5 Service and maintenance
58 |
266 MODBUS® multivariable transmitter User manual 2105216 Rev. AB
RTD wiring verification
Before finalizing the installation of the RTD, verify the RTD to transmitter cable is functioning properly. Perform the following
procedure to verify that the cable is free from damage.
1.
Verify that the RTD to transmitter cable length does not exceed the maximum distance of 100 ft.
2.
Use a digital voltmeter, set to ohms, to perform the following measurements at the cable end nearest the transmitter:
a.
Attach the voltmeter alligator clips to each white wire end. The measured value should be
≤ 2.5 ohms.
b.
Attach voltmeter alligator clips to each black wire end. The measured value should be
≤ 2.5 ohms.
3.
If either measurements are out of specification, the RTD to transmitter wire may be damaged. Further investigate cable for
damage or replace cable.
Removing the transmitter from service
If the transmitter is in production and needs to be removed from service, isolate the transmitter from the measurement stream by
decommissioning the transmitter.
1.
Open the equalizing valves (Figure 47, items A and B) on the manifold.
2.
Close the high and low pressure tap valves (Figure 47, items L and H) to block the process stream.
3.
Vent the system by opening the manifold vent valve (item C).
Figure legend:
A) Low side equalizer valve
B) High side equalizer valve
C) Manifold vent valve
H) High pressure side
L) Low pressure side
Figure 47: Transmitter with a 3-valve manifold (for illustrative purposes only)
H
L
H
L
A
B
C
Ven t/Test
Ven t/Test
Pro cess
Pro cess
Instrument
H
L
Orifice plate
Summary of Contents for 266 MODBUS
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