RTD Temperature Sensor Calibrates Itself

Endress+Hauser’s iTHERM TrustSens hygienic RTD is heralded as the world’s first self-calibrating temperature sensor. Its self-calibration process functions in situ and provides the necessary documentation to meet the conformance requirements for various regulatory agencies. The temperature sensor is calibrated after every sterilize-in-place (SIP) cycle, eliminating the risk of an undetected calibration drift and of bad batches.


The sensor measures temperatures from -40°C to +160°C (-40°C to +320°F), works in pressures up to 725 psi, and provides a 4 mA to 20 mA output with HART. The output represents the measured process variable, and the HART signal contains diagnostic and status information.


Other features include an integrated ceramic reference based on the Curie Point of the reference material, which means the temperature at which its ferromagnetic properties abruptly change. The change can be detected electronically. For applications using SIP operations, where steam at +121°C (+250°F) is used to sterilize equipment, TrustSens uses a reference material with a Curie Point of +118°C (+244°F). When the SIP process reaches 118°C, the reference sensor sends a signal. Simultaneously, the RTD measures the temperature. Comparison between these two values is a calibration identifying errors in the temperature sensor. If both sensors see 118°C, the RTD sensor is still in calibration. If the measured deviation is outside set limits, the device issues an alarm or error message, which is also displayed via a local LED.


The calibration procedure can store up to 350 calibrations and can also produce printable and uploadable audit-proof calibration certificates using asset management software such as Endress+Hauser’s FieldCare. The sensor is available with a variety of hygienic process connections (e.g., 1/2 to 3-in. Tri-Clamp, Varivent, etc.) and can be configured for direct immersion measurement or with a protective thermowell for easy removal from the process. More information is available on the iTHERM TrustSens page.


Endress+Hauser Inc.

Greenwood, IN


[email protected]