Author Topic: Analog amp meter over range  (Read 1830 times)

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Offline Tenkikun

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Analog amp meter over range
« on: March 27, 2015, 12:11:40 pm »
Im working on my Electric bike for spring time
and i was thinking it would be fun to see how much power the speed control is pulling from the batteries
Can i put a cheap analog amp meter rated for 10A (4$) even tho the control has a upper limit of 15A?
The amp meter im looking at is the picture attached.
And the battery is a 36V pack of 3 SLA 12v batteries

The only time the speed control would draw close to 15A is when taking off from a dead stop, and even then it alternate giving power and shutting off at about 4 times / second, not to strain the system too much.
Would these short peaks of 15A hurt the Amp meter?

I have tried searching this, but all info i get are about multimeters and such...
« Last Edit: March 27, 2015, 12:13:45 pm by Tenkikun »
 

Offline flynwill

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Re: Analog amp meter over range
« Reply #1 on: March 27, 2015, 02:32:40 pm »
I can't say for sure, but the answer is "probably not".  The ampmeter will "peg" but probably won't be harmed by a 50% overcurrent.  It's shunt will probably at twice it's rated power dissipation, so it will get hot pretty quickly.  But as long as its only a matter of a second or so it'll probably be ok.  I have seen analog meters where the needle was run into the post with such force that the needle was bent, but I suspect that was considerably more that 50% over.

 

Offline Seekonk

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Re: Analog amp meter over range
« Reply #2 on: March 27, 2015, 08:21:55 pm »
I'd say that is the one type of meter you can't destroy.   They are also very inaccurate.
 

Offline Tenkikun

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Re: Analog amp meter over range
« Reply #3 on: March 27, 2015, 10:37:42 pm »
I have seen analog meters where the needle was run into the post with such force that the needle was bent
Oh wow... yeah i dont think i would do that much destruction xD

I'd say that is the one type of meter you can't destroy.   They are also very inaccurate.

Sounds like the type of amp meter i need, its just something for the fun of it.
I will buy this amp meter and enjoy the build, thanks guys!  :bullshit:  ;D
 

Offline iamdarkyoshi

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Re: Analog amp meter over range
« Reply #4 on: March 28, 2015, 02:38:41 am »
I would take the meter apart, find the shunt, and put  a potentiometer voltage divider between the shunt and the coil. Then create a new scale using a scanner on the old one, then photoshop the scale to go to 15a. Print the new scale on paper, glue it to the old one, and then calibrate it to a known reference.
 

Offline Seekonk

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Re: Analog amp meter over range
« Reply #5 on: March 28, 2015, 05:17:24 am »
All this meter has is a magnet on the movement and two leads come out from the current bar.  The same meter is used for 100A, a wire clamp fits on the spade lugs that holds a #2 cable.  No electrical connection, just the magnetic field from the wire drives the meter.
 


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