KTY83-110 Polarity Determination

Did they furnish the electronics to read this sensor?

If it is a 2-wire RTD or a thermistor, there is no polarity, so it doesn't matter. If it is a thermocouple, polarity does matter. If you hook it up wrong, you will get a negative temperature; in that case, connect it the other way.

Tornado is correct.

It is a 2 wire RTD. Here is a link to the datasheet. Took 25 seconds on Google to find this.

Click Here.

Yes it is a 2 wire RTD but if you read more closely you will find this:

"The sensor must be operated with the lower potential at the marked connection"

Apparently with silicon sensors if they are used with incorrect polarity then they flat-top at around 120 degrees C - just where motor protection is critical. This is documented in the Lenze VFD manual as well as other places.

Good catch on the small print. I did not notice it.

In that case... I would...

Place the motor in a temperature controlled environment and bring it up to 130 deg., let it stabalize at that temperature for awhile so you can be sure the motor is at the same temperature. Then check your devices readings and see what it says.

As long as the motor is not powered, no harm should come to it by this process.

Check this link:

http://akb.lenze.de/AKB-englisch/infopool.nsf/HTML/200700609

Find out the polarities by a meter check. connect the anode end to the +ve terminal of the connector and cathode to the -ve.

Good Luck.

Musthafa.

It reads exactly the same both ways.

It seems the issue is up around 120 degrees C.

You are right Johny. We have a motor of 30kw with and embedded RTD which is now only in installation stage. I checked the resistance. As you said the value is around 260 ohm at 20 celcius both directions. I could not trace the terminals POS and NEG.The lead wires are both black and it is rated to 150 celcius PTC. But most of the broucher for the thermistor shows a mark like a ring at on side of the resitor,that should be identified as cathod which need to be connected to the negative terminal of the circuit of the controlling system, as seen in the boucher. (Example, Please refer www.emphy-mess.de for more information).

In this case, the value of the resistance should not change with both polarity configurations. Then my doubt is that, how a negative resistance possible with reverse connection? If it is a polarity independant, why it gives two values one positive and the other negative at different polarities, as per Tornado's quote.

Not good.

This link to the Lenze FAQs was where I was alerted to the issue.

http://akb.lenze.de/AKB-englisch/infopool.nsf/HTML/200700609

I my case it's not too bad as I can monitor the motor easily and check if the sensor plateaus at 120 degrees but I can see that believing that a motor was monitored when it really is not could be disastrous.