How To Check the Transducer Zero
Chapter Two: Installation
18
How To Check the Transducer Zero
Check the transducer zero prior to the initial operation and then periodically as required. The
zero can be set (or reset) by adjusting the zero potentiometer located on the top cover of the
transducer or, on the front panel of an MKS Power Supply/Readout, if you are using one. Refer
to Figure 1, page 7, for the location of the zero potentiometer on a low pressure 722 transducer;
Figure 3, page 8, for a high pressure 722 transducer.
How To Zero the 722 Transducer
To zero the 722 transducer, you must pump the unit, with the power on, down to a pressure less
than the transducer’s resolution (0.01% of Full Scale).
Note
The zero adjustment
must
be made at a pressure less than the
transducer’s resolution (0.01% of F.S.).
In addition, you should position the transducer in the
same orientation
as
it will be positioned when installed in your system.
Zeroing a transducer at a pressure 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
transducer zero, you may use a vacuum leak detector with sufficient
vacuum pumping (to achieve proper zeroing pressures). In this case,
mount the transducer on the leak detector
in the same plane of orientation
as it will be during actual use
.
To properly zero an absolute transducer, follow this procedure:
1.
Install the transducer in a system and connect a power supply/readout.
2.
Pump the system down to a pressure below the resolution of the transducer.
Refer to Table 6, page 19, for recommended pressure levels.
3.
Using a small screwdriver, adjust the
ZERO
pot until the readout displays zero (0000).
Refer to the figure listed below for the location of the
ZERO
pot.
Low Pressure 722 Transducer:
Figure 1, page 7,
High Pressure 722 Transducer:
Figure 3, page 8.
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