P/N: 974153 |
Rev: 072016
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ECO: 46503
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providing a window into the process
-24-
All of these effects can be compensated for by setting the transmitter zero after the machine has
stabilized at operating temperature.
6.2 UTILIZING THE ZERO AND SPAN ACTUATORS
When the transmitter output needs to be corrected due to mounting location and temperature shift the
zero actuator can be used (if a HART Communicator is not available.) Please wait until the process has
been brought to operating temperature before zeroing. The zero procedure is only recommended after
the process temperature has stabilized and the SPX electronics housing has been permanently installed.
When the actuator is depressed in a certain sequence, the output will be corrected to reflect 4 mA. This
is done by the transmitter electronics automatically by adjusting the LRV and URV settings
simultaneously to the offset required to obtain 4 mA. Normally a Zero calibration is all that is required
after installation since the Transmitter span has been calibrated at the factory. In the event the Full
Scale output is not correct when checked against a calibrated pressure source or dead weight tester, the
transmitter span can be adjusted via the Span actuator. This is performed by applying a known
calibrated full scale pressure to the transmitter and depressing the Span actuator in a certain sequence.
When complete, the transmitter electronics will have adjusted the URV to correct to output to equal 20
mA.
The span actuator should never be used to set the URV without zeroing the PT with the zero actuator
first.
If for some reason the calibration is incorrect and the user wishes to revert back to the Factory
Calibration, a procedure can be performed to revert the calibration back to factory state. Refer to
“Resetting to Factory Default Settings” in this Chapter.
6.2.1 ZERO AND SPAN PROCEDURE
1.
Connect Power Supply to SPX signal leads with 250 Ohm load and milliamp meter in series with
loop.
2.
If commissioning on the bench with a dead weight tester or calibrated pressure source, ensure
pressure connection is free of leaks.
3.
Apply power to the SPX transmitter and observe loop current with zero pressure applied. It
should be 4 mA. If other than 4 mA proceed to step 4.
4.
Perform Zero Function.
i.
Do not remove seal screw when the circuit is live in a hazardous area.
ii.
Remove zero pushbutton seal screw.
iii.
Using a 2mm or smaller Allen key, depress the pushbutton for a ½ second.
iv.
Release pushbutton for a ½ second.
v.
Depress the pushbutton again for a ½ second and release.
ATTENTION
ATTENTION
