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We appreciate your patience as we improve our online experience.
12-02-2013 04:34 AM
Hi ,
I recently installed NI Signal Express with Sound & Vibration Toolkit, while configuring the sensitivity of the B&K accelerometer 4393 V, I find the sensitivity is defined on NI Signal Express with V/g but it's definitely on the B&K accelerometer with pC/g (cf. The attached fig).
Until now I didn't find any conversion possible to input the correct value of the sensitivity in NI Signal Express.
Hoping to find some help from you, I'll be so thankful.
Regards
A.S.B
Solved! Go to Solution.
12-02-2013 09:37 AM
Ok , I spent the whole day trying to find the solution of this ''imaginary'' problem.
According to Brüel& Kjaer , I need a physical converter ( Type 2647 ) to have a 1 Volt for 1 pC but this converter needs a feeding on ICP by the DAQ.
But according to NI , the NI 9234 DAQ has to ability to convert the pC automatically to V without any need to the physical converter and it feeds the accelerometer by ICP.
To summarize, just put the accelerometer in BCN connection and make your acquisition.
Done.
ASB
12-03-2013 01:02 PM
I took a quick look at your accelerometer, and I a pretty sure that the information you got from B&K is correct, and you are going to need that Charger Converter in order to properly measure the accelerometer with the 9234. Here is some reference material for you... I recommend jumping down to the "Charge Mode Accelerometers" paragraph, which I believe describes the accelerometer that you are using.
http://www.pcb.com/techsupport/tech_accel.aspx#.Up4peMSfiKs
Cheers!
Logan
12-04-2013 02:59 AM - edited 12-04-2013 02:59 AM
Thanks Logan ,
But according to NI Technician, there's no need to charge converter. The QDAC do the conversion because it feed the sensor with ICP.
I tested it and it gives me the same data as with the B&K charge converter.
Thanks again.
12-05-2013 08:02 AM - edited 12-05-2013 08:11 AM
Your sensor is a charge source with XX pC/ms²
Together with it's capacitance (and more worse: the cable capacity and the input impedance) a charge convert to a voltage U=Q/C. That voltage is what you measure with your DAQ card.
Even more annoing is the effect of cable microphonie : Move the cable and it's capactance will change, so will the measured voltage.
Believe me, if you want to make reasonable measurements with this sensor you will absolutely need a charge amplifier to get a voltage
or (if your DAQ supports IEPE) a charge to IEPE conditioner.
Here I build a tube based one, but building a stable good charge amplifier is an art. 😉
12-05-2013 08:15 AM
Saad@cbe wrote:
But according to NI , the NI 9234 DAQ has to ability to convert the pC automatically to V without any need to the physical converter and it feeds the accelerometer by ICP.
ASB
Wrong: The 9234 supports ICP (=IEPE) accelerometers. ICP accelerometers have a charge to voltage converter already build in.
But you don't have a ICP sensor.
12-05-2013 08:19 AM
I have already the converter ...so even if the 9234 don't work, as NI said, The output to my DAQ is in Volt.
Regards
05-09-2017 03:20 AM - edited 05-09-2017 03:20 AM
I've got B&K Deltatron (IEPE???) 4396 and 4519 Sensors. They have pre-installed charge converter 2646. Data sheet says that it must have 2...20 mA constant current supply. If I use NI 9234, I'll have IEPE excitation current 2,0...2,1 mA. Is it the currrent that I need for correct work of the sensor? If I understood correctly, I could work with 9234 direct, right?
Thanks for help,
Best regards
05-09-2017 12:54 PM
@Suglob_Artur wrote:
I've got B&K Deltatron (IEPE???) 4396 and 4519 Sensors. They have pre-installed charge converter 2646. Data sheet says that it must have 2...20 mA constant current supply. If I use NI 9234, I'll have IEPE excitation current 2,0...2,1 mA. Is it the currrent that I need for correct work of the sensor? If I understood correctly, I could work with 9234 direct, right?
Thanks for help,
Best regards
Yes, sound reasonable so far.
Deltatron, ICP,( forgot the Kistler naming 😉 ) with minor differences all are IEPE or CCLD ... so again_ Yes 🙂