6
Service & Maintenance
30
Series 907 Analog Convection Transducer
Instruction Manual - #109070001
Figure 6-1: Transducer Calibration Points
6.6 Adjusting the Set Point
Attach a digital voltmeter to the Common tip jack and either the Setpoint 1 or Setpoint 2 tip jack on
the transducer. Adjust the corresponding potentiometer with a small screwdriver until the voltage
reading coincides with the desired set point pressure shown in Figure 5-2.
When an LED is ON, the measured pressure is below the set point value, the normally open relay
contact is closed, and the normally closed contact is open. When an LED is OFF, the measured
pressure is above the set point value, the normally open relay contact is open, and the normally
closed contact is closed. If a power or sensor failure occurs, the LED will turn OFF.
6.7 Leak Detection
Its inherent sensitivity to gas type makes the Series 907 Transducer useful for detecting leaks, at rates
greater than 10
-4
std cc/sec of helium, in foreline and roughing systems. It is a useful complement to
a mass spectrometer leak detector, which locates smaller leaks.
Probe the suspected leak areas with a gas that has a molecular weight different than that of the
system gas. Helium or argon gas is suitable for probing a system pumping air or nitrogen.
1.
Pump the vacuum system to a base pressure.
2.
Slowly and methodically probe with a small amount of gas. Flooding the leak or moving
quickly past the leak can confuse the search since time lags may be significant.
