IEPE Compliance Voltage of NI 9234

[akash90]

Hello 🙂

I use a Piezoelectric Accelerometer (Type 4519-003 from B&K) which has a DC Output Bias Voltage of 12 V at room temperature. The DAQ Module that I use (NI 9234) mentions a Compliance Voltage of maximum 19 V. I'm not sure whether this voltage is supplied from the DAQ Module to the IEPE Piezo sensor or is it the other way around?

What I'm trying to find out basically is what is the voltage supplied from the DAQ Module to the sensor during the normal operation (Since the IEPE electronics should require some supply for operation).

NI 9234 Datasheet: http://www.ni.com/pdf/manuals/374238a_02.pdf

Piezo sensor datasheet: https://www.bksv.com/media/doc/Bp2071.pdf

Thanks in advance 🙂

[GerdW]

Hi akash,

see page 8 of the NI9234 specs.

what is the voltage supplied from the DAQ Module

The module does NOT supply voltage. IEPE requires a current supply!

So the module will supply 2mA. The voltage will/have to not exceed 19V…

[akash90]

Thanks for your comment GerdW,

I agree with your answer that the sensor needs a current supply of 2 mA. (But a current source should have a varying supply voltage that maintains the current at a constant value, shouldn't it?)

At the same time, I'm not sure about how the integrated electronics (present in the IEPE sensor) get a supply voltage for their operation and also to generate an output of (a maximum of) 19 V. Is that all generated by the sensor itself?

Basically, I'm trying to calculate the power consumption of such a sensor.  Any pointers on that would be appreciated 🙂

P.S.: I'm a student trying to clear up my basics, so I apologize if I ask some basic questions.

[GerdW · Accepted solution]

Hi akash,

But a current source should have a varying supply voltage that maintains the current at a constant value, shouldn't it?

Yes, that's the basic principle of a current source: to provide a (constant) current…

I'm not sure about how the integrated electronics (present in the IEPE sensor) get a supply voltage for their operation

They get a supply current!

(Btw. Mr. Ohm once said "voltage equals current times resistance"…)

I'm trying to calculate the power consumption of such a sensor.

So you should look into the manual of the sensor - the power supply only has to be capable of supplying the power needed…

(Rough estimation: 2mA of current supply with a bias voltage of 12V results in 24mW. Bias voltage is the voltage over the sensor you get without any acceleration…)

[akash90]

Hello everyone 🙂

I'm having a problem regarding the compatibility of the DAQ Module NI 9234 (http://www.ni.com/pdf/manuals/374238a_02.pdf) for measuring the accelerometer from the Piezo sensor B&K 4519-003 (https://www.bksv.com/media/doc/Bp2071.pdf).

The compliance voltage of the DAQ is 19 V maximum. The datasheet of the DAQ Module mentions these values on page 8. Considering the maximum of all values (worst-case calculation), the sum of CMVR (which is 2 V), bias voltage of the sensor (which is 16 V) and the full-scale sensor voltage (which is 5 V) is 23 V, which is clearly higher than the maximum.

Does that mean that the module is not compatible for this sensor?

On the other hand, the module works with IEPE ON only in the AC coupled state. So that means that it reads only +/- 5 V from the sensor. That suggests that there is no issue using these two together.

Could someone please clarify this?

Thanks in advance 🙂

[Henrik_Volkers · Accepted solution]

You can use this sensor with a 9234 in IEPE configuration.

2