PeakTech TF-50 & TF-55:

On top is the PeakTech TF-50 with the TF-55 below.

These are two K-type thermocouple temperature sensor probes. Thermocouple sensors rely on a voltage difference that occurs at the junction of two dissimilar metals which is proportional to the temperature of the junction. The type TF-50 sensor has a measuring bead of only 1.5 mm in diameter and is suitable for measuring the temperature of surfaces and air in the range from -50 to + 250 ° C, the type TF-55 immersible probe encloses the thermocouple sensor inside a thin metal sheath 3 mm diameter and 75 mm long. This probe can be used in fluids (or even shoved into the family roast to test the core temperature!). It has a slightly extended temperature range of -50 to + 300 ° C. According to its spec the accuracy of the TF-50 is 0.5% while the TF-55 achieves 2.5%. My own test measurements indicated an error of just under 1% for the TF-50 and about 1.5% for the TF-55.

           But epic fail with the connector...
The leads of the two thermocouples are terminated in a standard 2-pin yellow thermocouple plug, designed to fit into the socket of a dedicated thermocouple thermometer unit. Unfortunately the spacing between the pins does not marry-up with the input spacing on my PeakTech DVM. That’s a shame because this DVM has a temperature range designed for K-type thermocouple sensors.
It can measure temperature…

 The mismatch is more of a failing on the part of the DVM rather than the probe but it was fairly easy to figure out a work-around using some leads and clips — not pretty but it gets the job done. It would have been nice if PeakTech had included an adapter terminating in two flying 4 mm plugs so that the sensor could be more neatly plugged into standard DVM sockets.


All in all, I can see that all the parts in the set would be very useful in a small electronics lab or home workshop. I especially liked all four clips because they are well made and stand up well in comparison with more expensive branded products or even surpass them in their ease of use and functionality. I also like the type 7025 measuring lead because it is universally applicable and stackable.
I did have a few gripes: First, there is the question of why two pairs of the 7020 test leads are in the kit and only one pair of the type 7025. Two sets of the 7025 stackable leads would have been more useful. Personally I would like to have seen three sets in the kit and left out the standard type 7020 leads completely. It’s a pity there is no adapter in the kit for the thermocouple plugs, this would make them easier to use with different equipment and allow a simpler hook up when using them in test circuits.
You could purchase all the items in this kit individually from PicoTech but you save about 10% by buying the kit and the tote bag comes free. The leads and probes are suitable for use with many types of lab equipment using standard 4 mm banana sockets.
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