RTD Input - Temperature Transmitters convert Platinum, Copper, Nickel RTD or resistance sensor input signals to 4-20mA or 0-10V DC outputs for interfacing to controllers or other instrumentation.  

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    657T, 658T: Single or Dual Channel, RTD Input, Loop-powered Transmitter

    • 100 ohm Pt, 120 ohm Ni, 10 ohm Cu (selectable type) input
    • 4 to 20mA DC output
    • 12-50V DC from output loop power
    • DIP-switch configuration, push-button calibration
    These units accept universal RTD or resistance input signals and output proportional DC current signals. The output can also be linearized to the input sensor signal.
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RTD Input Temperature Transmitters - Continued

RTD technology provides an excellent means of measuring the average temperature over a surface by spreading the resistance wire over that surface, and this ability to average temperature over a surface area (or an immersion depth) will be more desirable for some applications. The use of a platinum RTD sensor may be preferred when a temperature measurement accuracy of better than 1°F or 1°C is required. By comparison, thermocouple accuracy will be on the order of 2°C to 4°C, typical. However, for point-of-contact measurement at temperatures above about 800°C (the maximum temperature at which platinum RTDs can be used), a thermocouple is the better choice due to its higher rated operating temperature.

Top Considerations When Selecting RTD Types

  1. The RTDs Temperature Coefficient of Resistance (TCR)
  2. Its relative sensitivity
  3. Its accuracy and repeatability
  4. Interchangeability
  5. Stability and drift characteristics
  6. Insulation resistance
  7. Its response time
  8. Its packaging and the thermal transfer mechanism between the sensed material and the sensor element.
  9. The negative effects of corrosion and contamination
  10. Shock and vibration
  11. Self-heating
  12. Meter loading
  13. And in some cases, even thermoelectric effects

Learn more about temperature measurement in this Technical Paper