WIKA TR34 Intrinsically Safe Miniature RTD

WIKA TR34 intrinsically safe miniature resistance thermometer

The WIKA TR34 is the explosion-protected version of the company’s compact threaded RTD family. It keeps the small body, G¼ B fixed process connection and M12 x 1 plug of the TR31, but is built and marked as an intrinsically safe (Ex ia) instrument, so it can be installed in zones where an ordinary miniature probe cannot. WIKA states a range of -50 … +250 °C [-58 … +482 °F], pressures up to 140 bar with 3 mm and 270 bar with 6 mm sensor diameters, and 20 g vibration resistance depending on version. Seven Star LLC supplies the TR34 in Oman and the GCC as an independent supplier in Muscat.

What the TR34 is for

Where the TR31 targets machine and hydraulic OEMs, the TR34 targets the same compact installations that sit inside hazardous areas: skid-mounted equipment on oil and gas sites, solvent handling, fuel systems and similar duties. The datasheet lists machine building, plant and vessel construction, propulsion technology and hydraulics as the applications. The electrical connection is only through the M12 x 1 four-pin circular connector, with an optional adapter to a DIN EN 175301-803 angular connector.

TR34 technical specifications

Explosion-protection data you need before ordering the TR34

The Ex section of the datasheet lists gas markings II 1G Ex ia IIC T1 … T6 Ga, II 1/2G Ex ia IIC Ga/Gb and II 2G Ex ia IIC Gb, and dust markings II 1D Ex ia IIIC T135 °C Da, II 1/2D Da/Db and II 2D Db. For the 4 … 20 mA loop the maximum values are Ui = 30 V DC, Ii = 120 mA, Ci = 29.7 nF and negligible Li, with power Pi of 800 mW for gas and 750 / 650 / 550 mW for dust depending on ambient. For the direct-output Pt100 and Pt1000 circuits the datasheet gives separate maxima (up to 550 mA and 1,500 mW for gas, 250 mA for dust) with negligible capacitance and inductance. T6 applies at ambient up to +45 °C in the loop version, and a second table extends the ambient range from -50 °C to +80 °C for the gas marking. The maximum surface temperature is the medium temperature plus 15 K of self-heating.

Special conditions for safe use are stated in the data sheet and in the operating instructions. Check them against your barrier or isolator parameters before the loop is certified; a mismatch in Ui, Ii or Pi is the usual reason an installation fails inspection.

Accuracy and electrical behaviour of the transmitter version

Transmitter deviation is ±0.25 K and output error ±0.1 % (±0.2 % for a range that starts below 0 °C). The datasheet example for a 0 … 150 °C span gives a typical total of about 0.52 K and a worst case of 1.2 K. The load limit is RA ≤ (UB – 10 V) / 23 mA. Span is 20 … 300 K, units can be °C, °F or K, and error signalling follows NAMUR NE 043. Direct-output versions behave like any RTD: 2-wire adds lead resistance, 3-wire compensates, and 4-wire is not affected, and WIKA notes that cables of 30 m or more make the lead error visible.

TR34 compared with TR31 and TR33

Installation and commissioning tips

Seal the G¼ B thread with a gasket or sealant that suits the medium, hand-tighten the M12 coupling so the stated ingress rating is reached, and use a connection cable and barrier that are certified for the loop. If an extra protection tube is used, WIKA specifies a spring-loaded compression fitting. Keep the neck tube in place when the medium is hot so the electronics stay below 85 °C. After installation, record the serial number and TAG; the transmitter keeps TAG, description and message internally and holds configuration permanently, so a replacement unit can be set up quickly.

Applications in Oman and the GCC

Typical sites include gas compression packages, fuel and lube-oil skids, hydraulic units on wellhead and offshore-style equipment, solvent and chemical dosing units, and cooling circuits in refineries and petrochemical plants. High ambient temperatures, dust and washdown suit the sealed, vibration-tolerant body, while the intrinsically safe design avoids the weight and cost of flameproof enclosures for a small sensing point.

TR34 ordering checklist

• Direct Pt100 or Pt1000, or 4 … 20 mA output with transmitter
• Zone, gas or dust group, temperature class and ambient temperature
• Barrier or isolator parameters (Ui, Ii, Pi, Ci)
• Tube diameter, insertion length U1 and neck tube if the process exceeds 150 °C
• Class A or B, wiring method and cable length from the plug
• Seal material and process pressure

Information to send with an RFQ

Please send the type key, area classification, loop parameters, quantity and any certificate requirements. We confirm the configuration and the approvals for your exact combination before quoting.

Documents and quotation

The WIKA data sheet TE 60.34 for the TR34 is attached on this page. Send your configuration and quantity and we will reply with a quotation as an independent supplier in Muscat.