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Temperature has an effect on all analytical measurements. For this reason, nearly all Hamilton sensors have an option for temperature compensation. Temperature compensation comes in the form of a small resistance-based temperature element imbedded inside the sensor. This article details the types of temperature elements along with some basic information about applying temperature compensation in your applications.

Common Temperature Sensor Types

PT100

PT100 RTDs (Resistance Temperature Detectors) use a platinum element and produce 100 ohms at 0C. The element provides increasing resistance with temperature, thus at a typical ambient room temperature of 25°C the resistance will be around 110 ohms. PT100 RTD elements are an option with Hamilton traditional pH sensors.

PT1000

PT1000 RTDs also use a platinum element which produces 1000 ohms at 0°C. At room temperature the resistance is around 1097 ohms. PT1000 elements are found on Hamilton analog conductivity sensors, certain ORP sensors, and optional on Hamilton traditional pH sensors.

NTC Thermistors

NTC thermistors are resistance-based temperature elements that provide a decreasing response to increasing temperature. Hamilton uses the NTC 22 kohm thermistor element in all sensors with Arc intelligent technology as well as our optical dissolved oxygen sensors. These temperature elements output 22 kohm at an ambient temperature of 25°C.

Which temperature sensor do I use?

The type of temperature element will be influenced by the transmitter or control system which the sensor will be connected to. For instance, most pH transmitters will have several options for either PT100, PT1000, as well as several other temperature inputs. The selection of the temperature input in the transmitter must match the temperature element within the sensor for temperature to be displayed correctly.

Most modern analytical transmitters will auto-detect the temperature sensor based on the measured resistance which makes switching between sensors with different temperature elements very simple. Finally, Arc sensors have a built-in micro-transmitter at the sensor which performed the temperature compensation within the sensor so that the 4 - 20mA analog or Modbus digital output signal is already temperature compensated and no further corrections are needed.

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