differential pressure measuring in liquid flows?

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otaolafr
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Joined: Sun May 26, 2019 6:28 pm

differential pressure measuring in liquid flows?

Post by otaolafr » Sun May 26, 2019 6:38 pm

hello,

I am looking for some help in measuring the pressure drop of connection for water flow,

is there any family of sensors easy to connect and read the data with the micro python to do measures of differential pressure with liquids? I have found this type for gas flows but not for liquids if anyone has suggestions.... (the range of the pressure I am not sure for the moment.)

thanks, best regards.

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jimmo
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Re: differential pressure measuring in liquid flows?

Post by jimmo » Mon May 27, 2019 12:50 am

Hi,

So you'd like to be able to measure the liquid pressure at multiple different places in a system?

Often when I'm not sure where to begin on how to measure a physical thing, I do vague searches on the hobby/educational electronics shops looking for breakout boards and kits that do a similar purpose. In this case, this sensor came up in a few places -- https://core-electronics.com.au/gravity ... ensor.html

It's a piezoelectric strain gauge - 0 - 1.6 MPa. Very easy to interface to MicroPython as it's just an analog voltage, with a very linear response to pressure. Bear in mind though that it's 5V, whereas most MicroPython boards are 3.3V, so you'll need a 5V supply and a voltage divider for the analog input.

But yeah, this is definitely the DIY "measure the pressure difference of the pipes in my sprinkler system" kind of end of the spectrum. If you're doing actual science, this may not be the part for you... :)

Otherwise there's Digikey's parametric search... https://www.digikey.com.au/products/en/ ... ducers/512 (or any of the other suppliers, Mouser, Farnell, etc)
Here's a random example of one of the first results I found: https://www.digikey.com.au/product-deta ... -ND/726360 Much more expensive, but looks like it possibly has I2C output.

otaolafr
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Joined: Sun May 26, 2019 6:28 pm

Re: differential pressure measuring in liquid flows?

Post by otaolafr » Mon May 27, 2019 7:42 am

jimmo wrote:
Mon May 27, 2019 12:50 am
Hi,

So you'd like to be able to measure the liquid pressure at multiple different places in a system?

Often when I'm not sure where to begin on how to measure a physical thing, I do vague searches on the hobby/educational electronics shops looking for breakout boards and kits that do a similar purpose. In this case, this sensor came up in a few places -- https://core-electronics.com.au/gravity ... ensor.html

It's a piezoelectric strain gauge - 0 - 1.6 MPa. Very easy to interface to MicroPython as it's just an analog voltage, with a very linear response to pressure. Bear in mind though that it's 5V, whereas most MicroPython boards are 3.3V, so you'll need a 5V supply and a voltage divider for the analog input.

But yeah, this is definitely the DIY "measure the pressure difference of the pipes in my sprinkler system" kind of end of the spectrum. If you're doing actual science, this may not be the part for you... :)

Otherwise there's Digikey's parametric search... https://www.digikey.com.au/products/en/ ... ducers/512 (or any of the other suppliers, Mouser, Farnell, etc)
Here's a random example of one of the first results I found: https://www.digikey.com.au/product-deta ... -ND/726360 Much more expensive, but looks like it possibly has I2C output.
hello! thanks for the quick answer!!
as you thought, it is for measures in science experiences, actually for my PhD. I need to follow the pressure drop of different types of equipment with the flow to see the relation between pressure drop and mass flow of them. it is a PhD in chemical engineering so, it is not my goal to go till the last detail of it, more than I could have a reliable measure the easiest way possible, as it is not my field.
from what i look the first link you post is interesting, so, why not for science application ? (sorry for maybe the dumb question). and for the second and third link, they dont say if they are for liquids of gases.

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jimmo
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Re: differential pressure measuring in liquid flows?

Post by jimmo » Mon May 27, 2019 10:16 am

otaolafr wrote:
Mon May 27, 2019 7:42 am
from what i look the first link you post is interesting, so, why not for science application ?
Oh just because with voltage dividers and analog digital converters etc you're subject to a lot of factors affecting both your accuracy and precision. For example, the 0-5V to 0.3.3V conversion (i.e don't use a voltage divider with off-the shelf 1% resistors), or the 10-bit ADC in the microcontroller, means that you have a precision of 1.95 kPa. Plus you'll need to calibrate it somehow.
otaolafr wrote:
Mon May 27, 2019 7:42 am
and for the second and third link, they dont say if they are for liquids of gases.
Yeah, digi-key's parametric search doesn't cover everything. The specific one I linked to, its datasheet says:

* Beverage Dispensing Systems
* Water Pressure or Flow Monitor
* Medical Equipment
* Industrial Equipment/Hydraulics
* Tank Level Measurement
* Manifold Pressure

That's the analog one. The equivalent I2C one from the same series is https://www.digikey.com.au/product-deta ... ND/6005086 It has a range of 0-250psi (1724 kPa), built-in 14-bit ADC (so 16x the precision).

I2C is a digital protocol, so of course fantastic for integrating with any microcontroller (and especially easy on MicroPython).

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