Can Piezo Film detect tiny amounts of energy, like pulses from a narrow laser,
ElectricAye
Posts: 4,561
I've been wondering if Piezo Film can detect microsecond pulses from an IR laser that is very narrow (<1mm). I'm guessing that maybe the localized heating on the film might create a localized deformation of the film and therefore also create an output signal, but I really don't know. Can piezo film generally detect such a localized pulse of energy or does it require a larger scale deformation such as experienced during bending, etc.?
thanks,
Mark
thanks,
Mark
Comments
(page 34) Piezoelectric polymers, such as PVDF and its copolymers of VF2/VF3, are also pyroelectric. Pyroelectric
sensor materials are normally dielectric materials with a temperature-dependent dipole moment. As these
materials absorb thermal energy, they expand or contract, thereby inducing secondary piezoelectric signals.
As piezo film is heated, the dipoles within the film exhibit random motion by thermal agitation. This causes
a reduction in the average polarization of the film, generating a charge build up on the film surfaces. The
output current is proportional to the rate of temperature change (∆T). The amount of electrical charge
produced per degree of temperature increase (or decrease) is described by the pyroelectric charge
coefficient, ρ.
It goes on to calculate a 2.5 volt change due to a 1 degK temperature change under certain conditions. My guess would be that a one microsecond pulse on a small spot would not have much effect, but it would be interesting to try. Why can't you just use a photodetector?
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Tracy Allen
www.emesystems.com
Yeah, I was trying to figure out from the manual if a fast acting pinpoint heat source would create a signal, too. I can see how a temperature change in the overall strip can give a signal but I'm not smart enough to figure out if you heat just a little piece of the strip would it result in anything. These things are supposed to have ~1GHz frequency response, so I was hoping it might work to pick up fast localized pulses. I suppose the overall capacitance of the strip might just "suck up" all the energy from a tiny spot source, but I have no idea.
There will probably be an optically opaque layer between the activation source (laser pin point) and the sample being heated, and really what I think they want to measure is the acoustic energy that results from that localized heating. This would probably be more like a "photoacoustic" effect. All of this drama is supposed to happen inside a tiny test cell, so I thought I might be able to squeeze in a piezo film of some sort - I don't think I could get an off-the-shelf IR sensor into the test cell at this stage.
I've never dealt with piezo film, so I'm clueless in this matter.
many thanks,
Mary