For 1k ohm nickel temperature sensors, wire resistance can cause approximately 1F° (0.56C°) of error for every 250 ft (76 m) run of 18 AWG wire, or every 100 ft (31 m) run of 22 AWG wire. For 1k ohm platinum temperature sensors, wire resistance can cause approximately 1F° (0.56C°) of error for every 150 ft (46 m) run of 18 AWG wire, or every 50 ft (15 m) run of 22 AWG wire. To minimize error due to field wiring, limit the total resistance of all nickel temperature sensor wiring to 3 ohms, and all 1k ohm platinum temperature sensor wiring to 2 ohms.
To minimize wiring error in applications using 100 ohm platinum equivalent sensors, use the TQ-6000-1, 4 to 20 mA transmitter. Using a 4 wire (Kelvin) connection can also eliminate wiring error.
The 2.2k and 10k ohm thermistor applications permit wiring to be relatively long before wire resistance adds significantly to total resistance measured at the controller. As a general rule, a 150 ft (46 m) two-wire 18 AWG run contributes 2 ohms of error, or less than 1F° (0.56C°) error over the sensor operating temperature range.
Refer to the appropriate controller documentation for sensor wiring. See Table 1 for an explanation of the lead wiring color convention.
| Sensor type | Lead color |
|---|---|
| 1k ohm nickel | White |
| 1k ohm nickel averaging | White |
| 100 ohm platinum averaging | Red |
| 1k ohm platinum | White with blue strip |
| 1k ohm platinum averaging | Blue |
| 2.2k ohm thermistor | Red |
| 10k ohm thermistor | White with green stripe |