Teledyne HASTINGS 2002, Instruction Manual, Page: 13 / 49

page 13
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 arrow keys. The CAL light will start to flash,
signaling that the calibration can now be conducted.
3. Press, hold and release either the up or down arrow keys as necessary to adjust the display to
match the pressure indicated by the reference. Note: It may be necessary to hold the desired
key down for 5-10 seconds before any movement is seen.
4. Press and release the mode key as necessary to put the Model 2002 into 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 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 compo-
sition sensitive so 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 N
2
pressure readings. To select a different gas, refer to Table 1 to find the
number code of the gas to be entered. Press the blue circular up and down arrows simultaneously,
the GAS light will now flash. Use the up and down arrows to individually select the desired code.
Return the Model 2002 to the RUN mode.
TABLE 1
Gas Mode
Displayed Number
Gas
0.0 ............................ nitrogen
0.1 ................................ argon
0.2 ............................... helium
0.3 ....................... water vapor
0.4 .............................. custom
Note: Factory calibration is performed using nitrogen only. Displayed pressure mea-
surements using other gases are based on established gas thermal conductivity data.