Can I directly plug a B&K hydrophone (B&K 8103) onto a 9233 module?

[zenith]

Can I directly plug a B&K hydrophone (B&K 8103) onto a 9233 module?

Can 9233 be served as a charge amplifier?

Here is the datasheet file of B&K hydrophone (type 8103):

http://www.bksv.com/pdf/Bp0317.pdf

[duncan carter]

Some vendors make charge converters to solve this problem.  One such vendor is Wilcoxon:

http://www.wilcoxon.com/vi_index.cfm/CatS_ID=17/comp=y

PCB is another vendor:

http://pcb.com/products/browse_productlist.asp?RequestType=Search&CategoryType=Product%20Type&SearchCriteriaWithin=&cboProductType=363&cboMeasurementType=

[zenith]

Do you mean that I need to use a charge converter between crio-9233 and the hydrophone?

Thx!

[duncan carter]

You probably should ask B&K.  The spec sheet does give the sensitivity as pC/pA rather than the usual PC/V for charge.

[Travis_W]

Hi zenith,

To clarify, I believe duncan is referring to the considerations on the first page of this post.

The USB-9233 has a constant 4mA current source present on its analog inputs.  Furthermore, its measurements are always AC coupled.  If the sensor you mentioned would be disturbed by the 4mA excitation current, then a source follower amplifier would be necessary.  Otherwise, if the sensor would not be affected, then you could hook it up directly to the USB-9233.

Let me know if you have any more questions, and best of luck on the application.

Have a great day!
Travis W

Message Edited by Travis W on 09-05-2006 04:55 PM

[Garritt]

The B&K 8103 is a charge output sensor.  The sensitivity is pC/Pa (that's picocoulombs per Pascal), not pC/pA (picocoulombs per picoamp as an earlier reply suggested) so it puts out a charge that's proportional to sound pressure.

It would need an IEPE amplifier to work with IEPE measurement devices like the NI-9233. As an earlier replay pointed out, there are IEPE amplifiers for charge output devices generally available.

[Kallis]

Just a small correction on what Garritt wrote...

If the sensor outputs charge, you will need a charge amplifier.

IEPE sensors use dc current to power pre-amps embedded in the transducer. Some modules like NI-9233 provide this IEPE excitation (usually 4mA).

Kallis

[jcrooke]

The 8103 is a potted capped piezoelectric ceramic tube connected to a high quality low noise coaxial cable. It may be connected directly to a low noise voltage preamp and have the output converted to Pascals by taking into account the cable capacitance, which should be provided by B&K (and is probably pretty small).

Using an IEPE type FET buffer would work well, too. The benefit of the IEPE buffer is that it provides a low impedance output suitable for driving a long cable. This is why the IEPE accelerometers have the circuit built directly into the accelerometer casing, as close to the piezoelectric element as possible.

The 8103 already has a low noise cable (probably less than 25 feet long) and could be directly connected to a charge amplifier. With the charge amplifier, there is no need to do a cable capacitance correction, it provides an output voltage proportional to charge which is only generated by the piezoelectric tube even though it may be distributed between the cable and the tube. 

The 4 mA constant current supply of the 9233 may not like being attached to a capacitive load. It will never be able to drive 4 mA through the ceramic, but I doubt that will affect the amplifier section of the 9233, which must decouple the bias voltage normally present on the two wire IEPE signal anyway. I haven't tried it before, but my guess is that it will work. If it does, you will still have to do the cable correction to get an accurate measure of the pressure because the amplifier is a voltage amplifier.

Message Edited by jcrooke on 01-07-2010 04:57 PM