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| 9/13/2021 7:27 AM | |
Joined: 2/4/2015 Last visit: 7/1/2025 Posts: 72 Rating:
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Dear all, We have a servo motor with KTY84 sensor. We connected the sensor to S120 motor module and checked the temperature. Also we connected the sensor to Siemens AI Card 6ES7331-1KF02-0AB0 and checked the temperature. We found a temperature difference of around 4-7 deg.C at various temeperature levels. Why should there be such difference? Please suggest. I have attached the photograph. Regards Surendhar M ------------------------------------------------------------------------------------------ AttachmentKTY84 Measurement.docx (540 Downloads) |
Last edited by: Jen_Moderator at: 09/13/2021 11:53:52New subject after splitting |
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| 9/13/2021 4:08 PM | |
Joined: 3/28/2010 Last visit: 9/3/2025 Posts: 1170 Rating:
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The spec sheet for the universal input Siemens AI card mentions KTY84 in the header on page 1, but does not include KTY84 in the "input ranges for resistance thermometers" section, nor in the characteristic linearization" section, so there's no printed spec from Siemens regarding the accuracy/uncertainty for a KTY84 sensor. That might have been intentional on their part, given the uncertainty of the sensor itself. The KTY84 is a PTC thermistor, whose spec sheet here link shows it to be ±5-8 Deg C device, a very large uncertainty value (graph on page 6, upper left). Note on page 5 of the KTY84 spec sheet that the resistance at 70 Deg C can range from a minimum or 781 Ohms to a maximum or 831 Ohms. That quite a spread for temperature sensor at a given temperature. Presumably the AI's are calibrated to the middle of the range 806°C, but that's probably the source of the error, different AI's calibrated to different resistances. So the question is, at what resistance does the analog input read 70 Deg C (or any other temperature value of interest)? If you have a decade resistance box that you trust, connect it to each of the temperature inputs in turn and see what resistance is needed to display a 70°C value. It might be quite different on the motor module than it is on the AI card. It is also possible that in the time takes to change connections from one device to another, that the actual measured temperature changes. How to you know it doesn't? The sensor is installed in an operating motor, not in a dry block calibrator. |
Last edited by: danw at: 09/13/2021 16:09:14 |
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