Hello all,
Newbie here. I am working on a project that requires an analog ammeter to monitor the current draw on a dc motor. The 100 mA DC meter is fine when the motor is running at any of its controlled speeds, typically reading about 10-12 mA, but chatters violently during the in rush at start up, and also when powering down.
Is this the nature of the beast when monitoring these levels, or is there something I can do to prevent this?

Thanks,
Crumpter

 

Starting current of your motor will be much higher than normal running current. If you load the motor, current will go up. Do you know the internal resistance of your meter?

 

Hi,
Thanks for the reply. I don't know the internal resistance. It's a cheapo Hopesun panel meter #AIM60100. It just doesn't look like it will withstand too many power cycles like this. Is there a way to dampen its response?

Thanks Again

 

You could place a large cap in parallel with the terminals. Be sure to observe polarity on any electrolytic cap you use. Also be aware that it will slow ALL responses to current changes.

 

I'll second that!

I have a heap of ammeters with 2200uF caps across their terminals.

 

Any idea what size cap would help the situation?

 

Thanks Bill and RB,
That last reply overlapped. I'll try the 2200uf and let you know what happens.

 

I use 2200uF but most of the meters were 2A or 5A types.

A 100mA meter could use a smaller cap in the 100uF-470uF range, depending how much you want to damp those peak movements.

 

Thanks again RB. I'll try out something in that range instead.