On Sun, 21 Aug 2022 00:30:22 -0000 (UTC), Cydrome Leader
<presence@MUNGEpanix.com> wrote:

>jlarkin@highlandsniptechnology.com wrote:
>> 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...
>>
>> Similar hot-wire gadgets cost from less than $200 to close to $2000.
>> The Flukes and Omegas are over $1000.
>
>Omega is garbage these days. They struggled and failed to find a
>replacement for one of discontinued temp controllers. They clearly had no
>idea what they used to make, or what they make now.
>
>Went with Novus. Weird pre-sales support (they're in brazil), but it was
>legit and they have real distributors in the US. Will bump to the top of
>the list for anthing temp control. The omron stuff is just overly complex.
>
>> 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.
>
>Do you care about temperatures or the airflow numbers? It's sort of
>shocking that the cooling is poor/uneven in that chassis illustration.

We want air flow over the eight boards to cool parts. Some will have
local heat sinks here and there. I was hoping for 200 LFPM on the
worst board with the fans running at some tolerable noise level.

Any board that thinks it's getting too hot can request that the fan
speeds be increased.

As noted, the two fans are fire hoses of air. Slot 3, about in the
center, gets about a tenth the flow of slot 1, which gets a full fan
blast.

Blowing air out the front panel (it currently intakes) has upsides,
probably better distribution between boards. But it has downsides too.

On Sat, 20 Aug 2022 01:59:04 +0200, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:

>On 19-08-2022 21:02, John Larkin wrote:
>> 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
>>
>> 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.
>>
>
>Many of the Chinese ones has horrible CM noise

300 watts, $72, free shipping, and amazing voltage accuracy and
stability.

On 20-08-2022 18:00, Clive Arthur wrote:
> On 20/08/2022 16:12, jlarkin@highlandsniptechnology.com wrote:
>> On Sat, 20 Aug 2022 12:34:59 +0100, Clive Arthur
>> <clive@nowaytoday.co.uk> wrote:
>>
>>> On 20/08/2022 00:57, Klaus Vestergaard Kragelund wrote:
>>>
>>> <snip>
>>>
>>>> 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?
>>>
>>> There was a DIL chip for use as an inclinometer which had a miniature
>>> heater and two thermistors plus signal processing, and used the
>>> differential temperature due to air convection to provide tilt.  It was
>>> a long time ago, before MEMS.
>>
>> There were also electrolytic (liquid) inclinometers.
>>
>> I designed a level sensor system for the C5A Boresight Alignment Kit.
>> It used a Talyvel inclinometer, basically a pendulum and LVDT.
>
> Electrolevels could be very accurate and reliable.  Long ago, I
> installed many to monitor slope stability on an embankment and movement
> on a flyover in Wales, all cabled back to a hut which would get visited
> less and less frequently.  I expect they're still there after forty
> years or more.
>
> They obviously work, because the embankment hasn't slipped yet :-)
>

There is of course many solutions. The point of the one we did was that
this was for high volume, cost sensitive, so only a 1cent solution would
be allowed

jlarkin@highlandsniptechnology.com wrote:
> On Sun, 21 Aug 2022 00:30:22 -0000 (UTC), Cydrome Leader
> <presence@MUNGEpanix.com> wrote:
>
>>jlarkin@highlandsniptechnology.com wrote:
>>> 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...
>>>
>>> Similar hot-wire gadgets cost from less than $200 to close to $2000.
>>> The Flukes and Omegas are over $1000.
>>
>>Omega is garbage these days. They struggled and failed to find a
>>replacement for one of discontinued temp controllers. They clearly had no
>>idea what they used to make, or what they make now.
>>
>>Went with Novus. Weird pre-sales support (they're in brazil), but it was
>>legit and they have real distributors in the US. Will bump to the top of
>>the list for anthing temp control. The omron stuff is just overly complex.
>>
>>> 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.
>>
>>Do you care about temperatures or the airflow numbers? It's sort of
>>shocking that the cooling is poor/uneven in that chassis illustration.
>
> We want air flow over the eight boards to cool parts. Some will have
> local heat sinks here and there. I was hoping for 200 LFPM on the
> worst board with the fans running at some tolerable noise level.
>
> Any board that thinks it's getting too hot can request that the fan
> speeds be increased.
>
> As noted, the two fans are fire hoses of air. Slot 3, about in the
> center, gets about a tenth the flow of slot 1, which gets a full fan
> blast.
>
> Blowing air out the front panel (it currently intakes) has upsides,
> probably better distribution between boards. But it has downsides too.

just as a tip, nobody cares about the airflow numbers. It's all about
temperatures. Over 100 temp readings are possible in modern servers. None
of the instrumention is about airflow itself, because it just doesn't
matter once the minimums are met. For example, different sizes and shapes
of heatsinks in the same flow of air behave differently.

You may need to watch out if their air speeds are high and you want to
control air flow with a piece of swiss cheese. Noise and turbulence will
be your new friends.

If you want to go real extreme, use a blower and actual tubes/pipes to
distribute the air where you need it. Think irrigation system, or old
avionics.

On Mon, 22 Aug 2022 18:34:33 -0000 (UTC), Cydrome Leader
<presence@MUNGEpanix.com> wrote:

>jlarkin@highlandsniptechnology.com wrote:
>> On Sun, 21 Aug 2022 00:30:22 -0000 (UTC), Cydrome Leader
>> <presence@MUNGEpanix.com> wrote:
>>
>>>jlarkin@highlandsniptechnology.com wrote:
>>>> 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...
>>>>
>>>> Similar hot-wire gadgets cost from less than $200 to close to $2000.
>>>> The Flukes and Omegas are over $1000.
>>>
>>>Omega is garbage these days. They struggled and failed to find a
>>>replacement for one of discontinued temp controllers. They clearly had no
>>>idea what they used to make, or what they make now.
>>>
>>>Went with Novus. Weird pre-sales support (they're in brazil), but it was
>>>legit and they have real distributors in the US. Will bump to the top of
>>>the list for anthing temp control. The omron stuff is just overly complex.
>>>
>>>> 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.
>>>
>>>Do you care about temperatures or the airflow numbers? It's sort of
>>>shocking that the cooling is poor/uneven in that chassis illustration.
>>
>> We want air flow over the eight boards to cool parts. Some will have
>> local heat sinks here and there. I was hoping for 200 LFPM on the
>> worst board with the fans running at some tolerable noise level.
>>
>> Any board that thinks it's getting too hot can request that the fan
>> speeds be increased.
>>
>> As noted, the two fans are fire hoses of air. Slot 3, about in the
>> center, gets about a tenth the flow of slot 1, which gets a full fan
>> blast.
>>
>> Blowing air out the front panel (it currently intakes) has upsides,
>> probably better distribution between boards. But it has downsides too.
>
>just as a tip, nobody cares about the airflow numbers. It's all about
>temperatures. Over 100 temp readings are possible in modern servers. None
>of the instrumention is about airflow itself, because it just doesn't
>matter once the minimums are met. For example, different sizes and shapes
>of heatsinks in the same flow of air behave differently.
>
>You may need to watch out if their air speeds are high and you want to
>control air flow with a piece of swiss cheese. Noise and turbulence will
>be your new friends.
>
>If you want to go real extreme, use a blower and actual tubes/pipes to
>distribute the air where you need it. Think irrigation system, or old
>avionics.

Too late now. But getting fairly uniform air flow into 8 tubes could
get interesting too.

The baffle is a first approximation to a positive-pressure plenum with
controlled-resistance exits.

On 21/08/2022 22:17, Klaus Vestergaard Kragelund wrote:

<snipped>

> There is of course many solutions. The point of the one we did was that
> this was for high volume, cost sensitive, so only a 1cent solution would
> be allowed

Yes. For the required accuracy, it was a clever design. Ingenious.

--
Cheers
Clive

On Thu, 18 Aug 2022 19:34:32 -0700, jlarkin@highlandsniptechnology.com
wrote:

>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
>
>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
>
Hard to predict without an exhaust vent profile. if centered in
the rear, it can equalise flow through equalised back-pressure.

Looks like the boards are too close to the rear wall, but that can be
used to increase influence of the exhaust pattern.

Use of back pressure eventually means less net airflow.

RL

On Tue, 23 Aug 2022 08:18:22 -0400, legg <legg@nospam.magma.ca> wrote:

>On Thu, 18 Aug 2022 19:34:32 -0700, jlarkin@highlandsniptechnology.com
>wrote:
>
>>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
>>
>>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
>>
>Hard to predict without an exhaust vent profile. if centered in
>the rear, it can equalise flow through equalised back-pressure.

The back panels will have various cutout sizes that depend on how much
air flow each type of module needs. That of course complicates things
more.

>
>Looks like the boards are too close to the rear wall, but that can be
>used to increase influence of the exhaust pattern.

Would a rear plenum help? Our current rear plenum is the world.

>
>Use of back pressure eventually means less net airflow.

Sure. We want some guaranteed minimum flow in the worst slot, 200
f/min as a target.

>
>RL

On Tue, 23 Aug 2022 07:08:34 -0700, jlarkin@highlandsniptechnology.com
wrote:

>On Tue, 23 Aug 2022 08:18:22 -0400, legg <legg@nospam.magma.ca> wrote:
>
>>On Thu, 18 Aug 2022 19:34:32 -0700, jlarkin@highlandsniptechnology.com
>>wrote:
>>
>>>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
>>>
>>>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
>>>
>>Hard to predict without an exhaust vent profile. if centered in
>>the rear, it can equalise flow through equalised back-pressure.
>
>The back panels will have various cutout sizes that depend on how much
>air flow each type of module needs. That of course complicates things
>more.
>
>>
>>Looks like the boards are too close to the rear wall, but that can be
>>used to increase influence of the exhaust pattern.
>
>Would a rear plenum help? Our current rear plenum is the world.
>
>>
>>Use of back pressure eventually means less net airflow.
>
>Sure. We want some guaranteed minimum flow in the worst slot, 200
>f/min as a target.

An interesting number. You mean linear FPM ?

With local scrubbers (which is what you've been touting in the past),
your only interest would be delta T of the air, by the time it
leaves the box. No numbers on the drawing, but assuming an 18" rack
mount, that would mean >> 100 cubic feet / minute of air volume
delivered by the fans.

Check the fan spec sheets. What's the air volume capacity of the
fans at full speed?

100ft^3 is about 3m^3
standard air density 1.276 kg/m3
specific heat capacity of air is 1.006 kJ/kgK

So you're heating about 4Kg ( 3 x 1.276) of air every 60 seconds
- that's .067kg per second - .067kj or 67W for every degree C rise.

If the air volume halves, delta T doubles.
If energy absorption doubles, delta T doubles.

With an energy load of x watts, that gives you box air volume
requirements in your environment.

Air volume (feet per minute - linear or cubic) will depend on
back-pressure presented to the fans. I expect it will be
considerably less than 100 cubic feet / minute.

RL