Need help to understand hydrophone specs

[Alexei.Polkhanov]

I found a hydrophone unit that appears to be of very good performance, but then I looked at specs I see this:

Receiving Sensitivity ( at 1 kHz ) ............................... 115 +/- 2 dB rel 1 pC / 1 uPa

I am really unsure how to interpret it. I expected sensitivity to be a negative value in Db. as V/uPa but instead I see a positive Db value with 1pC/1uPa. What is pC ?
How can I convert it to V/uPa?

[fcb]

I agree, it looks like it needs more context.  Can you link to the datasheet?

[ConKbot]

PicoCoulomb, its a charge output transducer, but I agree that that is an odd value, cant really make sense of it in my head either.

[Alexei.Polkhanov]

link: http://www.ebay.com/itm/181769482491?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
No datasheet anywhere.

I found it, finally ... ufffff ... in some small old scanned paper from 1970s entitled "calibration of hydrophones".

pC stands for "charge sensitivity" and it is written as 1pC/uPa.

Sq = Sv * (Capacitance of hydrophone + Cable)

where Sq is a charge sensitivity and Sv is voltage sensitivity (V/uPa).

So in my case value 115 Db 1pC/uPa can be translated as V/uPa in dB

10*log10( 10^(115/10) / (11500e-12+1500e-12)) which is equal to 193.86 dB 1V/uPa. Huray!!! unless I made mistake somewhere 

Capacity was also given in small spec sheet that I have:
Capacity at  20 °C ....   ( at 1 kHz )   .............................. 11500 pF +/- 1500 pF
I ignore the cable because spec is for hydrophone without the cable.

193 dB is not bad but not exciting. I found few at 209-216 dB at similar prices.

[Alexei.Polkhanov]

PicoCoulomb, its a charge output transducer, but I agree that that is an odd value, cant really make sense of it in my head either.

Yes, you right pC it is picocoulomb - with relation to "charge sensitivity" it all make sense now!