Emerson Process Management 8732 manual 8714i Meter Verification, Test, Sensor Signature Values

					Reference Manual
Rosemount 8732				00809-0100-4663, Rev BA
						January 2010
Troubleshooting the	In the event that the 8714i Meter Verification test fails, the following steps can
8714i Meter Verification	be used to determine the appropriate course of action. Begin by reviewing the
Test	8714i results to determine the specific test that failed.
Figure C-1. Troubleshooting the
8714i Meter Verification Test	Test	Potential Causes of Failure				Steps to Correct
Table
	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

8714i Meter Verification Functionality

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.

375Transducer Block, Diagnostics, Advanced Diagnostics, 8714i Meter Verification, Sensor Signature, Signature Values, Coil Resistance

AMS Tab Config/Setup, 8714i

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.

375

AMS Tab

Transducer Block, Diagnostics, Advanced Diagnostics, 8714i Meter Verification, Sensor Signature, Signature Values, Coil Signature

Config/Setup, 8714i

C-14