Emerson Fisher 846 Instruction Manual page 28

Type 846 and Model 3311
2. Confirm the general functionality of the unit by
using the diagnostic features described earlier in this
section.
3. Confirm that the filter-regulator is not full of water
or oil and that supply air is reaching the unit. The air
supply pressure should be at least 0.2 bar (3 psi)
greater than the maximum calibrated output
pressure.
4. Confirm that there are no major leaks in the
output signal line or from the output gauge port.
5. Confirm that there are no obstructions and the
screens are clean in the stroke port or the exhaust
port.
WARNING
Personal injury or property damage
could result from an uncontrolled
process. Unscrewing the module
cover removes power from the
electronics and the output signal will
be 0.0 psi. Before removing the
module cover, ensure the process is
properly controlled.
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.
5–4
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 6-9.) 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 Section 6 for instructions on removing
the module final assembly from the module housing.
WARNING
Personal injury or property damage
could result from an uncontrolled
process. Unscrewing the module
cover removes power from the
electronics and the output signal will
be 0.0 psi. Before removing the
module cover, ensure the process is
properly controlled
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
Section 6, and figure 6-5 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 6-9 for an exploded view.
4. Inspect the porting on the module final assembly
to determine if large amounts of contaminants have
entered the transducer.
Instruction Manual
Form 5739
February 2002