Is it possible to read AC voltage and current with only one Analog Panel Meter?

Thread Starter

kinton cloud 1

Joined Mar 6, 2017
9
I'm currently working on a Project (Analog AC voltage and current meter). So, I just want to ask if is it possible to read both AC voltage and current by using only one analog panel meter?
 

Thread Starter

kinton cloud 1

Joined Mar 6, 2017
9
Yep. Add a series resistor and it will read voltage or connect a resistor in parallel (commonly called a shunt) and the meter will read current.
Thank you, just one more question. When I search for analog panel meter I saw a separate analog panel meter for voltage and current, can I use either of those two to read both?
 

dendad

Joined Feb 20, 2016
3,602
You will need to have a suitable "multiplier" and "shunt" resistor to suit the meter movement.
VoltAmpMeter.jpg
But really, an AC analog meter will most likely need an amplifier for current readings, or use a current transformer. So, for AC, it is not quite as easy as the circuit shown.
 

AlbertHall

Joined Jun 4, 2014
10,393
A meter sold as being a voltmeter will already include the series resistor and an ammeter will already include the shunt and these make it difficult to use for the other purpose. You need a meter which does not include the extra resistors or where the added resistors can be easily removed - this is often the case. To do this with an analogue meter you will probably also need to fit a custom scale.
http://www.tonnesoftware.com/meter.html
 

Thread Starter

kinton cloud 1

Joined Mar 6, 2017
9
Thank you for the replies, really appreciate it. I guess I need to start looking for a meter that don't have extra resistor or the one with extra resistor that can easily removed first. If not, i'm going to use two analog panel meters :c.
 

bertus

Joined Apr 5, 2008
20,756

Thread Starter

kinton cloud 1

Joined Mar 6, 2017
9
Probably for the AC current, you will be best to incorporate a current transformer instead of a shunt resistor.
Thank you for your suggestion, I'll try it since we still have almost a month to work for this project. But I never see and/or used a current transformer before, can you share some link for data sheets or how it looks like and it's name. The only current transformers I see when I search in the internet are those giant thing that we can see in electric companies.
 

dendad

Joined Feb 20, 2016
3,602
https://www.ebay.com.au/itm/HMCT103C-5A-5MA-Precision-Micro-Current-Transformer-Sensor-Module-New/282550319725?hash=item41c94fba6d:g:KMAAAOSwPWRZVi9x
A current transformer is a toroidal core with a winding on it.
This winding is fed into a rectifier followed by a termination resistor, and the output will go to your meter.
The circuit to be measured is attatched by feeding a current carying wire through the core. So it is safe to hook this up anywhere in the circuit as it is isolated well.
There are others available that open like jaws to just clip over existing wires.
https://www.ebay.com.au/itm/15-20-30-50-100A-Non-invasive-AC-Current-Sensor-Split-Core-Transformer-SCT-013/192272756990?hash=item2cc45970fe:m:mY3v_HlL-Q9ai4ahuvIpkpg
Google current transformers for more info.
 

Thread Starter

kinton cloud 1

Joined Mar 6, 2017
9
https://www.ebay.com.au/itm/HMCT103C-5A-5MA-Precision-Micro-Current-Transformer-Sensor-Module-New/282550319725?hash=item41c94fba6d:g:KMAAAOSwPWRZVi9x
A current transformer is a toroidal core with a winding on it.
This winding is fed into a rectifier followed by a termination resistor, and the output will go to your meter.
The circuit to be measured is attatched by feeding a current carying wire through the core. So it is safe to hook this up anywhere in the circuit as it is isolated well.
There are others available that open like jaws to just clip over existing wires.
https://www.ebay.com.au/itm/15-20-30-50-100A-Non-invasive-AC-Current-Sensor-Split-Core-Transformer-SCT-013/192272756990?hash=item2cc45970fe:m:mY3v_HlL-Q9ai4ahuvIpkpg
Google current transformers for more info.
Thank you very much. It helps a lot.
 

Thread Starter

kinton cloud 1

Joined Mar 6, 2017
9
Hello,

The following pages of the AAC eBook will tell you more about the resistors to be used:
https://www.allaboutcircuits.com/textbook/direct-current/chpt-8/voltmeter-design/
https://www.allaboutcircuits.com/textbook/direct-current/chpt-8/ammeter-design/
The pages are for DC, but will also apply for AC.

Here is the AC metering page of the AAC eBook:
https://www.allaboutcircuits.com/textbook/alternating-current/chpt-12/ac-voltmeters-ammeters/

Bertus
Hi Bertus, thank you for linking those eBooks. I just have some question about the first eBook you linked(about the voltmeter design). I just notice from the images there that the analog panel meter have a some ratings (e.g full-scale deflection rating=1mA ; coil resistance=500Ω). How can I know these ratings? Is it already written in the panel meter or do I need to measure it myself?
 
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