Seeking advice on the calibration of platinum thermoresistors
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I would like to ask the experts how they usually calibrate PT100 platinum resistance sensors. Is it by directly measuring their resistance value with a multimeter and then performing calculations (by subtracting 100 from the measured resistance value and multiplying the result by 0.385)? There is a problem: the platinum resistance thermometers on site are dual-core, with one set feeding the digital display unit on site and another set feeding the DCS. The values displayed on both devices are the same, but why does the resistance value measured directly with a multimeter at the wiring terminals of the platinum resistance thermometers turn out to be a few degrees higher than the values displayed (by 3-6 degrees)? And it is a common phenomenon. Is it the method that doesn’t work? How should one determine its true value? Thank you!
Is it possible for a 3-meter long resistance lead to have a value of a little over 2 ohms? Well, who knows
The error in the two-wire system is much larger than that in the three-wire system
Check the PT100 resistance table; in my opinion, if the digital display shows the same value as what the DCS indicates, then there is a problem with your multimeter. It is recommended to use a 4.5-digit multimeter to take new measurements.
I used two new multimeters from different brands, and the results were the same
It is possible to consider adding standard signals on-site to view the display values of the two circuits
Suture removal, multimeter reset, wire resistance, secondary meter, and actual measured temperature – all of these need to be taken into account.
The two temperatures output to the display instrument are different; this is likely caused by wiring or circuit issues. If the measured resistance differs from the value displayed, you can subtract the resistance between BC from the resistances measured between AB and AC. Additionally, before using the multimeter, set it to the 200 ohm range and short-circuit the test leads; the resistance in this case should be zero
By checking the specific PT100 data sheet, it’s not possible to carry out precise calculations; only approximate estimates can be made. Moreover, if you measure it on-site using a two-wire system, the displayed value will definitely be higher than the actual value, as the two-wire PT100 system takes the resistance between the wires into account during conversion, which results in an overestimated display value