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Model 2002 Vacuum Gauge Page 9 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
10
3
= 1000 10
-1
= 0.1
10
2
= 100 10
-2
= 0.01
10
1
= 10 10
-3
= 0.001
10
0
= 1 10
-4
= 0.0001
As an example: 7.60 x 10
+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.
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