Hello,
I have a nice vintage French panelmeter that works with ac and dc voltage according to a symbol on the front.
It has a scale up to 30 volts and i wanna use it to indicate a dc voltage that will be close to 18 volts. There is no polarity indicated. I tested it with a small battery and if i reverse the connection it gives the same result. Does this mean i can connect my power supply to it without any problem??
Because it is rated for both AC and DC there is no polarity indicated?
greetings, eduard
I have a nice vintage French panelmeter that works with ac and dc voltage according to a symbol on the front.
It has a scale up to 30 volts and i wanna use it to indicate a dc voltage that will be close to 18 volts. There is no polarity indicated. I tested it with a small battery and if i reverse the connection it gives the same result. Does this mean i can connect my power supply to it without any problem??
Because it is rated for both AC and DC there is no polarity indicated?
greetings, eduard
Sounds like this could be a 'Moving Iron' meter to me. These measure DC or AC and the needle movement is always the same irrespective of polarity.
This tells a bit about them (scroll down)
Ammeter - Wikipedia
https://emimnit.files.wordpress.com/2016/09/moving-iron-instruments-voltmeter-and-ammeter-_-eep.pdf
This tells a bit about them (scroll down)
Ammeter - Wikipedia
https://emimnit.files.wordpress.com/2016/09/moving-iron-instruments-voltmeter-and-ammeter-_-eep.pdf
I vaguely remember about these from technical college but I've forgotten a lot of it now. They were something you never really come across in modern electronics although they have their uses of course. They are quite non linear and the bottom part of the scale is usually quite squashed up.
I can't remember how sensitive they are generally either (ohms per volt kind of thing).
I can't remember how sensitive they are generally either (ohms per volt kind of thing).
Go for it
It would be interesting to wire a series DVM to it and get an idea of how much current it pulled when displaying your 18 volts.Old analogue multi-meters were often 20k ohms per volt on their DC ranges (which is the reciprocal of the typical 50uA meter movement used) i.e. 1/50E-6
AC ranges were typically much lower at 1000 ohm/volt.
Modern DVM's are 10Meg/volt and so load the circuit being measured very little.
Hello Mooly,
I checked the dcr with an ordinary handheld meter. It shows a dcr close to 500 ohm. Because my device uses a choke input i installed a bleeder. This meter will add some extra bleeder current. I dont need it to be precise just tell me if the circuit is drawing current because if there isnt the 1A current being drawn the Dc voltage will go close to 28 volts.
Could there be any negative side effects of the meter being there continuously?
Dont want any noise added after it has been filtered by the choke.
greetings, Eduard
I checked the dcr with an ordinary handheld meter. It shows a dcr close to 500 ohm. Because my device uses a choke input i installed a bleeder. This meter will add some extra bleeder current. I dont need it to be precise just tell me if the circuit is drawing current because if there isnt the 1A current being drawn the Dc voltage will go close to 28 volts.
Could there be any negative side effects of the meter being there continuously?
Dont want any noise added after it has been filtered by the choke.
greetings, Eduard
500 ohm... so quite low, but not low enough to be of concern if you are delivering an amp or so from the PSU. It would be different if it were a battery supply.
I can't really think of any problems in practice.
I suppose the coil could pick up stray fields but given the impedance of the meter they would be swamped by the PSU you connect to. More theoretical than anything.
I can't really think of any problems in practice.
I suppose the coil could pick up stray fields but given the impedance of the meter they would be swamped by the PSU you connect to. More theoretical than anything.
Yes, moving iron meters were inefficient and pulled way more current than equivalent moving coil ones.
The price to pay for having AC/DC compatibility with NO electronics involved.
30´s or earlier Technology.
They were also very robust and would handle peaks that woukd absolutely *destroy* moving coil ones.
The price to pay for having AC/DC compatibility with NO electronics involved.
30´s or earlier Technology.
They were also very robust and would handle peaks that woukd absolutely *destroy* moving coil ones.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.