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Amplifying signal from capacitive sensor

nulixos

New Member
Hi everyone, I building my home project and I built capacitive sensor. When sensor detect value raise just between 0.5 and 1pF. I need this signal to amplify for use on arduino and I don't have many components. Can you help me?

Thanks in advance!
 

JimB

Super Moderator
Most Helpful Member
What is the sensor measuring?
Where is it located?

One way to measure the small change in capacitance would be to incorporate the capacitance into an oscillator circuit, preferably one which was built very close to the sensor to minimise the effects of connecting wires, and use the arduino to measure the frequency of the oscillator.

JimB
 

gophert

Well-Known Member
Most Helpful Member
Hi everyone, I building my home project and I built capacitive sensor. When sensor detect value raise just between 0.5 and 1pF. I need this signal to amplify for use on arduino and I don't have many components. Can you help me?

Thanks in advance!
is it a change from 0.001 pF to 1.0pF,
or it a change from 500pF to 501pF?
 

gophert

Well-Known Member
Most Helpful Member
From ~ 50pF to 51pF
In theory, a circuit like this will give you a frequency shift from about 890 to 910 Hz. It is a big enough shift to hear with even average musical aptitude. But, theory and reality is all in parts selection and implementation.

you can use a timer on a microcontroller to measure the period of the amp output. The faster your microcontroller, the more resolution you will have... assuming you can get your capacitor to oscillate your circuit.

If you need your sensor to split hairs, like measure relative humidity from 0 to 100%, I think you'll need some more range in your sensor.

1E7C861E-C32B-44EB-9666-76D6C5507B1A.jpeg
 

gophert

Well-Known Member
Most Helpful Member
Are any of these of use...:
Capacitive Sensors
I figured, If you were making your own sensor, you'd want to make your whole sensor. But, yes, these are the parts you need if you know how to use SPI or I2C communication with a microcontroller (arduino). If one leg on your sensor is connected to ground, most of those will work. If you have a floating or non-grounded connection, then you'll have to search a bit harder. You are well into attoFarads at 16bits of real resolution at 20pF so you will have a bit of dynamic range to work with. Just make sure the chip you select can handle 50pF base capacitance and measure a difference from there. Sometimes a call to tech support or online chat gets a good recommendation of a part in a few minutes. Better than me searching through them for you.
Cheers.
 

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