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Temperature Compensation

Because pressure transducers consist of different materials, extreme temperature fluctuations may influence the transducer's output signal even though pressure remains constant. The rate of expansion or contraction of these different materials creates stresses within the transducer which may change the transducer's mechanical properties or electrical characteristics. Taber transducers are designed to minimize this influence and are compensated by electrically adjusting the transducer's output circuit.

 

Operating Temperature Range (OTR) - This is the temperature range over which the transducer can be safely operated without consideration of accuracy. The OTR is from the minimum operating temperature to the maximum operating temperature. Outside of this range, components may become damaged and the transducer may fail.

 

Compensated Temperature Range (CTR) - This is the range of temperature within which the transducer output is electronically corrected for errors induced by changes to materials or bridge resistance due to temperature.  This is also the range of temperature within which all tolerances specified for Thermal Zero Shift and Thermal Sensitivity Shift are applicable (temperature error).

 

Temperature Compensation vs. Output Type - Taber Industries' low-level pressure transducers include passive electronics that accommodate more extreme Compensated Temperature Ranges (CTR).  The typical maximums are -450°F to +70°F, or +70°F to +400°F.  The standard Operating Temperature Range (OTR) for Taber's Model 2211 is -100°F to +300°F.

High-level transducers (0-5Vdc isolated output) have a range of -65°F to +250°F for both the maximum CTR and OTR. This limitation is due to the active electronics, which cannot be subjected to temperatures beyond those ranges. The Taber 0-5Vdc non-isolated and 4-20mA circuit has a maximum CTR and OTR which is -40°F to +250°F.

 

There are several solutions to utilize a bonded-foil pressure transducer beyond its temperature limitations:

  1. Protect the high level transducers (0-5Vdc) from the extremes of heat and cold by cooling or warming the transducer.
  2. Insulate the transducer from the source of the heat / cold with an insulating material or distance the transducer away from the source of heat/cold via stand off plumbing (or use a combination of both).
  3. Use low level (3mV/V) transducers, whose passive electronic components allow use as low as -450°F or as high as +400°F.

 

IMPORTANT: Thermal errors are usually accounted for and specified separately from other errors that can affect transducer accuracy (e.g. linearity, repeatability, and hysteresis).