On Tuesday, January 11, 2022 at 4:25:45 PM UTC-8, jjhu...@gmail.com wrote:
> On Monday, January 10, 2022 at 10:26:19 PM UTC-5, jla...@highlandsniptechnology.com wrote:
> > We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
> > modular load boards. We want to measure all 9 currents so that we can
> > do some sorts of intelligent cutoffs if the eight boards threaten to
> > cave in the big supply.
> >
> > So we want nine mediocre-accuracy unipolar high-side current sensors
> > so we can digitize the currents with a grounded mux/adc.
> >
> > Does anyone have a favorite but cheap high-side current sense IC?
> >
> > We can add shunts, or I guess it could be some Hall thing.
> >
> >
> >
> > --
> >
> > I yam what I yam - Popeye
> I've used the ina168 and ina219. Liked the results - easy to use. The ina168 seems to meet your specs.
> https://www.digikey.com/catalog/en/partgroup/current-monitor/19066
>
> Just to play with, get the breakout board with I2C interface and connect to arduino or RPI for testing.
> J

The AD8479 handles up to 600V common mode. Couple this with a current shunt and you are good to go.
https://www.analog.com/media/en/technical-documentation/data-sheets/ad8479.pdf

onsdag den 12. januar 2022 kl. 02.10.07 UTC+1 skrev Flyguy:
> On Tuesday, January 11, 2022 at 4:25:45 PM UTC-8, jjhu...@gmail.com wrote:
> > On Monday, January 10, 2022 at 10:26:19 PM UTC-5, jla...@highlandsniptechnology.com wrote:
> > > We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
> > > modular load boards. We want to measure all 9 currents so that we can
> > > do some sorts of intelligent cutoffs if the eight boards threaten to
> > > cave in the big supply.
> > >
> > > So we want nine mediocre-accuracy unipolar high-side current sensors
> > > so we can digitize the currents with a grounded mux/adc.
> > >
> > > Does anyone have a favorite but cheap high-side current sense IC?
> > >
> > > We can add shunts, or I guess it could be some Hall thing.
> > >
> > >
> > >
> > > --
> > >
> > > I yam what I yam - Popeye
> > I've used the ina168 and ina219. Liked the results - easy to use. The ina168 seems to meet your specs.
> > https://www.digikey.com/catalog/en/partgroup/current-monitor/19066
> >
> > Just to play with, get the breakout board with I2C interface and connect to arduino or RPI for testing.
> > J
> The AD8479 handles up to 600V common mode. Couple this with a current shunt and you are good to go.
> https://www.analog.com/media/en/technical-documentation/data-sheets/ad8479.pdf

also much much more expensive than a current sense amplifier

On Tue, 11 Jan 2022 16:25:41 -0800 (PST), Three Jeeps
<jjhudak4@gmail.com> wrote:

>On Monday, January 10, 2022 at 10:26:19 PM UTC-5, jla...@highlandsniptechnology.com wrote:
>> We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
>> modular load boards. We want to measure all 9 currents so that we can
>> do some sorts of intelligent cutoffs if the eight boards threaten to
>> cave in the big supply.
>>
>> So we want nine mediocre-accuracy unipolar high-side current sensors
>> so we can digitize the currents with a grounded mux/adc.
>>
>> Does anyone have a favorite but cheap high-side current sense IC?
>>
>> We can add shunts, or I guess it could be some Hall thing.
>>
>>
>>
>> --
>>
>> I yam what I yam - Popeye
>
>I've used the ina168 and ina219. Liked the results - easy to use. The ina168 seems to meet your specs.
>https://www.digikey.com/catalog/en/partgroup/current-monitor/19066
>
>Just to play with, get the breakout board with I2C interface and connect to arduino or RPI for testing.
>J

If a data sheet looks clear, I wouldn't test the part.

We have room to put two different highside chips on the PCB and just
stuff the one we can get. TI and ADI maybe.

--

If a man will begin with certainties, he shall end with doubts,
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon

On Tue, 11 Jan 2022 14:44:57 -0800 (PST), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

>tirsdag den 11. januar 2022 kl. 23.31.35 UTC+1 skrev John Larkin:
>> On Tue, 11 Jan 2022 12:12:37 -0800 (PST), Lasse Langwadt Christensen
>> <lang...@fonz.dk> wrote:
>>
>> >tirsdag den 11. januar 2022 kl. 18.09.07 UTC+1 skrev jla...@highlandsniptechnology.com:
>> >> On Mon, 10 Jan 2022 22:34:08 -0800 (PST), whit3rd <whi...@gmail.com>
>> >> wrote:
>> >> >On Monday, January 10, 2022 at 7:26:19 PM UTC-8, jla...@highlandsniptechnology.com wrote:
>> >> >> We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
>> >> >> modular load boards. We want to measure all 9 currents ...
>> >> >
>> >> >So, is this regulated voltages, nine of 'em, and you want the output currents
>> >> >from nine low-V regulators, or is it input to the regulators, and is that input somewhere
>> >> >in the vicinity of 48VDC? Are these nine currents going to include initial
>> >> >charging of filter capacitors? How big are those capacitors? Are some of the
>> >> >regulators switchers?
>> >> >
>> >> >As for 'intelligent cutoffs', do you want to do that at the high-side? A secondary
>> >> >low-current power supply grounded at the high rail might be economic, if
>> >> >you want to have nine sensors and nine cutoffs all near the +48V source.
>> >> There will be eight user-programmable power supplies, each running off
>> >> +48, all off a common +48 bus fed from a kilowatt bulk power supply.
>> >> Users can potentially install modules and program and load the
>> >> supplies such as to cave in the main source, which would be really
>> >> ugly. That's against the rules in the manual, but we need to protect
>> >> things if they do it.
>> >
>> >there is quite a few high side load switches with short circuit protection
>> >and a combined current monitor / error output , but I think most of them
>> >are limited to a ~24V supply
>> The c code can shut down supply modules as needed. Each power supply
>> module has its own FPGA that the main controller can address. There's
>> no need to actually remove 48v power from the baby boards. The master
>> controller just needs to know the currents and have some reasonable
>> rules.
>
>check.
>
>depending on how good the ADC is, maybe just a resistivity divider on the 48V and after each shunt is good enough?
>
>
>
>

Looks like we can use the XADC in the Zynq, the main controller FPGA.
That's a 1-volt full-scale, pretty terrible ADC. The voltage drop
across a shunt might be 50 mV with a common-mode of 48 volts. So we
need some sort of high-side amp.

A flying capacitor mux would be fun, but too slow. And a dual SSR
would cost more than a current sense chip.

--

I yam what I yam - Popeye

On Tuesday, 11 January 2022 at 17:21:32 UTC-8, John Larkin wrote:
....
> If a data sheet looks clear, I wouldn't test the part.
>
> We have room to put two different highside chips on the PCB and just
> stuff the one we can get. TI and ADI maybe.
> --
....
I like the LTC6102.

It's not as cheap as some of the other solutions but has a very low offset voltage so the burden (and power dissipation in the shunt) can be very low. The architecture is the same as many others using a P-channel FET.

The vanilla one can tolerate 70v surges and there is a 100V part available as well. I'm using it in an automotive 48V design where surge tolerance is vital as well as automotive qualified.

kw

On Mon, 10 Jan 2022 19:26:09 -0800, jlarkin@highlandsniptechnology.com
wrote:

>We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
>modular load boards. We want to measure all 9 currents so that we can
>do some sorts of intelligent cutoffs if the eight boards threaten to
>cave in the big supply.
>
>So we want nine mediocre-accuracy unipolar high-side current sensors
>so we can digitize the currents with a grounded mux/adc.
>
>Does anyone have a favorite but cheap high-side current sense IC?
>
>We can add shunts, or I guess it could be some Hall thing.

https://wolfstreet.com/2022/01/12/after-the-shortage-a-glut-semiconductor-sales-hit-record-for-7th-month-hundreds-of-billions-in-new-investments-planned/

I'm guessing that

Cars use a lot of high-side current sensors

and

The semi shortage/glut cycle is swinging up

and

China is scary.

--

I yam what I yam - Popeye

Lasse Langwadt Christensen wrote:
> onsdag den 12. januar 2022 kl. 02.10.07 UTC+1 skrev Flyguy:
>> On Tuesday, January 11, 2022 at 4:25:45 PM UTC-8, jjhu...@gmail.com wrote:
>>> On Monday, January 10, 2022 at 10:26:19 PM UTC-5, jla...@highlandsniptechnology.com wrote:
>>>> We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
>>>> modular load boards. We want to measure all 9 currents so that we can
>>>> do some sorts of intelligent cutoffs if the eight boards threaten to
>>>> cave in the big supply.
>>>>
>>>> So we want nine mediocre-accuracy unipolar high-side current sensors
>>>> so we can digitize the currents with a grounded mux/adc.
>>>>
>>>> Does anyone have a favorite but cheap high-side current sense IC?
>>>>
>>>> We can add shunts, or I guess it could be some Hall thing.
>>>>
>>>>
>>>>
>>>> --
>>>>
>>>> I yam what I yam - Popeye
>>> I've used the ina168 and ina219. Liked the results - easy to use. The ina168 seems to meet your specs.
>>> https://www.digikey.com/catalog/en/partgroup/current-monitor/19066
>>>
>>> Just to play with, get the breakout board with I2C interface and connect to arduino or RPI for testing.
>>> J
>> The AD8479 handles up to 600V common mode. Couple this with a current shunt and you are good to go.
>> https://www.analog.com/media/en/technical-documentation/data-sheets/ad8479.pdf
>
> also much much more expensive than a current sense amplifier
>

Of course five LM358As, five dual 2N3906es, one 24V zener dropper, and
nine quad pack resistors would do it too.

Alternatively, a regular resistive diff amp using your garden variety op
amp and a decent quad pack could run off +26V and ground, say. With
unity gain, the output is near ground and the inputs are near +24V.
You'd have some offset due to resistor mismatch, but nothing horrible.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

onsdag den 12. januar 2022 kl. 02.21.32 UTC+1 skrev John Larkin:
> On Tue, 11 Jan 2022 16:25:41 -0800 (PST), Three Jeeps
> <jjhu...@gmail.com> wrote:
>
> >On Monday, January 10, 2022 at 10:26:19 PM UTC-5, jla...@highlandsniptechnology.com wrote:
> >> We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
> >> modular load boards. We want to measure all 9 currents so that we can
> >> do some sorts of intelligent cutoffs if the eight boards threaten to
> >> cave in the big supply.
> >>
> >> So we want nine mediocre-accuracy unipolar high-side current sensors
> >> so we can digitize the currents with a grounded mux/adc.
> >>
> >> Does anyone have a favorite but cheap high-side current sense IC?
> >>
> >> We can add shunts, or I guess it could be some Hall thing.
> >>
> >>
> >>
> >> --
> >>
> >> I yam what I yam - Popeye
> >
> >I've used the ina168 and ina219. Liked the results - easy to use. The ina168 seems to meet your specs.
> >https://www.digikey.com/catalog/en/partgroup/current-monitor/19066
> >
> >Just to play with, get the breakout board with I2C interface and connect to arduino or RPI for testing.
> >J
> If a data sheet looks clear, I wouldn't test the part.
>
> We have room to put two different highside chips on the PCB and just
> stuff the one we can get. TI and ADI maybe.

yeh, at the moment it makes sense to practice "defensive design" with multiple options

On a sunny day (Wed, 12 Jan 2022 08:09:56 -0800) it happened
jlarkin@highlandsniptechnology.com wrote in
<d7vttgldb6quk5stq411h5af307oi59a9o@4ax.com>:

>On Mon, 10 Jan 2022 19:26:09 -0800, jlarkin@highlandsniptechnology.com
>wrote:
>
>>We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
>>modular load boards. We want to measure all 9 currents so that we can
>>do some sorts of intelligent cutoffs if the eight boards threaten to
>>cave in the big supply.
>>
>>So we want nine mediocre-accuracy unipolar high-side current sensors
>>so we can digitize the currents with a grounded mux/adc.
>>
>>Does anyone have a favorite but cheap high-side current sense IC?
>>
>>We can add shunts, or I guess it could be some Hall thing.
>
>https://wolfstreet.com/2022/01/12/after-the-shortage-a-glut-semiconductor-sales-hit-record-for-7th-month-hundreds-of-billions-in-
>new-investments-planned/
>
>I'm guessing that
>
>Cars use a lot of high-side current sensors
>
>and
>
>The semi shortage/glut cycle is swinging up
>
>and
>
>China is scary.

Oh, and there is an other solution
Make a nice front panel with some of these for example:
https://www.ebay.com/itm/262960322005
there are cheaper ones from < 5 $, I use some with the Meanwells.
Now you have a nice user interface.
Then use a webcam and write the 7 segment number decoder, like I did:
http://panteltje.com/panteltje/7s_parser/index.html
digital clock time numbers to stdout:
https://www.youtube.com/watch?v=sDYmW6swL-M
pipe it through for example wcalc in Linux to do math with it and control things.
Why do it simple if you can do it complicated?
But actually there is a large application area to read instrument panels.

:-)
Was just one of those wild ideas, 'lemme try this'.
So simple..

On 11/01/2022 17.49, jlarkin@highlandsniptechnology.com wrote:
> On Tue, 11 Jan 2022 16:35:10 +0000, liz@poppyrecords.invalid.invalid
> (Liz Tuddenham) wrote:
>
>> <jlarkin@highlandsniptechnology.com> wrote:
>>
>>> We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
>>> modular load boards. We want to measure all 9 currents so that we can
>>> do some sorts of intelligent cutoffs if the eight boards threaten to
>>> cave in the big supply.
>>>
>>> So we want nine mediocre-accuracy unipolar high-side current sensors
>>> so we can digitize the currents with a grounded mux/adc.
>>>
>>> Does anyone have a favorite but cheap high-side current sense IC?
>>>
>>> We can add shunts, or I guess it could be some Hall thing.
>>
>> Current mirror using pairs of high voltage PNP transistors?
>
> I just posted something like that. It should be good enough. If the
> voltage drop across Q2 is pitched a little high, so there is a little
> positive measurement offset, we can math that out.
>
>
>
A single current sense amp, but switched to the different sense
resistors with a 50V ana mux. Syncronized to the ADC sampling

On Wed, 12 Jan 2022 21:00:23 +0100, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:

>On 11/01/2022 17.49, jlarkin@highlandsniptechnology.com wrote:
>> On Tue, 11 Jan 2022 16:35:10 +0000, liz@poppyrecords.invalid.invalid
>> (Liz Tuddenham) wrote:
>>
>>> <jlarkin@highlandsniptechnology.com> wrote:
>>>
>>>> We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
>>>> modular load boards. We want to measure all 9 currents so that we can
>>>> do some sorts of intelligent cutoffs if the eight boards threaten to
>>>> cave in the big supply.
>>>>
>>>> So we want nine mediocre-accuracy unipolar high-side current sensors
>>>> so we can digitize the currents with a grounded mux/adc.
>>>>
>>>> Does anyone have a favorite but cheap high-side current sense IC?
>>>>
>>>> We can add shunts, or I guess it could be some Hall thing.
>>>
>>> Current mirror using pairs of high voltage PNP transistors?
>>
>> I just posted something like that. It should be good enough. If the
>> voltage drop across Q2 is pitched a little high, so there is a little
>> positive measurement offset, we can math that out.
>>
>>
>>
>A single current sense amp, but switched to the different sense
>resistors with a 50V ana mux. Syncronized to the ADC sampling

We could mux on the high side, with a cheap 4051 type mux. We'd need a
highside power supply, just a zener, and some way to translate the mux
address lines.

--

If a man will begin with certainties, he shall end with doubts,
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon

On Wednesday, January 12, 2022 at 9:00:21 AM UTC-8, Phil Hobbs wrote:
> Lasse Langwadt Christensen wrote:

> > also much much more expensive than a current sense amplifier
> >
> Of course five LM358As, five dual 2N3906es, one 24V zener dropper, and
> nine quad pack resistors would do it too.

True; that's only the first step, though, it just makes a ground-referenced signal,
and next step is an ADC. Trouble is, this is a power signal, with surges expected,
so the sampling due to an ADC is problematic. Since low-power-using modules aren't the
most important to get accurate readings on, I'd note that an eightpack of VCOs
can deliver pulse streams that don't ignore any of the abrupt changes in their inputs,
and at the ground-referenced end it just takes counter inputs to digitize the averages
over any convenient period. Ten kilohertz center frequency, half-second average period,
beats the precision of a 1% shunt resistor. Total the counts to get that ninth number...

A bunch of TLC555 with the INAxxx current doing the capacitor charge is the general scheme. You'd
want the capacitors accurate, and/or adjust counter gate times after calibration, and a regulated
Vdd for the '555.

Less elaborate, capacitors in parallel with the low-end receive resistors to do averaging.

onsdag den 12. januar 2022 kl. 23.20.21 UTC+1 skrev whit3rd:
> On Wednesday, January 12, 2022 at 9:00:21 AM UTC-8, Phil Hobbs wrote:
> > Lasse Langwadt Christensen wrote:
>
> > > also much much more expensive than a current sense amplifier
> > >
> > Of course five LM358As, five dual 2N3906es, one 24V zener dropper, and
> > nine quad pack resistors would do it too.
> True; that's only the first step, though, it just makes a ground-referenced signal,
> and next step is an ADC. Trouble is, this is a power signal, with surges expected,
> so the sampling due to an ADC is problematic. Since low-power-using modules aren't the
> most important to get accurate readings on, I'd note that an eightpack of VCOs
> can deliver pulse streams that don't ignore any of the abrupt changes in their inputs,
> and at the ground-referenced end it just takes counter inputs to digitize the averages
> over any convenient period. Ten kilohertz center frequency, half-second average period,
> beats the precision of a 1% shunt resistor. Total the counts to get that ninth number...
>
> A bunch of TLC555 with the INAxxx current doing the capacitor charge is the general scheme. You'd
> want the capacitors accurate, and/or adjust counter gate times after calibration, and a regulated
> Vdd for the '555.
>
> Less elaborate, capacitors in parallel with the low-end receive resistors to do averaging.

the Zynq ADC is 1MSPS ...

On Wed, 12 Jan 2022 14:33:48 -0800 (PST), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

>onsdag den 12. januar 2022 kl. 23.20.21 UTC+1 skrev whit3rd:
>> On Wednesday, January 12, 2022 at 9:00:21 AM UTC-8, Phil Hobbs wrote:
>> > Lasse Langwadt Christensen wrote:
>>
>> > > also much much more expensive than a current sense amplifier
>> > >
>> > Of course five LM358As, five dual 2N3906es, one 24V zener dropper, and
>> > nine quad pack resistors would do it too.
>> True; that's only the first step, though, it just makes a ground-referenced signal,
>> and next step is an ADC. Trouble is, this is a power signal, with surges expected,
>> so the sampling due to an ADC is problematic. Since low-power-using modules aren't the
>> most important to get accurate readings on, I'd note that an eightpack of VCOs
>> can deliver pulse streams that don't ignore any of the abrupt changes in their inputs,
>> and at the ground-referenced end it just takes counter inputs to digitize the averages
>> over any convenient period. Ten kilohertz center frequency, half-second average period,
>> beats the precision of a 1% shunt resistor. Total the counts to get that ninth number...
>>
>> A bunch of TLC555 with the INAxxx current doing the capacitor charge is the general scheme. You'd
>> want the capacitors accurate, and/or adjust counter gate times after calibration, and a regulated
>> Vdd for the '555.
>>
>> Less elaborate, capacitors in parallel with the low-end receive resistors to do averaging.
>
>the Zynq ADC is 1MSPS ...

And kinda nasty. But we can scan fast and do a bit of signal averaging
in the FPGA. I only need the current measurements every millisecond,
to do my shutdown protection logic.

Exponential smoothing (1st order lowpass) is easy

Vout = Vout + (Vin-Vout) * K with smallish K

but my FPGA kids will probably want to do something fancier.

--

I yam what I yam - Popeye

On Tuesday, January 11, 2022 at 5:19:34 PM UTC-8, lang...@fonz.dk wrote:
> onsdag den 12. januar 2022 kl. 02.10.07 UTC+1 skrev Flyguy:
> > On Tuesday, January 11, 2022 at 4:25:45 PM UTC-8, jjhu...@gmail.com wrote:
> > > On Monday, January 10, 2022 at 10:26:19 PM UTC-5, jla...@highlandsniptechnology.com wrote:
> > > > We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
> > > > modular load boards. We want to measure all 9 currents so that we can
> > > > do some sorts of intelligent cutoffs if the eight boards threaten to
> > > > cave in the big supply.
> > > >
> > > > So we want nine mediocre-accuracy unipolar high-side current sensors
> > > > so we can digitize the currents with a grounded mux/adc.
> > > >
> > > > Does anyone have a favorite but cheap high-side current sense IC?
> > > >
> > > > We can add shunts, or I guess it could be some Hall thing.
> > > >
> > > >
> > > >
> > > > --
> > > >
> > > > I yam what I yam - Popeye
> > > I've used the ina168 and ina219. Liked the results - easy to use. The ina168 seems to meet your specs.
> > > https://www.digikey.com/catalog/en/partgroup/current-monitor/19066
> > >
> > > Just to play with, get the breakout board with I2C interface and connect to arduino or RPI for testing.
> > > J
> > The AD8479 handles up to 600V common mode. Couple this with a current shunt and you are good to go.
> > https://www.analog.com/media/en/technical-documentation/data-sheets/ad8479.pdf
> also much much more expensive than a current sense amplifier

Well, you might actually compare prices of a working circuit to the AD8479. I don't think you can.

On Thursday, January 13, 2022 at 3:52:39 PM UTC+11, Flyguy wrote:
> On Tuesday, January 11, 2022 at 5:19:34 PM UTC-8, lang...@fonz.dk wrote:
> > onsdag den 12. januar 2022 kl. 02.10.07 UTC+1 skrev Flyguy:
> > > On Tuesday, January 11, 2022 at 4:25:45 PM UTC-8, jjhu...@gmail.com wrote:
> > > > On Monday, January 10, 2022 at 10:26:19 PM UTC-5, jla...@highlandsniptechnology.com wrote:
> > > > > We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
> > > > > modular load boards. We want to measure all 9 currents so that we can
> > > > > do some sorts of intelligent cutoffs if the eight boards threaten to
> > > > > cave in the big supply.
> > > > >
> > > > > So we want nine mediocre-accuracy unipolar high-side current sensors
> > > > > so we can digitize the currents with a grounded mux/adc.
> > > > >
> > > > > Does anyone have a favorite but cheap high-side current sense IC?
> > > > >
> > > > > We can add shunts, or I guess it could be some Hall thing.
> > > >
> > > > I've used the ina168 and ina219. Liked the results - easy to use. The ina168 seems to meet your specs.
> > > > https://www.digikey.com/catalog/en/partgroup/current-monitor/19066
> > > >
> > > > Just to play with, get the breakout board with I2C interface and connect to arduino or RPI for testing.
> > > > J
> > > The AD8479 handles up to 600V common mode. Couple this with a current shunt and you are good to go.
> > > https://www.analog.com/media/en/technical-documentation/data-sheets/ad8479.pdf
> > also much much more expensive than a current sense amplifier.
>
> Well, you might actually compare prices of a working circuit to the AD8479. I don't think you can.

Mouser Electronics in Australia sell the AD8479 for $A11.67, so that part is do-able. A "working circuit" is a trifle unspecific - Flyguy won't have a clue what that might be, but somebody who knew something about electronics could probably come up with something. I'm not going to spend time trying - why do stuff for John Larkin for free - but anybody with more sense than Flyguy could probably manage it. It's not rocket science.

--
Bill Sloman, Sydney

On Wednesday, January 12, 2022 at 10:57:56 PM UTC-5, jla...@highlandsniptechnology.com wrote:
> On Wed, 12 Jan 2022 14:33:48 -0800 (PST), Lasse Langwadt Christensen
> <lang...@fonz.dk> wrote:
>
> >onsdag den 12. januar 2022 kl. 23.20.21 UTC+1 skrev whit3rd:
> >> On Wednesday, January 12, 2022 at 9:00:21 AM UTC-8, Phil Hobbs wrote:
> >> > Lasse Langwadt Christensen wrote:
> >>
> >> > > also much much more expensive than a current sense amplifier
> >> > >
> >> > Of course five LM358As, five dual 2N3906es, one 24V zener dropper, and
> >> > nine quad pack resistors would do it too.
> >> True; that's only the first step, though, it just makes a ground-referenced signal,
> >> and next step is an ADC. Trouble is, this is a power signal, with surges expected,
> >> so the sampling due to an ADC is problematic. Since low-power-using modules aren't the
> >> most important to get accurate readings on, I'd note that an eightpack of VCOs
> >> can deliver pulse streams that don't ignore any of the abrupt changes in their inputs,
> >> and at the ground-referenced end it just takes counter inputs to digitize the averages
> >> over any convenient period. Ten kilohertz center frequency, half-second average period,
> >> beats the precision of a 1% shunt resistor. Total the counts to get that ninth number...
> >>
> >> A bunch of TLC555 with the INAxxx current doing the capacitor charge is the general scheme. You'd
> >> want the capacitors accurate, and/or adjust counter gate times after calibration, and a regulated
> >> Vdd for the '555.
> >>
> >> Less elaborate, capacitors in parallel with the low-end receive resistors to do averaging.
> >
> >the Zynq ADC is 1MSPS ...
> And kinda nasty. But we can scan fast and do a bit of signal averaging
> in the FPGA. I only need the current measurements every millisecond,
> to do my shutdown protection logic.
>
> Exponential smoothing (1st order lowpass) is easy
>
> Vout = Vout + (Vin-Vout) * K with smallish K
>
> but my FPGA kids will probably want to do something fancier.
> --
>
> I yam what I yam - Popeye
For situations like this I tend to like using a simple moving average filter with the window being variable. If so inclined, could be made adaptive.
First or second order biquads can also be effective. I usually chose direct form one implementations

On Thu, 13 Jan 2022 06:53:28 -0800 (PST), Three Jeeps
<jjhudak4@gmail.com> wrote:

>On Wednesday, January 12, 2022 at 10:57:56 PM UTC-5, jla...@highlandsniptechnology.com wrote:
>> On Wed, 12 Jan 2022 14:33:48 -0800 (PST), Lasse Langwadt Christensen
>> <lang...@fonz.dk> wrote:
>>
>> >onsdag den 12. januar 2022 kl. 23.20.21 UTC+1 skrev whit3rd:
>> >> On Wednesday, January 12, 2022 at 9:00:21 AM UTC-8, Phil Hobbs wrote:
>> >> > Lasse Langwadt Christensen wrote:
>> >>
>> >> > > also much much more expensive than a current sense amplifier
>> >> > >
>> >> > Of course five LM358As, five dual 2N3906es, one 24V zener dropper, and
>> >> > nine quad pack resistors would do it too.
>> >> True; that's only the first step, though, it just makes a ground-referenced signal,
>> >> and next step is an ADC. Trouble is, this is a power signal, with surges expected,
>> >> so the sampling due to an ADC is problematic. Since low-power-using modules aren't the
>> >> most important to get accurate readings on, I'd note that an eightpack of VCOs
>> >> can deliver pulse streams that don't ignore any of the abrupt changes in their inputs,
>> >> and at the ground-referenced end it just takes counter inputs to digitize the averages
>> >> over any convenient period. Ten kilohertz center frequency, half-second average period,
>> >> beats the precision of a 1% shunt resistor. Total the counts to get that ninth number...
>> >>
>> >> A bunch of TLC555 with the INAxxx current doing the capacitor charge is the general scheme. You'd
>> >> want the capacitors accurate, and/or adjust counter gate times after calibration, and a regulated
>> >> Vdd for the '555.
>> >>
>> >> Less elaborate, capacitors in parallel with the low-end receive resistors to do averaging.
>> >
>> >the Zynq ADC is 1MSPS ...
>> And kinda nasty. But we can scan fast and do a bit of signal averaging
>> in the FPGA. I only need the current measurements every millisecond,
>> to do my shutdown protection logic.
>>
>> Exponential smoothing (1st order lowpass) is easy
>>
>> Vout = Vout + (Vin-Vout) * K with smallish K
>>
>> but my FPGA kids will probably want to do something fancier.
>> --
>>
>> I yam what I yam - Popeye
>For situations like this I tend to like using a simple moving average filter with the window being variable. If so inclined, could be made adaptive.
>First or second order biquads can also be effective. I usually chose direct form one implementations

I'm fond of making digital filters out of exponential lags or
integrators, starting with a classic analog filter and essentially
Spicing it inside the FPGA or uP. My fpga folk really don't like that
for some reason. Not enough Zs or something.

They like filters that have a constant of integration in the output,
and assume that nothing ever goes wrong to make it nonzero. A sinc3
filter terrifies me.

--

I yam what I yam - Popeye

jlarkin@highlandsniptechnology.com wrote:
> On Thu, 13 Jan 2022 06:53:28 -0800 (PST), Three Jeeps
> <jjhudak4@gmail.com> wrote:
>
>> On Wednesday, January 12, 2022 at 10:57:56 PM UTC-5,
>> jla...@highlandsniptechnology.com wrote:
>>> On Wed, 12 Jan 2022 14:33:48 -0800 (PST), Lasse Langwadt
>>> Christensen <lang...@fonz.dk> wrote:
>>>
>>>> onsdag den 12. januar 2022 kl. 23.20.21 UTC+1 skrev whit3rd:
>>>>> On Wednesday, January 12, 2022 at 9:00:21 AM UTC-8, Phil
>>>>> Hobbs wrote:
>>>>>> Lasse Langwadt Christensen wrote:
>>>>>
>>>>>>> also much much more expensive than a current sense
>>>>>>> amplifier
>>>>>>>
>>>>>> Of course five LM358As, five dual 2N3906es, one 24V zener
>>>>>> dropper, and nine quad pack resistors would do it too.
>>>>> True; that's only the first step, though, it just makes a
>>>>> ground-referenced signal, and next step is an ADC. Trouble
>>>>> is, this is a power signal, with surges expected, so the
>>>>> sampling due to an ADC is problematic. Since low-power-using
>>>>> modules aren't the most important to get accurate readings
>>>>> on, I'd note that an eightpack of VCOs can deliver pulse
>>>>> streams that don't ignore any of the abrupt changes in their
>>>>> inputs, and at the ground-referenced end it just takes
>>>>> counter inputs to digitize the averages over any convenient
>>>>> period. Ten kilohertz center frequency, half-second average
>>>>> period, beats the precision of a 1% shunt resistor. Total the
>>>>> counts to get that ninth number...
>>>>>
>>>>> A bunch of TLC555 with the INAxxx current doing the capacitor
>>>>> charge is the general scheme. You'd want the capacitors
>>>>> accurate, and/or adjust counter gate times after calibration,
>>>>> and a regulated Vdd for the '555.
>>>>>
>>>>> Less elaborate, capacitors in parallel with the low-end
>>>>> receive resistors to do averaging.
>>>>
>>>> the Zynq ADC is 1MSPS ...
>>> And kinda nasty. But we can scan fast and do a bit of signal
>>> averaging in the FPGA. I only need the current measurements every
>>> millisecond, to do my shutdown protection logic.
>>>
>>> Exponential smoothing (1st order lowpass) is easy
>>>
>>> Vout = Vout + (Vin-Vout) * K with smallish K
>>>
>>> but my FPGA kids will probably want to do something fancier. --
>>>
>>> I yam what I yam - Popeye
>> For situations like this I tend to like using a simple moving
>> average filter with the window being variable. If so inclined,
>> could be made adaptive. First or second order biquads can also be
>> effective. I usually chose direct form one implementations
>
> I'm fond of making digital filters out of exponential lags or
> integrators, starting with a classic analog filter and essentially
> Spicing it inside the FPGA or uP. My fpga folk really don't like
> that for some reason. Not enough Zs or something.
>
> They like filters that have a constant of integration in the output,
> and assume that nothing ever goes wrong to make it nonzero. A sinc3
> filter terrifies me.

Recursive filters can exhibit limit cycles, though. For a simple
example, if you put a step function into a one-pole IIR lowpass
implemented in fixed point, with a decrement of 0.01 (say), it will get
stuck somewhere around 50 units away from the 'true' value. That's DC,
but it's still a limit cycle. Fancier filters can have AC limit cycles.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

;

John Larkin wrote:
> On Wed, 12 Jan 2022 21:00:23 +0100, Klaus Vestergaard Kragelund
> <klauskvik@hotmail.com> wrote:
>
>> On 11/01/2022 17.49, jlarkin@highlandsniptechnology.com wrote:
>>> On Tue, 11 Jan 2022 16:35:10 +0000, liz@poppyrecords.invalid.invalid
>>> (Liz Tuddenham) wrote:
>>>
>>>> <jlarkin@highlandsniptechnology.com> wrote:
>>>>
>>>>> We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
>>>>> modular load boards. We want to measure all 9 currents so that we can
>>>>> do some sorts of intelligent cutoffs if the eight boards threaten to
>>>>> cave in the big supply.
>>>>>
>>>>> So we want nine mediocre-accuracy unipolar high-side current sensors
>>>>> so we can digitize the currents with a grounded mux/adc.
>>>>>
>>>>> Does anyone have a favorite but cheap high-side current sense IC?
>>>>>
>>>>> We can add shunts, or I guess it could be some Hall thing.
>>>>
>>>> Current mirror using pairs of high voltage PNP transistors?
>>>
>>> I just posted something like that. It should be good enough. If the
>>> voltage drop across Q2 is pitched a little high, so there is a little
>>> positive measurement offset, we can math that out.
>>>
>>>
>>>
>> A single current sense amp, but switched to the different sense
>> resistors with a 50V ana mux. Syncronized to the ADC sampling
>
> We could mux on the high side, with a cheap 4051 type mux. We'd need a
> highside power supply, just a zener, and some way to translate the mux
> address lines.
>

I still like an ordinary 36V dual or quad RRO op amp for this, running
off +26ish and ground, with a good quad pack such as an
ACASA1003S1003P100 (100k, 0.1% absolute, 0.05% relative), 37 cents.

That puts both inputs near +24V with the output near ground. There'll
be a little bit of offset, but nothing major, and since you can switch
off all the loads, you can measure it at POST. A little bit of
intentional imbalance will prevent the output from really going to zero,
so the op amp and ADC will both be on-scale at all times.

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

On Thu, 13 Jan 2022 11:26:28 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>John Larkin wrote:
>> On Wed, 12 Jan 2022 21:00:23 +0100, Klaus Vestergaard Kragelund
>> <klauskvik@hotmail.com> wrote:
>>
>>> On 11/01/2022 17.49, jlarkin@highlandsniptechnology.com wrote:
>>>> On Tue, 11 Jan 2022 16:35:10 +0000, liz@poppyrecords.invalid.invalid
>>>> (Liz Tuddenham) wrote:
>>>>
>>>>> <jlarkin@highlandsniptechnology.com> wrote:
>>>>>
>>>>>> We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
>>>>>> modular load boards. We want to measure all 9 currents so that we can
>>>>>> do some sorts of intelligent cutoffs if the eight boards threaten to
>>>>>> cave in the big supply.
>>>>>>
>>>>>> So we want nine mediocre-accuracy unipolar high-side current sensors
>>>>>> so we can digitize the currents with a grounded mux/adc.
>>>>>>
>>>>>> Does anyone have a favorite but cheap high-side current sense IC?
>>>>>>
>>>>>> We can add shunts, or I guess it could be some Hall thing.
>>>>>
>>>>> Current mirror using pairs of high voltage PNP transistors?
>>>>
>>>> I just posted something like that. It should be good enough. If the
>>>> voltage drop across Q2 is pitched a little high, so there is a little
>>>> positive measurement offset, we can math that out.
>>>>
>>>>
>>>>
>>> A single current sense amp, but switched to the different sense
>>> resistors with a 50V ana mux. Syncronized to the ADC sampling
>>
>> We could mux on the high side, with a cheap 4051 type mux. We'd need a
>> highside power supply, just a zener, and some way to translate the mux
>> address lines.
>>
>
>I still like an ordinary 36V dual or quad RRO op amp for this, running
>off +26ish and ground, with a good quad pack such as an
>ACASA1003S1003P100 (100k, 0.1% absolute, 0.05% relative), 37 cents.
>
>That puts both inputs near +24V with the output near ground. There'll
>be a little bit of offset, but nothing major, and since you can switch
>off all the loads, you can measure it at POST. A little bit of
>intentional imbalance will prevent the output from really going to zero,
>so the op amp and ADC will both be on-scale at all times.
>
>Cheers
>
>Phil Hobbs

I could mux into a single official highside measurement chip. But we'd
still need to control the mux without slowing down the scan much.

AC couple the mux selects? Or use a fast digital isolator, with
highside power.

If I can actually buy the highside sensor chips for 80 cents each, we
can just use 9 of them.

We plan to put a fuse on the +48 input to each of the power module
boards, to avoid internal forest fires.

Here's the box concept:

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

--

I yam what I yam - Popeye

On Thu, 13 Jan 2022 11:16:32 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>jlarkin@highlandsniptechnology.com wrote:
>> On Thu, 13 Jan 2022 06:53:28 -0800 (PST), Three Jeeps
>> <jjhudak4@gmail.com> wrote:
>>
>>> On Wednesday, January 12, 2022 at 10:57:56 PM UTC-5,
>>> jla...@highlandsniptechnology.com wrote:
>>>> On Wed, 12 Jan 2022 14:33:48 -0800 (PST), Lasse Langwadt
>>>> Christensen <lang...@fonz.dk> wrote:
>>>>
>>>>> onsdag den 12. januar 2022 kl. 23.20.21 UTC+1 skrev whit3rd:
>>>>>> On Wednesday, January 12, 2022 at 9:00:21 AM UTC-8, Phil
>>>>>> Hobbs wrote:
>>>>>>> Lasse Langwadt Christensen wrote:
>>>>>>
>>>>>>>> also much much more expensive than a current sense
>>>>>>>> amplifier
>>>>>>>>
>>>>>>> Of course five LM358As, five dual 2N3906es, one 24V zener
>>>>>>> dropper, and nine quad pack resistors would do it too.
>>>>>> True; that's only the first step, though, it just makes a
>>>>>> ground-referenced signal, and next step is an ADC. Trouble
>>>>>> is, this is a power signal, with surges expected, so the
>>>>>> sampling due to an ADC is problematic. Since low-power-using
>>>>>> modules aren't the most important to get accurate readings
>>>>>> on, I'd note that an eightpack of VCOs can deliver pulse
>>>>>> streams that don't ignore any of the abrupt changes in their
>>>>>> inputs, and at the ground-referenced end it just takes
>>>>>> counter inputs to digitize the averages over any convenient
>>>>>> period. Ten kilohertz center frequency, half-second average
>>>>>> period, beats the precision of a 1% shunt resistor. Total the
>>>>>> counts to get that ninth number...
>>>>>>
>>>>>> A bunch of TLC555 with the INAxxx current doing the capacitor
>>>>>> charge is the general scheme. You'd want the capacitors
>>>>>> accurate, and/or adjust counter gate times after calibration,
>>>>>> and a regulated Vdd for the '555.
>>>>>>
>>>>>> Less elaborate, capacitors in parallel with the low-end
>>>>>> receive resistors to do averaging.
>>>>>
>>>>> the Zynq ADC is 1MSPS ...
>>>> And kinda nasty. But we can scan fast and do a bit of signal
>>>> averaging in the FPGA. I only need the current measurements every
>>>> millisecond, to do my shutdown protection logic.
>>>>
>>>> Exponential smoothing (1st order lowpass) is easy
>>>>
>>>> Vout = Vout + (Vin-Vout) * K with smallish K
>>>>
>>>> but my FPGA kids will probably want to do something fancier. --
>>>>
>>>> I yam what I yam - Popeye
>>> For situations like this I tend to like using a simple moving
>>> average filter with the window being variable. If so inclined,
>>> could be made adaptive. First or second order biquads can also be
>>> effective. I usually chose direct form one implementations
>>
>> I'm fond of making digital filters out of exponential lags or
>> integrators, starting with a classic analog filter and essentially
>> Spicing it inside the FPGA or uP. My fpga folk really don't like
>> that for some reason. Not enough Zs or something.
>>
>> They like filters that have a constant of integration in the output,
>> and assume that nothing ever goes wrong to make it nonzero. A sinc3
>> filter terrifies me.
>
>Recursive filters can exhibit limit cycles, though. For a simple
>example, if you put a step function into a one-pole IIR lowpass
>implemented in fixed point, with a decrement of 0.01 (say), it will get
>stuck somewhere around 50 units away from the 'true' value. That's DC,
>but it's still a limit cycle. Fancier filters can have AC limit cycles.
>
>Cheers
>
>Phil Hobbs

If you do the exponential smoothing equation with K=0.01, in 32 bit
scaled integer math, it works fine.

In really dinky machines, the trick is to do

Out = Out + (In-Out)/2^n

which is just a right shift.

--

I yam what I yam - Popeye

jlarkin@highlandsniptechnology.com wrote:
> On Thu, 13 Jan 2022 11:26:28 -0500, Phil Hobbs
> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>
>> John Larkin wrote:
>>> On Wed, 12 Jan 2022 21:00:23 +0100, Klaus Vestergaard Kragelund
>>> <klauskvik@hotmail.com> wrote:
>>>
>>>> On 11/01/2022 17.49, jlarkin@highlandsniptechnology.com wrote:
>>>>> On Tue, 11 Jan 2022 16:35:10 +0000, liz@poppyrecords.invalid.invalid
>>>>> (Liz Tuddenham) wrote:
>>>>>
>>>>>> <jlarkin@highlandsniptechnology.com> wrote:
>>>>>>
>>>>>>> We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
>>>>>>> modular load boards. We want to measure all 9 currents so that we can
>>>>>>> do some sorts of intelligent cutoffs if the eight boards threaten to
>>>>>>> cave in the big supply.
>>>>>>>
>>>>>>> So we want nine mediocre-accuracy unipolar high-side current sensors
>>>>>>> so we can digitize the currents with a grounded mux/adc.
>>>>>>>
>>>>>>> Does anyone have a favorite but cheap high-side current sense IC?
>>>>>>>
>>>>>>> We can add shunts, or I guess it could be some Hall thing.
>>>>>>
>>>>>> Current mirror using pairs of high voltage PNP transistors?
>>>>>
>>>>> I just posted something like that. It should be good enough. If the
>>>>> voltage drop across Q2 is pitched a little high, so there is a little
>>>>> positive measurement offset, we can math that out.
>>>>>
>>>>>
>>>>>
>>>> A single current sense amp, but switched to the different sense
>>>> resistors with a 50V ana mux. Syncronized to the ADC sampling
>>>
>>> We could mux on the high side, with a cheap 4051 type mux. We'd need a
>>> highside power supply, just a zener, and some way to translate the mux
>>> address lines.
>>>
>>
>> I still like an ordinary 36V dual or quad RRO op amp for this, running
>> off +26ish and ground, with a good quad pack such as an
>> ACASA1003S1003P100 (100k, 0.1% absolute, 0.05% relative), 37 cents.
>>
>> That puts both inputs near +24V with the output near ground. There'll
>> be a little bit of offset, but nothing major, and since you can switch
>> off all the loads, you can measure it at POST. A little bit of
>> intentional imbalance will prevent the output from really going to zero,
>> so the op amp and ADC will both be on-scale at all times.

>
> I could mux into a single official highside measurement chip. But we'd
> still need to control the mux without slowing down the scan much.
>
> AC couple the mux selects? Or use a fast digital isolator, with
> highside power.

Run the logic outputs into the emitters of a quad PNP via resistors, and
use the same resistance on the high side. Hang the bases on the logic
supply. Works better at 3.3 or 5 V than lower rails--the logic threshold
is 30% to 70% of VDD.

> If I can actually buy the highside sensor chips for 80 cents each, we
> can just use 9 of them.

Sure. Press on, next problem.

> We plan to put a fuse on the +48 input to each of the power module
> boards, to avoid internal forest fires.

Good idea.
>
> Here's the box concept:
>
> https://www.dropbox.com/s/8ubv5if7cbnsjzn/P940-8_front.jpg?raw=1

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

torsdag den 13. januar 2022 kl. 17.49.33 UTC+1 skrev jla...@highlandsniptechnology.com:
> On Thu, 13 Jan 2022 11:26:28 -0500, Phil Hobbs
> <pcdhSpamM...@electrooptical.net> wrote:
>
> >John Larkin wrote:
> >> On Wed, 12 Jan 2022 21:00:23 +0100, Klaus Vestergaard Kragelund
> >> <klau...@hotmail.com> wrote:
> >>
> >>> On 11/01/2022 17.49, jla...@highlandsniptechnology.com wrote:
> >>>> On Tue, 11 Jan 2022 16:35:10 +0000, l...@poppyrecords.invalid.invalid
> >>>> (Liz Tuddenham) wrote:
> >>>>
> >>>>> <jla...@highlandsniptechnology.com> wrote:
> >>>>>
> >>>>>> We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
> >>>>>> modular load boards. We want to measure all 9 currents so that we can
> >>>>>> do some sorts of intelligent cutoffs if the eight boards threaten to
> >>>>>> cave in the big supply.
> >>>>>>
> >>>>>> So we want nine mediocre-accuracy unipolar high-side current sensors
> >>>>>> so we can digitize the currents with a grounded mux/adc.
> >>>>>>
> >>>>>> Does anyone have a favorite but cheap high-side current sense IC?
> >>>>>>
> >>>>>> We can add shunts, or I guess it could be some Hall thing.
> >>>>>
> >>>>> Current mirror using pairs of high voltage PNP transistors?
> >>>>
> >>>> I just posted something like that. It should be good enough. If the
> >>>> voltage drop across Q2 is pitched a little high, so there is a little
> >>>> positive measurement offset, we can math that out.
> >>>>
> >>>>
> >>>>
> >>> A single current sense amp, but switched to the different sense
> >>> resistors with a 50V ana mux. Syncronized to the ADC sampling
> >>
> >> We could mux on the high side, with a cheap 4051 type mux. We'd need a
> >> highside power supply, just a zener, and some way to translate the mux
> >> address lines.
> >>
> >
> >I still like an ordinary 36V dual or quad RRO op amp for this, running
> >off +26ish and ground, with a good quad pack such as an
> >ACASA1003S1003P100 (100k, 0.1% absolute, 0.05% relative), 37 cents.
> >
> >That puts both inputs near +24V with the output near ground. There'll
> >be a little bit of offset, but nothing major, and since you can switch
> >off all the loads, you can measure it at POST. A little bit of
> >intentional imbalance will prevent the output from really going to zero,
> >so the op amp and ADC will both be on-scale at all times.
> >
> >Cheers
> >
> >Phil Hobbs
> I could mux into a single official highside measurement chip. But we'd
> still need to control the mux without slowing down the scan much.
>
> AC couple the mux selects? Or use a fast digital isolator, with
> highside power.
>
> If I can actually buy the highside sensor chips for 80 cents each, we
> can just use 9 of them.

https://lcsc.com/product-detail/span-style-background-color-ff0-Current-span-Sensing-Amplifiers_Diodes-Incorporated-ZXCT1080E5TA_C151589.html
$0.5803 if you buy 100

torsdag den 13. januar 2022 kl. 05.52.39 UTC+1 skrev Flyguy:
> On Tuesday, January 11, 2022 at 5:19:34 PM UTC-8, lang...@fonz.dk wrote:
> > onsdag den 12. januar 2022 kl. 02.10.07 UTC+1 skrev Flyguy:
> > > On Tuesday, January 11, 2022 at 4:25:45 PM UTC-8, jjhu...@gmail.com wrote:
> > > > On Monday, January 10, 2022 at 10:26:19 PM UTC-5, jla...@highlandsniptechnology.com wrote:
> > > > > We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
> > > > > modular load boards. We want to measure all 9 currents so that we can
> > > > > do some sorts of intelligent cutoffs if the eight boards threaten to
> > > > > cave in the big supply.
> > > > >
> > > > > So we want nine mediocre-accuracy unipolar high-side current sensors
> > > > > so we can digitize the currents with a grounded mux/adc.
> > > > >
> > > > > Does anyone have a favorite but cheap high-side current sense IC?
> > > > >
> > > > > We can add shunts, or I guess it could be some Hall thing.
> > > > >
> > > > >
> > > > >
> > > > > --
> > > > >
> > > > > I yam what I yam - Popeye
> > > > I've used the ina168 and ina219. Liked the results - easy to use. The ina168 seems to meet your specs.
> > > > https://www.digikey.com/catalog/en/partgroup/current-monitor/19066
> > > >
> > > > Just to play with, get the breakout board with I2C interface and connect to arduino or RPI for testing.
> > > > J
> > > The AD8479 handles up to 600V common mode. Couple this with a current shunt and you are good to go.
> > > https://www.analog.com/media/en/technical-documentation/data-sheets/ad8479.pdf
> > also much much more expensive than a current sense amplifier
> Well, you might actually compare prices of a working circuit to the AD8479. I don't think you can.

the AD8479 is about 10x the price of a part made for the purpose