Abstract:
A microprocessor controlled distillation analyzer for petroleum products performs, computes, displays and records distillation data. An interactive/keyboard display and printer system reports and records test conditions and prompts user inputs to define test parameters. Before the initial boiling point, the heater is automatically controlled in two time intervals. Following the initial boiling point, the heater is controlled to keep the monitored distillation rate within a predetermined range. Upon attaining an automatically calculated volume of distillate, the final heat is incremented to a programmed level. In one mode, the end point is automatically detected by monitoring vapor temperature for a decline, followed by the cessation of meniscus movement to terminate the test. After measuring the residue, the analyzer automatically recomputes temperatures at a series of percentage volumes of evaporated sample. An IR beam meniscus detector is driven by a stepping motor screw-drive mechanism actuated via the microcomputer to find the initial meniscus position and track the rising meniscus. The vapor temperature sensor emergent stem error is compensated for by a platinum resistive element with opposite nonlinearity. Thermometer-like temperature lag is created by software.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates generally to distillation rate analysis and more particularly to automatic distillation analyzers for liquid hydrocarbons. 
     Over the years petroleum engineers have developed standards for commercial grade petroleum products. These standards are used by refineries in quality control to adjust process variables so that the resulting product more closely meets the prescribed standards. Wholesale purchasers of petroleum products such as gasoline and No. 2 fuel oil require the fuels they buy to meet these standards and manufacturers who design and build equipment which burns or otherwise uses these fuels and solvents rely on these standards. 
     Distillation profiles yield one of the major distinguishing features of motor gasolines, aviation gasolines, aviation turbine fuels, special boiling point spirits, naphthas, benzene, toluene, diesel fuel, white spirits, kerosenes, gas oils, distillate fuel oils, and similar petroleum products. For example, when gasoline is heated even slightly, the collected vapor can be condensed in an ice bath. Unlike water, for example, gasoline contains a diversified population of hydrocarbon molecules with different boiling points. Thus, in order to boil away or distill an entire sample of gasoline, the heat must be continually adjusted upwards and if one were to sense the vapor temperature above the boiling gasoline, it would reveal a characteristic increasing profile with respect to the evaporated percentage of the sample. 
     The test method for this type of distillation analysis has been prescribed by the American Society for Testing Materials (ASTM). Test designation D86, for example, prescribes a technique of performing laboratory distillation tests on gasoline. According to this test procedure, for example, a standard 125 millileter (ml) distillation flask with a 100 ml charge of gasoline are held to a beginning temperature between 55° and 65° F. The condenser bath must be 32° to 34° F. and the graduated cylinder or &#34;graduate&#34; for receiving the distillate must be between 55° and 65° throughout the test. The time from the first application of heat to the initial boiling point, i.e., first drop of distillate, must be between 5 and 10 minutes. The time from the initial boiling point to 5% (5 ml) recovered must be between 60 and 75 seconds. The uniform average rate of condensation from 5% recovered to 5 ml of the residue left in the flask must be 4 to 5 ml per minute (ml/min) and the time from the 5 ml residue to the end point must be in the range of 3 to 5 minutes. Vapor temperatures are read and recorded at the initial boiling point 5% recovered, 10% recovered and every 10 ml to 90% recovered, then 95% and at the end point (max. temp.). The percent recovered and residue are measured and recorded and percent loss is computed. The percent recovered is corrected to the prescribed percent evaporated by subtracting the loss percentage from the percent recovered. The thermometer reading at the prescribed evaporated percentages must then be determined and corrected for barometric pressure to represent the comparable reading at 760 millimeters (mm) pressure. 
     Because of the precise distillation rates required, this delicate procedure requires highly skilled laboratory technicians. Instrumentation has been developed which automatically adjusts the distillation flask heater in an attempt to stay within the prescribed distillation rate range. A travelling optical meniscus detector has been used before in this kind of apparatus to follow the liquid level in the receiving graduate. XY plotting strip chart recorders have been used to automatically record vapor pressure as the meniscus detector rises. These charts in and of themselves, however, do not yield the prescribed data without the barometric residue, and loss computations. Consequently, the temperature data must be read from the chart and recorded elsewhere for the prescribed evaporated percentages. This cumbersome recording process also applies to the time intervals for initial boiling point, 5% recovered and time from 5 ml residue to end point. 
     Even the automated D86 test for gasoline takes well over a half hour for each 100 ml sample not including whatever time is required for recomputation and recording of the variable parameters. Many of these instruments are installed at refineries where a variety of petroleum products are continuously produced. Thus, the plant engineers eagerly await the test results which may indicate that a process variable must be adjusted. In the meantime, unsaleable product may be produced. Accordingly, test errors or test results which must be scrapped because of erroneous procedure or recording techniques are very serious. Since the distillation rate test and recording requirements are complex, operator errors in the past have been frequent. Operators, being human, misrecord the sample identification number, neglect t precool the temperature sensor, forget to monitor or record the time from the initial boiling point to the 5% recovered mark, allow the condenser bath temperature to deviate from the norm during the test or fail to properly correct for loss in barometric pressure, etc. 
     To compound these difficulties, in prior instrumentation means for making the temperature sensor readings duplicate those of a laboratory thermometer standard have been lacking in accuracy. Moreover, the meniscus detector mechanism has heretofore been less precise than desired. 
     SUMMARY OF THE INVENTION 
     Accordingly, the general object of the invention is to simplify the task of automatic distillation analysis by programming the test parameters and automatically recording data in a manner that minimizes the need for operator interaction thus increasing the uniformity and accuracy of the test procedure. 
     These and other objects of the invention are achieved in a microprocessor controlled distillation analyzer for petroleum products which performs, computes, displays and records distillation rate data with automated precision. An interactive/keyboard display reports and records beginning test conditions and prompts user inputs to define desired parameters in accordance with laboratory standards. The control system implements three phases of distillation flask heater control. Heating before the initial boiling point is automatically controlled to specified wattage in two steps. Following the initial boiling point, the heater is controlled to keep the monitored distillation rate within a predetermined range. Following accumulation of a precalculated volume, the final heat is incremented to a programmed level. In one mode, the end point is automatically detected by software controlled monitoring the vapor temperature for a decline. Following measurement of the residue, the analyzer automatically recomputes vapor temperatures at a predetermined series of percentage volumes of evaporated sample. The microprocessor sounds an alarm to signal the approach of the end of the test requiring manual measurement of the flask residue or notification of the dry point. An infrared LED and photodiode actuated meniscus detector is driven by a stepping motor screw-drive mechanism actuated in fast, slow, up and down modes via the microcomputer to find and lock on the initial meniscus position and track the rising meniscus in the leading mode. 
     Vapor temperature is automatically corrected. The temperature lag characteristic of the laboratory thermometer standard is created by software. Internal diagnostic and timing mechanisms in software automatically abort the test under certain circumstances. Several normal test determination options are also available. Before the test begins, the operator can select test termination at a prescribed temperature, percent recovered, end point or dry point. However, the system is designed to preselect end point mode unless otherwise advised. Since the same station may perform repeated tests on the same product, a desirable feature of the system is that the entered test parameters during normal operation remain fixed until changed so that repeated tests can be made without &#34;reprogramming&#34; the instrument. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a pictorial front perspective view in elevation showing the exterior features of a preferred embodiment of the automatic distillation apparatus according to the invention. 
     FIG. 2 is a similar view of the apparatus of FIG. 1 with the doors and access panels open. 
     FIG. 3 is a detail front view in elevation of the receiving chamber mechanism assembly of the apparatus of FIG. 2. 
     FIG. 4 is a side view in elevation of the assembly of FIG. 3. 
     FIG. 5 is a top view of the assembly of FIG. 3 showing the stepper motor and graduate tilt solenoid. 
     FIGS. 6A, 6B, 6C and 6D are detail views of portions of the apparatus of FIGS. 3 and 5 taken along lines A--A, B--B C--C and D--D, respectively. 
     FIG. 7 is a schematic flow diagram of the condenser liquid illustrating the condenser bath and the cooling system for the distillate receiving chamber. 
     FIG. 8 is a system functional block diagram. 
     FIG. 9 is a graph illustrating an idealized representative curve of gasoline vapor temperature versus distillate volume as a percentage of the original sample volume. 
     FIG. 10 is a block diagram of the electronics for the microprocessor based control system of FIG. 8. 
     FIG. 11 is a front view of the keyboard/display panel of the apparatus of FIG. 1. 
     FIG. 12 is a perspective view of the electronics drawer with plural edge connected printed circuit boards carrying the electronics of FIG. 10. 
     FIG. 13 is a schematic diagram of the mother printed circuit board (backplane connector) of FIG. 12. 
     FIG. 14 is a schematic diagram of the CPU system of FIG. 10. 
     FIG. 15 is an electrical schematic diagram of the drop and meniscus detectors. 
     FIG. 16 is an electrical schematic diagram of the upper and lower meniscus detector limit switches and receivfng chamber door switch circuits. 
     FIG. 17 is a schematic diagram of a digital I/O circuit of FIG. 10. 
     FIG. 18A is a schematic diagram of the LED display driver and LED character display of the keyboard/display circuit of FIG. 10. 
     FIG. 18B is a schematic diagram of the keyboard and LED indicator lights of the keyboard/display circuit of FIGS. 10 and 11. 
     FIG. 19 is a schematic diagram of the analog I/O circuit of FIG. 10. 
     FIG. 20 is a schematic diagram of the AC I/O circuit of FIG. 10. 
     FIG. 21 is a pictorial representation of a typical printout. 
    
    
     This application also includes and incorporates by reference Appendices I and II filed with the original application. Appendix I is an annotated assembler listing of software instructions resident in the programmable read only memory of the CPU system of FIG. 14 in hexadecimal (&#34;HEX&#34;) digits (i.e., base 16) as well as in assembly language of the instruction repertoire for the Intel MCS85 microcomputer system (8085 CPU). Appendix II is a ROM table in HEX code. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The system described below was designed and constructed according to the invention to perform distillation tests according to the prescribed test methods in ASTM standards D86 Groups I-IV, for gasoline, diesel fuel, fuel oil and kerosene, for example, test D850 for benzene, for example, and D1078 for toluene, and equivalent European standards. The self-contained line-operated unit of FIGS. 1 and 2 is designed to be laboratory bench mounted at a suitable site at a petroleum refinery, for example. A typical refinery might have several of these units installed at different locations on the premises. A single free standing cabinet 10 houses all of the electronic and mechanical components of the distillation analyzer. A detailed description of the condenser bath and refrigeration package is omitted as these elements are conventional except as otherwise indicated below. The uppermost portion of the cabinet 10 houses a specially designed optional refrigeration package 12 (not shown) to accurately maintain the subambient condenser and distillate chamber temperatures without additional space requirements. However, coolant available from an external source can be substituted. The front panel of the unit is equipped with a keyboard/display panel 13 having a 16 character alphanumeric LED display 14 associated with a parameter programming key pad 16. Below the key pad 16 are a series of five buttons 18 and respective LED indicator lights 20 designating the type of ASTM test procedure chosen by the operator. One of the indicators 20 above the respective test button remains lighted during the test. At the bottom of the keyboard/display panel 13, a series of three distillation rate buttons 22 and associated indicator lights 24 are provided for nominal distillation rates of 4.5,6 and 9 ml/min. Adjacent to the rate buttons are a start button 26 and a dry point button 28. Directly above the start and dry point buttons are a pair of indicator lights 30 and 32 labelled &#34;meniscus&#34; and &#34;recovery&#34;. Directly above the keyboard/display panel 13 is a solid state self-contained printer module 34 (TELPAR, INC MODEL PL-20E) capable of printing lines up to 20 alphanumeric characters on printing tape 36. A single roll of printer tape has a typical capacity of up to 300 tests. 
     At the upper right hand portion of the front of the cabinet 10 are a series of five &#34;set point&#34; switches 38 with mechanical indicators for establishing the nominal range for the liquid in the condenser bath. Above the set point switches 38 is a numerical LED display 40 indicating the actual temperature of the condenser bath. LED indicators 42 and 44 indicate temperature control of the condenser and receiving chamber. 
     A sealed distillation flask compartment 46 with a tempered glass door 48 houses the standard side arm distillation flask 50. Flask 50 is supported by a distillation board 52 mounted on an elevation jack to adjust the height of the flask by means of knob 54, which, along with ON/OFF power switch 56, protrudes through the AC circuitry access door 58 below the distillation compartment, which is equipped with air jets for rapid cooldown. An elongated resistive temperature detector (RTD) 60 extends through a stopper 62 in the top opening in the neck of the flask 50. The RTD stem 64 extending above the stopper 62 is connected to the RTD electrical lead 66. In FIG. 1, the flask 50 and RTD 60 are shown as they would appear during a test. Before the test procedure begins, the RTD 60 is removed from the flask 50 and the end of the RTD 60 is inserted, with the lead and stopper attached to it, into RTD cooling port 68 which has an exterior opening above and extending into the distillate receiving chamber 70, as shown in FIG. 2. When in operation, chamber 70 is sealed by retractable door 72 which slides into a pocket between the chamber 70 and the panel 13 for access. A removable graduated cylinder or graduate 74 is placed inside the receiving chamber 70 with its opened upper end beneath the exiting lower end 76 of the conventional polished U-tube (not shown) which leads from the side arm of the standard flask 50 through the condenser bath (not shown) into the receiving chamber 70. The liquid distillate condensed from the petroleum product vapors drips from the end 76 to the U-tube into the graduate 74, as diagrammed in FIG. 8. 
     The receiving chamber mechanism shown pictorially in FIG. 2 and in detail isometric views in FIGS. 3-6D monitors the accumulation of distillate in the graduate 74 during a distillation test. 
     The receiving chamber mechanism assembly 80 shown in FIGS. 3 and 4 includes flat rectangular parallel plates 82 and 84, respectively affixed to opposite ends of parallel right and left guide rods 86 and 88 as viewed from the front of the unit. The graduate 74 stands on a central pedestal on the bottom plate 84. A drive screw 90 extends parallel to the guide rods 86 and 88 in the receiving chamber 70. The lower end of the drive screw 90 is journalled in the lower plate 84. The upper end of screw 90 is coupled to stepper motor 92 mounted on top of the upper plate 82. A parallel angle bracket 94 at the front left of the receiving chamber 70 is affixed at its upper and lower ends to the upper and lower plates 82 and 84 and extends parallel to the guide rods 86 and 88. 
     A drop detector 96 shown in more detail in FIG. 6A includes a generally U-shaped frame 98 affixed by means of set screws to the guide rods 86 and 88 as well as to the angle bracket 94. As shown in FIGS. 3 and 4 elongated bushings 86a and 88a received over the upper ends of the guide rods are used as an aide in defining the height of the drop detector 96. Frame 98 carries an infrared light source 100 and a phototransistor 102 spaced from and horizontally aligned with the infrared light source 100 such that the center line between the light source and phototransistor passes approximately through the center of the graduate. The infrared beam is momentarily interrupted by the first drop of distillate 104. 
     The graduate tilt collar 106 arranged to be horizontally disposed around the graduate 74 with sufficient clearance for installing the graduate, is affixed to the lower end of drive shaft 108 journalled through the upper plate 82. The upper end of drive shaft 108 extends above the top plate 82 and is connected through the link 110 to a graduate tilt solenoid 112 mounted on top of the upper plate 82. Actuation of the solenoid 112 results in pivoting of the drive shaft 100 about its axis by several degrees to tilt the graduate 74 after detection of the first drop so that subsequent drops of distillate run down the inside of the graduate instead of splashing on the meniscus. 
     The meniscus detector 114 shown in more detail in FIG. 6B includes a generally U-shaped carriage 116 slidably mounted on the guide rods 86 and 88 for vertical translation. Screw 90 is drivingly engaged by sleeve gear 118 journalled in the carriage 116. The carriage carries an IR light source 120 and a phototransistor assembly 122 horizontally aligned and spaced from the IR light source 120. The phototransistor itself is aligned behind a horizontal slit 122A formed transversely across the center line of the light beam. The center line of the meniscus detector light beam is at right angles with respect to the center line of the drop detector. A coiled cable 124 carrying the leads from the light source 120 and phototransistor 122 is carried on spindle 126 parallel to the drive screw 90 affixed to the carriage 116. The meniscus detector 114 is designed to travel between the bottom plate 84 and the drop detector 96. The excursion limits are defined by upper limit switch 128 connected to the angle bracket 94 at the location of the drop detector and lower limit switch 130 mounted on the bottom plate 84. 
     The top plate 82 also supports an electrical connector assembly 132 to which the cable 124 is connected. The apertured RTD cooling well 134 is angled through the upper plate 82 into the interior of the receiving chamber 70. The RTD sensor 60 is inserted into the well 134 via cooling port 68 such that the distal end of the RTD sensor is housed in the apertured lower end of the cooling well 134 as shown in FIGS. 3 and 4. A U-shaped bracket 136 is bolted below the front edge of the top plate 82 and carries a magnetic door closer 138 and a door limit switch 140 which signals when the door is open. 
     As shown in FIGS. 2 and 7, the back wall 70A of the receiving chamber 70 has a lower circular air supply vent 142 and an upper circular air exhaust vent 144. Fan 146 located in the air supply vent 142 draws air through the exhaust vent 144 via duct 148 through a heat exchanger 150 supplied with coolant from the condenser bath 152. A recirculating liquid pump 154 circulates a condenser bath liquid, typically water with antifreeze added to it, via a thermostatically controlled coolant solenoid valve 156. The door switch 140 (FIGS. 2 and 4) is connected to energize fan 146 when the receiving chamber door is closed as in FIG. 1. The desired temperature is maintained by controlling the flow of coolant through the heat exchanger with the solenoid valve 156. 
     FIG. 8 provides a functional overview of the operation of the automatic distillation analyzer according to the invention. The removable distillation flask 50 is heated by means of 1000 watts low mass plug-in electrical heating element 160 located beneath the distillation board 52 of FIG. 1. The side arm 50a extends through a snugly fitting stopper into conventional polished U-tube 162 which passes downward through the condenser bath 152. The bath is thermostatically controlled to within a degree of 33° F. by means of refrigeration and heating coils (not shown). 
     A microprocessor based control system 164 with associated display, printer and keyboard electronics receives inputs from the various sensors including the RTD sensor 60, drop detector 96 and meniscus detector 114. The control system enters and displays parameters and test data and actuates the various mechanical and temperature control devices such as the graduate tilt solenoid 112 and stepper motor 92. The organization of the electronics for the control system 164 is shown in FIG. 10. Software instructions are carried out by a central processing unit (CPU) system 166 based on the Intel 8085 single chip microprocessor and 12 kilobyte electronically programmable read only memories (EPROM). The functional blocks of FIG. 10 are organized to correspond one-for-one with printed circuit boards (PCB&#39;s ) of the same description in the Figures indicated in the boxes of FIG. 10. By means of a multiplexed data bus and address bus system, the CPU board 166 controls and receives inputs from a keyboard and display PCB 168 and a digital I/O PCB 170 which serves to interface the computer with an analog I/O PCB 172 and an AC I/O PCB 174. As indicated in FIG. 10, the prioritized interrupt request system characteristic of the 8085 microprocessor is employed as the input mechanism for the meniscus and drop detectors as well as for an independent timer contained in the digital I/O circuit. The I/O circuit itself receives digital signals from the drop and meniscus detectors as well as the upper and lower limit switches and the door switch. The I/O circuit also provides outputs in ASCII code to solid state tape printer 34. Digital control signals from the digital I/O circuit 170 based on instructions from the CPU 166 control the stepper motor 92 and tilt solenoid 112. Heating power is controlled from the digital I/O PCB 170 via the AC I/O PCB 174 along with the audible alarm and fan 146. The analog I/O PCB 172 is used primarily to multiplex analog variables to a single analog to digital converter in the digital I/O PCB 170. 
     As shown in FIG. 12, the PCB&#39;s 168, 170, 172 and 174 are conveniently mounted on a so called mother board 176 or backplane connector mounted in a slide-out drawer, the front of which comprises the keyboard/display panel 13. The keyboard/display PCB 166 is connected to the back of the display panel 13. 
     The edge connector terminal assignments of the mother board 176 are disclosed in FIG. 13. Edge connector 176a mates with the edge connector on the CPU PCB 168. The edge connector 176b is designed to mate with an optional computer interface board (not shown) known to the trade as an RS 232 IO in order to transmit data directly to the user&#39;s computer system. Edge connector 176c is designed to receive an optional XY plotter or recorder (not shown) for providing a stripchart graph of vapor temperature versus recovered volume. The digital I/O PCB 170 is received in edge connector 176d and the analog and AC control I/O boards 172 and 174 are received in edge connectors 176e and f of the mother board 176, respectively. 
     As shown in FIG. 14, the CPU circuit 166 includes a single chip 8 bit N channel microprocessor, namely, Intel 8085A using a multiplexed data bus system. The CPU 8085A is driven by a 5.185 MHz crystal clock. The INTR trap and hold inputs are grounded as shown. Random access memory IC209, 210, 216 and 217 is selected by way of the dual decoder IC218. The address is split between the 8 bit address bus and the 8 bit data bus. The read only memory comprises six 2K EPROMs IC201-IC206. The model numbers given directly below the IC numbers represent a standard commercially available part number for this type of circuit. Instructions are obtained from the PROMs via IC212, an 8 bit latch and IC211. IC&#39;s 209, 210, 216 and 217 are I/O decoders selected by dual decoder IC218. The address bus requires 12 bfts (A0-A11) to accommodate 12K of ROM. The twelve address lines are inverted in hex inverters IC207 and 208 and passed to the digital I/O board along with the data bus which is split by means of quad latches IC213 and IC220. The drop and meniscus detector circuits of FIG. 15 are physically located on the digital I/O board 170. The drop detector produces a square pulse output to interrupt request RST5.5 of the CPU whenever the first drop breaks the light beam sufficiently to trip the Schmitt trigger IC601. Similarly, the meniscus detector circuit of FIG. 15 as shown is designed to emit a pulse to the interrupt request RST6.5 of the CPu whenever the meniscus interrupts with the light beam. 
     The limit switch circuit of FIG. 16 is also located on the digital I/O board. With the sole exception of the door switch 140, the detectors and switches in FIGS. 15 and 16 also produce output signals to IC609 of FIG. 17, one of six 8 bit latches IC605, 609 and IC612. The remainder of the digital I/O PCB 170, as shown in FIG. 17 comprises additional interface equipment. The 8 bit latches are addressed or enabled by means of three dual decoders IC613, 614 and 615. The latches in turn perform various input or output functions. For example, IC605 signals the alarm, energizes the graduate tilt solenoid 112 and actuates the step motor 92 in either direction. Latch IC606 produces the multiplexer control signals necessary for the analog I/O circuit. IC607 generates the control and code signals for operating the printer 34. The other latches 608, 609, and 612 are input devices. In particular, IC608, only 1 bit of which is used, signals the low condenser level. IC609 provides the condition of the limit switches and drop in meniscus detector inputs. Finally, latch IC613 places the parallel digital outputs of either analog to digital A/D converter IC610 or IC611 on the data bus. A/D converter IC610 converts watts, chamber temperature and condenser temperature analog readings to digital values. IC611 converts the RTD vapor sensor reading and the barometer reading to digital values. 162 kHz clock signals are provided by binary counter IC620 which is connected to receive the 2.5925 MHz clock signal from the CPU board. Programmable interval timers IC616 and IC617 are arranged to place time out signals on the data bus on command. IC616 is closed at 60 Hz or 50 Hz by means of a zero crossing signal from NAND gate IC604 while IC617 is clocked at two special rates as shown in FIG. 17 which are derived by dividing the system clock signal and counters 620 and 621. A specific timer signal generated by the output zero of interval timer IC617 creates the interrupt request RST7.5 for the CPU. The interval timer is also gated by the zero crossing signal via input gate ONE and the corresponding output number ONE produces the TRIAC control signal for the heater 160 (FIG. 8). 
     The keyboard and display circuit 168 is shown in FIGS. 18A and 18B. Eight digit LED displays LED 301 and 302 are driven by display driver IC317 and scan decoders IC315 and 316 in the conventional manner as shown. The remainder of the keyboard/display circuitry is shown in FIG. 18B. The keyboard on the display panel 13 is comprised of reed switches S302, 315 and 317-327. The identification and condition of these switches is provided by means of display interface IC301 and decoder/demultiplexer IC314. As shown in FIG. 18B, the outputs of the keyboarded data is placed on the data bus. Another set of 8 bit latches IC302, 303 and 304 interfaces a dip switch S301 to identify the automatic distillation analyzer unit number on the back of the display panel 13, and a series of LED indicator lights driven by hex buffers IC307 and 308. Additional decoders IC310 and 306 use control signals from the CPU to select the various I/O features of the keyboard display apparatus. 
     The analog I/O PCB 172 is shown in FIG. 19. The lead 66 from the RTD vapor sensor 60 is connected to an analog detector circuit which produces one of two outputs to the A/D converter IC611 in FIG. 17 via multiplexor IC707. The other multiplexor IC704, also controlled by the multiplexor outputs from the digital I/O board latch IC606, introduces offset or normal feedback signals in the vapor temperature detector circuit. IC703 is a multiplier, IC702, 705 and 706 are operational amplifiers, and IC701 is a voltage reference. 
     The analog I/O PCB also carries a pressure transducer which is multiplexed along with the watts transducer filtered output to the respective A/D converter IC610 or IC611. A/D converter IC610 also receives multiplexed inputs representing the temperature of the receiving chamber and the temperature of the condenser from the analog I/O board as shown in FIG. 19. IC&#39;s 708 and 710 are operational amplifiers and the multiplexors IC704, 707, 709 and 711 are CMOS analog switches. 
     As shown in FIG. 20, the AC I/O board 174 includes a temperature sensor circuit comprising operational amplifiers IC801, 802, 803 and Schmidtt trigger IC804 arranged to energize relay IC805 to turn on the liquid solenoid valve in the event that the temperature in the receiving chamber climbs above the prescribed subambient temperature, typically 60° F. A chamber temperature analog output is also provided to the analog IO circuit 172. The condenser bath level indicator shown schematically in FIG. 20 provides an input to fluid detector IC806 whose output indicating a low level is passed to the digital I/O PCB 170. IC807 is a voltage converter. The door switch input from the digital I/O circuit limit switch causes relay IC809 to be actuated to turn on the blower or fan when the receiving chamber door is closed. The air solenoid signal from the digital I/O board actuates relay IC810 to initiate cooling of the distillation flask by air jets arranged in the chamber 46 of FIG. 1. An alarm input from the digital I/O board activates dual timer IC811 which produces an output tone signal to a speaker for a predetermined interval. The TRIAC control signal from the digital I/O board is passed via TRIAC driver IC812 which produces gating signals for the TRIAC shown in FIG. 20 which drives the heating element 160 via a watt transducer or watt meter which produces the watts input to the analog I/O circuit 172. The high side of the AC line current is rectified and opto-isolated in IC813 and fed to the digital I/O board as the zero crossover signal for use in software timing of the TRIAC control signal and calibration for 50 or 60 Hz. While the flask heater air solenoid and speaker controls originate from software via the CPU system and digital I/O circuit, the liquid solenoid and fan controls are software independent. In particular, the liquid solenoid for lowering the chamber temperature is subject to its own independent thermostatic sensor circuit and while the fan 146 is subject only to opening of the receiving chamber door 72. 
     SOFTWARE 
     The remaining operations of the automatic distillation analyzer of FIG. 1 are controlled by software. A complete annotated assembly language listing of the code in the PROMs (IC201-IC206) is contained in Appendix I. This listing was produced on an ISIS-II 8080-8085 macro assembler and is reproduced in a standard format based on the standard instruction repertoire designed for the Intel 8085A Microprocessor. In all there are 53 distinct declarations and routines listed in the directly of so called &#34;F1&#34; on the first page of Appendix I. Each routine is given its mnemonic name such as XTEST or ENDT. These routines are arranged serially according to the object code map on page 2 of Appendix I. Locator symbols such a these are used to indicate either the beginning of a routine or subroutine or other precise code location of interest. In the assembly listing, often instructions are included which refer the CPU to a completely different location in the read only memory. This new location is given a mnemonic which symbolizes the function of the instructions at the new location. Throughout this assembly listing, these transferee locations are referred to as &#34;&#34;PUBLICS&#34;. PUBLICS include whole routines as well as subroutines and portions thereof. All of the PUBLICS are designated by their ROM location in the OBJECT LOCATOR table beginning on page 3 of Appendex I. Following the OBJECT LOCATOR table, the actual software, a listing of RAM storge declarations indicating length and type of data employed in the program. Following the RAM declarations, the next routine entitled &#34;MESSAGE ROUTINE&#34; contains the data definitions of the messages used for display in printing. Each routine such as this one is preceded by an abstract of the function of the routine. It should also be noted that each routine in the assembly listing is treated as self-contained. That is, each routine is designated to begin at ROM location zero and the addresses of external routines are always given as &#34;0000&#34;. In reality, the address of the external routine, for example, in a jump or call instruction does reside adjacent to the instruction in ROM. However, in assembling the final machine code, the assembler automatically determines the order of the routines. From the user&#39;s standpoint it is not important where the external routine is located. However, it can be determined quickly for reference purposes by referring to the OBJECT LOCATOR or SYMBOL table beginning on page 3 of Appendix I. To the right of the source and statement in each of the routines are annotations describing the function of the corresponding instruction. 
     The software routines in Appendix I can be thought of as falling into five related categories: 
     1. Keyboard/Display Operation 
     ENTER DATE 
     DISPLAY DATE 
     UPDATE THE DATE 
     EDITOR 
     KEYBOARD INPUT 
     LED DISPLAY AND INSERT AND TRANSMIT (keyboard entries displayed) 
     MESSAGES 
     TRANSMIT 
     2. System Operation 
     INITIALIZE (sets devices and parameters to known state) 
     CALIBRATION (determines whether line voltage is 60 or 50 Hz) 
     START (called by &#34;START&#34; key, entered parmeters printed, heat settings computed) 
     CONTROL 1 (controls heat during first five minutes) 
     CONTROL 2 (distillation rate control after IBP) 
     MOTOR RESET (finds starting meniscus) 
     MOTOR DRIVER (stepper motor-fast/slow, up/down) 
     CHECK FOR END OF TEST (ENDT-checks programmed end mode and sets final heat) 
     END AT TEMPERATURE CONTROL (detects programmed end temperature, decrease in temperature or five minute limit) 
     END AT PERCENT RECOVERED (detects programmed volume, temperature decrease for five minute limit) 
     END AT END POINT (detects temperature decrease or five minute limit) 
     END AT DRY POINT (detects programmed drop time interval, temperature decrease, five minute limit or dry point key) 
     TEMPERATURE DECREASE AND TIME LIMIT (subroutine-temperature decrease or five minute limit) 
     END OF TEST (end within five minute limit) 
     END OF TEST BEFORE FINAL HEAT (for end at programmed temperature or percentage recovery) 
     DRAINAGE (wait for no meniscus movement) 
     RECOVERY, RESIDUE AND LOSS (request residue input, computes and prints totals) 
     EVAPORATED TEMPERATURE CORRECTION (computes and prints temps for evaporated sample in IP and DP modes) 
     CORRECTED LOSS AND TOTAL RECOVERY (computes and prints barometer-corrected loss and recovery) 
     3. Interrupt Request Service 
     RST 5.5 (drop detector-tilt graduate at IBP) 
     RST 6.5 (meniscus detector-calls motor) 
     RST 7.5 (counts 1 second timer to enable RST 5.5 at 1 minute and up heat at 5 minute mark) 
     4. Diagnostic Tests 
     CHECK SUM (EPROM) 
     RAM TEST 
     MOTOR TEST 
     BAROMETER TEST 
     TEMPERATURE TEST 
     X-Y RECORDER TEST 
     CONDENSER AND CHAMBER TEMPERATURE TEST 
     CONDENSER LEVEL TEST 
     WATT METER TEST 
     RS 232 TEST 
     5. General Utility 
     RAM STORAGE DECLARATIONS 
     BINARY TO BCD CONVERSION 
     BCD TO BINARY CONVERSION 
     MULTIPLY 
     DIVIDE 
     PRINTER FORMAT 
     PRINTER DRIVE 
     RS 232 
     X-Y RECORDER 
     READ ANALOG TO DIGITAL CONVERTER 
     TEMPERATURE LAG GENERATOR 
     FIG. 21 illustrates typical printout from printer 34 for a completed test on regular grade winter gasoline according to ASTM D86, Group I. In this type of test, the distillation results are first given according to the millileters of distillate recovered. The temperatures are then recomputed based on the manually measured residue left in the flask and the loss of sample, for example, condensate left on the walls of the flask and U tube. The specific data appearing on the printout is tailored to specific requirements of ASTM D86. For example, this test requires that the IBP be reached within five to ten minutes. Thus, the printout includes a message that the IBP was reached at the uncorrected temperature of 83.3° F. at 6.3 minutes from the time the start key was depressed. 
     Unit ID number 03 is preselected from 0 to 31 by setting the dip switches behind the display panel 13. 
     System Operation 
     To begin a test, the sample flask 50 is placed on the distillation board above the heater 160 with the RTD sensor 60 in place and the receiving graduate 74 in the receiving chamber 70 as shown in FIG. 8. Through the operator panel display 14, the microprocessor based control system 164 prompts each test parameter. As each parameter is entered, it is also verified by the display. When programming is complete, the operator simply pushes the &#34;START&#34; button 26 on the display panel 13 and the printer 34 prints all of the test parameters. The control system 164 can repeat all of these conditions automatfcally for subsequent testing or the operator can selectively change all or any of the entries. 
     When the first sample drop enters the graduate, the IBP is recorded. As the graduate fills, the distillate volume is continuously monitored by meniscus detector 114. The distillate sensing system can monitor all types of samples even those which are dark or cloudy. 
     During distillation, the control system 164 automatically scans fifteen functions to alert the operator of problems or improper test parameters. Should such a condition occur, a preprogrammed message will appear either on the operator display 14 or the printout 36. As a result, corrective action can be taken before the next test. The control system 164 also features a series of preprogrammed diagnostic/calibration tests which enable the operator to easily locate problems or calibrate the unit. 
     The following description is furnished to illustrate the operation of the distillation system, first, from the operator or user&#39;s point of view, second, from the machine&#39;s point of view. 
     Procedure 
     1. Set Condenser Temperature range. 
     2. Set Calendar/Clock (Initial power up). 
     3. Determine ASTM required settings. 
     4. Key: ASTM method/temperature range (If none keyed, automatic selection=D86, 32°-572° F.). 
     5. Key: Distillation Rate (If none keyed, automatic selection=4/5 ml/min.) 
     6. Message Sequence on Operator Display: Key input, [ENTER]. 
     Message 
     SAMPLE 0000000 
     INITIAL HT 000W 
     5 MINUTE HT 000W 
     INC. FIN HT 000W 
     END AT TEMP NO * 
     END AT DP NO * 
     END AT % REC NO * 
     EXPECT LOSS 0.0% 
     SAMPLE 0000000 
    
    
    
     7. Clean the inside of the distillation tube before each test. 
     8. Pre-cool the graduate 74 and RTD sensor 60 in the receiving chamber 70 and refrigerate Flask 50 and sample. 
     9. Fill the graduate with sample. Bottom of meniscus must be at 100 ml. mark. 
     10. Pour sample in proper size distillation flask 50. 
     11. Wipe outside of graduate, insert into keyed graduate pedestal (not shown) in chamber 70. Rest small cover plate (not shown) on top of the graduate. 
     NOTE: If the dry point is to be recorded, insert the standard drop guide (not shown) into the graduate. A small liquid residue will typically remain in the graduate after the sample is transferred into the distillation flask. This is desirable. Some solvents evaporate and no &#34;starting meniscus&#34; is present in the graduate. If this occurs, add five drops of a non-volatile sample (Kerosene) to the graduate so that a smal meniscus can be initially sensed. The control system 164 will correct for this initial volume. 
     12. Insert RTD vapor sensor 60 with cork stopper 62 into distillation flask 50 so that top of sensor end is aligned with side arm 50a. 
     13. Insert distillation flask side arm with cork, into distillation tube 162. Position flask in vertical position, adjust height of heater 160, close glass door 48 (FIG. 1). 
     14. Press [START] 
     Sequence of Operations 
     1. Meniscus detector 114 carriage is reset just above meniscus. 
     2. Printer 34 prints out: date, time, testing conditions, barometric pressure, condenser temperature, etc. 
     3. Flask heater 160 sets to the Initial Heat Wattage. 
     4. After 5 minutes, flask heater 160 sets to the 5 minute Heat Wattage. 
     5. The first drop is detected by drop detector 96 at the graduate 74. The &#34;Recovery&#34; light 32 (FIG. 1) blinks. The graduate 74 is tilted by tilt solenoid 112 to receive distillate along the wall. (For Dry Point Test, graduate is not tilted). 
     6. Printer records: 
     IBP Temp. 
     Total time to IBP 
     7. Distillation rate-controled heat, meniscus tracking Vol/Temp recorded at 5, 10%, 20% . . . 10% increments Distillation rate, ml/min. 
     8. Final heat set when distillate volume equal to 100 ml less expected loss and less 6 ml. Vol., temp. printed 
     9. End Point, Dry Point, % recovered, or temperature termination (FIG. 21). If End Point, temp. decline sensed. If dry point, DRY POINT keyed or drop detector interval timed for dry point 
     10. The heating is terminated, and air jets cool the heater compartment. During this cooling period, distillate &#34;drainage&#34; is monitored. If total recovered volume (meniscus) does not change for (1) minute, end. 
     11. &#34;RESIDUE&#34; message appears on operator display 14 Operator measures flask residue, keys input, [ENTER],. (Note: Key numbers on each side of decimal point, e.g., 2.0) 
     12. Printer records: 
     Volume/Temp. on evaporated basis for ASTM D86 tests, 
     groups 1, 2, 3. 
     Loss and total recovery automatically corrected for ambient barometric pressure (FIG. 21). 
     Keyboard/Display Interaction 
     Pressing the Line switch 56, located on the lower right front corner of the unit, as viewed in FIG. 1, turns the system on. Test parameters are initialized to zero. Distillation rate of 4.5 ml/min, D86 32-572 F. temperature range, and END POINT test termination are automatically selected. 
     The first message automatically displayed is GCA ADA III VX.X, which indicates the version number of the control program. This message is displayed for approximately 2 seconds, after which messages requesting date and time input are displayed. 
     Entering Date and Time 
     Whenever the unit is first powered on or when diagnostic testing is completed, date and time input are required. This information is automatically updated as long as system power is on. The following messages are displayed and valid input noted: 
     
         ______________________________________MESSAGE         VALID INPUT______________________________________ENTER YEAR 19   80 through 99ENTER MONTH     1 through 12ENTER DAY       1 through 31ENTER HOUR      1 through 23ENTER MINUTE    0 through 59______________________________________ 
    
     Operator input via keys [0] through [9] of keyboard 16 is visually displayed as input for each message is requested. Entering of non-valid input is not allowed. 
     EXAMPLE 
     to enter Jan. 20, 1982, 16:05 
     
         ______________________________________PRESS        DISPLAY______________________________________        ENTER YEAR      19[8]          ENTER YEAR      19 8[2]          ENTER YEAR      1982[ENTER]      ENTER MONTH[1]          ENTER MONTH     1[ENTER]      ENTER DAY[2]          ENTER DAY       2[0]          ENTER DAY       20[ENTER]      ENTER HOUR[16]         ENTER HOUR      16[ENTER]      ENTER MINUTE[5]          ENTER MINUTE    5[ENTER]      SAMPLE          0000000______________________________________ 
    
     After the date and time are initially entered, only the test parameter messages are displayed, starting with sample number. 
     Entering, Changing, Recalling Test Parameters 
     Distillation test parameters are entered via the keyboard and stored in RAM IC209, 210, 216, 217 (FIG. 14). The parameters once entered need not be re-entered for each sample, run if there are no changes in test conditions and system power is not turned off. Changing test parameters is accomplished using message prompts appearing on the operator display when a test is not in progress. Recalling test parameters previously entered for examination is done by successive key strokes of [RECALL] key on keyboard 16. 
     The following test parameter messages are displayed and their definitions are as follows: 
     SAMPLE 0000000: Identify a distillation test sample run with a numberic code. The operator may key in any seven digft numeric number with the exception of &#34;9876543&#34;, which is used to activate the resident diagnostic/calibration program. 
     EXAMPLE 
     to enter sample number 1296534 
     
         ______________________________________PRESS          DISPLAY______________________________________          SAMPLE        0000000[1]            SAMPLE        0000001[2]            SAMPLE        0000012[9]            SAMPLE        0000129[6]            SAMPLE        0001296[5]            SAMPLE        0012965[3]            SAMPLE        0129653[4]            SAMPLE        1296534[ENTER]        INITIAL HT    000W______________________________________ 
    
     INITIAL HEAT 000W: The next test parameter message displayed requests the operator to input the initial heat setting in watts. Valid input range is 000 through 999. This value is used as the heat setting when a distillation test is started. The heat is automatically maintained at this setting until five minutes into the test or the first drop is detected. 
     EXAMPLE 
     to enter 250 watts 
     
         ______________________________________PRESS          DISPLAY______________________________________          INITIAL HT  000W[2]            INITIAL HT  002W[5]            INITIAL HT  025W[0]            INITIAL HT  250W[ENTER]        5 MINUTE HT 000W______________________________________ 
    
     5 MINUTE HEAT 000W: The next test parameter message displayed requests the operator to input the 5 minute heat in watts. Valid input range is 000 through 999. This value is used as the heat setting desired after five minutes into the test or when the first drop is detected. 
     EXAMPLE 
     to enter 201 watts 
     
         ______________________________________PRESS          DISPLAY______________________________________          5 MINUTE HT 000W[2]            5 MINUTE HT 002W[0]            5 MINUTE HT 020W[1]            5 MINUTE HT 201W[ENTER]        INC FIN HT  000W______________________________________ 
    
     NOTE: During the distillation, the heater wattage will vary to maintain the distillation rate which was preselected. 
     INCREASE FINAL HEAT 000W: The next test parameter message displayed requests the operator to input the increase final heat setting in watts. Valid input range is -999 through 999. This value is used to either increase or decrease the heat setting during the final heat phase. 
     EXAMPLE 
     to enter 150 watts 
     
         ______________________________________PRESS         DISPLAY______________________________________         INC FIN HT   000W[1]           INC FIN HT   001W[5]           INC FIN HT   015W[0]           INC FIN HT   150W[+/-]         INC FIN HT   -150W[+/-1]        INC FIN HT   150W[ENTER]       EXPECT LOSS  0.0%______________________________________ 
    
     EXPECT LOSS 0.0%: The next test parameter message displayed requests the operator to input the expected loss setting in percent. Valid input range is 0.0 through 9.9. This value is used in determining the volume at which the final heat phase begins. 
     EXAMPLE 
     to enter 1.0% 
     
         ______________________________________PRESS         DISPLAY______________________________________[1]           EXPECT LOSS  0.0%[.]           EXPECT LOSS  0.1%[0]           EXPECT LOSS  1.0%[ENTER]       END AT TEMP  NO______________________________________ 
    
     END AT TEMPERATURE--NO: The next test parameter message displayed informs the operator that the method of ending a test is not at a pre-selected temperature. If ending a test at a specific temperature is desired, the operator need only key in the value. Valid input range is 000 through 999. The temperature units, Centigrade or Fahrenheit, are automatically determined from the temperature range previously selected. If this method of ending is not desired, input only the 1/2ENTER1/4 key. 
     EXAMPLE 
     End at temperature desired 
     
         ______________________________________PRESS         DISPLAY______________________________________         END AT TEMP  NO[2]           END AT TEMP  002C[9]           END AT TEMP  029C[5]           END AT TEMP  295C[ENTER]       SAMPLE       1296534______________________________________ 
    
     EXAMPLE 
     End at temperature not desired 
     
         ______________________________________PRESS          DISPLAY______________________________________          END AT TEMP     NO[ENTER]        END AT DP       NO______________________________________ 
    
     END AT DRY POINT--NO: The next test parameter message displayed informs the operator that the method of ending a test is not at the dry point. If ending a test at the dry point is desired, the operator need only key in the desired time in seconds between drops. 
     Valid input range is 0.0 through 9.9. The value is used during the final heat phase where the time between successive drops of liquid at the distillation tube 162 is measured. When the time interval is greater than this test parameter, the test is automatically ended. If this method of ending a test is not desired, input only the [ENTER] key. 
     EXAMPLE 
     End at DP desired: 
     
         ______________________________________PRESS          DISPLAY______________________________________          END AT DP  NO[1]            END AT DP  0.1S[.]            END AT DP  0.1S[0]            END AT DP  0.1S[ENTER]        SAMPLE     1296534______________________________________ 
    
     EXAMPLE 
     End at DP not desired: 
     
         ______________________________________PRESS          DISPLAY______________________________________          END AT DP    NO[ENTER]        END AT % REC NO______________________________________ 
    
     END AT % RECOVERED--NO: The next test parameter message displayed informs the operator that the method of ending a test is not at a selected recovery percentage. If ending a test with this method is desired, the operator need only key in the desired recovered volume percentage. Valid input range is 00 through 99. When this entered recovered percentage is reached, the test is automatically ended. If this method of ending a test is not desired, input only the [ENTER] key. 
     EXAMPLE 
     % REC desired: 
     
         ______________________________________PRESS         DISPLAY______________________________________         END AT % REC NO[9]           END AT % REC 09%[2]           END AT % REC 92%[ENTER]       SAMPLE       1296534______________________________________ 
    
     EXAMPLE 
     % REC not desired: 
     
         ______________________________________PRESS         DISPLAY______________________________________         END AT % REC NO[ENTER]       SAMPLE       1296534______________________________________ 
    
     If the operator enters data on any one of the messages: 
     END AT TEMP 
     END AT DP 
     END AT REC 
     the message selected is retained in memory and the other two messages are not displayed. 
     To correct an error in entry or if the wrong message (above) has been selected, 
     1. Press [RESET] 
     2. Press [ENTER] until the message in error is reached 
     3. Press [RESET] 
     This resets all three of the above messages, starting with: 
     END AT TEMP--NO 
     If no data entries are made on any of the above three messages, the control system 164 will automatically select: 
     END AT END POINT 
     Condenser temperatures are chosen according to the specific ASTM distillation test method. 
     1. Select the appropriate temperature range by depressing the desired temperature key 38 (FIG. 1). 
     2. For subambient operation (35° C. and lower), switch &#34;ON&#34; the Condenser Cooler 12. 
     3. When temperature equilibrium is reached, the condenser CONTROL light 42 will cycle on-off. 
     An internal circulating pump 154 (FIG. 7), and RTD controlled heating circuit (not shown) will maintain the selected bath temperature. 
     The receiving chamber temperature can be controlled as described above. For ambient chamber temperatures, however, the door must be left open. 
     ERROR AND DATA MESSAGES 
     In addition to operating parameter messages, the control system 164 also reports two classes of messages: ERROR MESSAGES and DATA MESSAGES. These messages will appear on the operator display or be printed out for hard copy record. 
     Error messages are reported in response to conditions which could prevent the unit from starting or completing a distillation test. These errors are classed into two groups: (1) fatal, and (2) non-fatal, errors. 
     Fatal errors, when detected, prevent using the system until the identified failure is corrected. These errors are detected automatically by the micro-processor system 164 and messages are indicated on the operator display. 
     Non-fatal errors, when detected, may not prevent using the system for the specific test programs selected. These errors are detected automatically by the microprocessor system and messages are indicated on the operator display. 
     Listed below are the fatal error messages and conditions under which they will occur. 
     BAD EPROM 012: Each time the unit is powered on, a check sum is automatically made of the contents of each EPROM located in the CPU circuit board (FIG. 14). If the calculated check sum for each EPROM is not correct, the EPROM is identified by number with a message on the operator display so that it can be replaced. 
     ZERO CROSSING: Each time the unit is powered on, an automatic determination of the AC line frequency, either 50 Hz or 60 Hz, is made. This is subsequently used for time keeping and heater power control. This message appears on the operator display and indicates a failure on either the Digital I/O circuit board (FIG. 17), the AC control I/O circuit board (FIG. 20), or interconnections between boards. To correct this error, verify the zero crossover signal output of the AC Control I/O board (FIG. 20). 
     READ PARAMETERS: Each time a distillation test is started, the following parameters are automatically read: barometric pressure, receiver compartment, and condenser chamber temperatures. The &#34;Read Parameters&#34; message appears on the operator display 14 and indicated a failure on the Digital I/O circuit board (FIG. 17). 
     Listed below are the non-fatal error messages and conditions under which they will occur. 
     RAM TEST FAILED: The RAM diagnostic program verifies the integrity of the random access memory. This message appears on the operator display when an error is detected. The operator must select this diagnostic program as described in &#34;Diagnostic Testing&#34; since this test is not automatically performed. 
     END POINT&gt;5.0 MIN: During a test, if the selected ending mode cannot be obtained within 5 minutes from the Final Heat adjustment point, this message is sent to the printer and the test is terminated. 
     NO MENISCUS MOVEMENT: When a distillation test is started and the first drop is detected, the microprocessor system 164 performs various control functions to assure compliance to ASTM test methods. One of the functions is to control wattage to the flask heater 160. In this way, the programmed distillation rate is maintained. If for some reason, the meniscus detector 114 does not move over a set time window, the distillation rate programmed cannot be maintained. When this condition is detected, this message is sent to the printer, and the test is terminated. 
     GRADUATE NOT PRESENT: If an attempt is made to start a distillation test without a graduate 74 present to collect the distillate, the test is not allowed to proceed. The microprocessor system 164 detects this condition, outputs this message to the printer 34, and the test is terminated. 
     UPPER LIMIT SWITCH: Limit switch 128 is activated by the meniscus detector 114 travelling along the lead screw 90 beyond the 100% point. If this switch is activated during a distillation test and after the first drop is detected, the microprocessor outputs this message to the printer 34 and the test is terminated. 
     This condition can occur if: 
     1. The meniscus tracking system &#34;ran away&#34; due to: dirty graduate (fingerprints, etc.) or improper meniscus sensitivity calibration. 
     2. Starting sample volume in excess of 100 ml. 
     3. Sample initially at subambient temperature but recovered at ambient (door open). 
     TEST TERMINATED: Once a distillation test is started, various conditions detected by the microprocessor can terminate normal completion of the test. The microprocessor outputs this message to the printer for the following conditions when either operator inputs [STOP] key, or a non-fatal error is detected which prevents completion of the particular test selected. 
     NO DROP IN 25.6 MIN: Once a distillation test is started, time information is automatically maintained to record the initial boiling point. If for any reason the IBP is not detected within 25.6 minutes from the start of the test, the microprocessor outputs this message to the printer and the test is terminated. 
     This condition can occur if there is insufficient initial heat and/or 5 minutes heater wattage, no sample in the distillation flask, or insufficient drop detection sensitivity. 
     LOSS IS BELOW 0.0 ML: At the end of the distillation, the operator inputs the RESIDUE volume. if the recorded volume and residue exceeds 100%, the microprocessor will not calculate a negative % loss. 
     This condition may occur if the initial sample was at a subambient temperature and recovered at ambient (door open), or the initial sample volume was in excess of 100 ml. 
     VAPOR CKT OPEN or VAPOR CKT SHORTED: Check vapor RTD sensor, cable, cable connections. If no open connections are found, check Analog and Digital I/O printed circuit boards. 
     CHAMBER CKT OPEN or CHAMBER CKT SHORTED: Check receiving chamber RTD, cable, cable connections. If no open connections are found, check AC I/O printed circuit board (FIG. 20). 
     Data Messages 
     Data messages are used in the reporting of test results and also to inform the operator on the status of the system during a distillation test. These messages will appear on the operator display 14, or be printed for a hard copy record. Listed below are the data messages and conditions under which they will occur. 
     RESET MOTOR: This message automatically appears on the operator display, after the [START] key is input. The reset motor drives the meniscus carriage to the lower limit switch and back up to the top of the meniscus film in the graduate. 
     ----PRINTING----: This message automatically appears on the operator display to indicate that the test parameters set up by the operator are being output to the printer. 
     TIME TO FIRST DROP, VAPOR TEMP., HEATER WATTAGE--XX.XMYYY.YC(F) ZZZW 
     This message automatically appears on the operator display after the printout of test parameters is completed. The time from the start of test is displayed as XX.X minutes. The flask vapor temperature is displaced as YYY.Y in °C. or °F. The actual flask heater wattage is displayed as ZZZ watts. This allows the operator to visually observe the distillation test while in progress. This message is displayed until the first drop is detected. 
     DISTILLATE VOLUME, VAPOR TEMP., HEATER WATTAGE--XX ML YYY.YC(F) ZZZW 
     This message automatically appears on the operator display after the first drop is detected. The distillate volume is displayed as XX milliliters. The flask vapor temperature is displayed as YYY.Y in °C. or °F. The actual flask heater wattage is displayed as ZZZ watts. This message is displayed until after the selected end mode is detected or the test is terminated. 
     During the test all three readings are continuously updated by the microprocessor. 
     **TRANSMITTING**: This message automatically appears on the operator display to indicate that the transmission of data is taking place via the optional RS232 computer interface. 
     Diagnostic Testing 
     The unit contains diagnostic test programs to individually verify, test, or calibrate all operational functions performed during a distillation test. 
     The diagnostic mode is accessed by entering a SAMPLE NUMBER of 9876543. The following message on the operator display indicates the diagnostic mode of operation: 
     SELECT TEST 0-9 
     When the SELECT TEST message is displayed, the operator keys in a number, [0] through [9], [ENTER] to select a functional test. 
     The [RESET] key terminates the diagnostic mode and control is returned to the normal mode of operation. 
     RAM TEST: When selected by the [0] key, the RAM is tested by writing various patterns to memory locations, reading these patterns, and verifying the results. When all memory locations are tested and verified, the following message appears on the display: RAM TEST PASSED 
     If any memory location fails, the following message is displayed: RAM TEST FAILED 
     If a RAM failure is indicated, proceed as follows: 
     1. Turn off line power switch 56. 
     2. Remove CPU board (FIG. 814). 
     3. Replace defective RAM, IC209, 210, 216, 217 one at a time to isolate defective RAM. 
     4. Repeat test. 
     The [RESET] key terminates this test and control is returned to diagnostic message, SELECT TEST 0-9. 
     MOTOR TEST (also Alarm, Graduate Tilt, Air Solenoid) 
     This test is selected by the [1] key. When selected, the operator may choose any of the following functions with a single key stroke: 
     [1]--turn alarm on 
     [4]--turn alarm off 
     [2]--energize graduate tilt solenoid 
     [5]--de-energize graduate tilt solenoid 
     [3]--energize air solenoid 
     [6]--de-energize air solenoid 
     [8]--jog up, step motor 1 step (repeat [8]) 
     [0]--jog down, step motor 1 step (repeat [0]) 
     [7]--the motor is driven down until the lower limit switch is energized and 0-400 C LED is illuminated. 
     [START]--The meniscus detector 114 is driven to the lower limit switch 130. Next, it is driven up until the meniscus detector is de-energized. At this point, the motor step software counter is zeroed. Next, the motor is driven up until either the meniscus detector is blocked or the upper limit switch 128 is energized. 
     [RESET]--This key returns control to the diagnostic message, SELECT TEST 0-9. 
     All other keys are ignored. 
     During this test, the status of the lower limit switch 130 is displayed on the D86 0-400 LED. The upper limit switch 128 status is displayed on the D86, 32-572 LED. 
     BAROMETER TEST: This test is selected by the [2] key. When selected, the transducer measuring barometric pressure is continuously sampled in mm Hg. The message on the operator display is as follows: BAROMETER=XXX 
     Adjustments to the transducer analog circuitry are easily made using this test. 
     VAPOR TEMPERATURE TEST. This test is selected by the [3] key. The platinum RTD measuring vapor temperature is continuously sampled and the corresponding temperature displayed. Any corrections normally made to temperature for barometric pressure are not performed during this diagnostic test. Any of the five temperature ranges: 0°-300° C., 0°-400° C., 30°-300° C., 32°-572° F., 32°-752° F., may be selected with the display reflecting the corresponding temperature. The 30°-300° C. range indicates the true temperature. All other ranges indicate temperature uncorrected for emergent stem error. The message displayed is as follows: TEMP=XXX.XC(F) VAP 
     RECEIVING CHAMBER TEMPERATURE TEST. This test is selected by the [5] key. The platinum RTD, measuring receiver chamber temperature, is continuously sampled and the corresponding temperature is displayed in °C. The message displayed during this test is: TEMP=XX.XC CHA 
     The [RESET] key returns control back to the diagnostic message, SELECT TEST 0-9. All other keys are ignored. 
     CONDENSER CHAMBER TEMPERATURE TEST. This test is selected by the [6] key. The platinum RTD, measuring condenser temperature, is continuously sampled and the corresponding temperature is displayed in °C. The message displayed during this test is: TEMP=XX.XC CON 
     CONDENSER LIQUID LEVEL TEST. This test is selected by the [7] key. The transducer measuring the level of the liquid in the condenser is continuously sampled and the corresponding status is displayed. The two possible messages displayed are: COND LEVEL LOW or COND LEVEL OK 
     FLASK HEATER TEST. This test is selected by the [8] key. The operator may enter set point wattage values. Control of the flask heater power to the entered value is performed. The watt transducer measuring the heater power is continuously sampled and the corresponding power is displayed in watts. The message displayed during this test is: SP=XXXW AC=YYYW 
     The keys [0] through [9] and [ENTER] allow the operator to input set point wattage values. 
     X-Y RECORDER TEST and EIA RS-232-C COMMUNICATION TEST. (Optional) These tests are selected by the [4] and [9] keys (see Appendix I). 
     ADVANTAGES 
     The chief advantage of the above described system, compared to prior art distillation analyzers is its operational simplicity. With only a few exceptions, the test procedure is under microprocessor control from the beginning to the end. For example, the only truly manual steps involved in the gasoline test are loading the flask and measuring the residue when requested by the control panel. The built in step-by-step declaration of test parameters and automatic running of the test make the system almost foolproof. Moreover, a hard copy record is created not only of the test data but all of the pertinent conditions as well as the date, time and sample number, all on one document which may be initialed and saved as a permanent record. The computer memory automatically retains test parameters for repeating the same test without entering new data. Moreover, the software automatically preselects the end at endpoint test unless otherwise (or previously) directed. The computer is employed to make nearly infallible temperature corrections for the evaporated sample if required. 
     Hardware improvements are also present particularly in the receiving chamber drop and meniscus detector mechanisms. The slotted mask for the phototransistor enhances its resolution while the stepper motor drive insures computer accuracy and facilitates control of the distillation rate as well as measurement of the instantaneous distilled volume. The RTD cooling well is a particularly beneficial feature which takes advantage of the automatic temperature control of the receiving chamber and the graduate so that the graduate and RTD vapor sensor begin at the same controlled temperature as required by ASTM standards. 
     In addition, sensor is forced to simulate a glass thermometer by introducing a time lag in software for the temperature reading. 
     These advantages result in reducing the error rate, thus increasing the throughput of test samples. The increased test capability avoids costly deviations from product specifications at the refinery and insures the product market of satisfaction of existing ASTM standards. The extreme operational simplicity of the unit according to the invention allows less sophisticated operators to achieve the same degree of accuracy and reliability in each of the relatively complicated test procedures required by ASTM petroleum product standards. 
     The foregoing description and drawings relate to a preferred embodiment of the invention meant to illustrate rather than restrict the scope of the invention. The system can be adapted, for example, to other equivalent computer configurations. 
     Alternatively, components of the described test system may be omitted or modified to suit other test requirements. These and many other variations may be made without necessarily departing from the spirit or scope of the invention, as indicated by the appended claims and equivalents thereto: