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 and DOWN switches as necessary to adjust the
display | to match the pressure indicated by the reference. Note: It may be neces- |
sary 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
TABLE 1
Gas Mode | Gas |
Displayed Number
0.0 | ............................... nitrogen |
0.1 | ................................... argon |
0.2 | ................................. helium |
0.3 | ..........................water vapor |
0.4 | ................................. custom |
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 light will now flash. Use the UP and DOWN switches to individually select the desired code. Return the Model 2002 to the RUN mode.
page 14 Model 2002
