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measuring the Capacitance and the impedance

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Electronman

New Member
Hello,

I have a pair of T&R ultrasonic Sensors (Those that are used as range metering).
They are given to me by a friend so I do not have the specification for them.
The question is how do I measure the Capacitance and the impedance of them please?

Besides, can I remove the capacitance behavior of them by an inductor? If so, How to calculate it?

Thanks.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
You could measure the impedance, but why would you want to?. Likewise capacitance, why would you want to?.

The transmitter is series resonant, and the receiver is parallel resonant, so it's easy to test which is which.
 

Electronman

New Member
You could measure the impedance, but why would you want to?. Likewise capacitance, why would you want to?.

The transmitter is series resonant, and the receiver is parallel resonant, so it's easy to test which is which.
Thanks For the replay,

I want to learn how to measure the impedance of them??
About the capacitance I wanted to measure it and then see if it is possible to reduce it by an inductor to get more eficency out of the sensors?

Do I need an Capacitance meter or something like that?
 

Sceadwian

Banned
How is adding an inductor going to make it more effcient? It's still going to use the same amount of power.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Thanks For the replay,

I want to learn how to measure the impedance of them??
About the capacitance I wanted to measure it and then see if it is possible to reduce it by an inductor to get more eficency out of the sensors?
Sorry, don't follow your reasoning? - I don't see how an inductor would help anything?.

Do I need an Capacitance meter or something like that?
A variable frequency generator, an oscilloscope (or AC millivoltmeter), and a resistor - that's all you need.

But knowing the impedance is really of little use, what good would it do you?.
 

Sceadwian

Banned
The only thing you really need to know about a piezo transducer is it's resonant frequency.
 

audioguru

Well-Known Member
Most Helpful Member
I think if an inductor is in series with a capacitance and they resonate then more current flows. The piezo is the capacitance.

But then the bandwidth might be too low.
 

Electronman

New Member
I think if an inductor is in series with a capacitance and they resonate then more current flows. The piezo is the capacitance.

But then the bandwidth might be too low.
Can you explain your saying? So then The sensor will have more output?

I think he wanted to convert the load to an resistance load while it was a more capacitance before using an inductor?
 

audioguru

Well-Known Member
Most Helpful Member
If the piezo transducer has an inductor in series that resonates with the capacitance of the transducer at the carrier frequency then the transducer will have a higher output level at that frequency.
But the bandwidth will probably be too narrow for speech.
 

Electronman

New Member
If the piezo transducer has an inductor in series that resonates with the capacitance of the transducer at the carrier frequency then the transducer will have a higher output level at that frequency..
Thats what I thought when I started this thread.

But the bandwidth will probably be too narrow for speech.
That is not so good, whats the reason?
 

audioguru

Well-Known Member
Most Helpful Member
An LC resonating circuit has a narrow bandpass.
A radio uses LC circuits so that you don't hear all the stations at the same time.
 
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