Emerson IFT9701 - Manual (Page 69)

Model IFT9701 Transmitter Instruction Manual 61
Troubleshooting continued
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To check integrity of sensor wiring circuits:
1. Disconnect the transmitter's power supply.
2. Disconnect sensor wiring from the transmitter's intrinsically safe terminal block in the sensor
wiring compartment. See Figure 8-1.
3. Use a DMM to measure resistance between wire pairs, as indicated in Table 8-4.
4. If the transmitter is remotely mounted from the sensor, repeat the measurements at the
terminal block in the sensor junction box to distinguish cable failure from sensor failure.
8.6 Over range and sensor failure conditions
If a sensor failure occurs, if the flowmeter cable is faulty, or if flow, temperature, or density goes
outside the sensor limits, all the following occur:
• The transmitter produces fault outputs.
• The diagnostic LED blinks ON 4 times per second.
• The optional LCD reads “SENS0”.
Table 8-3 Sensor terminal designations
Terminal number Wire color Function
1 Brown Drive +
2 Red Drive –
3 Orange Temperature –
4 Yellow Temperature lead length compensator
5 Green Left pickoff +
6 Blue Right pickoff +
7 Violet Temperature +
8 Gray Right pickoff –
9 White Left pickoff –
Table 8-4 Normal resistance and voltage ranges for flowmeter circuits
Notes
• Temperature sensor value increases 0.38675 ohms per °C increase in temperature.
• Nominal resistance values will vary 40% per 100 °C. However, confirming an open coil or shorted coil is more important
than any slight deviation from the resistance values presented below.
• Resistance across terminals 6 and 8 (right pickoff) should be within 10% of resistance across terminals 5 and 9 (left
pickoff).
• Resistance values depend on the sensor model and date of manufacture.
Circuit Wire colors
Sensor
terminals
Nominal resistance range
Drive coil Red to brown 1 to 2 8 to 2650
Ω
Left pickoff Green to white 5 to 9 15.9 to 300
Ω
Right pickoff Blue to gray 6 to 8 15.9 to 300
Ω
Temperature sensor Orange to violet 3 to 7 100
Ω
at 0°C + 0.38675
Ω
/°C
Lead length compensator Yellow to violet 4 to 7 100
Ω
at 0°C + 0.38675
Ω
/°C