Rosemount 8732

Reference Manual

00809-0100-4665, Rev AA August 2010

Troubleshooting the

8714i Meter Verification

Test

Figure C-1. Troubleshooting the

8714i Meter Verification Test

Table

8714i Meter Verification Functionality

In the event that the 8714i Meter Verification test fails, the following steps can be used to determine the appropriate course of action. Begin by reviewing the 8714i results to determine the specific test that failed.

Test

Potential Causes of Failure

 

Steps to Correct

Transmitter Verification Test

Unstable flow rate during

Perform the test with no

Failed

 

the verification test

 

flow in the pipe

 

Noise in the process

Check calibration with an

 

Transmitter drift

 

external standard like the

 

Faulty electronics

 

8714D

 

 

 

Perform a digital trim

 

 

 

Replace the electronics

 

 

 

 

 

Sensor Verification Failed

Moisture in the terminal

Remove the sensor and

 

 

block of the sensor

 

send back for recalibration.

 

Calibration shift caused by

 

 

 

 

heat cycling or vibration

 

 

 

 

 

 

 

Coil Circuit Health Failed

Moisture in the terminal

Perform the sensor checks

 

 

block of the sensor

 

detailed on page 6-8.

 

Shorted Coil

 

 

 

 

 

 

 

Electrode Circuit Health

Moisture in the terminal

Perform the sensor checks

Failed

 

block of the sensor

 

detailed on page 6-8.

 

Coated Electrodes

 

 

 

Shorted Electrodes

 

 

 

 

 

 

 

The 8714i Meter Verification diagnostic functions by taking a baseline sensor signature and then comparing measurements taken during the verification test to these baseline results.

Sensor Signature Values

The sensor signature describes the magnetic behavior of the sensor. Based on Faraday’s law, the induced voltage measured on the electrodes is proportional to the magnetic field strength. Thus, any changes in the magnetic field will result in a calibration shift of the sensor. Having the transmitter take an initial sensor signature when first installed will provide the baseline for the verification tests that are done in the future. There are three specific measurements that are stored in the transmitter’s non-volatile memory that are used when performing the calibration verification.

Coil Circuit Resistance

The Coil Circuit Resistance is a measurement of the coil circuit health. This value is used as a baseline to determine if the coil circuit is still operating correctly when the 8714i Meter Verification diagnostic is initiated.

Coil Signature

The Coil Signature is a measurement of the magnetic field strength. This value is used as a baseline to determine if a sensor calibration shift has occurred when the 8714i Meter Verification diagnostic is initiated

Electrode Circuit Resistance

The Electrode Circuit Resistance is a measurement of the electrode circuit health. This value is used as a baseline to determine if the electrode circuit is still operating correctly when the 8714i Meter Verification diagnostic is initiated.

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Emerson Rosemount 8732 manual Troubleshooting 8714i Meter Verification Test, 8714i Meter Verification Functionality