Emerson Process Management 225 ユーザーズマニュアル
7
MODEL 225
TROUBLESHOOTING
TROUBLESHOOTING
TABLE 1.
Temperature
Resistance
10°C
103.9
Ω
20°C
107.8
Ω
25°C
109.7
Ω
30°C
111.7
Ω
40°C
115.5
Ω
50°C
119.4
Ω
PROBLEM
PROBABLE CAUSE
SOLUTION
Off-scale reading
Wiring is wrong.
Verify and correct wiring.
RTD is open or shorted.
Check the RTD for open or short circuits.
See Figure 12.
See Figure 12.
Sensor is not in process stream.
Confirm that the sensor is fully submerged in
the process stream. See installation section.
the process stream. See installation section.
Sensor is damaged.
Perform isolation checks. See Figure 12.
Noisy reading
Sensor is improperly installed in the
Confirm that the sensor is fully submerged
process stream.
in the process stream. See installation section.
Sensor cable is run near high voltage
Move cable away from high voltage conductors.
conductors.
Sensor cable is moving.
Keep sensor cable stationary.
Reading seems wrong (lower
Bubbles are trapped in the sensor,
Install the sensor in a vertical pipe run with
or higher than expected)
particularly in the toroid opening.
the flow against the toroid opening. Increase
flow if possible.
flow if possible.
Sensor is not completely submerged in
Confirm that the sensor is fully submerged
the process stream.
in the process stream. See installation section.
Cell constant is wrong. Wall effects
Calibrate the sensor in place in the process
are present.
piping. See calibration section.
Wrong temperature correction algorithm
Check that the temperature correction is
is being used.
appropriate for the sample. See analyzer
manual for more information.
manual for more information.
Temperature reading is inaccurate.
Disconnect the RTD leads (Figure 12) and
measure the resistance between the in and
common leads. Resistance should be close
to the value in Table 1.
measure the resistance between the in and
common leads. Resistance should be close
to the value in Table 1.
Slow temperature response to sudden
Use an RTD in a metal thermowell for
changes in temperature.
temperature compensation.
Sluggish response
Sensor is installed in a dead area in the
Move sensor to a location more representative
piping.
of the process liquid.
Slow temperature response to sudden
Use an RTD in a metal thermowell for
changes in temperature.
temperature compensation.