Electronics > Beginners
Piezoresitive pressure sensors
(1/2) > >>
ZeroResistance:
I have a few piezo buzzers in my kitty.
And I see that If I connect a scope across the piezo, and hit the piezo it shows a spike on the scope. The piezo only shows a spike when there is a change of pressure, but I keep a constant pressure on it there is no output on the scope.

So that's what makes me wonder, if the piezoelectric effect only shows up when there is a change in pressure.
How do piezoresistive sensors work or generate an output on constant pressure?
ebastler:

--- Quote from: ZeroResistance on December 21, 2018, 06:59:04 am ---So that's what makes me wonder, if the piezoelectric effect only shows up when there is a change in pressure.
How do piezoresistive sensors work or generate an output on constant pressure?

--- End quote ---

Do such beasts exist? I think the static pressure sensors use other principles: Capacitive sensing mostly; not sure whether optical sensing of a membrane position is also used?

Piezo sensors generate a charge when pressure is applied (changes). With careful design, the discharge time constant can be made several (many) seconds long, so "quasi-static" measurements are possible. But I am not aware of piezo sensors which can provide true static, or absolute, pressure measurements.

One could of course try to add electronics which keep integrating and tracking the charge variations, to provide an absolute readout at any time. But I assume that these would suffer from drift problems over time -- unless you can assume the pressure to regularly drop back to a known baseline value.
CJay:
Yes, piezoelectric pressure sensors do exist.

There's a bunch of different technologies used for static pressure sensors but I think most 'traditional' sensors use a strain gauge type arrangement, either of the common platinum film bridge arrangement or a 'formed' element (usually piezo resistive), the other technologies (capacitive/inductive) tend to be rather more expensive.

ebastler:

--- Quote from: CJay on December 21, 2018, 09:03:58 am ---Yes, piezoelectric pressure sensors do exist.

--- End quote ---

Of course. But do piezoelectric sensors for static pressure exist?
ZeroResistance:

--- Quote from: ebastler on December 21, 2018, 09:23:27 am ---
--- Quote from: CJay on December 21, 2018, 09:03:58 am ---Yes, piezoelectric pressure sensors do exist.

--- End quote ---

Of course. But do piezoelectric sensors for static pressure exist?

--- End quote ---

Please have a look at the pressure sensors from Freescale semiconductor (Now NXP)
I would think a majority of them would be based on the "piezoresistive" effect.

https://www.nxp.com/products/sensors/pressure-sensors:DRSNSPRSSR

The attached block diagram is of one such sensor.
It has probably sensing elements (peizo resistors) in bridge arrangement.



Navigation
Message Index
Next page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod