What is a temperature transmitter and what is it used for
A resistance sensor produces a change in resistance and a thermocouple a voltage of only a few millivolts. Such a signal is sensitive to interference and cable resistance, so it cannot be transmitted reliably over longer distances. A temperature transmitter amplifies and linearises this signal and converts it into a standard 4-20 mA current signal, which is immune to interference and connects directly to a PLC, controller, digital indicator or SCADA system.
Resistance sensors and thermocouples
Resistance temperature detectors (RTDs), most commonly Pt100 and Pt1000, work on the change in resistance of platinum with temperature. They offer high accuracy and stability and are the standard for ranges up to about 500 °C. Thermocouples consist of two dissimilar conductors joined at the measuring end, and the voltage generated is proportional to the temperature difference between the measuring and cold junctions. Types J and K cover general industrial applications up to about 1000 °C, while types S and B cover high temperatures up to 1700 °C in furnaces and metallurgy.
Products in the Fadip range
Head-mounted transmitters GI-22-2 (RTDs and thermocouples, -200 to +1820 °C, ±0.05% accuracy, 8 to 35 V DC supply) and ATX-2 (Pt and Ni sensors, -200 to +850 °C, ±0.2% accuracy) fit directly into the sensor's connection head and are available in ATEX versions.
Smart transmitters with HART protocol LI-24 for DIN rail mounting in a control cabinet and LI-24ALW in a field housing with display work with RTDs and thermocouples, with accuracy up to ±0.05% and ATEX and IECEx certification.
Compact transmitters PT-25 (-50 to +100 °C, stainless steel housing) and APT-2000ALW (-70 to +550 °C, HART, Pt100 or type K thermocouple) combine sensor and transmitter in one device.
Temperature sensors: CT-25 with a Pt100 element for -40 to +100 °C and a DIN EN 175301-803 or M12 connector, CT X with thin flexible probes (Ø3, Ø6, Ø8 mm) as Pt100 or type J and K thermocouples, and CT TC type J, K, S and B thermocouples for temperatures up to 1700 °C.
How to choose a temperature transmitter and sensor
The temperature range determines the sensor type: Pt100 up to about 500 °C, type K thermocouple up to 1000 °C, and S and B above that. The mounting method determines the transmitter type: in the sensor head, on a DIN rail in a cabinet, or a compact device with an integrated sensor. The output signal is 4-20 mA, with HART chosen when remote configuration and diagnostics are needed. To protect against pressure and aggressive media, the sensor is fitted in a thermowell, and for hazardous areas an ATEX or IECEx version is chosen.
Applications
Temperature transmitters and sensors are used in power generation, district heating and boiler houses, in the food industry on pasteurisers, CIP systems and cold stores, in the chemical and petrochemical industries, in HVAC systems and on hydraulic power units. High temperature thermocouples work in industrial furnaces, foundries, glassworks and on exhaust gases.
A complete measuring point from one supplier
Because Fadip manufactures thermometers, you get the sensor, transmitter, thermowell and an analogue thermometer for local reading in one place. See also our thermometers and pressure transmitters.
For a quotation, send us the temperature range, medium, pressure, probe length and diameter, mounting method, output signal and hazardous area classification. Our technical team will recommend a suitable solution within 24 hours. Contact us.
