The following chart indicates some inherent advantages and disadvantages of RTD’s or thermocouples.
|Accuracy||Limits of error wider than RTD||Limits of error smaller than thermocouples|
|Ruggedness||Excellent||Sensitive to strain, shock, and pressure|
|Temperature||-400° to 4200°F||-200° to 1475°F|
|Size||Can be as small as .01” sheath material, tip sensitive||Size limited to 1/16”, temperature sensitive for length of bulb|
|Drift||Should be checked periodically, higher than RTD’s||0.01 to 0.1°C per year, less drift than thermocouple|
|Resolution||Must resolve millivolts per degree, lower signal to noise ratio||Ohms per degree, much higher
signal to noise ratio than thermocouple
|Cold Junction Reference||Required||Not required|
|Lead wire||Must match lead wire calibration to thermocouple calibration||Can use copper lead wire for extension wire|
|Response||Can be made small enough for millisecond response time||Thermal mass restricts time to seconds or more|
|Cost||Low||Higher than thermocouples|
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