MKS Baratron 122A Series, Manual, Page: 22 / 29

How To Adjust the Zero Chapter Four: Operation
16
Suggested Pressures for Zero Adjustment
Model Number Full Scale
Range
(Torr)
Lowest
Suggested
Pressure
Reading (Torr)
Lowest
Suggested
Pressure
Control (Torr)
Highest Base
Pressure for
Proper Zero
Adjust (Torr)
Warm-Up
Time Before
Adjusting Zero
(Minutes)
122AA-00010- 10 3 x 10
-3
5 x 10
-2
1 x 10
-3
30
122AA-00100- 100 3 x 10
-2
5 x 10
-1
1 x 10
-2
30
122AA-01000- 1000 3 x 10
-1
5 x 10
0
1 x 10
-1
30
Table 2: Suggested Pressures for Zero Adjustment
Lowest Suggested Pressure Reading
Lower readings are often possible, but not always practical; a stable operating environment
(temperature and air flow) permits lower readings. Optimum repeatability of low pressure
(<100 millitorr) measurement is achieved with temperature-controlled transducers.
Lowest Suggested Pressure Control
The pressures noted in this column are for reference, and represent the pressure reading of the
transducer at 50 millivolts signal output. A 50 millivolt DC signal is usually the preferred
minimum signal level, when integrating any electronic component into complex processing
systems.
Highest Base Pressure For Proper Zero Adjust
All capacitance manometers require initial and periodic zero adjustments be made at a pressure
lower than their minimum resolution in order to assure that the full dynamic range specified can
be achieved. Zeroing a transducer at some pressure above its stated minimum resolution will
create a “zero offset” relative (or unique) to the system on which the transducer is located. All
readings made subsequent to the offset will be linear and accurate relative to the offset zero value.