MKS Baratron 127A, Instruction Manual, Page: 27 / 38

Chapter Four: Operation How To Zero the Type 127/128 Transducer
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Chapter Four: Operation
How To Zero the Type 127/128 Transducer
You must zero the transducer initially when you install it into your system and periodically
thereafter. The zero must be set by adjusting the zero potentiometer.
Note
Make sure that the unit is fully stabilized before attempting to adjust the
zero.
1. Pump down the unit, with power on, to a pressure less than the resolution (0.01% F.S.)
for approximately two to four hours (eight hours are required for the 0.1 Torr range).
Table 3, page 19, lists the maximum pressure for each full scale range.
2. Adjust the zero by turning the Zero potentiometer, located on the top of the unit.
Refer to Figure 5, page 15, for the location of the Zero pot.
The zero adjustment may also be made at the front panel of an MKS supplied readout/power
supply unit, if used.
Maximum Pressure Reading for Zero Adjustment
Full Scale Range Maximum Pressure for Zero Adjustment
0.1 Torr 5 x 10
-6
Torr
1 Torr 5 x 10
-5
Torr
2 Torr 1 x 10
-4
Torr
10 Torr 5 x 10
-4
Torr
100 Torr 5 x 10
-3
Torr
1000 Torr 5 x 10
-2
Torr
5000 Torr 2.5 x 10
-1
Torr
10,000 Torr 5 x 10
-1
Torr
15,000 Torr 7.5 x 10
-1
Torr
20,000 Torr 1 Torr
25,000 Torr 1.25 Torr
Table 3: Maximum Pressure Reading for Zero Adjustment