Given:Piezoelectric coefficient of material, The material is in the form of slab
Piezoelectric materials can be poled and electroded as per your convenience. In that case, electrodes can be connected to volatge/charge measuring source though lead wires.
It depends on the pressure application (compression, bending…): different types of stress produce different voltage and charge levels. In my case (a piezoelectric patch, glued on a cantilever beam with an applied bending load), I used an oscilloscope as acquisition system (Tektronix, mod. TDS 5054B) with a high impedance probe (10 MΩ). If you are analysing a bulk material, be careful to identify piezoelectric cathode and anode (generally two opposite faces of the material). I hope it will be useful for you.
If you want to generate electricity using gas pressure you need to attach the piezo patch ( I suggest MFC or MIDE) to the cantilever beam and you need to have a vibration source. In this case, changing the pressure. It also can act as a sensor to warn you when pressure reaches some points. If you want to measure the voltage easily you can connect it to Multimeter ( I prefer to use NI) and you can record it using the software ( such as Signal express). If you just want to calculate that please read this papers about mathematical modelling. I have used Matlab to predict the voltage:
https://www.researchgate.net/publication/322920652_Optimizing_orientation_of_piezoelectric_cantilever_beam_for_harvesting_energy_from_human_walking
http://www.ssdsl.gatech.edu/wp-content/uploads/2012/11/SMS_2008.pdf
You can only measure changes in the hydrostatic pressure using a slab of piezo. The change in polarization P on applying a change in pressure Xh will be P = (d33 +2 d31) Xh, assuming you are measuring the charge on the electrodes normal to the poling direction. Remember d31 is approx -d33/2, so the effect may be quite small. The charge will be Q = P/A, where A is the area of the electrodes and the voltage generated will be Q/C where C is the capacitance. This method is OK for measuring changes with a short time constant ~< 1s, but not for slower variations.
Dear Andrew,
Thanks for your answer. Although I have come across another formula to find charge generated which is Q=d33*P*S, where P and S are pressure of the gas and S is the surface area on which gas pressure is applied.
It's in the following link.
Article Enhanced Hydrogen Sorption on Carbon and NiO in the Presence...
The didn't understand the time constant relevance here.
Dear Arun,
Thanks for your reply. I am applying gas pressure in a sealed chamber where these piezoeletric crysyals are kept. Is it necessary that the wires to measure voltage generated has to be of lead? Can steel contact be connected to the electrodes to measure the voltage using multimeter ?
Dear Antonio,
Thanks for your answer. in this case I am only applying gas pressure. And just want to see how much voltage and charges are generated.
Dear Saurabh,
Sorry for the confusion, it is just wire, simply a conductor. You can directly connect the wires from the electrodes of piezo to a DMM of good resolution in case you are applying time invariant pressure. In case of time variant pressure, a digital storage oscilloscope would be fine. If you are not able to measure the voltage produced, I am really doubtful about the sensitivity,Since you are using quartz crystals,try using with voltage amplifier. flexible piezo like PVDF or MFC will be good for pressure sensing.
Just remember, you can't measure a static pressure with a piezoelectric device.
You can measure the pressure in a traveling wave.
If you want to measure static pressure, you will need a strain gage or Bourdon tube device.
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