Fisher 846 - Page 28

Instruction Manual
D102005X012
846 Transducer
June 2017
28
WARNING
Personal injury or property damage could result from an uncontrolled process. Before removing the module cover, ensure
the process is properly controlled and the supply air to the transducer is turned off and vented. Unscrewing the module
cover removes power from the electronics and opens the supply and output air passages to atmosphere resulting in an
output signal of 0.0 psi.
WARNING
Personal injury or property damage could result from fire or an explosion. In explosive atmospheres, remove power and
shut off the air supply to the transducer before attempting to remove the terminal compartment cover or module cover.
Failure to do so could result in an electrical spark or explosion.
6. If applicable, remove the cover lock and screw to allow access to the terminal compartment cover.
7. Remove the terminal compartment cover (see Warning above), and use a milliammeter, or a digital voltmeter to
confirm that proper input current is supplied to the transducer.
8. Remove the terminal compartment cover (see Warning above), and short the loop across the positive (+) and the
negative (-) terminals to check the output. The output should be nearly 0 psi. If the output is not 0 psi, replace the
module final assembly.
9. Remove the terminal compartment cover (see Warning above), and, using a digital voltmeter, check the voltage
between the transducer positive (+) and negative (-) terminals. The voltage should measure 6.0 to 8.2 V. A lower
voltage can indicate a short in the input wires or defective controller. No voltage can indicate an open circuit in the
control loop. A voltage of greater than 8.5 volts indicates a problem with the transducer, a faulty or corroded
connection at the transducer, or an overcurrent condition. Replace the module final assembly. If the voltage is still
not in the proper range (6.0 to 8.2 V), remove the terminal block and terminal block connection board. Apply power
to the electrical feedthroughs. (Note the polarity of the feedthroughs, shown in figure 21.) Recheck the voltage. If
the voltage is in the proper range, replace the terminal block and terminal block connection board. If the voltage is
still not in the proper range, replace the housing.
10. Prepare to remove the module final assembly from the housing, or to remove the transducer from its mounting
bracket. Refer to Module Final Assembly in the Maintenance section for instructions on removing the module final
assembly from the module housing.
WARNING
Personal injury or property damage could result from an uncontrolled process. Before removing the module cover, ensure
the process is properly controlled and the supply air to the transducer is turned off and vented. Unscrewing the module
cover removes power from the electronics and opens the supply and output air passages to atmosphere resulting in an
output signal of 0.0 psi.
With the module final assembly removed from the housing, the following checks can be made.
1. Review the position of the Remote Pressure Reading jumper (if so equipped) and range jumper to confirm that they
are placed in the desired position. Refer to Electronic Circuit Board in the Maintenance section, and figure 18 for the
location of these jumpers and instructions on placement.
2. Observe the position and condition of the three module O‐rings to confirm they make a tight seal.
3. Verify that the O‐ring is correctly positioned in the groove on the flat face of the module cover. Refer to figure 21 for
an exploded view.