first operational amplifier 304 and a second operational 
amplifier 306. The amplifiers 304 and 306 are type LM353 amplifiers each 
having one rail connected to a source 138 of a positive 8 volts and the 
other rail electrically connected to a source 112 of a negative 8 volts. 
To provide amplification and low pass noise filtering, amplifier 304 has 
its noninverting input terminal electrically connected to the electrical 
common and its inverting input terminal electrically connected to: (1) 
conductor 262 through a 470 ohm resistor 308 and to a source 138 of a 
positive 8 volts through the resistor 308, a 27K resistor 310 and a 
variable 50K resistor 312 so as to permit adjustment of the input to 
operating current of the light sensor connected to conductor 262. The 
output of amplifier 304 is electrically connected to: (1) its inverting 
input terminal through a 56K resistor 314 and 150 pf (picofarad) capacitor 
316 electrically connected in parallel; and (2) to the noninverting input 
terminal of the amplifier 304 through a 47K resistor 318. 
To provide Schmidt trigger action, amplifier 306 has its output 
electrically connected to: (1) conductor 300 through a 4.7K resistor 320, 
a source 138 of a positive 8 volts through the resistor 320 and the 
forward resistance of a 1N273 diode 322; (3) and the electrical common 
through the reverse resistance of a 1N273 diode 324; (4) to its 
noninverting input terminal through a 1.2M resistor 326 and to the 
electrical common through the resistor 326 and a 47K resistor 328. 
In FIG. 12, there is shown a schematic circuit diagram of the direction 
circuit 292 (FIG. 10) having a divide-by-two circuit 330, an up-down 
counter circuit 332 and an input gating circuit 334. The input gating 
circuit 334 is electrically connected to conductors 300 and 302 to receive 
signals processed by channels 1 and 2 from the first and second sensors 
250 and 252 respectively (FIG. 8) and has its output electrically 
connected to the up-down counter circuit 332 which caused by backward 
movement of counts pulses proportional to the motor, by counting backwards 
from 15 and requiring recounting of those pulses in the forward direction 
for application to the divide-by-two circuit 330 and eventually to output 
conductor 290 to the frequency to voltage converter 272 (FIG. 9). 
The input gating circuit 334 includes four exclusive OR gates 336, 338, 340 
and 342 and one NOR gate 344. Conductor 300 is electrically connected to 
one input of each of the exclusive OR gates 338 and and conductor 302 is 
electrically connected to another input of the two input exclusive OR 
gates 338 and 342 and to: (1) an input of the exclusive OR gate 342 
through a 150K resistor 346; and (2) to the electrical common through the 
resistor 346 and a 120 pf capacitor 348. The output of exclusive OR gate 
338 is electrically connected to: (1) one of the two inputs of the 
exclusive OR gate 336; (2) the input of the NOR gate 344 through a 27K 
resistor 350; and (3) the electrical common through the resistor 350 and a 
120 pf capacitor 352. 
The output of the exclusive OR gate 342 is electrically connected to one of 
the two inputs of the exclusive OR gate 340, the other input being 
electrically connected to a source 138 of a positive 8 volts. The output 
of the exclusive OR gate 336 is electrically connected to a source 138 of 
a positive 8 volts. The output of the exclusive OR gate 336 is 
electrically connected to the up-down counter circuit 332 through a 
conductor 354 and the output of the OR gate 340 is electrically connected 
to the up-down counter circuit 332 through a conductor 356 to provide 
signals corresponding to the first and second sensor thereto modified so 
that signals received from the first sensor before the second count up and 
signals received by the second sensor before the first sensor count down. 
The up-down counter circuit 332 includes a type 4029 up-down counter 360 
and a type 4002B NOR gate 362. Conductor 354 is electrically connected to 
pin 15 of the counter 360 to cause it to count up and conductor 356 is 
electrically connected to pin 10 of the counter 360 to cause it to count 
down and to one of the four inputs of the NOR gate 362, the output of 
which is electrically connected to pin 5 to inhibit counting upon 
receiving a signal on conductor 356 passing through the NOR gate 362. 
Pins 2, 14 and 11 of the counter 360 are each electrically connected to: 
(1) a different one of the other three inputs of the NOR gate 362; and (2) 
a different one of the 10K resistor 364, 22K resistor 366 and 39K resistor 
368. The other end of the resistors 364, 366 and 368 are each electrically 
connected to: (1) pin 6 of the counter 360 through an 82K resistor 370; 
and (2) the electrical common through a 1K resistor 372. Pins 8 and 4 of 
the counter 360 are grounded and pins 16, 13, 12, 9 and 3 are electrically 
connected to the source 138 of a positive 8 volts to determine the output 
voltage of the counter. Pins 1 and 7 are electrically connected to 
conductors 374 and 376 to provide output positive 8 volt pulses as the 
counter counts in binary notation upwardly in response only to signals 
caused by rotation of the motor in the direction which enables the piston 
to force fluid from the cylinder of the pump. The counter counts 
downwardly in response to reverse rotation but is inhibited from counting 
past zero. 
To divide the binary signals applied on conductors 374 and 376 in two, the 
divide-by-two circuit 330 includes a type 4013B divider 374 having pins 3 
and 11 electrically connected to conductor 376 and pin 13: (1) 
electrically connected to conductor 374 and to pin 10 through a 2.7K 
resistor 380; and (2) to the electrical common through resistor 380 and a 
0.01 uf capacitor 382. Pins 9 and 14 of the divider 378 are each 
electrically connected to the source 138 of a positive 8 volts, pin 1 is 
electrically connected to conductor 290 to provide a frequency output 
representing the rate of flow of effluent from the pump, pins 2 and 5 are 
electrically connected together and pins 4, 6, 8 and 7 are each 
electrically connected to the electrical common. 
In FIG. 13, there is shown a schematic circuit diagram of a frequency to 
voltage converter 272 (FIG. 9) having an analog switch 390, an LM2907 
frequency to voltage converter 392 and a gain adjustment circuit 394. 
The frequency to voltage converter may be any suitable type, many of which 
are known in the art but in the preferred embodiment it is an integrated 
circuit sold by National Semiconductor under the disignation LM2907. Pin 1 
of that unit is electrically connected to conductor 290 to receive pulses 
from the tachometer disc and sensor system 58 (FIG. 3 and 8) through a 22K 
resistor 396. This circuit is part of a tachometer that produces an output 
voltage porportional to motor speed. 
The conductor 290 is also electrically connected to the electrical common 
through the resistor 396 and a 22K resistor 398 and to the system 
controller 22 (FIG. 1) through a 10K resistor 402 and a conductor 400 
where it may be used by the system to indicate the progress of the 
chromatographic run. The frequency to voltage converter 392 has pin 11 
electrically connected: (1) through a source 138 of a positive 8 volts and 
a 47K resistor 404 for biasing; and (2) through a 0.47 uf capacitor 406 
and a 15K resistor 408 to the electrical common in parallel to short out 
noise. Pins 7 and 12 are electrically connected to a source 112 of a 
negative 8 volts and to the electrical common through a 1 uf capacitor 
410, pins 8 and 9 electrically connected to a source 138 of a positive 8 
volts and to the electrical common through a 1 uf capacitor 412. 
To accommodate changes in pumping speed, the frequency to voltage converter 
392 has pin 2 electrically connected to: (1) the electrical common through 
an 820 pf capacitor 414; and (2) one lead of 4016 analog switch 390 
through an 820 pf capacitor 416. The gate of the analog switch 390 is 
connected to conductor 418 to receive a low range signal and the other 
level is electrically connected to the electrical common. 
The switch 390 doubles the gain of the frequency to voltage converter by 
doubling capacitance by switching capacitor 416 in parallel with 414 to 
provide low range operation at a high scale with an additional multiplier 
to be described hereinafter upon receiving a signal on conductor 418. 
To control the gain of the voltage conversion provided by frequency to 
voltage converter 392, the gain control circuit 394 includes a first 5K 
potentiometer 424 and a second 5K potentiometer 426 with the potentiometer 
426 being connected at one end to a source 138 of a positive 8 volts and 
at the other end to a source 112 of a negative 8 volts, its variable tap 
being electrically connected through a 10 megaohm resistor 427 to: (1) pin 
10 through a switch which may be opened or closed; (2) and pin 3 of the 
frequency to voltage converter 392; (3) pin 5 through a 0.022 uf capacitor 
428 and a 0.33 uf capacitor 430; and 4 and to the tap of the potentiometer 
424 through a 30.9K resistor 432. 
The potentiometer 424 is electrically connected at one end to a conductor 
280 and to pin 5 of the frequency to voltage converter 392 and at its 
other end to the electrical common through a 10K resistor 436 and directly 
to pin 5 of the frequency to voltage converter and to pin 5 of the voltage 
to frequency converter through the capacitor 430. Conductor 280 applies 
the voltage corresponding to the rate of flow of fluid to the exponential 
amplifier circuit 276 (FIG. 9) through conductor 280 and to the first 
compensation circuit 40 (FIG. 2). Conductor 280 is electrically connected 
to the source 94 of a negative 12 volts through a 604 ohm resistor 440. 
With this arrangement, the amplitude of the voltage output may be adjusted 
by potentiometer 424 and 426 to provide a voltage which varies in relation 
to the rate of flow of fluid as measured by the tachometer. This voltage 
is applied to the first compensation circuit 40 (FIG. 2) for application 
to the linear flow rate control circuit 38 (FIG. 2) and to the exponential 
amplifier circuit 276 (FIG. 9) through conductor 280 to control the 
nonlinear flow control circuit 42 (FIG. 2). 
In FIG. 14, there is shown a schematic circuit diagram of the multivibrator 
circuit 274 (FIG. 9) having a conventional astable multibrator 450 which 
may be of any conventional designation but in the preferred embodiment is 
a National Semiconductor 55 multivibrator connected as shown to provide a 
suitable frequency during a portion of the time normally required for a 
full piston stroke of the pump. The function of the multivibrator circuit 
is to reset the overload circuit and the ramp generator. 
To provide the proper frequency, the miltivibrator circuit 274 includes: 
(1) 3 capacitors 452, 454 and 456 having values of 1 uf, 0.01 uf and 2200 
pf respectively; (2) 2 resistors 458 and 460 having values of 680 ohms and 
39.2 ohms respectively; and (3) a 10K potentiometer 462 with pins 4 and 6 
of the multivibrator 450 being electrically connected to one end of the 
potentiometer 462, pin 7 being electrically connected to: (1) to the other 
end of the potentiometer 462 through the resistor 460; (2) pins 6 and 2 of 
the multivibrator 450 through the resistor 458; and (3) to the electrical 
common through the capacitor 456. The electrical common is also 
electrically connected to pin 1, to pin 5 through the capacitor 454 and to 
pins 4 and 8 through the capacitor 452. 
To reset the ramp generator 278 (FIGS. 9 and 16) and to the flow rate 
control circuit 32 (FIGS. 2, 3 and 4) the output, of the multivibrator 450 
is electrically connected to conductor 470 to apply a positive pulse 
thereto. To provide a signal to the ramp circuit to initiate a ramp, the 
multivibrator 274 includes a source 112 of a negative 8 volts electrically 
connected to conductor 470 through a 3.9K resistor 472 and a 1.82K 
resistor 474 with output conductor 476 being electrically connected to 
resistor 472 and 474 to change from a negative to a positive value upon 
receiving a signal from the multivibrator 450. conductor 476 is 
electrically connected to the ramp generator 278 (FIGS. 9 and 16) to reset 
it as described hereinafter in connection with FIG. 16. (FIG. 9). 
To provide a turn-off signal on conductor 84 to the flow rate circuit 32 
(FIGS. 2, 3 and 4) conductor 84 (FIGS. 4 and 14) is electrically connected 
to conductor 470 through a 680 ohm resistor 478, the reverse resistance of 
CR106 zener diode 480 and the forward resistance of a 1N914 diode 482. 
To reset the overcurrent sensor 60, (FIGS. 3 and 7) conductor 296 to the 
overcurrent sensor 60 is electrically connected through a 680 ohm resistor 
484 and through the forward resistance of a 1N914 diode 486 to conductor 
470 to apply a positive potential thereto, permitting the flow rate 
circuit 32 (FIGS. 2, 3 and 4) to operate. 
In FIG. 15, there is shown a schematic circuit diagram of the exponential 
amplifier circuit 276 (FIG. 9) having a first PNP 2N3702 transistor 490, a 
second PNP 2N4061 transistor 492, an adjustment circuit 496 and a bias 
circuit 494. The transistor 490 has a lower input impedance than 
transistor 492 and conducts approximately ten times the current through 
transistor 492. Thus, transistor 492 follows the potential on conductor 
280, and provides an exponential drop between the emitter and base of 
transistor 492. The two transistors cancel their temperature coefficients. 
The first transistor 490 receives an input signal from the frequency to 
voltage converter 272 (FIGS. 9 and 13) on conductor 280 indicating the 
speed of pumping and varies the emitter bias of the transistor 492 to 
cause an exponential amplification of the signal from the frequency to 
voltage converter 272 for application through a conductor to the ramp 
generator circuit 278 (FIG. 9). 
To provide emitter biasing to the first and second transistors 490 and 492, 
the emitters of each of these transistors is electrically connected to a 
source 98 of a positive 12 volts through a 1.18K resistor 502 and to a 
second such source through the 1.18K resistor 502 and a 33 ohm resistor 
500. 
To vary the emitter potential of the second transistor 490 in a manner 
related to the input amplitude on conductor 280 from the frequency to 
voltage converter 272 (FIGS. 9 and 13) so as to provide an exponential 
transfer function, the base of the transistor 490 is electrically 
connected to: (1) the electrical common through a 47.5 ohm resistor 508; 
(2) to input conductor 280 through a 1.40K resistor 504; and (3) to a 
source 106 of a positive 32 volts through a 45.3K resistor 506. The 
collector of the transistor 490 is electrically connected to a source 112 
of a negative 8 volts so that it will draw current through the emitter 
biasing circuit from the source 98 of a positive 12 volts and through the 
resistor 502 in proportion to the input signal on conductor 280 and thus 
cause a drop in the positive potential on the emitter of the transistor 
492 as the current increases. 
To provide a further adjustment on a sawtooth waveform to be controlled by 
the transistors 490 and 492, the adjustment circuit 496 includes a 1.18K 
resistor resistor 510, a 100K resistor 512 and a 5K potentiometer 514. To 
establish biasing, one end of the potentiometer 514 is electrically 
connected to a source 138 of a positive 8 volts and the other end is 
electrically connected to a source 112 of a negative 8 volts, with the 
movable tap being electrically connected to the base of the transistor 492 
through a 100K resistor 512. The base of the transistor 492 is also 
electrically connected to the electrical common through a 1.18K resistor 
510 to provide biasing. The collector of the transistor 492 is connected 
to conductor 520 to provide an exponentially decreasing amplification of 
the signal received on conductor 280. 
To provide a continuous bias on conductor 520, the bias circuit 494 
includes a 150K resistor 516 and a 500K potentiometer 518. The resistor 
516 and potentiometer 518 are electrically connected between a source 98 
of a positive 12 volts and the conductor 520 to permit adjustment of the 
voltage drop for application of a current to the ramp generator 278. 
In FIG. 16, there is shown a schematic circuit diagram of the ramp 
generator 278 (FIG. 9). To form a ramp which varies in slope in a manner 
related to the output from the exponential amplifier 276 (FIGS. 9 and 15) 
for application to the flow rate circuit 32 (FIGS. 2 and 4) the ramp 
generator circuit 278 includes a type TL011C current mirror 530 made and 
sold by Texas Instruments, a 2N3710 NPN transistor 532, a 2N4403 PNP 
transistor 534, and a 910 pf capacitor 536. The current mirror 530 has its 
input electrically connected to conductor 520 to receive the output of the 
exponential amplifier circuit 276 (FIGS. 9 and 15) and its output 
electrically connected to conductor 64 to apply current which decreases as 
the motor speed increases from a high output impedance source with a gain 
of 1 to draw current from capacitor 536 across to generate a negative 
going ramp from the capacitor. 
The common of the current mirror 530 is electrically connected to the 
collector of diode connector transistor 532 through which it conducts 
current. The emitter of the transister 532 is electrically connected to a 
source 112 of a negative 8 volts to control the bias on current mirror 
530. The 2.7K resistor 538 keeps the voltage at its collector of the 
transistor 532 relatively constant at about 7.3 volts regardless of the 
operation of the current mirror 530. 
To form a ramp from the output of the current mirror 530, conductor 64 is 
electrically connected to its output and to one plate of the capacitor 
536, the other plate of which is electrically connected to the emitter of 
transistor 534. With this arrangement, the current flowing from the output 
of the current mirror 530 charges capacitor 536 to form a ramp potential 
on conductor 64. 
To reset capacitor 536, the transistor 534 has its collector electrically 
connected to conductor 64 and its base electrically connected to the 
multivibrator circuit 274 (FIGS. 9 and 14) through conductor 476 so that 
when the multivibrator provides a negative pulse at the end of a ramp, 
transistor 534 becomes conducting to discharge capacitor 536. When 
transistor 534 becomes nonconducting at the end of the negative pulse at 
its input, the capacitor 536 receives a high impedance between one plate 
in conductor 64 and low impedance on the other to be in condition to 
charge and form a ramp potential on conductor 64 as current flows through 
the current mirror 530. 
The current mirror 530 may be any conventional circuit which results in a 
complementary current flow from its input. In the preferred embodiment, 
this is a commercial integrated circuit designated TL011c and sold by 
Texas Instrument. 
In FIG. 17, there is shown a schematic circuit diagram of the linear flow 
rate control circuit 38 (FIG. 2) having a reference voltage to current 
converter 540, a summing node 542, a switch 544, and a servoamplifier 
circuit 546. The reference voltage to current converter 540 receives a 
signal indicating the desired constant flow rate of the influent to the 
chromatographic column on conductor 46 and converts it to a current for 
application to the summing node 542 where it is summed with a feedback 
signal. Upon being gated by the gate 544, this signal is applied to the 
main servoamplifier circuit 546 where it is subtracted from certain other 
correction signals for application through conductor 62 to the flow rate 
circuit 32 (FIGS. 2, 3 and 4). 
To provide a feedback signal during the delivery portion of a pumping 
stroke, the summing node 542 receives: (1) a current set to represent the 
desired flow rate from resistor and low pass filter 540; and (2) a current 
from conductor 548 (FIG. 19) fed back from the motor circuit 30 (FIG. 2) 
representing the effluent as corrected by the first compensation circuit 
40 (FIG. 2) in a manner to be described hereinafter. 
This current is gated by the analog gate 544 under the control of a signal 
on conductor 550 to the inverting terminal of the servoamplifier 546 where 
it is summed with a signal from the first compensation circuit 40 (FIG. 2) 
through a conductor 598. 
The main servoamplifier 546 receives a signal from the second compensation 
circuit 44 (FIG. 2) through a conductor 554 and the difference between the 
two signals is applied to conductor 62. Conductor 62 at different times 
receives compensation circuits on conductors 556 to provide servo gain and 
certain compensations such as for compressibility of the fluids, logic 
signals on conductor 558, a refill gain correction signal on conductor 
560, and a gain from the braking circuit on conductor 562. 
To process the set point voltage on conductor 46 and apply to summing node 
542, the reference voltage to current converter 540 includes a 10K 
resistor 570, a 0.1 uf capacitor 572, and a 187K resistor 574. The 
resistor 570 is electrically connected at one end to conductor 46 and at 
its other end to the electrical common through the capacitor 572 and the 
summing node 542 through the resistor 574. 
The switch 544 is a type 4016 integrated circuit switch sold by the 
aforementioned National Semiconductor although any suitable electronically 
operated switch may be used. The switch 544 is electrically connected to 
be controlled by the first compensation circuit 40 (FIG. 2). 
To compare the signal on conductor 548 fed back from the motor tachometer, 
with the signal on conductor 46 indicating the desirable flow rate, the 
servoamplifier circuit 546 includes an LM 353 differential amplifier 580 
sold by National Semiconductor, four resistors 582, 584, 586 ad 590, a 22 
pf capacitor 592, and a 1N914 diode 594. The resistors are a 470 ohm 
resistor 582, a 10K resistor 584, a 47K resistor 586 and a 220 ohm 
resistor 590. The resistor 582 is electrically connected at one end to the 
output of the switch 544 and at its other end to: (1) the inverting input 
terminal of the amplifier 580 to supply a signal thereto representing the 
flow rate error signal; and (2) conductor 598 electrically connected to 
the first compensation circuit 40 (FIG. 2); and (3) to the output of the 
differential amplifier 580 through the capacitor 592. 
The output of the amplifier 580 is electrically connected to conductor 62 
through the resistor 590 and the amplifier has a source 138 of a positive 
8 volts connected as one rail at pin 8 and a source 112 of a negative 8 
volts connected as a second rail at pin 4. The noninverting input terminal 
of the amplifier is electrically connected to: (1) the electrical common 
through the resistor 586; (2) conductor 554 to receive the feedback 
pumping rate signal; and (3) a conductor 596 through the forward 
resistance of the diode 594 and the resistor 584 for placing the pump in 
the stop mode. Conductor 596 receives a signal from a start circuit under 
the control of the system controller 22 (FIG. 1). 
In FIG. 18, there is shown a block diagram of the first compensation 
circuit 40 (FIG. 2) as it is electrically connected to the linear flow 
rate control circuit 38 (FIGS. 2 and 17). The first compensation circuit 
40 includes a summing node compensation circuit 600 and a servoamplifier 
compensation circuit 602 each electrically connected to the linear flow 
rate control circuit 38 at different locations, with the summing node 
compensation circuit 600 being electrically connected to the summing node 
542 (FIG. 17) and the servoamplifier compensation circuit 602 being 
electrically connected to the servoamplifier inverting input at 598 and at 
its output as shown at 556, 558, 560 and 562 (FIG. 17). 
With this arrangement, the speed of the motor is corrected by the range of 
fluid that is flowing, the measured average flow of the influent into the 
chromatographic column and for certain factors such as the braking gain, 
refill gain, servo gain and liquid compensation or for braking values at 
the input to the servoamplifier. 
In FIG. 19, there is shown a schematic circuit diagram of the summing node 
compensation circuit 600 (FIG. 18) having a range selection circuit 608 
and coupling circuit shown generally at 604. The range selection circuit 
608 may energize either a high or low voltage levels current to be applied 
to the coupling circuit 604 which receives the variable amplitude voltage 
from the frequency to voltage converter 272 (FIGS. 9 and 13) on conductor 
280 and converts it to a current applied through conductor 548 to the 
summing node. The magnitude of the current depends on whether a high or 
low range is selected. While a range selection circuit 608 is shown 
connected to conductor 630, in the preferred embodiment, a signal from the 
microprocessor is used to energize the transister 610 and open switch 640. 
In this specification, a high signal is applied to terminals 628 to select 
a one-tenth scale set point and corresponding feedback signals and 
terminals 626 or 418 from a low range in which the signals are subject to 
less attenuation by a factor of 10. 
To provide a larger or smaller current depending on the selection of a high 
or low range, the range selection circuit 608 includes a 2N3704 NPN 
transistor 610, a 2N3704 NPN transistor 612 and seven resistors which are 
respectively a 2.2K resistor 614, a 2.2K resistor 616, a 230 ohm resistor 
618, a 2.43K resistor 620, 1K resistor 622, and a 22K resistor 624. 
To provide a low range current, the transistor 610 has its emitter 
electrically connected to a source 112 of a negative 8 volts, its base 
electrically connected to: (1) a source 94 of a negative 12 volts through 
the resistor 622; and (3) a source 138 of a positive 8 volts through 
resistors 618 and 620 in series and has its collector electrically 
connected to: (1) a contact 626 within the range selection circuit 608 for 
a low range current; (2) the base of transistor 612 through resistor 624; 
and (3) a source 138 of a positive 8 volts through the resistor 616. 
The emitter of the transistor 612 is electrically connected to a source 112 
of a negative 8 volts and its collector is electrically connected to a 
source 138 of a positive 8 volts through the resistor 614. The range 
selection circuit 608 has a movable contact which connects a source of 
positive potential to either the low range switch 626 or the high range 
switch 628, the low range switch placing a voltage on conductor 630 and 
the high range switch placing a voltage on conductor 632. 
The conductor 630 is electrically connected through conductor 418 to the 
frequency to voltage converter 272 (FIGS. 9 and 13) to ground the 
capacitor 410 (FIG. 13), thus increasing the amplitude of the output 
potential. 
To convert potential to current for application to the summing node 542 
(FIG. 17) through conductor 548, the coupling circuit 604 includes an 
analog switch 640, a 0.047 uf capacitor 642, three resistors and a 5K 
potentiometer 652. The three resistors are an 11.5K resistor 646, a 49.9K 
resistor 648 and a 4.7K resistor 650. Conductor 280 from the output of the 
voltage to frequency converter 272 (FIGS. 9 and 13) is electrically 
connected to: (1) the input of the switch 640 through the potentiometer 
652 and the resistor 648; and (2) electrical common through the resistor 
650 and the capacitor 642. The gate of switch 640 is electrically 
connected to conductors 630 and 418 and its output is electrically 
connected to electrical common through the resistor 448 and the capacitor 
642. 
In FIG. 20, there is shown a block diagram of the servoamplifier 
compensation circuit 602 (FIG. 18), having a braking gain circuit 660, a 
refill gain circuit 662, a servo gain and compensation circuit 664, a 
delivery logic circuit 666, and an acceleration time generator circuit 
668. Each of these circuits generates signals relating to the timing of 
the acceleration of the pump motor and applies the signal to the linear 
flow rate control circuit 38 (FIGS. 2 and 17) through a plurality of 
analog switches. The analog switches are 670, 672 and 674. 
For this purpose, the acceleration time generator circuit 668 applies 
signals to the delivery logic circuit 666 and to conductor 550 through one 
conductor and to the switch 672 through another conductor. The switch 670 
is controlled by a signal on conductor 72 from the brake circuit 52 (FIGS. 
3 and 5) to apply a brake gain through conductor 560 and a servo gain from 
the servo gain and compensation circuit 664 through conductor 558 by 
opening switch 674. The refill gain is applied from the refill gain 
circuit 662 upon being opened by a signal from the acceleration time 
generator circuit 668 indicating a refill cycle. 
In FIG. 21, there is shown a schematic circuit diagram of the braking gain 
circuit 660, the refill gain circuit 662, and the servo gain and 
compensation circuit 664 and their associated switches 670, 672 and 674 
(FIG. 20). The braking gain circuit 660 is controlled by switch 670, the 
refill gain circuit 662 is controlled by switch 672 and the servo gain and 
compensation circuit 664 is controlled by the switch 674 to which they are 
connected to apply currents through conductor 598 to the flow rate control 
circuit 38 (FIGS. 2 and 17) to change the speed of the motor in accordance 
with corrections required for braking, refill and servo gain and 
compensation. 
The braking gain circuit 660 includes a 4.7M resistor 680 electrically 
connected at one end to the output switch 670 and at its other end to 
conductor 598 to attenuate the signal on conductor 598 during a braking 
cycle. Switch 670 has its gate input electrically connected to conductor 
72 from the brake circuit 52 (FIG. 3) and its input electrically connected 
to the conductor 558. The analog switch controls the gain and applies an 
attenuated voltage of the servo amplifier. The level of the set point 
signal on conductor 46 is level shifted by the 7.5K resistor 677, the 
negative source 112 and the 2.05K resistor 675 to be applied to conductor 
816 when switch 673 is opened. 
The refill gain circuit 662 includes a 68K resistor 682 and a 1.2M (megohm) 
resistor 684. The resistor 682 is electrically connected to the electrical 
common at one end and connected to the one lead of the switch 672 and the 
resistor 682 is electrically connected at one end to conductor 598 to 
apply a signal to the linear flow rate control circuit 38. Switch 672 has 
its gate electrically connected to conductor 560 to the delivery logic 
circuit 666 (FIG. 20) and the second drain electrically connected through 
conductor 686 to the second compensation circuit 44 (FIG. 2). 
To control servo gain and thus to provide servo stability, the servo gain 
and compensation circuit 664 includes an analog switch 688, two 3.3M 
resistors 690 and 692, a 180K resistor 694, a 0.22 uf capacitor 696 and a 
0.047 uf capacitor 698. One lead of the switch 688 is electrically 
connected through the resistor 690 and the capacitor 696 in series to 
conductor 598 to apply a compensation signal thereto. The other lead of 
the switch 688 is electrically connected to: (1) the capacitor 696 through 
resistor 694; (2) one lead of the switch 694; (3) conductor 598 through 
the resistor 692 and the capacitor 698 in series. 
To control the servo gain and compensation circuit, the switch 674 has its 
gate electrically connected to the delivery logic circuit 666 (FIG. 20) 
through conductor 700 (FIG. 20). With this arrangement, signals from the 
delivery logic circuit 666 are applied to the gate of switch 674 to close 
this switch and carry signals from resistors 692 and 694 and switch 688 
providing the required compensations. 
The refill gain circuit 662 (FIG. 20) upon receiving a signal on conductor 
566 from the acceleration time generator circuit 668 indicating a refill 
cycle provides a feedback path for the servo amplifier through a resistive 
network including resistors 682, 684 and 685 to conductor 598 and the 
servo gain and compensation circuit 664 closes an additional feedback path 
for the servo amplifier through a resistance network including a signal 
applied to switch 688 on conductor 702. 
In FIG. 22, there is shown a block diagram of the acceleration timer 
generator circuit 668 (FIG. 20) having an acceleration timer 710 and an 
acceleration timer output circuit 712. The acceleration timer 710 is 
electrically connected to conductor 76 to receive a refill inception 
signal, conductor 418 to receive a signal indicating the compressibility 
of the fluid being pumped and a signal on conductor 46 indicating the set 
flow rate. 
The acceleration timer 710 processes these signals and applies a signal to 
the acceleration timer output circuit 712 and two conductors 550 and and 
556 to speed up the motor at the end of fluid delivery at an accelerating 
rate to make up for fluid flow that will be lost during a time period 
before delivery commences again. 
The acceleration timer 710 receives a signal indicating the start of the 
refill cycle and causes a time limit on motor acceleration while there is 
no flow so that the cylinder is filled across the period of time 
controlled by the timer. The motor may also be caused to accelerate in a 
forward stroke in a manner controlled by the acceleration timer 710 if the 
forward stroke starts during this time period. The time is increased as 
the flow rate increases. 
In FIG. 23, there is shown a schematic circuit diagram of the acceleration 
timer 710 having a monostable multivibrator 714, a 2N4403 PNP transistor 
716 and an analog switch 718. The multivibrator 714 is type 555 sold by 
National Semiconductor Corporation identified above but any monostable 
multivibrator may be used provided it is designed to have satisfactory 
parameters in a manner known in the art. 
To provide an output signal to conductor 724 related to the motor 
acceleration, the acceleration timer 710 has a time duration circuit 720, 
a connection to lead 418 which carries a signal indicating the 
compressiblity of the fluid being pumped and an output conductor 724, all 
of which are electrically connected to the multivibrator 714 so that the 
amplitude adjustment circuit 720 provides correction amplitude for high or 
low range, calibration and compression of liquids. 
To trigger the monostable multivibrator 714, conductor 76A from the output 
of the comparator 184 (FIG. 6) drives conductor 724 high at inception of 
the refill stroke and goes low at the end of the signal and a short time 
later. It is differentiated by capacitor 762 to trigger the multivibrator 
to high and maintaining lead 724 high until the timer drops low under the 
control of capacitor 150 and current through transistor 716 to remove 
potential from conductor 724. 
To permit adjustment of the signal on conductor 744 electrically connected 
to the collector of the transistor 716, the emitter of the transistor is 
electrically connected to a source 138 of a positive 8 volts through a 
16.5K resistor 746 and a 10K potentiometer 748. The transistor 716 is a 
type 2N4403 and the adjustment of the potentiometer 748 adjusts the 
current applied to conductor 744 through its collector so as to permit 
adjustment of the acceleration time of the motor. 
Conductor 744 is electrically connected to pins 6 and 7 and to the source 
112 of a negative 8 volts through a 1 uf timing ramp capacitor 150, the 
source 112 being electrically connected to pin 1 and pins 4 and 8 being 
electrically connected to the source 138 of a positive 8 volts, whereby 
the time duration of the output pulse width from the multivibrator 714 is 
adjusted. Pin 5 of the multivibrator 714 is electrically connected to 
electrical common through a 0.01 uf capacitor 752 and pin 3 is 
electrically connected to conductor 724 through the forward resistance of 
a diode 1N914 754 to apply the output to conductor 724. The multivibrator 
714 is triggered on by the tailing edge of a signal applied through 
conductors 76A and 76B from the refill initiator. 
To trigger the multivibrator 714, the trigger circuit 722 includes a 1N914 
diode 760, a 0.22 uf capacitor 762, a 1N273 diode 764, a 47K resistor 766 
and a 3.74K resistor 768. Conductor 76B is electrically connected to 
conductor 76 through the resistor 768. Conductor 76B is electrically 
connected to conductor 76 through the resistor 768 and to pin 2 of the 
multivibrator 714 through the capacitor 762. Pin 2 is also electrically 
connected to the source 138 of a positive 8 volts through the resistor 766 
and the forward resistance of the diode 764. Conductor 76A is electrically 
connected to conductor 724 through the forward resistance of diode 760 and 
to the cathode of the diode 754 so that, a pulse differentiated by 
capacitor 762 and resistor 47K triggers the multivibrator 714 to apply a 
potential to conductor 724. 
In FIG. 24, there is shown a schematic circuit diagram of the acceleration 
timer output circuit 712 (FIG. 22) which receives a signal on conductor 
724 to establish acceleration across a predetermined period of time and 
supplies signals to conductors 686 to close switch 672 (FIG. 21) and apply 
compensation from the refill gain circuit 662 (FIGS. 20 and 21) and 
conductor 550 to open switch 544 (FIG. 17) to disconnect potential from 
the summing node 542 (FIG. 17) to the servoamplifier 580 (FIG. 17). 
To generate a signal for conductor 556, the output circuit includes a first 
LM 311 comparator 770 having its inverting input terminal electrically 
connected to conductor 724 and its noninverting input terminal 
electrically connected to: (1) electrical common through a 2.43K resistor 
772; and 2 to a source 112 of a negative 8 volts through a 4.7K resistor 
774. The comparator 770 has one rail electrically connected to a source 
138 of a positive 8 volts and the other rail electrically connected to a 
source 112 of a negative 8 volts. Its inverted output terminal is 
electrically connected to conductor 556 and to a source 112 of a negative 
8 volts through a 10K resistor 776. 
To apply a signal to switch 544 (FIG. 17), the acceleration timer output 
circuit 712 (FIG. 22) includes a 2N3704 NPN transistor 780 having its base 
electrically connected to: (1) conductor 724 through a 15K resistor 782; 
and (2) to a source 112 of a negative 8 volts through a 2.2K resistor 784. 
The emitter of the transistor 780 is electrically connected to the source 
112 of a negative 8 volts and to a source 138 of a positive 8 volts 
through a 1 uf capacitor 786. The source 138 of a positive 8 volts is 
electrically connected to the collector of the transistor 780 through a 
4.7K resistor 788 and the collector of the transistor 780 is electrically 
connected to conductor 550 through a 22K resistor 790. Conductor 550 is 
connected to electrical common through a 0.1 uf capacitor 792. 
In FIG. 25, there is shown a schematic circuit diagram of the delivery 
logic circuit 666 (FIG. 20) having three NAND gates 800, 802 and 804, 
respectively, and a differential amplifier 806. The differential amplifier 
806 has its noninverting input terminal electrically connected to 
conductor 556 to receive the output from the main servoamplifier 546 (FIG. 
17) through a 10K resistor 810 and a 68K resistor 812 in series. The 
inverting input terminal of the differential amplifier 806 is electrically 
connected to: (1) conductor 816 to receive a level shifted set point 
signal during braking; and (2) the electrical common through a 47K 
resistor 818 and through a 0.1 uf capacitor 820 in parallel to slow the 
motor when it is near its constant speed point. 
The noninverting input terminal of the differential amplifier 806 is 
electrically connected to the electrical common through a 220 pf capacitor 
822 and through the resistor 812 and a 0.1 uf capacitor 824. With this 
arrangement, the differential amplifier 806 transmits a negative going 
signal to one input of the two-input NAND gate 804 during braking. The 
other input of the NAND gate 804 and conductor 700 are electrically 
connected to the output of a flip-flop comprising NAND gate 802, one input 
of the NAND gate 802 being electrically connected to conductor 550 and its 
other input electrically connected to the output of NAND gate 800. 
Conductor 550 goes to a low potential at the start of refill, setting the 
flip-flop composed of NAND gates 800 and 802. The output of NAND gate 802 
is electrically connected to one input of the NAND gate 800 and the other 
input is electrically connected to: (1) a source 138 of a positive 8 volts 
through a 4.7K resistor 830 and the forward resistance of a 1N914 diode 
832; (2) the source 138 of a positive 8 volts through the resistor 830 and 
a 220K resistor 834; and (3) the output of differential amplifier 806 
through the resistor 830, a 0.001 uf capacitor 838 and a 10K resistor 840 
in series in the order names. At the end of the braking period, the servo 
amplifier output voltage on lead 556 drops below the level shifted 
setpoint voltage on lead 816. This produces a negative transition at the 
output of differential amplifier 806 which resets flip-flop 800 and 802 
through resistor 840, capacitor 838 and resistor 830. The output of the 
differential amplifier 806 is electrically connected to one of the two 
inputs of the NAND gate 804 so as to provide a low output signal for 
braking only when the flop-flop including NAND gates 800 and 802 is set 
and the output of differential amplifier 806 is high. 
In FIG. 26, there is shown a block diagram of the second compensation 
circuit 44 having a refill acceleration compensation circut 850, a sample 
and hold amplifier circuit 852 and a servo voltage multiplier and offset 
circuit 854. The refill acceleration compensation circuit 850 receives 
signals on conductor 46 indicating the flow rate and on conductor 418 from 
the compensation circuit and applies a signal to the ramp generator 278 
(FIG. 9 and 16) through conductor 282 when a switch 856 is closed by a 
signal on conductor 700. 
To apply a speed-up signal to the servo amplifier, conductor 700 is 
electrically connected to gate 858 to open this gate and apply the servo 
gain and compensation to the servo voltage multiplier and offset circuit 
854. Upon receiving a signal indicating fluid delivery on conductor 862 
from the delivery logic circuit 666 (FIG. 20), the switch 864 is closed to 
store the servo feedback signal from the output of the servo amplifier in 
the sample and hold amplifier circuit 852. The sample and hold amplifier 
circuit 852 is connected to the serve voltage multiplier and offset 
circuit 854 to be corrected and to apply the signal through gate 858 to 
the input 554 of the servoamplifier for acceleration. 
In FIG. 27, there is shown a schematic circuit diagram of the refill 
acceleration compensation circuit 850 having a first analog switch 852, a 
second analog switch 854 and a 2N3704 NPN transistor 857. The transistor 
857 applies a signal through switch 864 to conductor 282 to correct for 
the acceleration compensation with a compressibility correction being 
applied to its base. To apply an acceleration offset to the transistor 857 
conductor 46 carrying the set point signal is electrically connected to: 
(1) the base of transistor 857 through a 10K resistor 868; (2) to the 
analog switch 854 through the resistor 868; (3) to a source 94 of a 
negative 12 volts through a 1K potentiometer gate 70, a 500 ohm resistor 
872 and a 1K resistor 874 in series in the order named. 
With this arrangement, the potentiometer gate 870 may be adjusted to 
provide different base current to the transistor 857. The emitter of the 
transistor 856 is electrically connected to a source of a negative 8 volts 
112 and its collector is electrically connected to the source of the 
switch 864 through a 46.4K resistor 880 to provide a signal to the output 
conductor 282 upon receiving a signal on conductor 700. To provide 
compressibility compensation, conductor 418 is electrically connected to 
the switch 864 through a 1.8M resistor 882. 
To provide a signal to conductor 520 to modify the rate of acceleration 
which commences at the start of refill when a low range signal is received 
on conductor 626 by the switches 852 and 854, conductor 46 is electrically 
connected to the source of the one level of switch 852 through: (1) the 
resistor 858 and a 24.9K resistor 884; (2) through the resistor 868, a 
2.7K resistor 886 and the resistor 884. Conductor 46 is connected to the 
electrical common through the resistor 868 and a 649 ohm resistor 888. 
In FIG. 28, there is shown a schematic of the sample and hold amplifier 
circuit 852 having a switch 890, a storage capacitor 892 and an 
operational amplifier 894. The switch 890 is electrically connected to the 
output of the servoamplifier through conductor 556 and to conductor 282 to 
receive a signal during the delivery portion of the pumping cycle. The 
switch 890 has one lead electrically connected to: (1) one plate of the 
0.22 uf storage and noise filtering capacitor 892 through a 680K resistor 
896 and a 3.3M resistor 898; (2) to the noninverting terminal of the 
amplifier 894 through the resistors 896 and 898; (3) to the electrical 
common through a 1 uf storage and noise filtering capacitor 900; and (4) 
to a source 138 of a positive 8 volts through the 22M resistor 902. The 
capacitor 892 is a 0.22 uf capacitor having one of its plates connected to 
the output of the switch 890 and its other connected to electrical ground. 
The capacitors 892 and 900 store a voltage representing the drive signal 
to the pump motor during the delivery portion of the pumping. 
The output of the operational amplifier 894 is electrically connected to 
its inverting input terminal and to a conductor 904 from the servo voltage 
multiplier and offset circuit 854 (FIG. 26). With this circuit 
arrangement, a value of potential equivalent to the drive signal to the 
motor stored on capacitors 892 and 900 and applied with an offset to 
conductor 904 to the servo voltage multiplier and offset circuit 854. 
In FIG. 29, there is shown a schematic circuit diagram of the servo voltage 
multiplier and offset circuit 854 (FIG. 26) having an operational 
amplifier 910, a first potentiometer 912, an analog switch 914, and a 
second potentiometer 916. The potentiometer 916 is electrically connected 
at one end to a source 138 of a positive 8 volts and at the other end to a 
source 112 of a negative 8 volts to permit selection of a potential to be 
applied to the source of switch 914 and the potentiometer 912 is 
electrically connected at one end to conductor 904 of the sample and hold 
amplifier circuit 852 (FIGS. 26 and 28) through a 1K resistor 918. 
The potentiometer 916 is a 10K potentiometer and the potentiomenter 912 is 
a 2K potentiometer. The other end of the potentiometer 912 is electrically 
connected through a 6.19K resistor 920 and a 100K resistor 922 to the 
inverting input terminal of the operational amplifier 910. The inverting 
input terminal of the operational amplifier 910 is also electrically 
connected to conductor 558 through a 100K resistor 924 to receive a signal 
from the output of the servoamplifier. 
The output of the amplifier 910 is electrically connected through a 220 ohm 
resistor 926 to one side of the resistor 922 and through a 22 pf capacitor 
928 to the other end of the resistor 922 and to the inverting input 
terminal of the amplifier 910. The noninverting input of the amplifier 910 
is electrically connected to the electrical common so that the input 
signal from the output of the main servoamplifier on conductor 558 is 
applied to the inverting input terminal of the amplifier 910. The output 
of the amplifier 910 is applied to one end of the servo voltage multiplier 
where its magnitude is adjusted by the servo offset and servo voltage 
multiplier potentiometers and by the signal on conductor 904 for 
application through the switch 914 and conductor 554 to the input of the 
servoamplifier, thereby providing a feedback circuit which incorporates a 
sample and hold circuit and certain corrections. 
When switch 914 closes and connects the wiper of potentiometer 912 to 
conductor 554, a negative signal from the sample and hold circuit at 904 
is applied through the main servoamplifier 580 (FIG. 17) and inverted in 
amplifier 910. The signal is transmitted from conductor 904 on the output 
of the amplifier 894 (FIG. 28) in the sample and hold amplifier circuit 
852 (FIGS. 26 and 28), through the potentiometer 912 and conductor 554 to 
the noninverting input of servoamplifier 580 (FIG. 17) and to the 
inverting input of operational amplifier 910. The amplifier 910 includes 
equal input and feedback resistors 922 and 924 establishing a potential at 
927 on the output of the inverter 910 connecting resistors 920, 922 and 
926 which is inverted but equal to the potential at 558. 
The servoamplifier 580 (FIG. 17) is a high gain amplifier and causes the 
potential at 554 to be close to zero. Because amplifier 910 is a part of a 
negative 1 gain inverter, point 927 is the inverted value of the output of 
the servoamplifier at 558. Since the potential at the wiper of 
potentiometer 912 is not far from zero volts, being not far from the 
potential at 554, the potential at 927 is a multiple of the potential at 
904 established by the voltage divider including the resistance from the 
wiper to the point 927 and from the wiper to point 904. The voltage at 927 
is a multiple of the sample and hold voltage which is equivalent to the 
motor drive signal during delivery and the output signal at 558 is the 
inverted value of the potential at 927 to represent a multiple of the 
motor drive signal during delivery. 
During acceleration, 686 goes high to close 914 connecting it to 
potentiometer 916. The offset on 916 is set to cause the servoamplifier to 
go negative when switch 914 closes. Voltages on 554 to servoamplifier, 
when switch 914 is closed, reaches a balance depending on potentiometer 
setting 912. With the arrangement, the servoamplifier generates a signal 
to cause acceleration of the motor until terminated by the acceleration 
time generator circuit, causing the total volume of fluid per stroke to 
tend to equalize and thus reduce pulsations of current through the 
chromatographic column. The acceleration is related to the signal on 
conductor 558 reflecting the sample and hold voltage stored during 
delivery. 
In FIG. 30, there is shown a schematic sectional view of a pump 14 (FIG. 1) 
having a cam 950, a cam follower 952, and a pump head 954. The cam 950 is 
mounted to the output shaft of the motor 50 (FIG. 3) for rotation thereby. 
The cam follower 952 is mounted to move in the direction of the pump head 
954 and the direction of the output shaft as the cam rotates to provide a 
reciprocating motion for a piston within the pump head 954. 
The pump head 954 includes an outlet port 956 and an inlet port 958, closed 
by pressure-activated valves so that when the piston is moved inwardly in 
response to the cam follower 952, fluid is drawn into the cylinder 960, 
the outlet port 956 being closed and the inlet port 958 being open. 
Similarly, when the piston is moved forwardly, fluid is forced from the 
outlet port 956 and fluid is blocked from entering or leaving the inlet 
port 958 by check valves therein. The high pressure pump itself and the 
electric motor are not part of the invention themselves except that the 
rotatable masses thereof are sufficient to provide a flywheel effect to 
the pump itself. This and other flywheel implements reduce the effect of 
friction and increases repeatability. Bearings are selected for low 
friction. 
In FIG. 31, there is shown a schematic circuit diagram of a circuit 1000 
for presetting a liquid flow rate from the pump to adjsut the amplitude of 
the current on conductor 46 having a keyboard 1002, a clock source 1004, 
an updating circuit 1006, and a current source 1003. The current 46, of 
course, may be set by any analog circuit including a manual potentiometer 
in a manner known in the art. 
In the preferred embodiment, it is set by a software program utilizing an 
8031 microcomputer of the type manufactured by Intel, containing 128 bytes 
of RAM, a serial port and two counter/timers. An EPROM in the unit 
contains instruction codes for controlling the pump. The software program 
for monitoring the current 46 to maintain a constant average flow rate as 
follows: 
__________________________________________________________________________ 
MCS-S1 MACRO ASSEMBLER HPLC RECIP PUMP, 11.059 CRYSTAL AND SERIAL 
INSTALLED 
L00 OBJ LINE 
SOURCE 
__________________________________________________________________________ 
03B9 
22 763 RET ;TO MISS ONE IN TIMING ALSO 
764 ; 
765 ; CALCULATIONS FOR THE SECONDARY ADJUSTMENTS BASED ON 
EACH RATE 
766 ; JUMPED TO BY INTERRUPT 
767 ; BASEC CONTROL EQUATION IS: 
768 ; 
769 ; DAC --ADJUST1=(DAC --OLD*833.3*TIME)/(PULSES*FL 
OW --BIN) 
770 ; DAC --OLD = DAC --ADJUST1 OF LAST READING 
771 ; 
772 ; WHERE SOME ADDED CONVERSION FACTORS ARE 
NEEDED 
773 ; AND PULSES 100 OR 300 AND TIME IS MEASURE, BUT 
NOT 
774 ; ACTUALLY STORED IN A REGISTER 
775 ; ADDITIONALLY, THE VALUES ARE LIMITED TO A 
ADJUSTMENT 
776 ; OF 2% AT .5 ML LINEARLY INCREASING TO 25% AT 
.01 ML 
777 ; 
778 ; 
03EA 
C0D0 779 CALC: PUSH PSW ;PUSH RS0 AND RS1 WITH PSW 
03EC 
D2D3 780 SETB RSO 
03EE 
D2D4 781 SETB RS1 
03FO 
902001 
782 MOV DPTR, #CO --1 
;LOAD IN TIMER VALUE 
03F3 
E0 783 MOVX A,@DPTR 
03F4 
FD 784 MOV R5,A 
03F5 
E0 785 MOVX A,@DPTR 
03F6 
FE 786 MOV R6,A 
03F7 
7F00 787 MOV R7,#00H 
03F9 
900306 
788 MOV DPTR #NUMBER --OF --TIMES 
03FC 
E0 789 MOVX A,@DPTR 
03FD 
04 790 INC A 
03FE 
F0 791 MOVX @DPTR,A ;PUT NUMBER BACK 
03FF 
203805 
792 JB A100 --PULSES,CHK --15 
0402 
B40507 
793 CONE A,#05H,KEEP --COUNTING 
0405 
8014 794 SJMP RESET --COUNTER 
0407 
B40F02 
795 CHK --15; CJNE A,#0FH,KEEP --COUNTING 
040A 
800F 796 SJMP RESET --COUNTER 
040C 
203806 
797 KEEP --COUNTING: 
JB A100 --PULSES,LOAD --ONLY --100 
040F 
71E0 798 ACALL 
LOAD --OTHER --COUNTSA 
0411 
71C3 799 ACALL 
LOADEROF300 
0413 
800E 800 SJMP KEEP --COUNT 
0415 
71E0 801 LOAD --ONLY -- 100: 
ACALL 
LOAD --OTHER --COUNTSA 
0417 
71CD 802 ACALL 
LOADEROF100 
0419 
8008 803 SJMP KEEP --COUNT 
041B 
7400 804 RESET --COUNTER: 
MOV A,#00H 
041D 
F0 805 MOVX @DPTR,A 
041E 
121770 
806 LCALL 
INIT --ADJUST 
;LOCATED RIGHT AFTER KRUN 
0421 
A1BE 807 AJMP CLEAR --OUT ;GET OUT OF HERE 
0423 
7AFF 808 KEEP --COUNT: MOV R2,#0FFH ;LOAD IN 65535 (FFFF) 
0425 
7BFF 809 MOV R3, #0FFH 
0427 
7C00 810 MOV R4,#00H 
0429 
B1D4 811 ACALL 
BINSUB ;SUBT 65535-COUNT --VALUE 
042B 
AA20 812 MOV R2,20H 
042D 
AB21 813 MOV R3,21H ;MULT BY 2560 
042F 
7C00 814 MOV R4,#00H 
0431 
7D00 815 MOV R5,#00H 
0433 
7EOA 816 MOV R6,#0AH 
0435 
7F00 817 MOV R7,#00H 
03A4 
C24F 708 TO --MAIN: 
CLR START --UP ;IF MADE IT THROUGH, THEN IS 
STARTED UP 
03A6 
0201CB 
709 LJMP 
MAIN 
710 ; 
711 ; 
712 ; THE FOLLOWING SUBROUTINES (GUASI --INT,NO --PRESS 
--UPDA,LOADEROFXXX, AND 
713 ; CALC ALL BELONG TO THE THE FLOW RATE ALORITHM, QUASI 
--NT IS USED WHEN THE 
714 ; INTERRUPTS HAVE BEEN DISABLED AND AFTER RENABLING, THE 
INTERRUPT BIT FOR 
715 ; EXTERNAL IS SET. IT PULLS A "FAKE" INTERRUPT TO 
MAINTAIN THE ALGO. 
716 ; ALSO, THE SUBROUTINES ADJUST --REF, TAKE --CARE 
--HIGH, AND TAKE --CARE LOW 
717 ; ARE USED IN THE ALGORITHM AT DIFFERENT TIMES 
718 ; 
03A9 
209605 
719 QUASI --INT: 
JB P1.6,CALL --CALC1 
03AC 
D23C 720 SETB 
GATED ;GATE OFF PRESSURE 
03AE 
D23A 721 SETB 
GATED1 ;MESSAGE TO OTHER LOOPS TO 
03BO 
22 722 RET ;START INITIAL ALGORITHM MODE 
03B1 
61EA 723 CALL --CALC1: 
AJMP 
CALC ;RETURN IS IN CALC 
724 ; 
725 ; 
726 ; REAL INTERRUPTS FROM EXTERNAL JUMP TO THIS SPOT 
727 ; 
03B3 
209606 
728 NO --PRESS -- 
JB P1.6,CALL --CALC 
UPDA: 
03B6 
D23C 729 SBTB GATED ;SET TO GATE OFF PRESSURE 
03B8 
D23A 730 SETB GATE1 ;USED IN MAIN, RAPID, AND AGAIN 
03BA 
8002 731 SJMP SKIDOO 
03BC 
71EA 732 CALL --CALC: ACALL 
CALC ;NOT A REFILL PULSE BUT A TIMER 
PULSE 
03B5 
D083 733 SKIDO0: FOP DPH 
03C0 
D082 734 FOP DFL 
03C2 
32 735 RETI 
736 ; 
737 ; THESE ROUTINES LOAD THE TACH COUNTER (CO --2) 
738 ; 
739 
03C3 
902002 
740 LOADEROF300: MOV DPTR,#CO --2 
03C6 
742B 741 MOV A,#2BH ;LOAD 299 SINCE FIRST PULSE LOADS 
IN 
742 ;THE COUNT VALUE AND SO IS MISSED 
03C6 
F0 743 MOVX @DPTR,A 
; 
03C9 
7401 744 MOV A,#01H ; 
03C8 
F0 745 MOVX @DPTR,A 
03CO 
22 746 RET 
03CD 
902002 
747 LOADEROF100: MOV DPTR,# CO --2 
03D0 
7463 748 MOV A,#063H ;LOAD IN 99 FOR SAME REASON AS 
300 
03D2 
F0 749 MOVX @DPTR,A 
03D3 
7400 750 MOV A,#00H 
03D5 
F0 751 MOVX @DPTR,A 
03D6 
22 752 RET 
03D7 
902000 
753 LOAD --other -- 
MOV DPTR,#CO --C 
COUNTS: 
03D8 
74BA 754 MOV A,#OEAH ;LOAD DO --C WITH 17,698 
03BC 
F0 755 MOVX @DPTR,A ;TIMERS LINKED TO 32 BITS 
03DD 
7445 756 MOV A,#45H 
03DF 
F0 757 MOVX @DPTR,A 
03EO 
902001 
758 LOAD --OTHER -- 
MOV DPTR,#CO --1 
COUNTSA: 
03E3 
74FD 759 MOV A,#OFDH ;SO CO --1 COUNTS AT,01SEC 
03E3 
F0 760 MOVX @DPTR,A ;DOWN FROM 65533 
03E6 
74FF 761 MOV A,#OFFH ;65533 SINCE FIRST PULSE LOADS 
03E8 
F0 762 MOVX @DPTR,A ;VALUE AND IS MISSED AND SEEMS 
0437 
B1E8 818 ACALL 
BINMUL 
0439 
AA23 819 MOV R2,23H 
043B 
AB24 820 MOV R3,24H 
043D 
AC25 821 MOV R4,25H 
043F 
203816 
822 JB A100 --PULSES,ONLY --100 
0442 
7D46 823 MOV R5,#46H ;ADD 1282=502H (RNDING IN 
NEXT) 
0444 
7E05 824 MOV R6,#05H ;12/2/85 ADD 1350=546H 
0446 
7F00 825 MOV R7,#00H 
0448 
B1C1 826 ACALL 
BINADD 
044A 
AA20 827 MOV R2,20H 
044C 
AB21 828 MOV R3,21H ;***12/2/85 CNG REF TO 
833.3*** 
044E 
AC22 829 MOV R4,22H 
0450 
7D8C 830 MOV R5,#06CH ;DIVBY 2563=A034=(300*7500/878) 
0452 
7E0A 831 MOV R6,#0AH ;WHERE 7500 IS 2000UL REF WORD 
0454 
7F00 832 MOV R7,#00H ;*12/2/85 (300*7500/833.3)=2700 
0456 
8014 833 SJMP CALL --DIVIDER 
;2700=A8CH 
0458 
7DC2 834 ONLY --100: MOV R5,#0C2H ;ADD 427 FOR ROUNDING (854/2) 
045A 
7B01 835 MOV R6,#01H ;427=1ABH 
045C 
7F00 836 MOV R7,#00H ;**12/2/85 450=1C2H=(900/2) 
045E 
B1C1 837 ACALL 
BINADD 
0460 
AA20 838 MOV R2,20H 
0462 
AB21 839 MOV R3,21H 
0464 
AC22 840 MOV R4,22H 
0466 
7D84 841 MOV R5,#084H 
0468 
7E03 842 MOV R6,#03H ;DIVBY 854=356H=(100*7500/878) 
046C 
7F00 843 MOV R7,#00H ;**12/2/85 900=384H=(100*7500/833. 
3) 
046D 
D1AD 844 CALL --DIVIDER: 
ACALL 
BINDIV 
046E 
AA20 845 MOV R2,20H ;GET RESULT 
0470 
AB21 846 MOV R3,21H 
0472 
AC22 847 MOV R4,22H 
0474 
205206 
848 JB CALIBRATED,DIVOTHER 
0477 
AD46 849 MOV R5,FLOW --BIN 
;MULTIPLY BY FLOWRATE BINARY 
FORM (0 TO 187 
5 BINARY FOR 0 TO 500 UL/MIN) 
0479 
AE47 850 MOV R6,FLOW --BIN+1 
047B 
8004 851 SJMP DIV --NORM 
047D 
AD5F 852 DIVOTHER: MOV R5,FLOW --BIN --CAL ;IF CALIBRATED, USE 
THIS # 
047F 
AE60 853 MOV R6,FLOW --BIN --CAL+1 
0481 
7F00 854 DIV --NORM: MOV R7,#00H 
0483 
B1E8 855 ACALL 
BINMUL 
0485 
AA23 856 MOV R2,23H ;ADD 50 FOR DIVISION ROUNDING 
0487 
AB24 857 MOV R3,24H 
0459 
AC25 858 MOV R4,25H 
048B 
7D32 859 MOV R5,# 50 
048D 
7B00 860 MOV R6,#00 
048P 
7F00 861 MOV R7,#00 
0491 
B1C1 862 ACALL 
BINADD 
0493 
AA20 863 MOV R2,20H ;DIVIDE BY 100 
0495 
AB21 864 MOV R3,21H 
0497 
AC22 865 MOV R4,22H 
0499 
7D64 866 MOV R5,#064H 
049B 
7E00 867 MOV R6,#00H 
049D 
7F00 868 MOV R7,#00H 
049F 
D1AD 869 ACALL 
BINDIV 
04A1 
AA20 870 MOV R2,20H 
04A3 
AB21 871 MOV R3,21H 
04A5 
AC22 872 MOV R4,22H 
04A7 
AD59 873 MOV R5,DAC --ADJUST1 
04A9 
AE5A 874 MOV R6,DAC --ADJUST1+1 
04AB 
7F00 875 MOV R7,#00H 
04AD 
B1E8 876 ACALL 
BINMUL ;MULTIPLY OLD BY CURRENT# 
04AF 
7F00 877 MOV R7,#00H 
04B1 
AA23 878 MOV R2,23H 
04B3 
AB24 879 MOV R3,24H 
04B5 
AC25 880 MOV R4,25H 
04B7 
7D00 881 MOV R5,#00H 
04B9 
7E05 882 MOV R6,#05H 
04BB 
7F00 883 MOV R7,#00H 
04BD 
B1C1 884 ACALL 
BINADD ;ADD 1280 FOR ROUNDING 
04BF 
AA20 885 MOV R2,20H ;DIVIDE BY 2560 BY MOVING OVER 
04C1 
AB21 886 MOV R3,21H ;ONE BYTE WHEN STORING 
04C3 
AC22 887 MOV R4,22H 
04C5 
7D00 888 MOV R5,#00H 
04C7 
7E0A 889 MOV R6,#0AH 
04C9 
7F00 890 MOV R7,#00H 
04CB 
D1AD 891 ACALL 
BINDIV 
04CD 
AA20 892 MOV R2,20H 
04CF 
AB21 893 MOV R3,21H 
04D1 
AC22 894 MOV R4,22H 
04D3 
900300 
895 MOV DPTR,#DAC --OLD 
04D6 
E559 896 MOV A,DAC --ADJUST1 
04D8 
F0 897 MOVX @DPTR,A 
04D9 
A3 898 INC DPTR 
04DA 
E55A 899 MOV A,DAC --ADJUST1+1 
04DC 
F0 900 MOVX @DPTR,A 
04DD 
AD59 901 MOV R5,DAC --ADJUST1 
04DF 
AE5A 902 MOV R6,DAC --ADJUST1+1 
04E1 
8A59 903 MOV DAC --ADJUST1,R2 
;MOV NEW IN DAC --ADJUST 
04E3 
8B5A 904 MOV DAC --ADJUST1+1,R3 
04E5 
B1D4 905 ACALL 
BINSUB ;SUBT NEW FROM OLD 
04E7 
4069 906 JC BEELOW ;CARRY THEN ADJUST IS BELOW REF 
04E9 
7A75 907 MOV R2,#75H ;USE 102+885/FLOW --BIN AS 
LIMIT 
04EB 
7B03 908 MOV R3,#03H 
04ED 
7C00 909 MOV R4,#00 
04EF 
AD46 910 MOV R5,FLOW --BIN 
04F1 
AE47 911 MOV R6,FLOW --BIN+1 
04F3 
7F00 912 MOV R7,#00 
04F5 
1206AD 
913 LCALL 
BINDIV 
04F8 
AA20 914 MOV R2,20H 
04FA 
AB21 915 MOV R3,21H 
04FC 
AC22 916 MOV R4,22H 
04FE 
7D66 917 MOV R5,#102 
0500 
7E00 918 MOV R6,#00 
0502 
7F00 919 MOV R7,#00 
0504 
1205C1 
920 LCALL 
BINADD 
0507 
AD20 921 MOV R5,20H 
0509 
AE21 922 MOV R6,21H 
050B 
AF22 923 MOV R7,23H 
050D 
900300 
924 MOV DPTR,#DAC --OLD 
0510 
E0 925 MOVX A,@DPTR ;LOAD OLD NUMBER TO MAKE 2% LIM 
0511 
FA 926 MOV R2,A 
0512 
A3 927 INC DPTR 
0513 
E0 928 MOVX A,@DPTR 
0514 
FB 929 MOV R3,A 00H 
0515 
7C00 930 MOV R4,#00H 
0517 
1205E8 
931 LCALL 
BINMUL 
051A 
AA23 932 MOV R2,23H ;DIVIDE BY 100 
051C 
AB24 933 MOV R3,24H ;ADD 50 FIRST FOR ROUNDING 
051E 
AC25 934 MOV R4,25H 
0520 
7D32 935 MOV R5,#50 
0522 
7E00 936 MOV R6,#00H 
0524 
7F00 937 MOV R7,#00H 
0526 
B1C1 938 ACALL 
BINADD 
0528 
AA20 939 MOV R2,20H 
052A 
AB21 940 MOV R3,21H 
052C 
AC22 941 MOV R4,22H 
052E 
7D64 942 MOV R5,#100 
0530 
7E00 943 MOV R6,#00 
0532 
7F00 944 MOV R7,#00 
0534 
D1AD 945 ACALL 
BINDIV 
0536 
A820 946 MOV R0,20H ;STORE IN TWO PLACES 
0538 
A921 947 MOV R1,21H 
053A 
AA20 948 MOV R2,20H 
053C 
AB21 949 MOV R3,21H 
053B 
AC22 950 MOV R4,22H 
0540 
AD59 951 MOV R5,DAC --ADJUST1 
0542 
AE5A 952 MOV R6,DAC --ADJUST1+1 
0544 
7F00 953 MOV R7,#00H 
0546 
B1D4 954 ACALL 
BINSUB ;SUBSTRACT NEW FROM 2+% VALUE 
0548 
4002 955 JC TIMES --102 
;IF CARRY THEN USE 2+% VALUE 
054A 
806A 956 SJMP DACCY 
054C 
8859 957 TIMES --102: MOV DAC --ADJUST1,R0 
054B 
895A 958 MOV DAC --ADJUST1+1,R1 
;LOAD IN 2+% VAL 
0550 
8064 959 SJMP DACCY 
0552 
7A75 960 BEELOW: MOV R2,#75H 
0554 
7B03 961 MOV R3,#03H 
0556 
7C00 962 MOV R4,#00H 
0556 
AD46 963 MOV R5,FLOW --BIN 
055A 
AE47 964 MOV R6,FLOW --BIN+1 
055C 
7F00 965 MOV R7,#00H 
055E 
1206AD 
966 LCALL 
BINDIV 
0561 
AD20 967 MOV R5,20H 
0563 
AE21 968 MOV R6,21H 
0565 
AF22 969 MOV R7,22H 
0567 
7A62 970 MOV R2,#98 
0569 
7B00 971 MOV R3,#00H 
056B 
7C00 972 MOV R4,#00H 
056D 
1205D4 
973 LCALL 
BINSUB 
0570 
AD20 974 MOV R5,20H ;MULT BY 98-885/FLOW --BIN 
0572 
AB21 975 MOV R6,21H ;WILL DIVIDE BY 100 TO GET A 
0574 
7F00 976 MOV R7,#00H ;2+PERCENT LIMIT TO CHECK WITH 
0576 
900300 
977 MOV DPTR,#DAC --OLD 
0579 
E0 978 MOVX A,@DPTR 
057A 
FA 979 MOV R2,A 
057B 
A3 980 INC DPTR 
057C 
B0 981 MOVX A,@DPTR 
1750 
ADJUSTER: ;THIS SUBROUTINE PREES THE TIMER (8253) 
1751 ;FOR THE NEXT T OF THE CONTROL ALGORYTHM 
1752 
1753 
0B38 
7A40 1754 MOV R2,#40H ;WAIT 40,000 CYCLES BEFORE 
CHECK 
0B3A 
7B9C 1755 MOV R3,#90H ;EQUIVALENT TO .08 SEC 
0B3C 
DAFE 1756 
ZEROSA: DJNZ R2,ZEROSA 
0B3E 
DBFC 1757 DJNZ R3,ZEROSA 
0B40 
30B311 
1758 JNB R3,3,NOADJUST 
;IF STILL GATED, DISREGARD 
0B43 
C23A 1759 CLR GATED1 ;GATE INTERRUPT HAS BEEN 
HANDELED 
0B45 
20640C 
1760 JB PREP --HEAD,NOADJUST 
;NOADJUSTMENTS FOR 
PREP 
0B48 
307D09 
1761 JNB MICROL,NOADJUST 
;OR FOR HIGH FLOWS 
0B4B 
E531 1762 MOV A,FLOW --RATE+1 
0B4D 
B40502 
1763 CJNE A,#05H,CHK --FURTHER 
;ADJUSTS UP TO 499 UL/MIN 
0B50 
8002 1764 SJMP NOADJUST 
0B52 
4001 1765 
CHK --FURTHER JC OK 
0B54 
22 1766 
NOADJUST: RET 
0B55 
E531 1767 
OK: MOV A,FLOW --RATE+1 
;READJUST FOR NEXT 
UPDATES 
0B57 
B40103 
1768 CJNE A,#01H,IS --LOWER 
;IS IT LESS THAN 100UL 
0B5A 
020B5F 
1769 JMP NO --SET 
0B5D 
4004 1770 
IS --LOWER: JC SET --IT --HI ;IF IS, USE 100 PULSES 
0B5F 
C238 1771 
NO --SET: CLR A100 --PULSES 
0B61 
8010 1772 SJMP LOAD --300 
0B63 
D238 1773 
SET --IT --HI: 
SETB A100 --PULSES 
0B65 
1203D7 
1774 LCALL 
LOAD -- OTHER --COUNTS 
0B68 
1203CD 
1775 LCALL 
LOADEROF100 
0B6B 
900306 
1776 MOV DPTR,#NUMBER --OF --TIMES 
0B6E 
7400 1777 MOV A,#00H ;CLEAR THIS 
0B70 
F0 1778 MOVX @DPTR,A 
0B71 
800C 1779 SJMP SET --CLOCK --COUNT 
0B73 
1203D7 
1780 
LOAD --300: LCALL 
LOAD --OTHER --COUNTS 
0B76 
1203C3 
1781 LCALL 
LOADEROF300 
0B79 
900306 
1782 MOV DPTR,#NUMBER --OF --TIMES 
0B7C 
7400 1783 MOV A,#00H ; 
0B7E 
F0 1784 MOVX @DPTR,A 
0B7F 
D296 1785 
SET --CLOCK --COUNT: 
SETB P1.6 
0B81 
22 1786 RET 
1787 
; 
1788 
; 
1789 
; 
1790 
; 
1791 
; BRANCH ON KEYBOARD ENTRY 
1792 
; 
0B82 
12168E 
1793 
KEYBD: LCALL 
BOP 
0B85 
900801 
1794 MOV DPTR,#DISPLAY --CONTROL 
0B88 
7440 1795 MOV A,#40H ;READ KEYBOARD 
0B8A 
F0 1796 MOVX @DPTR,A 
0B8B 
A3 1797 INC DPTR 
0B8C 
EO 1798 MOVX A,@DPTR 
0B8D 
23 1799 RL A 
0B8E 
547E 1800 ANL A,#01111110B 
;MASK ACTIVE KEYS 
0B90 
F8 1801 MOV R0,A ;SAVE COPY 
0B91 
900B9D 
1802 MOV DPTR,#ADTABLE 
0B94 
04 1803 INC A 
0B95 
93 1804 MOVC A,@A+DPTR ;CREATE RETURN ADDRESS 
057D 
FB 982 MOV R3,A 
057E 
7C00 983 MOV R4,#00H 
0580 
B1E8 984 ACALL 
BINMUL 
0582 
AA23 985 MOV R2,23H ;DIVIDE BY 100 
0584 
AB24 986 MOV R3,24H ;ADD 50 FIRST FOR ROUNDING 
0586 
AC25 987 MOV R4,25H 
0588 
7D32 988 MOV R5,#50 
058A 
7E00 989 MOV R6,#00H 
058C 
7F00 990 MOV R7,#00 
058E 
B1C1 991 ACALL 
BINADD 
0590 
AA20 992 MOV R2,20H 
0592 
AB21 993 MOV R3,21H 
0594 
AC22 994 MOV R4,22H 
0596 
7D64 995 MOV R5,#100 
0598 
7E00 996 MOV R6,#00 
059A 
7F00 997 MOV R7,#00 
059C 
D1AD 998 ACALL 
BINDIV 
059E 
A820 999 MOV R0,20H ;STORE IN TOW PLACES 
05A0 
A921 1000 MOV R1,21H 
05A2 
AA20 1001 MOV R2,20H 
05A4 
AB21 1002 MOV R3,21H 
05A6 
AC22 1003 MOV R4,22H 
05A8 
AD59 
1004 MOV R5,DAC --ADJUST1 
05AA 
AE5A 1005 MOV R6,DAC --ADJUST1+1 
05AC 
7F00 1006 MOV R7,#00H 
05AE 
B1D4 1007 ACALL 
BINSUB ;SUBSTRACT NEW FROM 2% VALUE 
05B0 
4004 1008 JC DACCY ;IF CARRY THEN USE OLD VALUE 
05B2 
8859 1009 MOV DAC --ADJUST1,R0 
05B4 
895A 1010 MOV DAC --ADJUST1+1,R1 
05B6 
7959 1011 
DACCY: MOV R1,#DAC --ADJUST1 
05B8 
901000 
1012 MOV DPTR,#ANALOG --LO 
05BB 
1214DC 
1013 LCALL 
DAC5 
05BE 
D0D0 1014 
CLEAR OUT: POP PSW ;RETURN RBANK SELECTS 
05C0 
22 1015 RET ;RETURN TO INT HANDLE 
1016 ;OR TO CALLING SUBROUTINE 
1017 ;IF NOT AN ACTUAL INTERRUPT 
1018 
1019 
1020 
1021 
; 
1022 
; 
1023 
;********** BINARY NUMBER MATH ROUTINES ********** 
1024 
; 
1025 
;W+X=Y W-X=Y W/X=YZ W*X=YZ 
1026 
; 
1027 
; 
05C1 
E51A 1028 
BINADD: 
MOV A,01AH 
05C3 
251D 1029 ADD A,01DH 
05C5 
F520 1030 MOV 20H,A 
05C7 
E51B 1031 MOV A,1BH 
05C9 
351E 1032 ADDC A,1EH 
05CB 
F521 1033 MOV 21H,A 
05CD 
E51C 1034 MOV A,1CH 
05CF 
351F 1035 ADDC A,1FH 
05D1 
F522 1036 MOV 22H,A 
__________________________________________________________________________ 
In addition to a source which may be adjusted by a potentiometer and the 
use of a computer as is done in the preferred embodiment, a hardward 
circuit may be used as shown in FIG. 1 in which a keyboard 1002 initiates 
clock pulses from a source 1004 and a value into the updating circuit 
1006. A source of pulses from the tachometer is applied through conductor 
400 to the updating circuit and the number of tachometer pulses in one 
cycle of the pump are counted sequentially and compared with an idealized 
number, with the current course being increased if the number lags so that 
the computer averages the amount of flow across a cycle of the pump to 
maintain a constant average flow rate by admusting the current source in 
addition to the other adjustments hereinbefore described. 
To monitor the tachometer pulses, the updating circuit includes first and 
second counters 1010 and 1012, first and second digital-to-analog 
converters 1014 and 1016 and a comparator 1018. The counter 1010 has 
counted into it from the clock 1004 the clock pulses in a cycle of the 
pump before being reset and the clock rate is set to equal the number of 
tachometer pulses which should be received in one pump cycle. The counter 
1012 is reset by the same pulse that resets the counter 1010 but counts 
the tachometer pulses as they actually occur. Digital-to-analog converter 
1014 generates an analog voltage equivalent to the counts in counter 1010 
and digital-to-analog converter 1016 generates an analog signal equivalent 
to the counts of counter 1012. The comparator 1018 compares the analog 
outputs from the digital-to-analog converters 1014 and 1016 and adjusts 
the current source 1003 with the signal so as to maintain a signal on 
conductor 46 which will compensate for deviations of flow from the pump 
from cycle to cycle. 
Before operating the pump, it is calibrated to avoid cavitation while the 
motor accelerates from the start of a refill cycle to pull fluid into the 
pump until a predetermined period of time has elapsed from the start of 
the acceleration. This is accomplished by adjusting potentiometers 916 and 
912 (FIG. 29), 514 (FIG. 15) and 857 (FIG. 27) while pumping water and 
monitoring the pressure output from stroke to stroke to detect cavitation. 
The values, which affect the acceleration, when properly set reduce the 
cavitation and variation in flow rate with pressure variations and may be 
maintained for maximum operation of the pump. 
Once the pump is calibrated, it is operated by setting a flow rate, priming 
the pump, filling its cylinder and expelling fluid. In expelling the 
fluid, near an end portion of the stroke, the pump is run at a constant 
speed until it reaches the end of the expulsion stroke, at which time a 
refill signal is generated and the piston begins a refill stroke in a 
return direction. When it reaches a start of the refill stroke, the pump 
motor begins to accelerate at the controlled rate and continues to 
accelerate for a predetermined amount of time related to the operating 
conditions, at which time it slows to the preset rate for constant flow. 
In setting a flow rate in the preferred embodiment, the flow rate is keyed 
into the keyboard and a software circuit retains it, generating a set 
point signal for application to an analog voltage generator of a 
conventional type. The analog set point signal controls the flow rate. 
The preset flow rate is compared with tachometer pulses generated during 
the forward stroke of the piston of the pump and, if the average pumping 
rate is below that preset, the voltage on conductor 46 is increased. 
Although a computer is used for this function in the preferred embodiment, 
it can be accomplished by a hardware circuit such as that shown in FIG. 31 
in which a count representing an ideal tachometer rate is set into a 
counter 1010 (FIG. 31) and converted to a digital-to-analog signal in the 
digital-to-analog converter 1014. The tachometer pulses as they are 
counted on conductor 400 are also converted to an analog signal in 
digital-to-analog converter 1016 and the analog signals are compared to 
adjust the current source so that a basic linear feedback circuit related 
to liquid influent flow into the chromatographic column and injector 
system 18 (FIG. 1) is provided. 
Of course, the current for conductor 46 may be set by a simple source of 
potential and variable resistor or by any other technique in which a 
current directly proportional to the flow rate is provided. This current 
will, in general, control through a linear circuit the flow rate 
regardless of how it is obtained and exert a tendency to maintain it 
constant as influent to the chromatographic column. 
During a refill cycle and the first part of the cycle forcing fluid out of 
the pump, the motor 50 (FIG. 3) receives a signal from the nonlinear flow 
rate control circuit 42 (FIG. 2 and 9) having a time duration controlled 
by a timer and initiated at a point during the refill cycle and continuing 
for a time thereafter related to rate of flow which has been set for flow 
into the chromatographic column. The time of acceleration is related to 
the charge on capacitor 150 (FIG. 5) which is modulated by transistor 716 
(FIG. 23) in response partly to the signal on conductor 46 (FIG. 23) from 
the set point value. The amount of acceleration is related to the closed 
loop servo signal which was last driving the pump, that value being 
obtained by a sample and hold circuit electrically connected to the output 
of the servo amplifier to store the signal during the last part of a 
pumping cycle when the pump is pumping at a constant rate under closed 
loop control of a motor speed rotation signal. The sample and hold 
amplifier circuit (FIGS. 26 and 28) stores a signal on a capacitor 900 and 
892 (FIG. 28). The rate of acceleration is adjusted by offset and 
multiplication values during calibration by adjusting potentiometers 916 
and 912. The signal from potentiometer 912 is applied as a closed loop 
control signal to the amplifier 580 (FIG. 17) in which the feedback signal 
has been closed by analog switch 914 and the amplifier 910. 
With this arrangement, the pump is maintained during a portion of a pumping 
cycle at a constant speed under a tachometer feedback circuit using analog 
circuitry and a digital control which adusts the constant current control 
for the flow rate. During the refill cycle, the motor is accelerated 
continuously while the piston is controlled by a cam to accelerate and 
decelerate to zero and then accelerate again, with the motor acceleration 
terminating at a time controlled by a timer to reduce pulsations in flow 
to a minimum. 
From the above description, it can be understood that the pump of this 
invention has several advantages, such as: (1) the time during which no 
liquid is pumped through the outlet port is low; (2) the pump is 
relatively uncomplicated because the acceleration time of the motor is 
time-limited rather than distance limited; (3) the pump is able to 
accomodate a wider range of flow rates without cavitation; (4) the pump 
maintains an accelerating velocity during the return portion while 
refilling coming to a stop at the end and accelerating upwardly under 
constant positive driving of a motor through a cam, with the motor 
receiving a continuous accelerating voltage so as to reduce noise which 
might otherwise be caused by inertial effects as the motor speed is 
changed; (5) the average flow rate is continuously monitored and adjusted 
by adjusting a current input signal representing the preset flow rate of 
fluid; and (6) the flow rate remains constant as pressure varies. 
Although a preferred embodiment of the invention has been described with 
some particularity, many modifications and variations are possible in the 
preferred embodiment without deviating from the invention. Therefore, it 
is to be understood that, with the scope of appended claims, the invention 
may be practiced other than as specifically described.