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Series 820 Instruction Manual Chapter 3 Operation
IM-82-C 3-3
Zero and Span Adjustments
The zero and span potentiometers are
accessed through the ports marked on
the side of the transducer. Normally,
span adjustments are not made unless
you are calibrating the transducer. The
span adjustment should not be used
unless you have a known, precise non-
zero flow rate that you wish to match.
Before making any zero adjustments,
confirm that the system has reached its
normal operating temperature and pres-
sure and the transducer is mounted in
its final position.
For transducers without the digital display:
1. Power the transducer and allow at least 30 minutes of warm up
time before attempting any adjustments. Set gas flow to zero.
Confirm that no flow exists.
2. Connect a digital multimeter to Pin 3 (0-5 Out) or, Pin 9 (4-20 Out)
and Pin 7 (Power Common). Check the reading. If it does not indi-
cate 0± .05 VDC, (or 4.0± .016mA) adjust the zero potentiometer.
Since the output does not indicate negative numbers, it is neces-
sary to adjust down from a slightly positive reading. Begin by
slowly rotating the zero pot clockwise until a positive reading is
indicated. To complete the zero adjustment, slowly turn the pot
counterclockwise until zero is achieved.
For transducers with the digital display:
1. Power the transducer and allow at least 30 minutes of warm up
time before attempting any adjustments. Set gas flow to zero.
Confirm that no flow exists.
2. Observe the reading on the digital display. If the reading is
greater than 1.5% of full scale, adjust the zero potentiometer.