On Thu, 02 Sep 2010 21:31:25 +0100, glutinous
wrote:

On the image the meter says "FS 254V" or something like that. Exactly
what is the number, where is the decimal point (if there is on)? This
will be the full scale voltage reading, most likely. I'd connect the
bare meter to a variable AC source (start at a very low voltage,
perhaps a volt or so) and see what reading, and current is drawn by
this meter.

Also, clearly the meter was salvaged from something else, so I suspect
that what you have is something that was kobbled together by a hobiest
like Jon, designed to kill the unwary. I'd be very, very careful about
applying more than a few hundred volts to it.

On Fri, 03 Sep 2010 08:34:34 -0400, PeterD wrote:

On Thu, 02 Sep 2010 21:31:25 +0100, glutinous
wrote:

On the image the meter says "FS 254V" or something like that. Exactly
what is the number, where is the decimal point (if there is on)? This
will be the full scale voltage reading, most likely. I'd connect the
bare meter to a variable AC source (start at a very low voltage,
perhaps a volt or so) and see what reading, and current is drawn by
this meter.

Also, clearly the meter was salvaged from something else, so I suspect
that what you have is something that was kobbled together by a hobiest
like Jon, designed to kill the unwary. I'd be very, very careful about
applying more than a few hundred volts to it.

Thank you very much for the reply, Peter.

There is no decimal point, it's:
F.S. 254V.

Since this is near as dammit to the UK mains voltage, I'd rather
thought that was its reference point. I'd also assumed that the meter
was AC (hence the 'calibrated at 50~') but supposed that in use it was
intended to be fed via rectification: though on opening the box there
is none.

The Jacob's Ladder I referred to is built and functions well, using
(and I always get a childish pleasure out of saying this) a 10kv FART
transformer from a neon rig.

I was thinking of doing something along the lines you more precisely
suggest, as against just whacking the full 10kv through the larger
resistor just to see what happened... Standing well back and with a
camcorder running, o.c. ...

On Sat, 04 Sep 2010 11:28:23 +0100, glutinous wrote:

On Fri, 03 Sep 2010 08:34:34 -0400, PeterD wrote:

On Thu, 02 Sep 2010 21:31:25 +0100, glutinous
wrote:

On the image the meter says "FS 254V" or something like that. Exactly
what is the number, where is the decimal point (if there is on)? This
will be the full scale voltage reading, most likely. I'd connect the
bare meter to a variable AC source (start at a very low voltage, perhaps
a volt or so) and see what reading, and current is drawn by this meter.

Also, clearly the meter was salvaged from something else, so I suspect
that what you have is something that was kobbled together by a hobiest
like Jon, designed to kill the unwary. I'd be very, very careful about
applying more than a few hundred volts to it.

Thank you very much for the reply, Peter.

There is no decimal point, it's:
F.S. 254V.

Since this is near as dammit to the UK mains voltage, I'd rather thought
that was its reference point. I'd also assumed that the meter was AC
(hence the 'calibrated at 50~') but supposed that in use it was intended
to be fed via rectification: though on opening the box there is none.

The Jacob's Ladder I referred to is built and functions well, using (and
I always get a childish pleasure out of saying this) a 10kv FART
transformer from a neon rig.

I was thinking of doing something along the lines you more precisely
suggest, as against just whacking the full 10kv through the larger
resistor just to see what happened... Standing well back and with a
camcorder running, o.c. ...


It looks to me as if the middle "thing" is a pushbutton. Is that right?
In that case, it looks as if it would have been used to short out the
resistor (assuming that the lead went to the red terminal) to give a
scale multiplier.

In no way would that instrument ever have read 25kV directly. It simply
doesn't have enough terminal insulation to prevent flashover at anything
above 1kV or so (probably 600v). More likely it would have read the
output voltage from a variac. That voltage would have fed a step-up
transformer and rectifier, giving 0-25kV DC (approximately).

Personally, I would start with low AC voltages fed via a resistor and see
what it reads. If I'm right it will give fsd at about 250vAC - but start
a lot lower than that.


--
Mick (Working in a M$-free zone!)
Web: http://www.nascom.info
Filtering everything posted from googlegroups to kill spam.

On Thu, 02 Sep 2010 21:31:25 +0100, glutinous wrote:

Firstly, it's a moving iron meter, and secondly, that resistor looks like it
might be the multiplier so it can read 254Vac. Is it not connected?

On Tue, 07 Sep 2010 17:51:06 +0800, Ross Herbert
wrote:

On Thu, 02 Sep 2010 21:31:25 +0100, glutinous wrote:

Firstly, it's a moving iron meter, and secondly, that resistor looks like it
might be the multiplier so it can read 254Vac. Is it not connected?

Thanks for the reply.

Nope, res. not connected. As someone else mentioned, it looks like
someone was experimenting with multipliers...

On 06 Sep 2010 21:09:48 GMT, mick wrote:

On Sat, 04 Sep 2010 11:28:23 +0100, glutinous wrote:

On Fri, 03 Sep 2010 08:34:34 -0400, PeterD wrote:

On Thu, 02 Sep 2010 21:31:25 +0100, glutinous
wrote:

On the image the meter says "FS 254V" or something like that. Exactly
what is the number, where is the decimal point (if there is on)? This
will be the full scale voltage reading, most likely. I'd connect the
bare meter to a variable AC source (start at a very low voltage, perhaps
a volt or so) and see what reading, and current is drawn by this meter.

Also, clearly the meter was salvaged from something else, so I suspect
that what you have is something that was kobbled together by a hobiest
like Jon, designed to kill the unwary. I'd be very, very careful about
applying more than a few hundred volts to it.

Thank you very much for the reply, Peter.

There is no decimal point, it's:
F.S. 254V.

Since this is near as dammit to the UK mains voltage, I'd rather thought
that was its reference point. I'd also assumed that the meter was AC
(hence the 'calibrated at 50~') but supposed that in use it was intended
to be fed via rectification: though on opening the box there is none.

The Jacob's Ladder I referred to is built and functions well, using (and
I always get a childish pleasure out of saying this) a 10kv FART
transformer from a neon rig.

I was thinking of doing something along the lines you more precisely
suggest, as against just whacking the full 10kv through the larger
resistor just to see what happened... Standing well back and with a
camcorder running, o.c. ...


It looks to me as if the middle "thing" is a pushbutton. Is that right?
In that case, it looks as if it would have been used to short out the
resistor (assuming that the lead went to the red terminal) to give a
scale multiplier.

In no way would that instrument ever have read 25kV directly. It simply
doesn't have enough terminal insulation to prevent flashover at anything
above 1kV or so (probably 600v). More likely it would have read the
output voltage from a variac. That voltage would have fed a step-up
transformer and rectifier, giving 0-25kV DC (approximately).

Personally, I would start with low AC voltages fed via a resistor and see
what it reads. If I'm right it will give fsd at about 250vAC - but start
a lot lower than that.

I'd rather figured that whacking 10kv across it wouldn't be very
sensible! When I first made the Jacob's Ladder, I just connected the
rod terminals to the wood of the box I was using, just to see if the
kit worked. It did: the carbonised track across the wood was
unmistakable (I can't remember what I then obtained is called now, but
it's transluscent insulating board). Even if this meter could take it,
I wouldn't be very happy about having 10kv so close to the outside of
the box, just the other side of a bit of glass!

I was trying to think how I could put a reduced voltage across it (via
a resistor). I just remembered I have a 240 to 110 travel transformer,
so I'll give that a go.

Thanks for the observations!