JUMO 902550 Surface RTD Temperature Probes for Pipes and Flat Surfaces

Strap-on surface probes that measure without cutting into the pipe

The JUMO 902550 family of surface RTD temperature probes is the preferred choice for measuring temperatures on closed pipe systems and other round or flat surfaces between -50 and +260 degC. The probes install with tightening bands or cable ties, so the measuring location needs no mechanical modification. Only basic types 902550/10 and /11 have a hole for screw-fitting to a surface such as a heating plate. Because the indirect method does not disturb the flow, pressure and chemicals cannot shorten the probe life.

The low thermal mass of the probe has little influence on the measured object, and heat-conducting paste is available to improve transfer; JUMO cautions that large differences between medium and surroundings will influence the measurement and recommends additional insulation in such cases. The standard insert is a Pt100 to DIN EN 60751 class B in 2-wire circuit, with Pt500 and Pt1000 as options. The range is completed by the 902554 pipe contact probe with a cable socket housing, available with an analog transmitter.

Technical specifications

Which 902550 or 902554 type fits the surface?

Pick the cable-connected 902550 types for tight spaces and the housing-type 902554 probes for clean installation in building services. Order code for the cable types is basic type – cable code – measuring insert – tolerance class – cable end – cable length / extra codes, for example 902550/10 – 386 – 1003 – 1 – 11 – 2500 / 000. The housing types use basic type – operating temperature – insert – class / extra code, for example 902554/41 – 365 – 1003 – 1 / 000.

Operating range 474 (-40 to +80 degC) is valid only with extra codes 330 or 333, which add a 4 to 20 mA or 0 to 10 V analog transmitter to a Pt100 probe (data sheet 707030). Extra code 242 (spring-cage terminals) cannot be combined with a transmitter.

Getting accurate readings from a surface probe

A surface probe measures the wall, not the fluid, so the reading lags the true medium temperature and is lower than it on a hot pipe if heat escapes to the room. Fit the probe on clean bare metal, apply heat-conducting paste, tighten the band, and insulate over the sensor and the adjacent pipe so the sensor sees the pipe and not the air. The installation kit is rated for pipes up to 100 mm diameter. Mount on the side of horizontal pipes rather than the bottom to avoid sediment or condensate effects (general practice).

The silicone, PTFE and stainless-sheathed cables cover different ambient exposures along the cable route, so pick the one matching the hottest point the cable passes. Applications include heating and chilled-water return lines, boiler flow lines, hot-water storage, heat meters, compressors and steam trace lines, as well as heating plates and platens through the screw-fitted types.

Choose the mounting style from the surface and temperature. Types 902550/10 and /11 have a fastening hole for plates, 902550/20 and /30 to /31 use fittings of stainless steel or aluminium for clamping, and the 902554 housing types are for building services pipes and flat walls. Housing temperature codes are 361 (-50 to +90 degC), 365 (-50 to +120 degC), 573 (-30 to +90 degC) and 474 (-40 to +80 degC, only with transmitter extra codes 330 or 333). Strain-relief spring or hose can be added to cable types, and spring-cage terminals to the 902554/44 housing. The installation kit is a separate sales item.

Documents and quotation

The JUMO data sheet 902550 is attached below. Seven Star LLC supplies JUMO sensors from Muscat; state the basic type, cable or housing option, element, cable length and any transmitter so we can quote. More probes are grouped under https://omansevenstar.com/product-category/sensors-transmitters/temperature/.