Varian 959D, Руководство по эксплуатации

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959D Leak Detector
2-13
2.5.2 Use of a Capillary Type Calibrated Leak for Tuning to He
To calibrate using a capillary type of calibrated leak:
Follow the procedure for checking calibration using a calibrated leak, Section 2.5.1
“Calibrating with a Calibrated Leak” on page 2-11, except:
❑
Apply helium (from a source) as a substitute for opening the valve on the calibrated
leak
❑
Remove helium as a substitute for closing the valve on the calibrated leak.
2.5.3 Tuning the Spectrometer Tube Using a Calibrated Leak for Tuning to He
When tuning is done carefully, the day-to-day changes will be very small and subsequent
calibration may require only slight adjustment of the CAL control. The 959D should be
warmed up before you attempt to tune the spectrometer tube. The controls referred to in the
following procedure are shown in Figure 2-2 on page 2-2 and Figure 2-4 on page 2-4.
To tune the spectrometer tube using a calibrated leak:
1. Perform steps 1 through 7 of the calibration procedure on page 2-11.
2. Turn RANGE to the value of the exponent indicated on the calibrated leak.
If the bar graph display is <1 or >9, move RANGE until the bar graph displays between
1 and 9.
3. Slowly adjust FOCUS for a maximum on the leak rate display.
It is now necessary to be sure that the spectrometer tube is tuning to a helium peak and
not another element such as carbon or hydrogen.
a. Close the valve on the calibrated leak.
b. The leak rate should drop to zero (one bar lit).
If the leak rate does not drop to zero, repeat the FOCUS adjustment and verification.
4. Slowly adjust ION on the secondary panel for a maximum on the leak rate display.
The ION control is a 10-turn potentiometer and normally needs to be adjusted only
slightly for a maximum peak on the display. When tuned to helium, the outer dial on the
ION control at the 12 o'clock position should indicate between 2 and 8.
5. Close the valve on the calibrated leak.