air flow sensor on PCB...

[John Larkin]

On Tue, 18 Apr 2023 08:05:55 -0700 (PDT), M Nelson
<drmcnelson@gmail.com> wrote:

On Tuesday, April 18, 2023 at 10:05:35?AM UTC-4, M Nelson wrote:
As noted, the flow sensor needs to be on a controller board that plugs
into a generic VME crate. That board has no access to the fans.
Fine, then the choices would seem to be (a) thermal conduction of moving air, (b) propagation of sound, or (c) direct pressure on a deformable object. All three are cheap. The first and third are probably the most reliable, the third might be the more accurate with changes in temperature, humidity, and air pressure.

Another perhaps more exotic idea that comes to mind is deflection of electrons. But I think the first three might be more practical.


One more almost out of the box idea. Many MCUs and CPUs nowadays have temperature sensors. They are in effect thermal conduction type anemometers. Find a cheap one, and running a simple loop, clock it just fast enough to produce a small increment in temperature over the ambient when the fan is off. You have to admit, in some ways its a pretty relevant measurement for the purpose.

That is interesting, compute something useless to raise chip
temperature. But I\'d prefer to poke the sensor up off the board, into
the air stream.

My plan so far is to measure the temperature of a TO92 transistor at
two different power dissipations and so some math on that. A TO92 is
about 200 K/W in still air, maybe half that at 200 LFPM.

OK, I need an ARM in a TO92 package.

 

[M Nelson]

> OK, I need an ARM in a TO92 package.

Or if you want to do as little work as possible, get a cheap arduino, teensy, stm or whatever, put it on two rows of 0.1inch headers, and connect to it over whatever you like to get the data. You could use it to read your TO92 transistor too if you like.

 

[M Nelson]

On Tuesday, April 18, 2023 at 1:16:58 PM UTC-4, M Nelson wrote:

OK, I need an ARM in a TO92 package.
Or if you want to do as little work as possible, get a cheap arduino, teensy, stm or whatever, put it on two rows of 0.1inch headers, and connect to it over whatever you like to get the data. You could use it to read your TO92 transistor too if you like.

You could put it in a tall header also, if you want it in the air stream - after a fashion

 

[Jasen Betts]

On 2023-04-06, John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:

Given a PC board in a crate, like PCIe or PXI or VME or something,
what would be a good way to check air flow across the board, to verify
that the box fans and filters are OK? Assume this board can\'t access
the fan tachs or anything like that.

I was thinking that I might stick a small thinfilm RTD in the air
stream and measure its temperature at two different voltages, to
estimate its self-heating, which would vary with air flow.

The classic broken light bulb hot-wire anemometer is a nuisance.

Carbon comp resistor?

This can\'t be a new problem. Any other suggestions?

on a whim I put \"MAF sensor LCSC\" into google and that lead me to the
LCSC page on flow sensors on that page I found

Goertek SF15M-001

and

Honeywell AWM92205VPP

both less than a buck in small quantities, neither in stock.

Digikey has the frist one and even a leaked data sheet, which aeems to
have been tranlated, badly, from some other language. Also the second
as a marketplace product with no datasheet or photo...

the first seems to measure air flow via a vertical tunnel,
..
the second is mystery meat,
--

Jasen.
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