Eddy Current Probe measurement with NI9234, how?

[pbrm]

Dear NI people and users,

I see that in Signal Express when I choose Eddy Current as input, it gives me the option is using the NI9234 card to connect a Eddy current probe,

we now use these probes : Sensonics Eddy Current Probe wich are very good but until now required a driver and power supply for each probe to use.

If there is a way that I can use a Compaq Daq module to do the same, I would be a verry happy man 🙂

So anyone any ideas if this is somehow possible?

And if not with the NI9234 cDaq card, any other (cDaq) card?

Or maybe I must use other types of Eddy current probes?

Philippe,

Belgium

[Henrik_Volkers]

If you read the spec sheet you will see that you need a -24V power supply and 30mA  for each channel, and the sensor output range seems to be 0 to -20V.

With the help of a voltage divider (two resistors) you can scale the -20V sensor output to the -5V input range of the 9234, however , keep in mind the output (50Ohm) and input (305kOhm) impedances 😉   Another point to check would be the maximum input voltage range to GND  (less serious if you use a voltage divider that makes your source 'less' low impedance.....)

BUT you will need a external powersupply since the IEPE source has the wrong polarity AND only 2mA.

Since I don't know the all the NI products I would collect all important informations  (No. of channels needed, needed resolution, needed accuracy, needed bandwidth, ..... ) and call NI 😉

[Henrik_Volkers]

Answered about the same question here

http://forums.ni.com/t5/Multifunction-DAQ/can-I-connect-a-bently-nevada-prximity-sensor-3300XL-to-4/...

I'm not a NI app engineer , however as far as I know there is no NI-DAQ with a -24 V powersupply and a -20V input range.

Maybe the other way: What do need to measure ? ... .. maybe look for another sensor?

[preston_johnson]

Thanks for the conversation. 

Most industrial eddy current probes (used for measuring shaft vibrations in journal bearing machines) are delivered and calibrated with their modulator/demodulator.  These external signal conditioners do power the probe (using a -24V power supply) and demodulate the eddy current into a 0 to -20/-25V signal.

National Instruments has two C series modules, the 9230 and the 9232 modules that are designed with the voltage range in mind to work with eddy current probes.  The 9230 has ample bandwidth and it is very cost effective. 

http://sine.ni.com/nips/cds/view/p/lang/en/nid/213063

I would look at proximity probes with their driver from www.ctconline.com.  https://www.ctconline.com/__proximity_probes_.aspx  These are widely used in the power generation industry and work well with the NI 9230 and NI 9232.  They are also the most cost effective probes I have found. 

Hope this helps. 

Preston Johnson

Allied Reliability Group