WIKA TR31 OEM Miniature Resistance Thermometer

WIKA TR31 OEM miniature resistance thermometer

The WIKA TR31 is a very compact, threaded resistance thermometer built for machines, hydraulics and drive systems rather than for large process plants. Its protection tube has a fixed G¼ B process connection, the electrical side is an M12 x 1 circular connector or a directly attached cable, and the output is either a raw Pt100 or Pt1000 signal or a 4 … 20 mA signal from a built-in transmitter. WIKA gives the range as -50 … +250 °C [-58 … +482 °F], with pressure ratings up to 140 bar for 3 mm and 270 bar for 6 mm sensor diameters, depending on version. Seven Star LLC supplies the TR31 in Oman and the GCC as an independent supplier in Muscat.

TR31 variants and what the type code tells you

The datasheet covers two designs: the TR31-3 with M12 x 1 plug connection and the TR31-K with a directly connected cable. In the ordering key, the ending decides the output: -Px is a Pt100 sensor, -Sx a Pt1000 sensor and -TT the 4 … 20 mA version with integrated transmitter. The transmitter is a Pt1000-based loop device with a measuring current below 0.3 mA, so self-heating can be ignored.

TR31 technical specifications

How the 4 … 20 mA version performs

The transmitter version combines the class A element with a transmitter error of ±0.25 K and an output error of ±0.1 % (±0.2 % when the range starts below 0 °C). Influences are listed as 0.1 % of the set span per 10 K ambient change, ±0.025 % per volt of supply change and ±0.05 % per 100 Ω of load. The datasheet works through a 0 … 150 °C example in which the typical total deviation is about 0.52 K and the worst case 1.2 K. Output current values for fault signalling follow NAMUR NE 043, and the permissible load is RA ≤ (UB – 10 V) / 23 mA. TAG number, damping, range and unit (°C, °F or K) are set with the free WIKAsoft-TT software and the PU-548 programming unit.

Wiring: Pt100 and Pt1000 direct output

For the direct-output versions, 2-wire connections add lead resistance as an error, 3-wire compensates for it, and 4-wire makes it irrelevant; WIKA notes that at cable lengths of 30 m or more the lead resistance matters for 2-wire installations. The temperature at the connector must not exceed 85 °C, which is why a neck tube is used when the process is hot.

Where the TR31 fits in the WIKA range

The datasheet points to related models: the TR33 threaded miniature resistance thermometer and the TF35 OEM threaded thermometer with plug connection. The TR34 is the intrinsically safe sibling of the TR31, with similar dimensions and an Ex ia approval set. The TR31 itself is also described with intrinsically safe versions for hazardous areas, with Ex ia markings for gas (II 1G, 1/2G and 2G, T1 to T6) and dust (T135 °C) shown in the datasheet; the ambient limits and surface temperatures in that section must be checked for your zone.

Mounting the TR31 and keeping it reliable

The thermometer is screwed directly into the process through its fixed G¼ B thread, so seal choice and torque matter. If it must run in an extra protection tube, WIKA says a spring-loaded compression fitting is required, and that fitting lowers the maximum pressure (stainless steel fitting 100 bar, PTFE ferrule 8 bar). The ambient range at the connector is -40 … +85 °C for the plug version, with an FKM O-ring version starting at -20 °C, and -20 … +80 °C for the cable version. Route cables with a drip loop, tighten the M12 coupler by hand so the stated IP rating is met, and use the optional adapter if the plant wiring uses a DIN EN 175301-803 form A angular connector.

Applications in Oman and the GCC

The listed uses are machine building, plant and vessel construction, propulsion technology and hydraulics. In the Gulf region this suits hydraulic power units on drilling and lifting equipment, gearbox and bearing oil temperature on compressors and skids, packaged chillers, small cooling circuits and OEM machines built for export. The compact size and 20 g vibration rating help on rotating equipment, while IP67 or IP69K ratings tolerate dust, wash-down and humid coastal air.

TR31 ordering checklist

• Plug version (TR31-3) or fixed cable (TR31-K), and cable length if applicable
• Output: Pt100, Pt1000 or 4 … 20 mA, plus wiring method for direct output
• Sensor class A or B and the measuring range needed
• Tube diameter, insertion length U1 and whether a neck tube is required
• Seal material (standard or FKM O-ring) and operating pressure
• Transmitter range, damping and TAG text if factory-set
• Hazardous-area marking if the intrinsically safe version is needed

Information to send with an RFQ

Send the complete TR31 type key, quantity, process medium, pressure and temperature, the connector or cable arrangement and any Ex requirements. For OEM batches, tell us the planned annual volume and whether a customer-specific design is needed, as the maker offers custom versions.

Documents and quotation

The WIKA data sheet TE 60.31 for the TR31 is attached on this page. Send your type key and quantity and we will reply with a quotation from Muscat as an independent supplier.