readout for accelerometer

[engr_joni_ee]

I am working at the readout of the piezoelectric accelerometer B&K 4516 which needs a current source between 2 mA to 20 mA. Do we have any reference design with components that delivers constant current to the piezoelectric accelerometer ?

 

[KlausST]

Hi,

what about doing an internet search on your own for "current source schematic"?
Did you contact the manufacturer for support?

Klaus

 

[FvM]

Due to the wide current range, a stable voltage source with series resistor will already work for the purpose, at least for a first test, You'll probably end up with a simple transistor current source.

 

[dick_freebird]

A question is whether the current "can vary 2-20mA
as it pleases, no prob" or "can be anywhere in that
range, but then must stay put". The former, call it a
resistor.

 

[FvM]

I read the data sheet so that the sensor has a constant voltage output within in the specified current range.

https://www.bksv.com/-/media/literature/Product-Data/bp2067.ashx

 

[D.A.(Tony)Stewart]

Pick any current between 20 and 20 mA and make it a precision low-noise high impedance constant current source over the entire vibration spectrum for the CCLD active accelerometer with a built-in charge amp that translates the output into mV/g.

 

[engr_joni_ee]

I found LM317 adjustable which can be used to deliver 12.5 mA current with R1 100 Ohm. Additionally I have drawn how to connect the accelerometer and oscilloscope for probing. Kindly have a look and let me know if any thing missing. Thanks in advance.

 

[D.A.(Tony)Stewart]

This will work however the bandwidth or fall slew rate is unknown for the acceleration to be measured. The LM317 is a Darlington source drive with no sink drive.

 

[engr_joni_ee]

We have slow acceleration which we need to measure. I am not sure about the values but what is the bandwidth of measurement if we use LM 317 current source solution. ?

Have a look at the circuit diagram again I provided in the last post. If due to acceleration the voltage across the accelerometer is change, how about the current ? would it be constant through LM 317 current source in to the accelerometer ?

 

[FvM]

According to LTspice model, LM317 has 1 MOhm output impedance below 1 kHz, falling factor 10/decade at higher frequency. Should work well for your application.

 

[KlausST]

If due to acceleration the voltage across the accelerometer is change, how about the current ? would it be constant

Basically that´s the idea of a constant current source ....


Mind:
For the current source to work properly it needs sufficent high input voltage.
If I´m not mistaken then the accelerometer has a bias voltage output of about 10V.
If so, then its a good idea to choose the total supply voltage to be a bit higher than 2 x 10V = 20V.

Klaus