anemometer...

J

John Larkin

Guest
https://www.newark.com/multicomp-pro/mp780109/hot-wire-thermal-anemometer-0/dp/42AH0486?gclid=EAIaIQobChMInZqCp6PM-QIVvxOtBh1IywWdEAQYBCABEgKoUfD_BwE&mckv=_dc|pcrid|529552134213|plid||kword||match||slid||product|42AH0486|pgrid|125501399753|ptaid|pla-812313528682|&CMP=KNC-GUSA-GEN-SMART-SHOPPING-Private-Label


This looks pretty good. The probe fits into tight places where a
propeller type meter won\'t.

It agrees with other velocity meters pretty well.

The manual and user interface make no sense. The directions are in
some language a little like English.
 
On Thursday, August 18, 2022 at 7:10:13 PM UTC-4, John Larkin wrote:
https://www.newark.com/multicomp-pro/mp780109/hot-wire-thermal-anemometer-0/dp/42AH0486?gclid=EAIaIQobChMInZqCp6PM-QIVvxOtBh1IywWdEAQYBCABEgKoUfD_BwE&mckv=_dc|pcrid|529552134213|plid||kword||match||slid||product|42AH0486|pgrid|125501399753|ptaid|pla-812313528682|&CMP=KNC-GUSA-GEN-SMART-SHOPPING-Private-Label


This looks pretty good. The probe fits into tight places where a
propeller type meter won\'t.

It agrees with other velocity meters pretty well.
Click to expand...

I wonder how it compensates for humidity? The photo doesn\'t show the sensor.

--

Rick C.

- Get 1,000 miles of free Supercharging
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John Larkin <jlarkin@highland_atwork_technology.com> Wrote in message:r
> https://www.newark.com/multicomp-pro/mp780109/hot-wire-thermal-anemometer-0/dp/42AH0486?gclid=EAIaIQobChMInZqCp6PM-QIVvxOtBh1IywWdEAQYBCABEgKoUfD_BwE&mckv=_dc|pcrid|529552134213|plid||kword||match||slid||product|42AH0486|pgrid|125501399753|ptaid|pla-812313528682|&CMP=KNC-GUSA-GEN-SMART-SHOPPING-Private-LabelThis looks pretty good. The probe fits into tight places where apropeller type meter won\'t.It agrees with other velocity meters pretty well.The manual and user interface make no sense. The directions are insome language a little like English.

Mulitcomp pro used to be Tenma.
At least it\'s designed in Taiwan.

Cheers
--


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On Thu, 18 Aug 2022 22:09:46 -0400 (EDT), Martin Rid
<martin_riddle@verison.net> wrote:

John Larkin <jlarkin@highland_atwork_technology.com> Wrote in message:r
https://www.newark.com/multicomp-pro/mp780109/hot-wire-thermal-anemometer-0/dp/42AH0486?gclid=EAIaIQobChMInZqCp6PM-QIVvxOtBh1IywWdEAQYBCABEgKoUfD_BwE&mckv=_dc|pcrid|529552134213|plid||kword||match||slid||product|42AH0486|pgrid|125501399753|ptaid|pla-812313528682|&CMP=KNC-GUSA-GEN-SMART-SHOPPING-Private-LabelThis looks pretty good. The probe fits into tight places where apropeller type meter won\'t.It agrees with other velocity meters pretty well.The manual and user interface make no sense. The directions are insome language a little like English.

Mulitcomp pro used to be Tenma.
At least it\'s designed in Taiwan.

Cheers
Click to expand...

After a couple hundred pseudorandom button pushes I managed to get it
to show velocity in FPM. Maybe I\'ll never have to push those buttons
again.

We have 8 pcb\'s in a box. The two fans are fire hoses of air, so some
boards get a lot and slot 3 gets almost none. Air is perverse.

https://www.dropbox.com/s/8ubv5if7cbnsjzn/P940-8_front.jpg?raw=1

The new idea is to make a big rectangular plastic baffle that hangs
down from the top cover, just in front of the boards. We\'d punch some
hole patterns in that, low air transmission near the fans and very
open where we need it. We need the hot-wire probe to sneak in between
the boards, through 8 small holes in the top cover, and see how we\'re
doing as we tune the baffle.
 
On 8/18/22 19:34, jlarkin@highlandsniptechnology.com wrote:

We have 8 pcb\'s in a box. The two fans are fire hoses of air, so
some boards get a lot and slot 3 gets almost none. Air is perverse.

https://www.dropbox.com/s/8ubv5if7cbnsjzn/P940-8_front.jpg?raw=1

The new idea is to make a big rectangular plastic baffle that hangs
down from the top cover, just in front of the boards. We\'d punch
some hole patterns in that, low air transmission near the fans and
very open where we need it. We need the hot-wire probe to sneak in
between the boards, through 8 small holes in the top cover, and see
how we\'re doing as we tune the baffle.
Click to expand...

The idea is a wiffle ball. Fail.
 
On 19-08-2022 01:10, John Larkin wrote:
https://www.newark.com/multicomp-pro/mp780109/hot-wire-thermal-anemometer-0/dp/42AH0486?gclid=EAIaIQobChMInZqCp6PM-QIVvxOtBh1IywWdEAQYBCABEgKoUfD_BwE&mckv=_dc|pcrid|529552134213|plid||kword||match||slid||product|42AH0486|pgrid|125501399753|ptaid|pla-812313528682|&CMP=KNC-GUSA-GEN-SMART-SHOPPING-Private-Label


This looks pretty good. The probe fits into tight places where a
propeller type meter won\'t.

It agrees with other velocity meters pretty well.

The manual and user interface make no sense. The directions are in
some language a little like English.
Click to expand...
Quite cheap. Guess they are using calibration techniques to get it to
have only 1% accuracy. I mean, for a hot wire anemometer...
 
On 19-08-2022 01:10, John Larkin wrote:
https://www.newark.com/multicomp-pro/mp780109/hot-wire-thermal-anemometer-0/dp/42AH0486?gclid=EAIaIQobChMInZqCp6PM-QIVvxOtBh1IywWdEAQYBCABEgKoUfD_BwE&mckv=_dc|pcrid|529552134213|plid||kword||match||slid||product|42AH0486|pgrid|125501399753|ptaid|pla-812313528682|&CMP=KNC-GUSA-GEN-SMART-SHOPPING-Private-Label


This looks pretty good. The probe fits into tight places where a
propeller type meter won\'t.

It agrees with other velocity meters pretty well.

The manual and user interface make no sense. The directions are in
some language a little like English.



Stop posting about instruments, now I had to go buy one also ;-)
Click to expand...

Fun read:

https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/

The Myriad Maxims to Maximally Master TEAcquisition

1. Test equipment (TE) will expand to fill all space available. And then
some.
2. It\'s never \"just a blown fuse.\"
3. That bodge will come back to bite you in the ass.
4. The availability of service documentation varies inversely with your
current level of diagnostic frustration.
5. There\'s always more to fix than you first think.
6. Thou shalt use a probe prophylactic.
7. There is no substitute for exhaustive burn-in testing.
8. The TE you have on hand is never the TE you need to fix the TE you want.
9. Capacitors are Murphy\'s footsoldiers.
10. The adhesive used to apply a label is always stronger than the label
itself.
11. Masochism is endemic, perhaps even mandatory.
12. To get the best deals, you have to be prepared to walk away.
43. Never buy the cheapest chinesium, unless it is for explosion
investigation purposes.
99. Want > Have > Need
 
On Thu, 18 Aug 2022 20:42:45 -0700, corvid <bl@ckb.ird> wrote:

On 8/18/22 19:34, jlarkin@highlandsniptechnology.com wrote:

We have 8 pcb\'s in a box. The two fans are fire hoses of air, so
some boards get a lot and slot 3 gets almost none. Air is perverse.

https://www.dropbox.com/s/8ubv5if7cbnsjzn/P940-8_front.jpg?raw=1

The new idea is to make a big rectangular plastic baffle that hangs
down from the top cover, just in front of the boards. We\'d punch
some hole patterns in that, low air transmission near the fans and
very open where we need it. We need the hot-wire probe to sneak in
between the boards, through 8 small holes in the top cover, and see
how we\'re doing as we tune the baffle.

The idea is a wiffle ball. Fail.
Click to expand...

The idea is controlled air flow impedance into each slot. Why would
that fail?

The thing about air flow is that a lot of people make intuition-based
guesses, with mumbled keywords, and are usually wrong. We are tuning
this by experimant, taping over holes in the baffle until we get
fairly balanced air velocity across the boards.
 
On Fri, 19 Aug 2022 15:44:11 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:

On 19-08-2022 01:10, John Larkin wrote:


https://www.newark.com/multicomp-pro/mp780109/hot-wire-thermal-anemometer-0/dp/42AH0486?gclid=EAIaIQobChMInZqCp6PM-QIVvxOtBh1IywWdEAQYBCABEgKoUfD_BwE&mckv=_dc|pcrid|529552134213|plid||kword||match||slid||product|42AH0486|pgrid|125501399753|ptaid|pla-812313528682|&CMP=KNC-GUSA-GEN-SMART-SHOPPING-Private-Label


This looks pretty good. The probe fits into tight places where a
propeller type meter won\'t.

It agrees with other velocity meters pretty well.

The manual and user interface make no sense. The directions are in
some language a little like English.



Quite cheap. Guess they are using calibration techniques to get it to
have only 1% accuracy. I mean, for a hot wire anemometer...
Click to expand...

Similar hot-wire gadgets cost from less than $200 to close to $2000.
The Flukes and Omegas are over $1000.

The little propeller things start below $50.

20% accuracy would suit us. We are trying to tune a system to get
approximate equal air flow through 8 channels, so we really don\'t need
accuracy.

I made my own hot-wire anemometer once... broke the glass off a small
light bulb as the sensor. We calibrated it using a bicycle with a
speedometer. The multicomp has a ceramic thick-film sensor, probably a
heater on one side and a thermistor on the other. Not literally a hot
wire.
 
On Fri, 19 Aug 2022 16:12:32 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:

On 19-08-2022 01:10, John Larkin wrote:


https://www.newark.com/multicomp-pro/mp780109/hot-wire-thermal-anemometer-0/dp/42AH0486?gclid=EAIaIQobChMInZqCp6PM-QIVvxOtBh1IywWdEAQYBCABEgKoUfD_BwE&mckv=_dc|pcrid|529552134213|plid||kword||match||slid||product|42AH0486|pgrid|125501399753|ptaid|pla-812313528682|&CMP=KNC-GUSA-GEN-SMART-SHOPPING-Private-Label


This looks pretty good. The probe fits into tight places where a
propeller type meter won\'t.

It agrees with other velocity meters pretty well.

The manual and user interface make no sense. The directions are in
some language a little like English.



Stop posting about instruments, now I had to go buy one also ;-)
Click to expand...

At least I\'m not posting about girls or Maseratis.


Fun read:

https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/

The Myriad Maxims to Maximally Master TEAcquisition

1. Test equipment (TE) will expand to fill all space available. And then
some.
2. It\'s never \"just a blown fuse.\"
Click to expand...

On a Fluke, it\'s an afternoon project.

3. That bodge will come back to bite you in the ass.
4. The availability of service documentation varies inversely with your
current level of diagnostic frustration.
5. There\'s always more to fix than you first think.
6. Thou shalt use a probe prophylactic.
7. There is no substitute for exhaustive burn-in testing.
8. The TE you have on hand is never the TE you need to fix the TE you want.
9. Capacitors are Murphy\'s footsoldiers.
10. The adhesive used to apply a label is always stronger than the label
itself.
11. Masochism is endemic, perhaps even mandatory.
12. To get the best deals, you have to be prepared to walk away.
43. Never buy the cheapest chinesium, unless it is for explosion
investigation purposes.
99. Want > Have > Need
Click to expand...

One volumetric advantage that I have is that people keep borrowing
stuff and don\'t give it back.
 
fredag den 19. august 2022 kl. 16.55.35 UTC+2 skrev jla...@highlandsniptechnology.com:
On Fri, 19 Aug 2022 15:44:11 +0200, Klaus Vestergaard Kragelund
klau...@hotmail.com> wrote:

On 19-08-2022 01:10, John Larkin wrote:


https://www.newark.com/multicomp-pro/mp780109/hot-wire-thermal-anemometer-0/dp/42AH0486?gclid=EAIaIQobChMInZqCp6PM-QIVvxOtBh1IywWdEAQYBCABEgKoUfD_BwE&mckv=_dc|pcrid|529552134213|plid||kword||match||slid||product|42AH0486|pgrid|125501399753|ptaid|pla-812313528682|&CMP=KNC-GUSA-GEN-SMART-SHOPPING-Private-Label


This looks pretty good. The probe fits into tight places where a
propeller type meter won\'t.

It agrees with other velocity meters pretty well.

The manual and user interface make no sense. The directions are in
some language a little like English.



Quite cheap. Guess they are using calibration techniques to get it to
have only 1% accuracy. I mean, for a hot wire anemometer...
Similar hot-wire gadgets cost from less than $200 to close to $2000.
The Flukes and Omegas are over $1000.

The little propeller things start below $50.

20% accuracy would suit us. We are trying to tune a system to get
approximate equal air flow through 8 channels, so we really don\'t need
accuracy.
Click to expand...

eight RTDs and eight voltmeters? in series with enough current to get some self heating
 
On Fri, 19 Aug 2022 08:29:08 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

fredag den 19. august 2022 kl. 16.55.35 UTC+2 skrev jla...@highlandsniptechnology.com:
On Fri, 19 Aug 2022 15:44:11 +0200, Klaus Vestergaard Kragelund
klau...@hotmail.com> wrote:

On 19-08-2022 01:10, John Larkin wrote:


https://www.newark.com/multicomp-pro/mp780109/hot-wire-thermal-anemometer-0/dp/42AH0486?gclid=EAIaIQobChMInZqCp6PM-QIVvxOtBh1IywWdEAQYBCABEgKoUfD_BwE&mckv=_dc|pcrid|529552134213|plid||kword||match||slid||product|42AH0486|pgrid|125501399753|ptaid|pla-812313528682|&CMP=KNC-GUSA-GEN-SMART-SHOPPING-Private-Label


This looks pretty good. The probe fits into tight places where a
propeller type meter won\'t.

It agrees with other velocity meters pretty well.

The manual and user interface make no sense. The directions are in
some language a little like English.



Quite cheap. Guess they are using calibration techniques to get it to
have only 1% accuracy. I mean, for a hot wire anemometer...
Similar hot-wire gadgets cost from less than $200 to close to $2000.
The Flukes and Omegas are over $1000.

The little propeller things start below $50.

20% accuracy would suit us. We are trying to tune a system to get
approximate equal air flow through 8 channels, so we really don\'t need
accuracy.

eight RTDs and eight voltmeters? in series with enough current to get some self heating
Click to expand...

Yes, you could make a good flowmeter with just one RTD. I guess we
could have an air flow sensor on every production board, but that\'s
kinda silly. We will have temperature sensors on every board and servo
fan speeds.

Our test box has 8 small holes in the top cover, so we can poke in the
anemometer probe.

I was thinking of a modulated heater with a temp sensor downstream.
Measure air transport delay.

I was questioning the direction of air flow in some of the slots
between our PC boards. It\'s not inconceivable that some slots could
have reverse flow, and a hot-wire flowmeter won\'t show that. A little
strip torn off a Kleenex shows the sign. They were all the same way,
front to back.

Maybe the propeller meter things indicate direction. Or you can at
least look at the spinner. They need spirals, like on a jet engine.
 
fredag den 19. august 2022 kl. 18.14.41 UTC+2 skrev jla...@highlandsniptechnology.com:
On Fri, 19 Aug 2022 08:29:08 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

fredag den 19. august 2022 kl. 16.55.35 UTC+2 skrev jla...@highlandsniptechnology.com:
On Fri, 19 Aug 2022 15:44:11 +0200, Klaus Vestergaard Kragelund
klau...@hotmail.com> wrote:

On 19-08-2022 01:10, John Larkin wrote:


https://www.newark.com/multicomp-pro/mp780109/hot-wire-thermal-anemometer-0/dp/42AH0486?gclid=EAIaIQobChMInZqCp6PM-QIVvxOtBh1IywWdEAQYBCABEgKoUfD_BwE&mckv=_dc|pcrid|529552134213|plid||kword||match||slid||product|42AH0486|pgrid|125501399753|ptaid|pla-812313528682|&CMP=KNC-GUSA-GEN-SMART-SHOPPING-Private-Label


This looks pretty good. The probe fits into tight places where a
propeller type meter won\'t.

It agrees with other velocity meters pretty well.

The manual and user interface make no sense. The directions are in
some language a little like English.



Quite cheap. Guess they are using calibration techniques to get it to
have only 1% accuracy. I mean, for a hot wire anemometer...
Similar hot-wire gadgets cost from less than $200 to close to $2000.
The Flukes and Omegas are over $1000.

The little propeller things start below $50.

20% accuracy would suit us. We are trying to tune a system to get
approximate equal air flow through 8 channels, so we really don\'t need
accuracy.

eight RTDs and eight voltmeters? in series with enough current to get some self heating
Yes, you could make a good flowmeter with just one RTD. I guess we
could have an air flow sensor on every production board, but that\'s
kinda silly. We will have temperature sensors on every board and servo
fan speeds.

Our test box has 8 small holes in the top cover, so we can poke in the
anemometer probe.
Click to expand...

I was just imagining using eight sensors for testing, instantly tells you if the flows are the same
no need for absolutes
 
On 8/19/22 07:46, jlarkin@highlandsniptechnology.com wrote:
On Thu, 18 Aug 2022 20:42:45 -0700, corvid <bl@ckb.ird> wrote:

On 8/18/22 19:34, jlarkin@highlandsniptechnology.com wrote:

We have 8 pcb\'s in a box. The two fans are fire hoses of air, so
some boards get a lot and slot 3 gets almost none. Air is
perverse.

https://www.dropbox.com/s/8ubv5if7cbnsjzn/P940-8_front.jpg?raw=1

The new idea is to make a big rectangular plastic baffle that
hangs down from the top cover, just in front of the boards. We\'d
punch some hole patterns in that, low air transmission near the
fans and very open where we need it. We need the hot-wire probe
to sneak in between the boards, through 8 small holes in the top
cover, and see how we\'re doing as we tune the baffle.

The idea is a wiffle ball. Fail.

The idea is controlled air flow impedance into each slot. Why would
that fail?
Click to expand...

A flight instructor realized that I was using differential braking to
steer a AA5B Tiger down the runway on takeoff. Don\'t do that, use the
rudder, he told me.

Your baffle appears to use the same logic as brakes on takeoff.

The thing about air flow is that a lot of people make
intuition-based guesses, with mumbled keywords, and are usually
wrong. We are tuning this by experimant, taping over holes in the
baffle until we get fairly balanced air velocity across the boards.
Click to expand...

Look at the wing flaps of the Douglas dive bomber.
https://en.wikipedia.org/wiki/Douglas_SBD_Dauntless#/media/File:Air_Zoo_December_2019_086_(Douglas_SBD-3_Dauntless).jpg
 
Klaus Vestergaard Kragelund <klauskvik@hotmail.com> Wrote in message:r
On 19-08-2022 01:10, John Larkin wrote:> > > https://www.newark.com/multicomp-pro/mp780109/hot-wire-thermal-anemometer-0/dp/42AH0486?gclid=EAIaIQobChMInZqCp6PM-QIVvxOtBh1IywWdEAQYBCABEgKoUfD_BwE&mckv=_dc|pcrid|529552134213|plid||kword||match||slid||product|42AH0486|pgrid|125501399753|ptaid|pla-812313528682|&CMP=KNC-GUSA-GEN-SMART-SHOPPING-Private-Label> > > This looks pretty good. The probe fits into tight places where a> propeller type meter won\'t.> > It agrees with other velocity meters pretty well.> > The manual and user interface make no sense. The directions are in> some language a little like English.> > > Stop posting about instruments, now I had to go buy one also ;-)Fun read:https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/The Myriad Maxims to Maximally Master TEAcquisition1. Test equipment (TE) will expand to fill all space available. And then some.2. It\'s never \"just a blown fuse.\"3. That bodge will come back to bite you in the ass.4. The availability of service documentation varies inversely with your current level of diagnostic frustration.5. There\'s always more to fix than you first think.6. Thou shalt use a probe prophylac
tic.7. There is no substitute for exhaustive burn-in testing.8. The TE you have on hand is never the TE you need to fix the TE you want.9. Capacitors are Murphy\'s footsoldiers.10. The adhesive used to apply a label is always stronger than the label itself.11. Masochism is endemic, perhaps even mandatory.12. To get the best deals, you have to be prepared to walk away.43. Never buy the cheapest chinesium, unless it is for explosion investigation purposes.99. Want > Have > Need
Click to expand...

Haha, I bought one of those switching lab supplies after John
posted about one.
Boy I was sorry I did. Those suckers are really noisy.

Cheers
--


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https://piaohong.s3-us-west-2.amazonaws.com/usenet/index.html
 
On Fri, 19 Aug 2022 09:49:25 -0700, corvid <bl@ckb.ird> wrote:

On 8/19/22 07:46, jlarkin@highlandsniptechnology.com wrote:
On Thu, 18 Aug 2022 20:42:45 -0700, corvid <bl@ckb.ird> wrote:

On 8/18/22 19:34, jlarkin@highlandsniptechnology.com wrote:

We have 8 pcb\'s in a box. The two fans are fire hoses of air, so
some boards get a lot and slot 3 gets almost none. Air is
perverse.

https://www.dropbox.com/s/8ubv5if7cbnsjzn/P940-8_front.jpg?raw=1

The new idea is to make a big rectangular plastic baffle that
hangs down from the top cover, just in front of the boards. We\'d
punch some hole patterns in that, low air transmission near the
fans and very open where we need it. We need the hot-wire probe
to sneak in between the boards, through 8 small holes in the top
cover, and see how we\'re doing as we tune the baffle.

The idea is a wiffle ball. Fail.

The idea is controlled air flow impedance into each slot. Why would
that fail?

A flight instructor realized that I was using differential braking to
steer a AA5B Tiger down the runway on takeoff. Don\'t do that, use the
rudder, he told me.

Your baffle appears to use the same logic as brakes on takeoff.
Click to expand...

Brakes? Takeoff?

Logic even?



The thing about air flow is that a lot of people make
intuition-based guesses, with mumbled keywords, and are usually
wrong. We are tuning this by experimant, taping over holes in the
baffle until we get fairly balanced air velocity across the boards.

Look at the wing flaps of the Douglas dive bomber.
https://en.wikipedia.org/wiki/Douglas_SBD_Dauntless#/media/File:Air_Zoo_December_2019_086_(Douglas_SBD-3_Dauntless).jpg
Click to expand...

They were trying to solve a very different problem.

What\'s interesting is that airframe designers have the smartest people
and the best fluid dynamics software and the biggest supercomputers
available. And still use wind tunnels.
 
On Fri, 19 Aug 2022 09:41:35 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

fredag den 19. august 2022 kl. 18.14.41 UTC+2 skrev jla...@highlandsniptechnology.com:
On Fri, 19 Aug 2022 08:29:08 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

fredag den 19. august 2022 kl. 16.55.35 UTC+2 skrev jla...@highlandsniptechnology.com:
On Fri, 19 Aug 2022 15:44:11 +0200, Klaus Vestergaard Kragelund
klau...@hotmail.com> wrote:

On 19-08-2022 01:10, John Larkin wrote:


https://www.newark.com/multicomp-pro/mp780109/hot-wire-thermal-anemometer-0/dp/42AH0486?gclid=EAIaIQobChMInZqCp6PM-QIVvxOtBh1IywWdEAQYBCABEgKoUfD_BwE&mckv=_dc|pcrid|529552134213|plid||kword||match||slid||product|42AH0486|pgrid|125501399753|ptaid|pla-812313528682|&CMP=KNC-GUSA-GEN-SMART-SHOPPING-Private-Label


This looks pretty good. The probe fits into tight places where a
propeller type meter won\'t.

It agrees with other velocity meters pretty well.

The manual and user interface make no sense. The directions are in
some language a little like English.



Quite cheap. Guess they are using calibration techniques to get it to
have only 1% accuracy. I mean, for a hot wire anemometer...
Similar hot-wire gadgets cost from less than $200 to close to $2000.
The Flukes and Omegas are over $1000.

The little propeller things start below $50.

20% accuracy would suit us. We are trying to tune a system to get
approximate equal air flow through 8 channels, so we really don\'t need
accuracy.

eight RTDs and eight voltmeters? in series with enough current to get some self heating
Yes, you could make a good flowmeter with just one RTD. I guess we
could have an air flow sensor on every production board, but that\'s
kinda silly. We will have temperature sensors on every board and servo
fan speeds.

Our test box has 8 small holes in the top cover, so we can poke in the
anemometer probe.


I was just imagining using eight sensors for testing, instantly tells you if the flows are the same
no need for absolutes
Click to expand...

Iterating the baffle holes with tape takes time. Poking one probe into
8 holes in the top cover is really incremental.

So far, varying fan speed doesn\'t seem to affect the relative
distribution of air in the 8 slots.
 
On Fri, 19 Aug 2022 14:08:39 -0400 (EDT), Martin Rid
<martin_riddle@verison.net> wrote:

Klaus Vestergaard Kragelund <klauskvik@hotmail.com> Wrote in message:r
On 19-08-2022 01:10, John Larkin wrote:> > > https://www.newark.com/multicomp-pro/mp780109/hot-wire-thermal-anemometer-0/dp/42AH0486?gclid=EAIaIQobChMInZqCp6PM-QIVvxOtBh1IywWdEAQYBCABEgKoUfD_BwE&mckv=_dc|pcrid|529552134213|plid||kword||match||slid||product|42AH0486|pgrid|125501399753|ptaid|pla-812313528682|&CMP=KNC-GUSA-GEN-SMART-SHOPPING-Private-Label> > > This looks pretty good. The probe fits into tight places where a> propeller type meter won\'t.> > It agrees with other velocity meters pretty well.> > The manual and user interface make no sense. The directions are in> some language a little like English.> > > Stop posting about instruments, now I had to go buy one also ;-)Fun read:https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/The Myriad Maxims to Maximally Master TEAcquisition1. Test equipment (TE) will expand to fill all space available. And then some.2. It\'s never \"just a blown fuse.\"3. That bodge will come back to bite you in the
ass.4. The availability of service documentation varies inversely with your current level of diagnostic frustration.5. There\'s always more to fix than you first think.6. Thou shalt use a probe prophylactic.7. There is no substitute for exhaustive burn-in testing.8. The TE you have on hand is never the TE you need to fix the TE you want.9. Capacitors are Murphy\'s footsoldiers.10. The adhesive used to apply a label is always stronger than the label itself.11. Masochism is endemic, perhaps even mandatory.12. To get the best deals, you have to be prepared to walk away.43. Never buy the cheapest chinesium, unless it is for explosion investigation purposes.99. Want > Have > Need

Haha, I bought one of those switching lab supplies after John
posted about one.
Boy I was sorry I did. Those suckers are really noisy.

Cheers
Click to expand...

I added noise filters to mine.

https://www.dropbox.com/s/6a5nmgnermxii5b/Koco_Filters.jpg?raw=1

But I\'m powering some big switching amps, so a little more noise just
adds to the chorus.
 
fredag den 19. august 2022 kl. 20.45.47 UTC+2 skrev John Larkin:
On Fri, 19 Aug 2022 09:49:25 -0700, corvid <b...@ckb.ird> wrote:

On 8/19/22 07:46, jla...@highlandsniptechnology.com wrote:
On Thu, 18 Aug 2022 20:42:45 -0700, corvid <b...@ckb.ird> wrote:

On 8/18/22 19:34, jla...@highlandsniptechnology.com wrote:

We have 8 pcb\'s in a box. The two fans are fire hoses of air, so
some boards get a lot and slot 3 gets almost none. Air is
perverse.

https://www.dropbox.com/s/8ubv5if7cbnsjzn/P940-8_front.jpg?raw=1

The new idea is to make a big rectangular plastic baffle that
hangs down from the top cover, just in front of the boards. We\'d
punch some hole patterns in that, low air transmission near the
fans and very open where we need it. We need the hot-wire probe
to sneak in between the boards, through 8 small holes in the top
cover, and see how we\'re doing as we tune the baffle.

The idea is a wiffle ball. Fail.

The idea is controlled air flow impedance into each slot. Why would
that fail?

A flight instructor realized that I was using differential braking to
steer a AA5B Tiger down the runway on takeoff. Don\'t do that, use the
rudder, he told me.

Your baffle appears to use the same logic as brakes on takeoff.
Brakes? Takeoff?

Logic even?

The thing about air flow is that a lot of people make
intuition-based guesses, with mumbled keywords, and are usually
wrong. We are tuning this by experimant, taping over holes in the
baffle until we get fairly balanced air velocity across the boards.

Look at the wing flaps of the Douglas dive bomber.
https://en.wikipedia.org/wiki/Douglas_SBD_Dauntless#/media/File:Air_Zoo_December_2019_086_(Douglas_SBD-3_Dauntless).jpg
They were trying to solve a very different problem.

What\'s interesting is that airframe designers have the smartest people
and the best fluid dynamics software and the biggest supercomputers
available. And still use wind tunnels.
Click to expand...

formula one has for years had limit on how much CFD and windtunnel time they can use
they can mix CFD and windtunnel time with 1 TeraFLOP = 1 hour windtunnel
 
On 19-08-2022 20:50, John Larkin wrote:
On Fri, 19 Aug 2022 09:41:35 -0700 (PDT), Lasse Langwadt Christensen
langwadt@fonz.dk> wrote:

fredag den 19. august 2022 kl. 18.14.41 UTC+2 skrev jla...@highlandsniptechnology.com:
On Fri, 19 Aug 2022 08:29:08 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

fredag den 19. august 2022 kl. 16.55.35 UTC+2 skrev jla...@highlandsniptechnology.com:
On Fri, 19 Aug 2022 15:44:11 +0200, Klaus Vestergaard Kragelund
klau...@hotmail.com> wrote:

On 19-08-2022 01:10, John Larkin wrote:


https://www.newark.com/multicomp-pro/mp780109/hot-wire-thermal-anemometer-0/dp/42AH0486?gclid=EAIaIQobChMInZqCp6PM-QIVvxOtBh1IywWdEAQYBCABEgKoUfD_BwE&mckv=_dc|pcrid|529552134213|plid||kword||match||slid||product|42AH0486|pgrid|125501399753|ptaid|pla-812313528682|&CMP=KNC-GUSA-GEN-SMART-SHOPPING-Private-Label


This looks pretty good. The probe fits into tight places where a
propeller type meter won\'t.

It agrees with other velocity meters pretty well.

The manual and user interface make no sense. The directions are in
some language a little like English.



Quite cheap. Guess they are using calibration techniques to get it to
have only 1% accuracy. I mean, for a hot wire anemometer...
Similar hot-wire gadgets cost from less than $200 to close to $2000.
The Flukes and Omegas are over $1000.

The little propeller things start below $50.

20% accuracy would suit us. We are trying to tune a system to get
approximate equal air flow through 8 channels, so we really don\'t need
accuracy.

eight RTDs and eight voltmeters? in series with enough current to get some self heating
Yes, you could make a good flowmeter with just one RTD. I guess we
could have an air flow sensor on every production board, but that\'s
kinda silly. We will have temperature sensors on every board and servo
fan speeds.

Our test box has 8 small holes in the top cover, so we can poke in the
anemometer probe.


I was just imagining using eight sensors for testing, instantly tells you if the flows are the same
no need for absolutes




Iterating the baffle holes with tape takes time. Poking one probe into
8 holes in the top cover is really incremental.

So far, varying fan speed doesn\'t seem to affect the relative
distribution of air in the 8 slots.
Click to expand...

I did an experiment once where we had a problem with the orientation of
a product. So burned power into a resistor on the PCB, surrounded by 4
NTC resistors. We did in fact detect orientation. in 2 planes. But then,
what about the third plane?
 
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