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You can't.RDL2004 said:Hi,
I know this is a simple question, but how would I convert a 5A ammeter to a 500mA ammeter ?
No.RDL2004 said:Would it be better to use a 500mA and convert it to 5A?
You can use a 1mA full scale meter and adapt it to display 500mA full scale or 5000mA full scale.RDL2004 said:I am looking to have a dual range ammeter in a power supply project.
eblc1388 said:You can't.RDL2004 said:Hi,
I know this is a simple question, but how would I convert a 5A ammeter to a 500mA ammeter ?
No.RDL2004 said:Would it be better to use a 500mA and convert it to 5A?
You can use a 1mA full scale meter and adapt it to display 500mA full scale or 5000mA full scale.RDL2004 said:I am looking to have a dual range ammeter in a power supply project.
eblc1388 said:All very sweet talking about using current shunt, when one finally have to buy/make one.
Where can I find or build a 0.0364 ohm shunt which pass 4.5A to drop 0.164V that my 0.5A meter needs?
Nigel Goodwin said:In any case, you have to buy/make one if you're using a 1mA meter just the same!.
Nigel Goodwin said:eblc1388 said:All very sweet talking about using current shunt, when one finally have to buy/make one.
Where can I find or build a 0.0364 <a href="#">ohm</a> shunt which pass 4.5A to drop 0.164V that my 0.5A meter needs?
You build it with a thick piece of wire!, or a piece of metal plate!, or even a PCB track!. Or you can buy standard value ones (see RS Components), but it's more cost effective making your own.
In any case, you have to buy/make one if you're using a 1mA meter just the same!.
eblc1388 said:Nigel Goodwin said:In any case, you have to buy/make one if you're using a 1mA meter just the same!.
Of course it is not the same. With a 1mA meter, I can have the shunt at standard value(e.g. n resistors in parallel) and insert variable resistor to the meter coil to trim the meter to scale.
Nigel Goodwin said:But, to go back to the 'just the same' quote, you 'could' add a variable resistor in series with the 500mA meter to make it adjustable, it just needs to be a lower value pot.
eblc1388 said:Nigel Goodwin said:But, to go back to the 'just the same' quote, you 'could' add a variable resistor in series with the 500mA meter to make it adjustable, it just needs to be a lower value pot.
You are venturing into something you don't know about. It all good in theory, until you need to find the pot.
A 500mA current meter has only 0.5 ohms resistance max. or less so if you want to insert a variable resistor to adjust the current for 10% in both ways, you need to find a variable resistor of 0.1 ohms, 500 mA current rating.
Just show us where we can easily find such a variable resistor, cheaply. No point paying many pounds or dollars for such a variable resistor, don't you say?
On the other hand, if a 1mA meter movement is used, one can use any garden variety variable resistor for the adjustment.
Nigel Goodwin said:On the other hand, if a 1mA meter movement is used, one can use any garden variety variable resistor for the adjustment.
But, again!, it's a poor idea - do the job properly with the correct value shunt.