Meriam M4 Series Precision Calibrator Data Logger Manual - Manual (Page 36)

ZM4 Instruction Manual 9R87-B June 2012
36
Zeroing and Field Recalibration
To maintain the accuracy of the M4 it is recommended that both the pressure
and Volts/mA sensor be zeroed prior to use. Zero is located on the main
measure screen once the sensor is selected or under the Sensor setup
screen. Differential and Gauge sensors shall be vented to atmosphere before
executing a zero. Absolute pressure sensors must be pulled down to a
complete vacuum of 200 microns or less for optimum results.
To zero the Volts/mA sensor the shorting plug included with the unit must be
installed across the banana jacks. Follow the instructions on the screen to
perform the zero.
Periodic recalibration of M4 may be needed to maintain optimum
performance. The calibration menu is located under each sensor in the setup
menu. Simply follow the screen and apply the values requested.
Field recalibration should only be executed by qualified personnel using
suitable primary standards. These standards should meet the accuracy
requirements of your company or industry. Meriam recommends using
primary standards at least 4 times more accurate than the unit under test.
For pressure transmitters up to 200 PSI, Meriam recommends a deadweight
tester of at least ±0.0015% of reading for field recalibration. For transmitter
ranges of 200 PSI and above, a deadweight tester of at least ±0.0030% of
reading. When calibrating using a dead weight tester referenced to inches of
water, be sure the M4’s inches of water reference temperature matches that
of the dead weight tester.
If an error is made during field recalibration the restore factory defaults option
is located under the sensor in the setup menu.