# piezo sensors's resonant impedance

I'd like to know what does the term "piezo resonance impedance" mean. It is commonly available with the datasheets of piezo sensors such as this. Is it the same as the piezo transducer's insulation leakage resistance as shown in this link?

And how does this resonance impedance effect the response of the sensors.

When the piezo resonates it's impedance changes dramatically and, at resonance, according to the data sheet linked, it looks like a resistance of 500 ohms (maximum). This doesn't tell you nominally what the resistance is of course. The piezo exhibits an impedance that looks somewhat like this: -

The lowest point on the graph is the point where the resistance is specified at 500 ohms (max).

Is it the same as the piezo transducer's insulation leakage resistance as shown in this link?

Probably not, but you linked to a wiki page with a lot of detail and I never caught sight of what you referred to.

And how does this resonance impedance effect the response of the sensors.

At resonance, the piezo exhibits an impedance that makes it easily driven electrically. In simple terms the L and C in the left hand limb of the equivalent circuit cancel out leaving just the series resistance across the terminals and this is the resistance specified in the data sheet. It's a little more complex than that because of Cp also forming a parallel (anti-resonance) impedance very close to the series resonance.

• Does the resonance impedance and frequency have any relationship with the noise presence in the output? I've tested multiple sensors with multiple frequencies and impedance (with the same load) and I found out that when two sensors have the same size, the one with the highest resonant frequency and impedance had less noise and more signal selectivity. Unfortunately, I couldn't point of the parameter that controls this as the sensors which had better response had high resonance frequencies as well as high impedance. I'm trying to understand the effect of these parameters in the overall response – Isra May 29 '17 at 10:19
• Apologies, the part that I was referring to in the wiki link is in the second paragraph of the Electrical properties section. thank you very much for clearing that up – Isra May 29 '17 at 10:19
• I can't answer your question about noise because more than likely it is a function of the circuit you used it in and it seems you are using the piezo as a sensor and not an emitter (?). The reference in the second paragraph has nothing to do with the 500 ohms (max) specified in the data sheet. With ref to that wiki page, the 500 ohms would be in series with Ce and Lm. – Andy aka May 29 '17 at 10:24
• yes, I'm using it as a sensor. Thank you very much this helped clear things up – Isra May 29 '17 at 10:41