Target DAQ

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Explanations associated with the target data acquisition system go here.

Contents

Target DAQ training

Target DAQ training exists. To take this training please contact Chad. At a future time, a link will be put here to the appropriate training procedure document.

Outside the cryostat

The following is a simplified diagram that shows how the flow meters, pressure transducers, pneumatic valves and pumps and so on are arranged outside of the cryostat. The purpose is to show the overall picture so as not to get lost in the details. This is not the actual complete flow diagram. Note that the section labeled "for venting hydrogen" in the 2001-09-10 version shown below is a bit too far simplified and also out of date. A new version will be posted. In the meantime, if you're interested in that detail or other details missing from this diagram, see the actual flow diagram itself.

Inside the cryostat

The following diagram shows how the thermometers and heaters are arranged inside the cryostat.

The electronics cabinet

This contains:

The Omega meters

  • The Omega meters power some of the pressure transducers as well as read and digitally display what they measure.
  • The manual for the Omega meters is here.
  • Some of the Omega meters have an analog output that allows them to be read by our DAQ and some don't. From testing them by observing the voltage across where the output is supposed to be, there are a total of three that have working analog outputs: the ones positioned at the top second from right, middle far left and middle second from left. These three have a label on the front that says "ANLG OUT". You can also verify that the box you're interested in has an analog output by cycling through the options available when repeatedly pressing the MENU button. If one of the options that appears is OT.CF (output configuration), then this means that it has an analog output.
  • Our ADCs read voltage in the range of -10 to +10 volts so we use the two ANALOG OUT terminals that say VOLT and RTN.

The MKS Meter

  • The meter in the bottom left is actually not Omega but MKS. It is model PDR-D-1 (here's a photograph of its nameplate which is not visible when it's installed in the cabinet).
  • The manual for that one is here.

The Thermometers

The thermometers are silicon diode thermometers. Most are SI-410 C from Scientific Instruments. The typical response curve is here

Scientific Instruments 9600-1 temperature controllers

  • The manual for these ones is here.
  • When setting these up, you need to know how to wire the RS232 connections. Instead of an RS232 connector, there are three terminals on the back that are labeled 1,2,3. The function of these is shown in figure 2-3 on page 2-9 of the manual: 1 is signal ground, 2 is transmit data from the 9600, and 3 is receive data to the 9600. These are the numbered labels that are written on the back of the 9600-1; they are not the same as the numbered labels that are given on the RS232 cables.
  • To make the homemade extensions, a regular straight-through RS232 cable with one male end and one female end was cut in half. A male-to-female gender changer was put on the male end. The gender changer connects all pins straight through (1 to 1, 2 to 2, 3 to 3, ... 9 to 9), so there are now two functionally identical cables with a female connector on one end and bare wires on the other end. Both halves of the cable have the wiring color scheme given in this photo: 1 = black; 2 = brown; 3 = red; 4 = orange; 5 = green; 6 = blue; 7 = maroon; 8 = gray; 9 = white. We need wires 5 (green, which goes to terminal 1 of the 9600), 2 (brown, which goes to terminal 2), and 3 (red, which goes to terminal 3). The other 6 wires of the cable are not used. Here is a drawing showing how the RS232 cables are connected between one of the 9600 modules and the PC.

Scientific Instruments 9700 temperature controllers

We have two of these. Each one has two thermometers and one heater. The heater operates on feedback with either one of the two thermometers. The manual is here.

Lakeshore temperature readouts

The Lakeshore 218 reads out eight thermometers. It does not have any heaters. Its manual is here

Wiring: general overview

  • All signals that go to the data acquisition PC first pass through the electronics cabinet. They are either analog or RS232.
  • To come:
    • State which ones are analog, which ones are RS232.
  • Most of the pressure transducers are connected to an Omega meter. The Omega meters are located in the electronics cabinet and convert the analog voltage or current from the pressure transducers to a digital reading on an LED display and sometimes have an analog output.
  • When the Omega meter has an analog output, the PT signals are connected from the analog output to the ADC card. When they don't have an analog output, the output directly from the pressure transducer is read in the ADC card instead of being passed from the Omega meter. In the case where a PT is read by an Omega meter with no analog output, each of the Omega signal inputs has one wire coming from the PT and one wire going to the ADC card.
  • Some pressure transducers are not connected to an Omega meter so are connected directly to the ADC card.
  • To see how to connect a given pressure transducer to the electronics cabinet, see the specific entry for that pressure transducer.
  • To see how the shields and grounds are wired, see the section on grounding and shielding.
  • To see how to wire the analog signals to the ADCs, see the entry that is specific to the wiring of the analog signals.
  • To see how the thermometers are wired between the cryostat and the electronics cabinet, and then from the electronics cabinet to the computer, see the the thermometer wiring.
  • To see how the flow meters are connected to the electronics cabinet... (to come: finish this sentence)

The data acquisition PC

Time synchronization

  • The PC uses ntpd to synchronize its clock with hazel.
  • Here is a site that explains how to get ntp to work.
  • If the clocks are out of sync and you want to get them synchronized:
    1. Switch to root user.
    2. #service ntpd stop
    3. #ntpdate -u hazel
    4. The link above says that you might want to do the previous step three times.
  • The configuration file is /etc/ntp.conf
    • The server line just needs to be set to "server hazel".
  • To set up NTP so that it starts at boot:
    • #chkconfig ntpd on

The ADC card

The two six-port serial cards

  • To come: explain a bit about this.

Hydrogen gas handling cabinet

This is the blue cabinet at ground level that contains FM101, PT102, PT103 and PT105.

PT102, PT103 and PT105

Brief overview

  • All three of the pressure transducers in the gas handling cabinet are Omega model number PX880-100GI.
  • The manual is here.
  • They measure gauge pressure over the range of 0-100 PSIG, provide 4-20 mA DC output and use a 12-40 V DC power supply.

Wiring and configuration

  • The layout of the wiring that these pressure transducers require is explained on page 2-4 of the manual. However, that explanation is confusing and appears to contradict itself. What follows is hopefully a less confusing explanation of how they are wired.
  • Each pressure transducer is connected to an Omega box in the electronics cabinet. The cable connecting the pressure transducer to the Omega box has three connections: a white wire, a black wire and a shield.
  • The pressure transducer is wired as shown in this photo. White is TP+, black is TP-, and the shield is grounded through the case.
  • The Omega meter is wired as shown in this photo and this photo. White is +E and black is +S. -E and -S are shorted together and the shield is tied to the ground in the power line.
  • The dip switches are set as COCCOOOO where O=open, C=closed and switches are given in the order 1,2,3,4,5,6,7,8.
  • See section 4.1 of the manual for how to specify the input of the Omega meter as 0-20 mA DC. The manual says that this should be done after and in addition to having selected the dip switches appropriately for 0-20 mA DC.

Calibration

  • The method for calibration of PT102, PT103 and PT105 is explained in section 4.3 of the manual for the Omega meter. Calibration involves applying two known pressures to the pressure transducer (around the minimum and the maximum of its range) and configuring the Omega meter so that it reports the appropriate values at those two pressures. From experience, it seems that the reading on the Omega meter should be gauge pressure. In other words, at atmospheric pressure the Omega meter should read approximately zero. We're assuming this to be the case since if we set zero to be zero absolute, then the calibration does not work.

FM101

Brief overview

  • FM101 is Sierra Instruments Top-Trak model No.: 822S-L-8-OV1-PV1-V1-MP.
  • It used to be model number 822S-L-8-OV1-PV1-V1-HP, however this changed in February/2012, and the new one that we currently have is the only one that's ever been used since then.
  • The manual for it is here or here.

Wiring

  • The power to FM101 is provided by an AC-DC adaptor that plugs into a regular wall outlet and into the DC power jack of the flow meter (see page 2-4 of the manual).
  • The 0-5 V DC analog signal is carried by a cable that passes through the conduit from the flow control cabinet and reappears in the corner behind the electronics cabinet. It's labeled FM101 and has white (signal), black (common) wires and shield. According to the manual (p 3-1), the output is proportional to the flow rate with 0 V corresponding to 0 slpm and 5 V corresponding to the maximum on the nameplate of the flow meter which is 15 SLPM.

Pressure transducers in and around the vent isolation cabinet

PT107, PT201, PT301 and PT302

Brief overview

  • PT107 and PT201 are both Omega model PX203-030A5V. The manual is here or here.
  • PT301 and PT302 are both Omega model PX303-050A5V. The manual is here or here.

Wiring

  • PT107, PT201, PT301 and PT302 are powered and read by the Omega meters in LH2 electronics cabinet. On the end of each of these PTs is a DB9 connector which has been made with the following pin/wire combinations: 2 - black (COMMON); 4 - ground (EARTH); 6 - red (+EXC); 9 - white (+OUT). PT301 and PT302 have no EARTH, only COMMON. On Sep 27/2011 some extension wires were made that are colored consistently with this convention.
  • PT201 and PT107 require 7-35 V DC excitation and produces a 0.5-5.5 V signal (from what's written on the transducer itself).
  • PT301 and PT302 require 12-32 V DC excitation and produces a 0.5-5.5 V signal (from what's written on the transducer itself).
  • For PT107, PT201, PT301 and PT302, the dip switches on the Omega meters are set to CCOOOOOC in the order 1,2,3,4,5,6,7,8.
  • A photograph of the wiring of PT201 at the Omega meter is shown here. The connector that's shown in the top plugs into the top right-hand side of the meter (looking from the back) and the other one plugs in below it. PT301 is done in the same way.

PT106

  • PT106 is Omega PX303-100A5V. The manual is here or here (the same manual as for PT302).
  • PT106 is powered by the PPS system. We receive a signal cable with black (signal) and white (common) and shield.
  • When PT106 is hooked up directly to the Omega meter (i.e. not through the PPS system), then it is hooked up as in this photo. Red is +E excitation voltage, black is -S, white is +S and green is ground. -E and -S are tied together. The dip switches are set to ccoooooc (from left to right looking from the back of the Omega meter, c=closed, o=open). When PT106 comes from the PPS, it has a black (positive), white (negative) and shield. It is hooked up as in this photo: white is -S, black is +S and shield is tied to the power line ground.
  • The pressure transducer itself has a range of 0 to 6.9 bar, or 0 to 100 psi. ZT recorded in target log book III on 2011/11/9 that the relief valve RV104 starts to release at a pressure of 1650 torr. We have configured the PT106 Omega meter so that it reaches the maximum of its voltage output range at 2000 torr. The conversion is therefore pressure in torr = (voltage in volts)/0.002.

PT204

To come:

  • Show how PT204 is connected to the PC.
  • Mention what units it uses.

The RGA

NB: Read This When Turning on the PPM

When the PPM has been turned off and on again, the RS232 configuration is set to the default settings and the relays are put into the inactive state and manual mode. If the RS232 settings are in their default configuration, then the data acquisition PC cannot communicate with the PPM. If the relays are put into the inactive state and manual mode, then the Target Signal Processing System (which controls warnings and alarms and pneumatic valves) will be in a safe mode that prevents us from operating normally. To set the RS232 to its appropriate configuration, see the Communications and Readout Configuration section below. To set the relays to the correct mode for operation, see the Relay Configuration and Wiring section below.

Brief Overview

  • A Residual Gas Analyzer (RGA) is a sensitive mass spectrometer that is attached to a vacuum system to measure residual gas contents at low pressures. Ions are created by bombarding residual gas molecules with electrons that are emitted from a heated filament.
  • To acquire data, the filament has to be turned on, but since the filament wears out with use and eventually needs to be replaced, it is important to turn the filament off when it is not needed. To turn the filament off, press the “FILAMENT” button at the top left of the PPM. If the green light next to this button is on, then this indicates that power to the filament is on. If the filament is off, then when in the “Monitor” display mode of the PPM (available from a menu button at the bottom of the screen labeled “Monitor”), the various channel readouts should all say “FILAMENT OFF”. To turn the filament back on again, press the FILAMENT button again.
  • After turning the filament on, it is necessary to wait a few minutes for the filament to heat up before taking data.
  • Warning: Do not operate the RGA if the pressure in the chamber is greater than 10-4 torr.
  • The RGA is Stanford Research Systems model RGA100 and its manual is here.
  • The RGA is accompanied by a controller (the PPM) which is Stanford Research Systems model PPM100 for which the manual is here.

Communications and Readout Configuration

  • The data acquisition computer communicates with the RGA through the PPM.
  • To view the residual gas readings, it is sufficient to have only the PPM100 connected to the RGA. A common way to do so is from the Main Menu of the touchscreen display (to get to the Main Menu, select a button at the bottom that is labeled “Back” until a button labeled “Menu” is available at the bottom left and then select this “Menu” button) to press the “Monitor” button. This then shows all of the 8 separate readings.
  • To adjust which gas is associated with which one of the 8 readouts that are visible in the Monitor screen, use the touchscreen to select the one of the 8 that you're interested in and to gain access to the setup menu. For example, you can change the gas to a known one by selecting “Set via library” and then choosing one of the preprogrammed options.
  • NB: The setup of a given PPM channel (e.g. which gas partial pressure it measures) should not be modified while data acquisition is in progress. The data acquisition software assumes that each channel (PP1, PP2, PP3 etc) corresponds to a defined reading. If any of the channels are going to be or have been changed while data acquisition is in progress, then it is necessary to inform the person in charge of the data acquisition software.
  • The RGA is attached to the vacuum system in the vent isolation cabinet and the PPM sits on top of the target electronics cabinet.
  • However, to record data to disk we use the data acquisition computer. The computer is connected to the PPM by RS232 which is in turn connected to the RGA, also by RS232. Both cables are regular 9-pin straight-through serial cables.
  • To connect the RGA to the PPM, the 9-pin output labeled RS232/DCS/28.8k on the RGA should be connected to the 9-pin port of the PPM100 that is labeled RGA RS-232.
  • On the PC we communicate with the PPM using the port /dev/ttyD2. Connect the 9-pin output on the PPM to the serial port on the PC that is labeled D2.
  • In order for the RGA and the data acquisition program to communicate, the RS232 settings in the PPM need to be configured properly. To adjust these settings, go first to the main menu on the touchscreen of the PPM. This is a screen that says "Main" at the top that has options Utitilities, Remote, Screen, etc. If you're not at this screen then look for a button on the bottom that says "Back" and press it until you see a button that says "Menu". From the main menu, select "Remote" and then "RS232".
  • Here are some settings that work:
    • Baud Rate: 9600
    • Word length: 8
    • Parity: None
    • Flow control: Hardware
    • Rga pass through: Normal operation

Relay Configuration and Wiring

  • The PPM has eight process control relays on the back.
  • Each relay can be configured to be linked with a particular partial pressure reading. To do so, from the Main Menu on the touchscreen of the PPM, select the "Process" menu.
  • At the Process menu, you can select one of 8 process control channels, each of which corresponds to one of the 8 relays.
  • To adjust the relay settings, select “Process” from the Main Menu and then select the process control channel that you're interested in.
  • The relays have two states: ACTIVE and INACTIVE.
  • The process control channels can be set to be in Manual Mode or Auto Mode. Manual means that the state of the relay is determined and fixed by the user whereas auto means that it is determined by the rules that have been configured for that particular channel.
  • On p. 5-3 of the PPM manual (titled Process Control Warnings), it explains that the safe setting is the INACTIVE state. When the PPM is turned on, all process control channels are set to Manual Mode, INACTIVE. Therefore, the safe settings should correspond to the relay being in the INACTIVE state.
  • NB: When the PPM is turned on, and everything is ready and safe for normal operation, the relay channels should be turned from Manual mode to Auto mode in order for the relays to respond appropriately.
  • On the back of the PPM, each relay has three pins: COMMON (C), INACTIVE (I,normally closed) and ACTIVE (A,normally open).
  • The Signal Processing System box which processes the signals from the relays expects the relays to be set as normally closed. In other words, use the C and I pins. Do not use the A pin.
  • There are two pairs of wires coming from the SPS, each one corresponding to one relay. Channel 1 controls the He level warning and channel 2 controls the helium level alarm.
  • The cables coming from the PPS box are too short, so there is a 4-wire extension cable that extends to the relay connector on the back of the PPM. This extension has 4 wires: red, green, white and black. Each two-wire cable coming from the SPS has one white and one black wire.
  • These wires are connected as follows: red – 1C; green – 1I; white – 2C; black – 2I. This corresponds to the white of the warning cable being connected to 1I, the black of the warning cable being connected to 1C, the white of the alarm cable being connected to 2C and the black of the alarm being connected to 2I.
  • The two cables from the SPS are labeled 2106842 (warning) and 2106843 (alarm).
  • Warning: The relay settings should not be changed without notifying the relevant people in charge.

Helium flow and helium purge

As with PT106, the pressure transducers and flow meters in the helium flow and helium purge manifolds are powered by the PPS group. We receive the raw analog voltage signals as if they were coming directly from the pressure transducers and flow meters themselves. As for PT106, the signal cable has a black (signal), white (common) and shield.

PT701, PT501

  • These are MKS model 722A. The manual is here.
  • PT501 is 722A13TGA2FA and operates over the range of 0-1,000 torr with analog output 0-10 V DC.
  • PT701 is 722A14TCE2FJ and operates over the range of 0-10,000 torr with analog output 0-10 V DC.
  • On p 21 of the manual, it explains that the signal produced is proportional to pressure with 10 V = 1000 torr for PT501 and 10 V = 10,000 torr for PT701. PT501 has a factor of 10 better resolution.
  • According to the manual (p 17) for the MKS PDR-D-1 readout box that is in the electronics cabinet, it's possible to read one of these gauges using that readout box.
  • PT501 is connected to the MKS box as follows: white to S GND, black to PRESS IN and shield to power line ground. Based on observation, the voltage out of the MKS box is the same as if it were coming from the pressure transducer itself.
  • PT701 is connected directly to the ADCs through the breakout box in the cabinet.

FM701, FM501

  • These are Omega model FMA 1706-24VDC.
  • The manual is here or here.
  • On p. 8 of the manual you can see that the output signal is calibrated by default to be 0 V at 0 slpm and 5 V at the max range on the nameplate which is 50 mL/min for both FM501 and FM701. The conversion from volts to flow rate is linear.

Wiring and calibration of analog signals

To come: clean up this section.

The ADC card

  • All of the analog signals pass through the electronics cabinet and are read by the ADC card in the data acquisition PC.
  • Although the ADC card is inside the PC, all of complicated analog wiring is done inside the electronics cabinet, so it is discussed in this section.
  • The ADC card plugs into the mother board of the data acquisition PC and is model DAQe-2213 from ADLink.
  • The manufacturer's website is here. The manual for the card is here. The manual for programming the card in C is here.
  • The pin assignments on the card are shown on p. 20 of the manual. We use the CN1 connector and do not use the CN2 connector. The CN1 connector is the one that's on the right-hand side when you're looking at the back of the PC. The card is connected to the electronics cabinet by a grey SCSI cable that plugs into the right-hand connector on the PC and into the green breakout board that is mounted on a DIN rail at the back right-hand side (when looking from the front) of the cabinet. The pin labeling on the breakout board corresponds to the pin labeling given on p. 20 of the manual for the ADC card: if you connect a wire to some given pin number on the board in the cabinet, then that will in fact be connecting it to the same pin number on the card.
  • In total, the card has 16 analog inputs and two separate ground reference inputs.
  • To learn about how to physically connect wires to the card, it's important to first read thoroughly pages 19-20, 23 and 26-28 of the manual.
  • Each analog input can be set up to correspond to either (i) a floating signal (not referenced to the power line ground) or (ii) a ground-referenced signal.
  • Each analog input can also be set up to correspond to either (i) differential inputs (one channel using two of the 16 possible inputs) or (ii) single-ended input (one of the 16 inputs plus one of the two possible grounds). So before wiring any signal, it's good to have figured out two things: 1) whether the signal is referenced to ground or is floating; and 2) whether you want to use differential input or single-ended input.
  • In the C program that controls the data acquisition, the card is configured inside the function D2K_AI_CH_Config as either: AI_RSE (referenced single-ended mode, each channel to the AIGND pin, relevant for signals referenced to a ground that is floating relative to the power line ground); AI_NRSE (Non-referenced single-ended mode, one channel relative to the AISENSE pin, relevant for signals referenced to the power line ground); or AI_DIFF (Differential mode, which requires two channels and can be used either for floating signals or ground-referenced signals).
  • If a floating signal is set up to be read between differential inputs, then note that a bias return path to AIGND must be provided, as shown in figure 3-4 of the manual.


Analog signal wiring

  • The following table summarizes what electronics we have that produces analog signals and shows whether they are floating or ground-referenced:
signal source floating or ground referenced [5] differential or single-ended [5] cables to cabinet come from where? displayed by the TSPS? displayed by an Omega/MKS meter? comments/instructions
FM101 ground referenced single-ended GHC [2] no no Connect wires directly from GHC to ADC card. [8]
PT102 not read by the ADC card [1] not read by the ADC card [1] GHC no yes Connect wires from GHC to Omega meter but do not connect Omega meter to ADC card.
PT103, PT105 floating single-ended GHC no yes Connect wires from GHC to Omega meter S- and S+. These Omega meters have analog outputs. Connect wires from Omega meter VOLT and RTN to ADC breakout board.
PT106 ground referenced differential TSPS yes yes Connect wires from TSPS to +S IN, -S IN of Omega meter. This Omega meter has an analog output. Connect the VOLT and RETURN pins of the Omega meter to the ADC breakout box. [7]
PT107, PT201 floating single ended VIC [3] no yes Connect wires from pressure transducers to Omega meter S- and S+. Since the Omega meters used for these PTs do not have analog outputs, just connect directly from S- and S+ to the ADC breakout board.
PT301, PT302 floating single ended VIC no yes Connect wires from pressure transducers to Omega meter S- and S+. Since the Omega meters used for these PTs do not have analog outputs, just connect directly from S- and S+ to the ADC breakout board.
FM501 ground referenced [6] single-ended TSPS [4] no no Connect wires directly from TSPS to ADC breakout box.
PT501 floating single-ended TSPS no yes Connect wires from TSPS to MKS box. Wires from TSPS are ground referenced. Connect wires from MKS box to ADC breakout board. Wires from MKS are floating.
FM701 ground referenced single-ended TSPS yes no Connect wires directly from TSPS to ADC breakout box.
PT701 ground referenced single-ended TSPS yes yes

[1] - Since the Omega meter that reads PT102 does not produce an analog output, and since the transducer itself produces an analog current signal, and since the ADC card reads voltages, we would need to convert the current from PT102 to a voltage in order to read it. Since PT102 is redundant with PT103, it's not worth the trouble of doing so. But PT102 is still displayed on one of the Omega meters.
[2] - GHC refers to the Gas Handling Cabinet which is the blue cabinet underneath the vent isolation cabinet platform.
[3] - VIC refers to the Vent Isolation Cabinet which sits on the platform partway between ground level and mezzanine level in the area outside the entrance of the cave.
[4] - TSPS refers to the Target Signal Processing System which is the electronics panel that has a touch screen and is also under the VIC platform.
[5] - floating or ground referenced and differential or single-ended refer to the signal that is fed to the ADC card.
[6] - all signals from the TSPS are relative to the power line ground.
[7] - the signal wire from the TSPS is black. The ground wire is white. Note that this is the opposite of wiring from the GHC.
[8] - the signal wire from the GHC is white. The ground wire is black. Note that this is the opposite of wiring from the TSPS.

Ground loops and shielding

An interesting discussion of shielding strategies can be found in the book "Noise Reduction Techniques in Electonic Systems" of which someone has posted the relevant section here.

Since VOLT, RTN, S+, S-, E+ and E- of the Omega meter all have no continuity to the power line ground, it's possible to wire PT102, PT103 and PT105 with all of the necessary grounding of signals and shield at both ends without introducing any ground loops. The drawing here shows how. ACTUALLY, WE SHOULDN'T DO IT THIS WAY. To come: I'LL REWRITE THIS.

To come: in cases where it matters record which cable has shield grounded where.

Calibration of the pressure transducers

name model voltage range pressure range nominal conversion IN1 RD1 IN2 RD2 comments about RD1, IN1, RD2, IN2
PT107 Omega PX203-030A5V 0.5 - 5.5 V 0 - 30 psia P = [(30 psia) ÷ (5 volts)] x [V - 0.5 volts] 506 0 4978 1393 They were determined using actual pressure measurements.
PT201 Omega PX203-030A5V 0.5 - 5.5 V 0 - 30 psia P = [(30 psia) ÷ (5 volts)] x [V - 0.5 volts] 0128 000 2486 0754 They were done using actual measurements between 0 torr absolute pressure and 739 torr absolute pressure although the 739 was recorded as 754 torr as shown here. Since we don't care about the pressure all that much, we don't care about the fact that RD2 is slightly high. For this pressure transducer and PT301 we are only ever interested in whether we see vacuum or not vacuum. Beyond that, the units could actually be totally arbitrary. Note that for some reason the offset in PT201 is different from what's specified (see the IN1 column or the next table below).
PT301 Omega PX303-050A5V 0.5 -5.5 V 0 - 50 psia P = [(50 psia) ÷ (5 volts)] x [V - 0.5 volts] 501 0 5885 2820 They were determined using actual pressure measurements. Like PT201, we are only ever interested in whether we see vacuum or not vacuum.
PT302 Omega PX303-050A5V 0.5 -5.5 V 0 - 50 psia P = [(50 psia) ÷ (5 volts)] x [V - 0.5 volts] 0515 000 3558 1550 have not been verified but are probably close to correct
PT701 MKS 722A14TCE2FJ 0 -10 V 0 -10,000 torr absolute P/torr = V/(1000 volts) Does not go to an Omega meter. The calibration has not been redone by us but is as specified by the manufacturer.
PT501 MKS 722A14TCE2FJ 0 -10 V 0 -1000 torr absolute P/torr = V/(100 volts) Does not go to an Omega meter. The calibration has not been redone by us but is as specified by the manufacturer. PT501 is actually not being used.

The following table shows pressure and voltage pairs that are used when converting voltages to pressures in the DAQ. The voltage output by the pressure transducer is a straight line versus pressure, so in principle you just need two points to define the calibration.

name V1 (volts) P1 (torr) V2 (volts) P2 (torr) resulting conversion comments
PT107 0.506 0 4.978 1393 P=(311.3 torr/volt)x(V-0.506 volts) Just taken from IN1, RD1, IN2 and RD2 above.
PT201 0.128 0 2.486 739 P=(313.4 torr/volt)x(V-0.128 volts) From actual voltage measurements with the DAQ software and a pressure measurement at atmosphere with the mensor gauge. Note that for some reason the offset in PT201 is different from what's specified.
PT301 0.511 0 1.957 739 P=(511.1 torr/volt)x(V-0.511 volts) From actual voltage measurements with the DAQ software and a pressure measurement at atmosphere with the mensor gauge.
PT302 0.515 0 3.558 1550 P=(508.7 torr/volt)x(V-0.515 volts) Just taken from IN1, RD1, IN2 and RD2 above.
PT701 0 0 10 10,000 P=(1000 torr/volt)xV From the formula specified by the manufacturer.
PT501 PT501 is not being used.


The following is a table of pressure ranges and voltage ranges of the pressure trandsucers that go to Omega meters with an analog output. Also given are the calibration settings of the Omega meter.


name model pressure range IN1 RD1 IN2 RD2 RD1 OUT.1 RD2 OUT.2 note
PT102 Omega PX880-100GI 0-100 psig 2004 0 9648 0976 N/A N/A N/A N/A The Omega box of PT102 does not have an analog output, nor do we read the analog current out of PT102. Our ADCs measure voltage. We could of course measure current, but since PT102 isn't all that important we don't worry about it.
PT103 Omega PX880-100GI 0-100 psig 1977 0 6341 2961 0 00.00 5000 10.00 RV102 and RV103 are designed to release at 100 psid. Although we're usually dealing with pressures that are smaller than 100 psid, we still want to be able to see these higher pressures in PT103 and PT105 when they occur.
PT105 Omega PX880-100GI 0-100 psig 2080 0 7054 2959 0 00.00 5000 10.00 RV102 and RV103 are designed to release at 100 psid. Although we're usually dealing with pressures that are smaller than 100 psid, we still want to be able to see these higher pressures in PT103 and PT105 when they occur.
PT106 Omega PX303-100A5V 0-100 psia 205 0 723 1315 0 00.00 1800 09.00 Since RV104 releases at about 1600 torr, we set the max voltage output defined by RD and OUT.2 to be 2000 torr at 10 V.

Calibration of flow meters

The flow meters output analog voltages between 0 and 5 volts that are proportional to the flow rate.
The conversion for FM101 is (flow rate)/slpm = 3.0*(V/volts). Flow rate in slpm is just three times the voltage in volts.
The conversion for FM701 and FM501 is (flow rate)/(mL/min) = 10.0*(V/volts). Flow rate in mL/min is just ten times the voltage in volts.

Note that to convert the flow rate of hydrogen gas to a fill rate of hydrogen liquid, you can use the density of hydrogen liquid which is given in Leachman, Jacobsen, Penoncello and Lemmon, J. Phys. Chem. Ref. Data 38, 721 (2009) here: http://jpcrd.aip.org/resource/1/jpcrbu/v38/i3/p721_s1


To come:

  • Include the diagram showing how to connect all of the analog signals to the breakout board in the cabinet.
  • Show how to connect the breakout board to the PC.

Wiring of the RS232

To come:

  • Show how the thermometers are connected to the temperature readouts and temperature controllers in the cabinet.
  • Show how the temperature readouts and controllers are connected to the PC.

Wiring of the thermometers

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