MKS 937B - 6.7 Leak Testing Procedures

MKS 937B Operation Manual
47
@002ACKOFF;FF
The following serial command turns on/off the degas power for a hot cathode gauge connected to
937B remotely.
@254DGn!ON;FF
Here, n=1,3,5, which is corresponding to the gauge connected to channels A1, B1, and C1,
respectively.
If the command is properly sent, the corresponding response will be:
@002ACKON;FF
Use the following command to turn off the degas power:
@254DGn!OFF;FF
The expected response is as follows:
@002ACKOFF;FF
6.7 Leak Test Using the 937B Controller
6.7.1 Leak test principle applied for the 937B
A leak test with the Series 937B Controller is not intended to replace mass spectrometer leak
detectors. It offers a simple and inexpensive method for locating leaks in high vacuum systems.
Under ideal conditions, a Pirani sensor can detect leaks as small as 1x10
-4
Torr l/s and the cold/hot
cathode sensor can be used to detect leaks as small as 1x10
-7
Torr l/s.
The principle for detecting a leak with the 937B controller is based on the gas dependency of the
pressure reading for the pirani (due to thermal conductivity differences between gases) and the ion
gauge (due to the difference in the ionization probability in the gases), that is, when different gases
(such as helium or argon) enter into the vacuum system, a change in gas composition will lead to a
change in “indicated pressure”, thus, indicating a leak in the system.
Leak Test Mode will work with all sensors except the capacitance manometer, which is not gas
dependent. If the LED indicated channel is a capacitance manometer, no leak checking status will be
displayed on the LCD screen.
6.7.2 Procedures for a leak test with the 937B
1. With the controller on, use either the or key to select a desired
sensor (must be a gas dependent sensor, Pirani, Convection Pirani, CCG, or
HCG) with the assistance of the green LED.
2. Pump down the system to base pressure, and make sure the pressure is
stabilized.
3. Press the
Leak
Check
key to display the leak check status on the LCD screen.
Once the
Leak
Check
key is pressed, the pressure indication for the corresponding
leak checking channel will turn to blue.
4. Press
Beeper
if you want to use the beeper to provide audible assistance for the leak
checking.
Beeper
Zero
Leak
Check