# Get electrical signal of a piezoelectric with ultrasound

• hugo_faurand
In summary, the conversation was about measuring the electrical signal generated by a piezoelectric device for an ultrasound probe. The experiment involved comparing the signal with a mathematical model and using a piezoelectric device found in a watch. Questions were raised about the sensitivity of the device and whether it needed amplification. The frequency range and accuracy needed for the measurement were also discussed. The conversation then shifted to using an oscilloscope and the material between the emitter and sensor. Suggestions were given to study piezoelectric transducers and the use of charge amplifiers. The conversation also mentioned using a piezoelectric microphone or crystal earphones for lower frequencies.
hugo_faurand
TL;DR Summary
What material do I need to measure the signal generated by a piezoelectric device with ultrasounds ?
Hello everyone !
I'm working on ultrasound probes, and I wanted to measure the electrical signal generated by a piezoelectric device (a transducer).
Here is a sketch of the experiment :
The goal of the experiment is to compare the electrical signal of the piezoelectric cell and compare it with a mathematical model.
However, my school can only give me this type of piezoelectric device that you can find in a watch :

I don't think this kind of device will be sensitive to the ultrasounds. So here is my first question, at the place of the square with "Piezo" written in it, what electrical component should I put?
Does this kind of device work ? Here

I also wonder if I should amplify the signal of the piezo... If I have to I don't know how...

Regards :)

hugo_faurand said:
I'm working on ultrasound probes, and I wanted to measure the electrical signal generated by a piezoelectric device (a transducer).
Do you want to measure the ultrasonic sound wave in air or in a liquid?
What range of frequency will you be using?
How accurately do you need to measure the amplitude?

Baluncore said:
Do you want to measure the ultrasonic sound wave in air?
What range of frequency will you be using?
How accurately do you need to measure the amplitude?

I think I'll plug the ultrasound emitter on the oscilloscope also but I'm not particularly interested in measuring the ultrasonic sound wave. I'd like to use ultrasound wave with a frequency from 1 to 15 MHz ( these frequencies are used in ultrasound). About the accuracy I don't know what to answer. I think the piezo cell will generate a voltage of some mV (I think) so having an accuracy of tens of mV should be fine.

I would try it with the oscilloscope before asking the question.

sophiecentaur
What will the ultrasonic probe be used for?
What "material" is between the probe emitter and the sensor you will use to monitor the signal?

Baluncore said:
What will the ultrasonic probe be used for?
What "material" is between the probe emitter and the sensor you will use to monitor the signal?
In a first approach there is no probe, just a system acting like transducer that you can find in probes, to analyze the electrical signal received. I'll work in the air in a first time and then in water. But my question is which component should I use to simulate the behaviour of the piezo transducer.

I suggest that you take a step back and spend a little time studying piezoelectric transducers. PCB has a general discussion that is a good place to start: https://www.pcb.com/resources/technical-information/general-piezoelectric-theory.

After reading through that, you will understand the difference between a piezoelectric crystal with wires attached, and a piezoelectric transducer with integrated electronics. If you have a piezoelectric crystal by itself, you will need a charge amplifier to measure the output. The input impedance of an oscilloscope will short circuit the piezoelectric crystal, so you will read nothing. Try search terms piezoelectric charge amplifier to start learning about charge amplifiers. A good hit to get started is https://www.allaboutcircuits.com/technical-articles/understanding-and-implementing-charge-amplifiers-for-piezoelectric-sensor-s/. It's very much simplified, but is enough to get you started.

If you are working with a transducer that comes with electronics, be aware of the bandwidth of the electronics. Make sure that the electronics bandwidth includes the range of frequencies that you plan to work with.

sophiecentaur
If you care to start at a lower frequency to get an idea of what is needed, try using a piezoelectric microphone, also known as a crystal microphone.

There are also crystal earphones which may be easier or cheaper to obtain. Crystal earphones are sometimes called 'high impedance' earphones.

The cheapest ones you can find (under US\$10) are fine for getting started. You may want to buy two because they can be used as the transmitter (sender) if you supply a signal, and as a receiver if you connect them to a measuring device (oscilloscope, etc.)

Many, especially the cheaper ones, can be used somewhat above the audio range where they have a mechanical resonance. Operating them at resonance makes them more sensitive.

Cheers,
Tom

Klystron, jrmichler and sophiecentaur

## 1. How does a piezoelectric material produce an electrical signal with ultrasound?

Piezoelectric materials have the ability to convert mechanical energy into electrical energy, and vice versa. When ultrasound waves are directed towards a piezoelectric material, they cause the material to vibrate at a specific frequency. This vibration creates a small electrical charge within the material, which can be detected as an electrical signal.

## 2. What types of piezoelectric materials can be used to get an electrical signal with ultrasound?

There are many types of materials that exhibit piezoelectric properties, including crystals such as quartz, ceramics, and certain polymers. Each of these materials has different properties and can be used for different applications. It is important to choose the right material for the specific ultrasound signal being used.

## 3. How is the electrical signal from a piezoelectric material amplified and measured?

Once the electrical signal is produced by the piezoelectric material, it needs to be amplified and measured. This is typically done using an amplifier and oscilloscope. The amplifier increases the strength of the signal, while the oscilloscope displays the signal as a graph, allowing for measurement and analysis.

## 4. Can ultrasound signals be used to control the electrical signal from a piezoelectric material?

Yes, ultrasound signals can be used to control the electrical signal from a piezoelectric material. This is known as the inverse piezoelectric effect. By applying a specific ultrasound signal to the material, the material will vibrate at the same frequency and produce an electrical signal with the same frequency.

## 5. What are the applications of getting an electrical signal from a piezoelectric material with ultrasound?

The ability to produce an electrical signal with ultrasound has many practical applications. Some common uses include medical imaging, non-destructive testing, and acoustic sensors. This technology is also being explored for energy harvesting, where the vibrations from ultrasound waves can be converted into electrical energy to power devices.

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