Instruction manual
Troubleshooting
continued
RFT9739 Field-Mount Transmitter Instruction Manual
73
Before You Begin Getting Started Mounting
Power-Supply and
Sensor Wiring
Output Wiring Startup Troubleshooting
7.5 Power supply
Check for specified power at the transmitter terminals.
• If the transmitter power terminals are labeled "L" (line) and "N"
(neutral), the transmitter accepts an 85-250 VAC power supply.
• If the transmitter power terminals are labeled "+" (positive) and "–"
(negative), the transmitter accepts a 12-30 VDC power supply.
• Check all fuses.
7.6 Wiring
For transmitter wiring instructions, refer to
Chapter 4
, "Power-Supply
and Sensor Wiring," page 15; and
Chapter 5
, "Output Wiring," page 25.
Wiring problems are often incorrectly diagnosed as a faulty sensor. At
initial startup of the transmitter, always check the following:
1. Proper sensor cable, and use of shielded pairs
2. Proper wire termination
a. Wires on correct terminals
b. Wires making good connections at transmitter terminals
c. Wires making good connections at the sensor terminals
d. Wires properly connected at any intermediate terminal junction,
such as the user-supplied junction box between a Model DT
sensor and transmitter
If a fault condition is indicated, follow these instructions:
1. Disconnect the transmitter's power supply.
2. Unplug the terminal blocks from the transmitter electronics module.
3. Use a digital multimeter (DMM) to measure resistance between wire
pairs at the transmitter terminals:
• Drive coil, check terminals 1 and 2 (brown and red)
• Left pickoff coil, check terminals 5 and 9 (green and white)
• Right pickoff coil, check terminals 6 and 8 (blue and gray)
• RTD, check RFT9739 terminals 3 and 7 (yellow and violet)
4. If the measured resistance is outside the range listed in
Table 7-7
,
repeat the measurements at the sensor terminals.
5. Reinsert the terminal blocks and restore power to the transmitter.
6. Use the DMM to troubleshoot the flowmeter.
Table 7-7. Normal resistance 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 Brown to red 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
per °C
Lead length compensator Yellow to violet 4 to 7 100
Ω
at 0°C + 0.38675
Ω
per °C