On Thursday, April 14, 2022 at 4:31:35 AM UTC-7, Commander Kinsey wrote:
> On Thu, 14 Apr 2022 12:16:28 +0100, Clive Arthur <cl...@nowaytoday.co.uk> wrote:
>
> > On 14/04/2022 11:45, Commander Kinsey wrote:
> >> Where can I buy a large analogue meter? Big enough to show to a room of
> >> people, about a foot long pointer.
> >
> > R/C servo with pointer, PIC with ADC, code.

> This shouldn't be necessary, in the 80s in school we had enormous voltmeters and ammeters for demonstrations. Just a simple coil meter with a long lightweight pointer.

Not so simple if you want accuracy. For one thing, the pointer ought to be counterweighted, not
just lightweight. For another, the glass pane that protects the pointer must be grounded,
or electrostatic charge will disrupt the reading. A d'Arsonval movement is hard to scale up
and keep rugged; taut-band and such are improvements, but... servo is what's easily available for
a DIY project.

On 4/14/2022 4:04 PM, whit3rd wrote:
> On Thursday, April 14, 2022 at 4:31:35 AM UTC-7, Commander Kinsey wrote:
>> On Thu, 14 Apr 2022 12:16:28 +0100, Clive Arthur <cl...@nowaytoday.co.uk> wrote:
>>
>>> On 14/04/2022 11:45, Commander Kinsey wrote:
>>>> Where can I buy a large analogue meter? Big enough to show to a room of
>>>> people, about a foot long pointer.
>>> R/C servo with pointer, PIC with ADC, code.
>> This shouldn't be necessary, in the 80s in school we had enormous voltmeters and ammeters for demonstrations. Just a simple coil meter with a long lightweight pointer.
> Not so simple if you want accuracy. For one thing, the pointer ought to be counterweighted, not
> just lightweight. For another, the glass pane that protects the pointer must be grounded,
> or electrostatic charge will disrupt the reading. A d'Arsonval movement is hard to scale up
> and keep rugged; taut-band and such are improvements, but... servo is what's easily available for
> a DIY project.
Ah, had not thought about the counter weight, I suggested a higher
current meter, thinking that would
counter the extra weight.
                      Mikek

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amdx wrote:
================
Whitless IDIOT whit3rd wrote:
>
> > Not so simple if you want accuracy. For one thing, the pointer ought to be counterweighted, not
> > just lightweight. For another, the glass pane that protects the pointer must be grounded,
> > or electrostatic charge will disrupt the reading. A d'Arsonval movement is hard to scale up
> > and keep rugged; taut-band and such are improvements, but... servo is what's easily available for
> > a DIY project.
>
> Ah, had not thought about the counter weight,
>

** Moving coil meters all have them - excepting maybe some edge reading types.

Essential to keep the scale linear.

https://thefactfactor.com/facts/pure_science/physics/ammeter-and-voltmeter/5931/

...... Phil

On Thu, 14 Apr 2022 22:04:28 +0100, whit3rd <whit3rd@gmail.com> wrote:

> On Thursday, April 14, 2022 at 4:31:35 AM UTC-7, Commander Kinsey wrote:
>> On Thu, 14 Apr 2022 12:16:28 +0100, Clive Arthur <cl...@nowaytoday.co.uk> wrote:
>>
>> > On 14/04/2022 11:45, Commander Kinsey wrote:
>> >> Where can I buy a large analogue meter? Big enough to show to a room of
>> >> people, about a foot long pointer.
>> >
>> > R/C servo with pointer, PIC with ADC, code.
>
>> This shouldn't be necessary, in the 80s in school we had enormous voltmeters and ammeters for demonstrations. Just a simple coil meter with a long lightweight pointer.
>
> Not so simple if you want accuracy. For one thing, the pointer ought to be counterweighted, not
> just lightweight. For another, the glass pane that protects the pointer must be grounded,
> or electrostatic charge will disrupt the reading. A d'Arsonval movement is hard to scale up
> and keep rugged; taut-band and such are improvements, but... servo is what's easily available for
> a DIY project.

These were for large voltages and currents (well something like 10V and 5 amps).

On 4/14/2022 8:22 PM, Phil Allison wrote:
> amdx wrote:
> ================
> Whitless IDIOT whit3rd wrote:
>>> Not so simple if you want accuracy. For one thing, the pointer ought to be counterweighted, not
>>> just lightweight. For another, the glass pane that protects the pointer must be grounded,
>>> or electrostatic charge will disrupt the reading. A d'Arsonval movement is hard to scale up
>>> and keep rugged; taut-band and such are improvements, but... servo is what's easily available for
>>> a DIY project.
>> Ah, had not thought about the counter weight,
>>
> ** Moving coil meters all have them - excepting maybe some edge reading types.
>
> Essential to keep the scale linear.
>
> https://thefactfactor.com/facts/pure_science/physics/ammeter-and-voltmeter/5931/
>
>
>
> ..... Phil
>
  Ya, I've had enough meters apart that after it was said, I remembered
the counterweight on the opposite end of the pointer.
                                                     Mikek

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On Friday, April 15, 2022 at 9:00:21 AM UTC-4, amdx wrote:
> On 4/14/2022 8:22 PM, Phil Allison wrote:
> > amdx wrote:
> > ================
> > Whitless IDIOT whit3rd wrote:
> >>> Not so simple if you want accuracy. For one thing, the pointer ought to be counterweighted, not
> >>> just lightweight. For another, the glass pane that protects the pointer must be grounded,
> >>> or electrostatic charge will disrupt the reading. A d'Arsonval movement is hard to scale up
> >>> and keep rugged; taut-band and such are improvements, but... servo is what's easily available for
> >>> a DIY project.
> >> Ah, had not thought about the counter weight,
> >>
> > ** Moving coil meters all have them - excepting maybe some edge reading types.
> >
> > Essential to keep the scale linear.
> >
> > https://thefactfactor.com/facts/pure_science/physics/ammeter-and-voltmeter/5931/
> >
> >
> >
> > ..... Phil
> >
> Ya, I've had enough meters apart that after it was said, I remembered
> the counterweight on the opposite end of the pointer.

It helps with clock hands as well. I have a cheap wall clock that would die when the battery didn't have enough power to move the second hand uphill. I added a counterweight and it runs a couple of months more now before I need to replace the battery.

That used to be a standard feature on clock hands when they were wind up. A lot of electric clocks don't bother. Also they often don't have second hands. The leverage on the minute and hour hands is a lot greater.

--

Rick C.

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