Emerson PN 51A-404 instruction sheet Troubleshooting, Problem Probable Cause Solution

MODEL 404WIRING

TROUBLESHOOTING

PROBLEM	PROBABLE CAUSE	SOLUTION
Off-scale reading	Wiring is wrong.	Verify wiring.
	Temperature element is open or shorted.	Check temperature element for open or
		short circuits. See Figure 9.
	Sensor is not in process stream.	Be sure sensor is completely submerged in
		process stream.
	Variopol cable is not properly seated.	Loosen connector and reseat.
	Sensor has failed.	Perform isolation checks. See Figure 10.
Noisy reading	Sensor is improperly installed in process	Be sure sensor is completely submerged
	stream.	in process stream.
	Variopol cable is not properly seated.	Loosen connector and reseat.
Reading seems wrong (lower	Bubbles trapped in sensor.	Be sure sensor is properly oriented in
or higher than expected)		pipe or flow cell. See Figure 1.
		Apply back pressure to flow cell.
	Wrong temperature correction algorithm.	Check that temperature correction is
		appropriate for the sample. See analyzer
		manual for more information.
	Wrong cell constant.	Verify that the correct cell constant has
		been entered in the analyzer and that the
		cell constant is appropriate for the conductivity
		of the sample. See analyzer manual.
Sluggish response	Electrodes are fouled.	Clean electrodes.
	Sensor is sampling a dead area.	Move sample line to a location more
		representative of the process liquid.

FIGURE 9. Checking Temperature Element

Disconnect leads and measure resistance shown. The meas- ured resistance should be close to the value in the table.

FIGURE 10. Checking Continuity and Leakage

Disconnect electrode leads and measure resistance and continuity as shown. Sensor must be dry when checking resistance between electrode leads.

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