Teledyne 2002 User Manual 2
TELEDYNE
HASTINGS
INSTRUMENTS
INSTRUCTION MANUAL
MODEL 2002
VACUUM GAUGE
Manual Print History
The print history shown below lists the printing dates of all revisions and addenda created for this manual.
The revision level letter increases alphabetically as the manual undergoes subsequent updates. Addenda,
which are released between revisions, contain important change information that the user should incorporate
immediately into the manual. Addenda are numbered sequentially. When a new revision is created, all
addenda associated with the previous revision of the manual are incorporated into the new revision of the
manual. Each new revision includes a revised copy of this print history page.
Revision C (Document Number 149-052002) ...........................................................................May 2002
Revision D (Document Number 149-102002) ..................................................................... October 2002
Revision E (Document Number 149-062004)............................................................................ June 2004
Revision F (Document Number 149-082005 .........................................................................August 2005
Revision G (Document Number 149-102005) ..................................................................... October 2005
Revision H (Document Number 149-082008) .......................................................................August 2008
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CAUTION
Refer to accompanying documents
CAUTION
If Equipment is not used in the manner specified
By this manual, protection provided
By the equipment man be impaired.
Hastings Instruments reserves the right to change or modify the design of its equipment without
any obligation to provide notification of change or intent to change.
Model 2002 Vacuum Gauge Page 2 of 37
Table of Contents
1.
GENERAL INFORMATION......................................................................................................................................... 4
1.1. FEATURES................................................................................................................................................................. 4
1.2. MODEL 2002 SENSORS.............................................................................................................................................. 4
1.3. MODEL 2002 CONTROL UNIT ................................................................................................................................... 4
1.4. SPECIFICATIONS........................................................................................................................................................ 5
2. INSTALLATION.............................................................................................................................................................6
2.1. RECEIVING INSPECTION ............................................................................................................................................ 6
2.2. QUICK START............................................................................................................................................................ 6
2.3. TRANSDUCER INSTALLATION.................................................................................................................................... 6
2.4. CONTROL UNIT INSTALLATION................................................................................................................................. 7
2.5. INITIAL OPERATION .................................................................................................................................................. 7
3. FRONT PANEL OPERATION...................................................................................................................................... 8
3.1. OVERALL FUNCTIONAL DESCRIPTION....................................................................................................................... 8
3.2. RUN MODE .............................................................................................................................................................. 9
3.3. HIGH AND LOW SET POINT MODES......................................................................................................................... 10
3.4. CAL MODE............................................................................................................................................................. 10
3.5. GAS MODE............................................................................................................................................................. 12
3.6. UNITS MODE......................................................................................................................................................... 13
4. REAR PANEL DESCRIPTION................................................................................................................................... 14
4.1. REMOTE ZERO INPUT.............................................................................................................................................. 14
4.2. ANALOG OUTPUT.................................................................................................................................................... 14
4.3. TTL OUTPUTS......................................................................................................................................................... 16
4.4. POWER ENTRY MODULE.........................................................................................................................................16
5. THEORY OF OPERATION........................................................................................................................................17
5.1. PIEZORESISTIVE SENSOR......................................................................................................................................... 17
5.2. PIRANI SENSOR....................................................................................................................................................... 19
5.3. DUAL SENSOR OPERATION ..................................................................................................................................... 21
6. COMMUNICATIONS OPTION BOARD.................................................................................................................. 22
6.1. RS-232-E INTERFACE SPECIFICATIONS................................................................................................................... 22
6.2. INTERFACE CONNECTOR PIN ASSIGNMENTS FOR RS-232 ....................................................................................... 23
6.3. OPERATION OF THE SERIAL INTERFACE .................................................................................................................. 23
7. RELAY INTERFACE OPTION BOARD ................................................................................................................... 27
7.1. RELAY BOARD SPECIFICATIONS ............................................................................................................................. 27
7.2. RELAY CONNECTOR PIN ASSIGNMENT ................................................................................................................... 27
8. 4-20 MA INTERFACE OPTION BOARD.................................................................................................................. 28
8.1. 4-20 MA INTERFERENCE CONNECTOR PIN ASSIGNMENTS....................................................................................... 28
8.2. OPERATION............................................................................................................................................................. 29
9. 0-10V INTERFACE OPTION BOARD......................................................................................................................30
10. TROUBLESHOOTING GUIDE.................................................................................................................................. 32
11. WARRANTY.................................................................................................................................................................33
11.1.
WARRANTY REPAIR POLICY................................................................................................................................... 33
11.2. NON-WARRANTY REPAIR POLICY .......................................................................................................................... 33
12. DIAGRAMS AND DRAWINGS.................................................................................................................................. 34
Model 2002 Vacuum Gauge Page 3 of 37
1. General Information
The Model 2002 is a wide range vacuum measuring instrument consisting of a digital microprocessor-based
display unit, a miniature, rugged, thin film based sensing element that measures from below 1x10-4 up to
100 Torr, a piezoresistive sensor that measures from 1 to 1000 Torr, EEPROM (Electrically
Erasable/Programmable Read Only Memory), and an interconnecting cable. Together, these components
provide accurate vacuum measurement over 7 decades of vacuum from 1x10-4 to 1000 Torr. This
instrument is a new design approach based on over 50 years of experience by Hastings Instruments with
well-known and widely used thermal conduction vacuum measurement techniques. The Model 2002 is
designed for quick, easy installation and will provide the user with long lasting, trouble free, accurate vacuum
measurement.
1.1. Features
• Wide dynamic range: 1x10-4 to 1000 Torr
• Compact rugged design
• Attitude insensitive
• Fast dynamic response
• Withstands 150 psig positive pressure
• Linear per decade
• Bakeable to 2500C
• TTL output process control
• Interchangeable transducer
• Corrosion resistant
1.2. Model 2002 Sensors
The Model 2002 transducer is comprised of an ion implanted piezoresistive, direct force sensor and a thin
film Pirani type sensor. The Pirani sensing element is a Pt thin film serpentine element (see Figure 5.3a)
deposited on a 1 micron thick Si3N4 membrane. The membrane is peripherally supported by a Si box
shaped die and is covered by a thick Si lid parallel to the membrane and open on two ends (see Figure 5.3b).
The piezoresistive unit is an ion implanted Wheatstone bridge in a 50 micron thick Si membrane peripherally
supported by a Si box shaped die which has been anodically bonded to a Pyrex substrate.
The dual sensor assembly is encased in a corrosion resistant 316 stainless steel tube shell. The durable tube
design withstands high pressure (150 psig/10.2 bar) and high pressure surges. Since the Pirani sensor is
miniaturized and employs a Pt thin film on a Si3N4 membrane (instead of a conventional long fragile wire),
the transducer can withstand high levels of mechanical shock.
The Model 2002 is designed for fast response. The micro machined sensing elements have a very small mass
and operate in a constant temperature (Pirani) and a constant current (piezo) feedback mode. This makes
response time very fast as compared to other commercially available sensors which have to change the
temperature of a significant mass to reflect pressure changes and have a large internal volume which must
equalize in pressure with the system before the sensor can reach its final value. The transducer’s small
internal volume (<1.5cc) permits rapid pneumatic response to system pressure changes. Further, the small
geometry of the transducer prevents a thermal convection current which allows the sensor to be mounted in
any orientation without calibration shifts.
1.3. Model 2002 Control Unit
The Model 2002 control unit consists of the power supply, Pirani resistance bridge control, signal processing
and display circuitry. The user interface consists of a flat panel display with smooth operating tactile
switches and large green LED digits (0.56"/14.2mm). The pressure is displayed in scientific format using a 3
digit mantissa and a 1 digit (plus the sign) exponent. The pressure can be displayed in Torr, mbar or Pascal.
The instrument comes standard with 2 alarm setpoints that have TTL level digital outputs. An optional dual
relay board can be internally mounted to trip on the alarm setpoints to turn on/off various equipment such as
pumps, valves, heaters, bake out ovens and safety equipment. An optional 4-20 mA or 0-10V analog output
Model 2002 Vacuum Gauge Page 4 of 37
board is also available. The Model 2002 instrument accepts an external TTL level "Remote Zero" to zero
the instrument when another instrument (e.g. an ion gauge) indicates that the pressure is less than 1x10-5
Torr. The standard analog output is linear per decade directly corresponding to the control unit’s display.
The Model 2002 comes calibrated for nitrogen. Conversion factors for other gases are selectable by the user
(see section 3.5). This direct readout display allows for flexibility in user system configurations which
operate with various gases.
An optional serial interface board can be installed to provide RS232 or RS485 support. The Model 2002
control unit fits a standard DIN 43700 insert (1/4 DIN) and mounts into a 3.62 in. (92 mm) square hole.
The case is constructed of NORYL rated UL-94-V1 (self-extinguishing plastic) and is equipped with
mounting brackets that are adjustable up to 3/16” (4.8mm).
1.4. Specifications
Measuring range .................................................................................................................. 1x10-4 to 10+3 Torr
....................................................................................................................................1.3x10
Accuracy (N2, T=230C) .................................................................. + 20% of reading (5x10
......................................................................................................... + 1.5% of reading (5x10
Ambient temperature operating range ............................................................................................... 0
Bakeout temperature (with transducer electronics removed)....................................................................250
-4
to 1.3x10+3 mbar
-4
to 5x10+1 Torr)
+1
to 1x10+3 Torr)
0
to 500C
0
C
Analog output.................................................................................. 1.0-4.5 Volts (0.5 VDC linear per decade)
Process control ................................................................................... 2 TTL outputs (1 TTL auto zero input)
Digital readout......................................................... four green LED - resolution is three digit (plus exponent)
Equipment operating range ................................................................................. 120/240 V~, 0.25A, 50/60 Hz
.........................................................................................A 6 ft., 3-wire power cord is provided with each unit.
Fuse ............................................................................................................................................... 250 V, 1/4 A.
Transducer mounting...................................................................................Any position without recalibration.
Transducer internal volume .....................................................................................................................<1.5cc
Wetted material .........................................................................................................Au, Si
............................................................................................................................................ Kovar
, Si, Pt, PyrexTM,
3N4
TM
and 316 SS
Stability with voltage ..................................................................................... Variation in reading undetectable
...................................................................................................as power fluctuates within power specification.
Weight (display, cable, and sensor)..................................................................Net: 2.5 lbs., Shipping: 3.4 lbs.
Transducer response time ...................................................................... typically, less than 150 msec for a step
....................................................................................................................change from 10
-3
Torr to 10+3 Torr.
Positive pressure.................................................................................. 150 psig, Recalibration may be required
..................................................................... if unit is exposed to pressures greatly exceeding measuring range.
Model 2002 Vacuum Gauge Page 5 of 37
2. Installation
This section is designed to assist in getting a new pressure gauge into operation as quickly and easily as
possible. Please read the following instructions thoroughly before installing the instrument.
2.1. Receiving Inspection
Carefully unpack the Hastings Model 2002 Instrument (part # HPM-2002), transducer (part #HPM-2002s)
and cable (part # CB 2002). Inspect all items for any obvious signs of damage due to shipment. Immediately
advise the carrier who delivered the shipment if any damage is suspected.
Compare each component shipped against the packing list. Ensure that all parts are present (i.e. transducer,
power supply, cables, etc.). In addition to the components listed on the packing list, the shipment includes:
AC power cord, panel mounting hardware, 9-pin female D connector. Optional equipment or accessories
will be listed separately on the packing list.
2.2. Quick Start
Follow this procedure to get your new Model 2000 vacuum gauge up and running.
1. Remove sensor from protective packaging.
2. Transducer tube may be installed in any orientation. However if condensation is likely to occur, then the port
should be orientated downward.
3. When installing 1/8” NPT style transducer tube, use the 7/16” wrench flats on the tube stem.
4. Connect transducer cable (orange) to controller.
5. Connect other end of transducer cable to transducer. A finger tight connection is adequate for proper operation.
6. If you have computer interface or process control options, these cables can now be attached.
7. I/O port diagram is given in the manual.
8. Connect the AC power cord. The Model 2002 automatically adjusts for 120/240 VAC 50/60 Hz.
9. Turn on power switch. Gauge is now reading pressure in units of “Torr” (default).
10. For best accuracy, the gauge should now be zeroed. Pump the vacuum system down to low 10-6 Torr (if
possible). Ideally the gauge should be operated in this condition for one hour.
11. Place the Model 2002 in the “CAL” mode by using the mode switch. Press the up and down arrows
simultaneously (“CAL” light is now flashing).
12. Press the “ZERO” switch once and return to the “RUN” mode using the mode switch.
The gauge is now ready for normal operation and the display is a true indication of the system pressure (P <
8 Torr is N2 equivalent).
2.3. Transducer Installation
The transducer may be installed in any orientation. Although the transducer is rugged and will perform well
in many harsh environments, the tube should be installed in a clean and careful manner. The tube is
configured with the vacuum fitting requested. If your vacuum environment is highly contaminated or has
unique fitting requirements, a Hastings filter or special adapter may be needed. Please contact the Hastings
Instruments Sales Department for assistance in your system configuration.
Model 2002 Vacuum Gauge Page 6 of 37
2.4. Control Unit Installation
• Environment:
• Indoor use
• Altitude up to 2000 meters
• Operating temperature range from 50 to 400C
• Maximum relative humidity: 80% for temperatures up to 310C decreasing linearly to 50% relative
humidity at 400C
• Installation category II
Panel Mount Instructions:
The control unit can be panel mounted. See detail on page 43. The dimensions of the hole on the panel are
3.62" x 3.62"(92.8mm x 92.8 mm). Slide the neoprene gasket that was shipped with the control unit onto the
case from the back. Slide the controller through the panel cutout. Hold the hardware against the side and
tighten the two screws.
Transducer Cable Attachment:
The threaded connector attaches to the transducer. A finger tight connection is adequate for proper
operation. The 9-pin male “D” connector attaches to the back panel (See Figure 4.2). The transducer cable
connects to the left hand connector when looking at the back.
I/O Cable Attachment:
The mating male plug to the I/O connector is supplied with the unit. An I/O cable can be wired with the 9pin female “D” connector to use the analog output, digital alarms or the remote zero functions. The
connector will accept 20 gauge or smaller wire. The pinout is shown in Figure 4.2 (back panel figure). A
detailed description of these pins is given in Section 4.
2.5. Initial Operation
Upon applying power to the control unit a pressure measurement will be given in Torr for nitrogen.
However, it is recommended that the user follow the instructions for zeroing and adjusting the output at
atmospheric pressure in Section 3.4 ("Cal Mode").
Model 2002 Vacuum Gauge Page 7 of 37
3. Front Panel Operation
3.1. Overall Functional Description
The front panel of the control unit is shown in Figure 3.1. The four circular blue buttons are used for the
selection of display readout and the input of data. The green data field displays the data as determined by
mode selection. The MODE switch toggles the control unit in a clockwise fashion among the six modes of
operation:
RUN Normal operation, pressure is displayed in scientific notation. The analog to digital converter
speed can be adjusted and the factory calibration can also be restored in this mode.
See Section 3.2 for further information.
HIGH High set point is displayed in scientific notation, above this pressure the HIGH TTL output
will be +5V.
LOW Low set point is displayed in scientific notation, below this pressure the LOW TTL output
will be +5V.
CAL Pressure is displayed and can be adjusted.
GAS Gas number is displayed and selection may be changed.
UNITS Units used to display pressure are selected.
In the RUN, HIGH, and LOW modes, it is possible to see the display indicate that the data is out of range.
Over range is indicated by X.XX x10- . Under range is indicated by 0.0 x10-. A measured pressure below
1x10-4 Torr is indicated by 0.0 x10+. In the case of an unconnected or faulty sensor(s), it is possible to see
“X”, “XX” OR “XX” See trouble shooting section (section 8) for more detail.
All six modes of the Model 2002 have features which can be accessed and modified after bypassing the front
panel interlock. The interlock is in place to prevent the accidental corruption of the instrument’s
configuration and calibration. The interlock is bypassed using the following steps:
1. Place the instrument in one of the six modes.
®
Model 2002
Control Unit
Front Panel
Fig 3.1
2. Simultaneously press the up and down switches.
The mode light will now flash indicating that the interlock has been bypassed.
Model 2002 Vacuum Gauge Page 8 of 37
Scientific Notation
The Model 2002 measures pressure that spans more than seven decades. In order to easily display these
readings, Hastings Instruments has employed scientific notation. In scientific notation, the mantissa (the
fixed point part) is multiplied by some power of 10 (given by the exponent).
Powers of 10
3
10
10
10
10
As an example: 7.60 x 10
= 1000 10-1 = 0.1
2
= 100 10-2 = 0.01
1
= 10 10-3 = 0.001
0
= 1 10-4 = 0.0001
+2
Torr
{
mantissa exponent
"7.60 multiplied by 100" = 760 Torr which is one atmosphere of pressure.
3.2. RUN Mode
Normal Operation
The Model 2002 will automatically enter RUN mode upon start-up. This is the mode for normal operation
and the mode in which the instrument will typically spend most of its time. In the run mode, the Model 2002
unit will continuously monitor the pressure and update the alarm conditions at the speed of the A/D
converter and will update the display about four times per second.
A/D Speed Adjust
The Model 2002 utilizes a 24 bit sigma-delta analog to digital converter. This type of converter averages the
input over time to reject interference. Longer averaging times result in more accurate readings. Increasing
the A/D speed will respond to sudden pressure changes faster.
While in the RUN mode, the user can adjust the A/D speed of operation. At start-up, the instrument will be
operating with an A/D frequency of about 60 Hz. The speed can be adjusted one step faster or slower. Each
step will increase or decrease the A/D frequency by a factor of two.
To adjust the A/D speed, press the MODE switch until the RUN light is illuminated. Then simultaneously
press the up and down switches. The RUN light will now flash indicating that the interlock has been
bypassed and the A/D speed can be adjusted. Push the up switch to speed up the A/D converter one step
and decrease the response time. This will result in a faster triggering of alarms or relays if a sudden
catastrophic failure occurs. Pressing the switch after the limit is reached has no effect.
Pushing the down switch will slow down the A/D converter and increase its accuracy. This will improve the
ability to resolve low pressure readings. If a certain speed is desired, press the UP or DOWN switch three
times and then press the other switch to select the other speed.
On older units. There will be no indication of the operating speed other than the least significant digits of the
display will tend to run at higher speeds. On units with software version 1.60 and above, press the ZERO
switch to display the decimation ratio (filtering). The larger the ratio, the longer the response time.
EEPROM Calibration Restoration
There are interlocks built into the CAL mode to minimize the chance of accidental alteration of the
calibration coefficients, but if calibration alteration does occur, the EEPROM calibration data can be restored
in the RUN mode by pressing the UP and DOWN switches simultaneously (RUN light will flash), then
press the “ZERO” switch, UP and DOWN switches (all three) simultaneously.
Model 2002 Vacuum Gauge Page 9 of 37
This will not correct the calibration if the tube has become contaminated or damaged. This reset will not
affect the gas selection, units or setpoints.
Also see unit’s mode for default calibration restoration.
3.3. High and Low Set Point Modes
The Model 2002 provides TTL outputs for process control. The I/O cable is attached via a 9-pin sub-D
connector to the rear panel of the control unit. The pinout is shown in Figure 4.2.
To view the high set point, place the Model 2002 in the HIGH mode by pressing the MODE switch to
illuminate the HIGH light and no other mode light. The display will show the set point selected. During
normal operation the alarm light will illuminate and the TTL output (pin # 3) will go high (+5 V) if the
pressure exceeds the set point.
Similarly, to view the low set point access LOW mode by pressing the mode switch until the LOW light is lit
and no other mode light is illuminated. During normal operation, the LOW light will illuminate and the
LOW alarm TTL output (pin # 4) will go high (+5 V) if the pressure becomes less than the set point.
The alarm lights cannot indicate an alarm condition while in the set point modes. Therefore, it is advisable
not to leave the instrument in these modes for extended periods.
To adjust a set point, press the mode switch until the set point is viewed. Then simultaneously press the UP
and DOWN switches. The active mode light will now flash indicating that the interlock has been bypassed
and the set point can be adjusted. The display shows the present set point.
Enter the new set point by using the UP and DOWN switches. Press and hold the UP switch to increase the
set point and the DOWN switch to decrease the setpoint. Allow a few seconds for the circuitry to respond.
Holding the button for and extended period of time, it will increase the adjustment rate. Release the button
and press again to get finer control of the exact trigger point.
At this point, the new set point is in temporary memory. If the instrument were unplugged now, the Model
2002 would revert back to the original set point upon restarting. Return the 2002 to the RUN mode to store
the set point in permanent memory.
Once the interlock has been bypassed in the HIGH mode, it will stay active until the CAL mode is entered.
This will allow the user to set both setpoints without repeating the interlock bypass.
3.4. CAL Mode
Optimal performance of the Model 2002 is achieved by performing in situ adjustments to the calibration
coefficient in the CAL mode. There are three calibration coefficients. These are the zero coefficient, the
midrange coefficient and the atmosphere coefficient. Once a tube has been fully calibrated the midrange
coefficient should never need further adjustment, but it may be helpful to adjust the zero coefficient or the
atmosphere coefficient under certain situations. Even though the operator inputs may be identical for
adjustment of all three coefficients, microprocessor will detect the power level of the tube and adjust the
proper coefficient for pressure level of the adjustment.
The CAL MODE presupposes that the operator is applying a known pressure of the correct gas
composition (see GAS MODE). The factory calibration points are 800 Torr, 7 Torr, and <1e-6 Torr. The
users calibration points are not required to be exactly those values, but should be somewhat close, and must
be within the ranges shown in the following figure. The HPM-2002 detects the voltage signal within the
sensor tube, which is converted and displayed as a pressure reading. The resulting pressure reading
determines which of the three coefficients will be adjusted.
To adjust a calibration coefficient press the MODE switch until the CAL light is illuminated. Then
simultaneously press the up and down switch. The CAL light will now flash indicating that the interlock has
been bypassed and the calibration can be adjusted. Press and hold the up switch to increase the displayed
value or the DOWN switch to decrease the displayed value. If the switch is held down for an extended
period of time the adjustment rate will start to increase. Release the switch and then press and hold again to
regain finer control of the displayed number.
Model 2002 Vacuum Gauge Page 10 of 37
An important point to be noted is the fact that after the adjustment, the new calibration coefficient is only in
temporary memory. If the instrument were unplugged at this point, it would revert back to the original
displayed value upon restarting. Place the Model 2002 back in the RUN mode to store all of the current
calibration coefficients in permanent memory.
To perform a full calibration on the Model 2002 system, first use the Zero Coefficient Adjustment
Procedure. Followed by the Midrange Coefficient Adjustment Procedure, and finally perform the
Atmosphere Coefficient Adjustment Procedure.
Zero Coefficient Adjustment
The zero coefficients corrects for the constant power level which is present over the entire pressure range.
Typically, this adjustment corrects for low pressure errors. The instrument will need to be re-zeroed often if
measurements are being made in the 10-4 Torr range, especially if the ambient temperature changes. The
transducer may have a temperature coefficient of up to 2x10-4 Torr/oC. The instrument remote zero input
will allow an external gauge such as an ion gauge to automatically re-zero the Model 2002 whenever the
pressure drops below the desired pressure level (if it has a TTL output).
NOTE: Do not attempt to zero the Model 2002 in pressures above 10-2 Torr; the microprocessor will not accept a
zero above this pressure.
To manually adjust the zero uses the following procedure:
1. If possible, evacuate the vacuum system into the low 10-6 Torr (1.33x10-6 mbar) range or as low as possible
below 10-4 Torr.
2. Allow the sensor to operate in this condition for a minimum of 15 minutes.
Model 2002 Vacuum Gauge Page 11 of 37
3. Place the instrument in the CAL mode, then simultaneously press the UP and DOWN switches to bypass the
interlock. The CAL light will start to flash indicating that the calibration mode has been activated.
4. Press the ZERO switch once if below 6x10-5 Torr otherwise use the UP and DOWN switch to adjust the
display of the Model 2002 to match the pressure indi cat ed by the refe rence. If using the UP and DOWN switch
to adjust the display, wait 20 seconds between presses at very low pressure to allow the adjustment to take
affect the data to settle.
5. The unit is now fully zeroed. Place the Model 2002 back in the RUN mode to store the zero in permanent
memory.
Midrange Coefficient Adjustment
The midrange coefficient corrects for errors in the slope of the power curve of the thin film Pirani.
Typically, this is due to the geometry of a particular sensor and will only need to be performed once in the
lifetime of the sensor. This adjustment might be needed if a full calibration is being performed in a gas other
than nitrogen. The zero adjustment will need to be performed before making this adjustment.
To adjust the midrange coefficient use the following procedure:
1. Evacuate the vacuum chamber and refill with the desired gas to a pressure of 7 Torr, as indicated by a reference
vacuum gauge.
2. Press the MODE switch repeatedly until the CAL mode is illuminated.
3. Simultaneously, press both the UP and DOWN switches. The CAL light will start to flash, signaling that the
calibration can now be conducted.
4. Press, hold and release the UP and DOWN switches as necessary to adjust the display to match the pressure
indicated by the reference. Note: It may be necessary to hold the desired switch down for a few seconds before
any movement is seen.
5. Press and release the MODE switch as necessary to return the 2002 to the RUN mode and store the coefficients
to permanent memory.
Atmosphere Coefficient Adjustment
If a reference high pressure gauge is not available, the ambient barometric pressure acquired from the
weather channel or other weather service can be used to adjust the proper reading.
To adjust the atmosphere coefficient, use the following procedure:
1. Press the MODE switch a sufficient number of times to enter the CAL mode.
2. Simultaneously, press both the UP and DOWN switches to bypass the interlock. The CAL light will start to
flash, signaling that the calibration can now be conducted.
3. Press, hold and release either of the UP or DOWN switches as necessary to adjust the display to match the
pressure indicated by the reference. Note: It may be necessary to hold the desired switch down for a few
seconds before any movement is seen.
4. Press and release the MODE switch as necessary to return the Model 2002 to the RUN mode and store the
coefficients to permanent memory.
3.5. GAS Mode
The Model 2002 can provide true pressure measurements in many gas environments. At pressure levels
above 32 Torr where the direct force piezoresistive sensor is operative, the instrument is gas composition
insensitive and measures the true pressure regardless of gas composition. The Pirani is gas composition
sensitive so below 32 Torr, the actual composition must be known and the Pirani calibrated in that gas.
When the vacuum system’s gas composition is dominated by a single gas species (for example, during system
venting with an inert gas), the user can enter a gas selection into the Model 2002. To view the gas selection,
place the instrument in the GAS mode and reference Table 1.
The Model 2002 is factory set to display N2 pressure readings. To select a different gas, refer to Table 1 to
find the number code of the gas to be entered. Press the UP and DOWN switches simultaneously, the GAS
Model 2002 Vacuum Gauge Page 12 of 37
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