Chapter Four: Operation How To Check the Pressure Transducer Zero
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Chapter Four: Operation
How To Check the Pressure Transducer Zero
Check the pressure transducer zero before operating the unit initially and then periodically as
required. The zero can be set (or reset) by adjusting the zero potentiometer located on the top
cover of the 649 controller or, on the front panel of an MKS Power Supply/Readout, if you are
using one.
Note
The outlet port serves as the pressure transducer inlet port. Figure 1, page
14, shows the flow direction arrow.
To zero the pressure transducer within the 649 controller, you must pump the unit, with the power
on, down to a pressure less than the pressure transducer’s resolution (0.01% of Full Scale).
Note
The zero adjustment
must be made at a pressure less than the pressure
transducer’s resolution (0.01% of F.S.).
In addition, you should position the unit in the same orientation as it will
be positioned when installed in your system.
Zeroing a pressure transducer above its stated minimum resolution creates a zero offset relative to
true absolute pressure. All subsequent readings are then linear and accurate relative to the offset
value.
Note
If your system cannot achieve a sufficiently low pressure to set the
pressure transducer zero, you may use a vacuum leak detector with
sufficient vacuum pumping (to achieve a proper zeroing pressure). In this
case, mount the unit on the leak detector in the same plane of orientation
as it will be during actual use.
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