MKS Baratron 631D, Instruction Manual, Page: 45 / 64

Chapter Four: Operation
37
Chapter Four: Operation
How To Zero the Type 631D Transducer
MKS pressure transducers are precision measuring instruments, and will require initial and
periodic zero adjustments. Prior to initial operation and during periodic maintenance you must
check the transducer zero to verify the proper output. The zero can be set (or reset) by adjusting
the
ZERO
potentiometer located on the top of the transducer (refer to How To Adjust the Zero
Potentiometer, page 38) or at the front panel of any MKS Power Supply/Readout being used. If
the
ZERO
potentiometer fails to provide sufficient adjustment, the
COARSE ZERO
switch may be
used (refer to How To Adjust the Coarse Zero Switch , page 39).
To achieve the full dynamic range specified for the transducer, the zero adjustment must be made
at a pressure less than the transducer’s resolution (refer to Table 7: Highest Pressures Suggested
for Proper Zero Adjustment). Low range transducers should be pumped for at least one hour after
exposure to air to remove any moisture and to allow the pressure to stabilize. Zeroing a
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 available pressures are not sufficiently low 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 .