RE: [Electronics_101] Re: old ammeter
- I make my low resistance shunts out of thin steel wire although heating
element wire can be used too. The trick is to accurately measure it.
[mailto:Electronics_101@yahoogroups.com] On Behalf Of Kerim F
Sent: Wednesday, February 13, 2013 6:13 AM
Subject: [Electronics_101] Re: old ammeter
--- In Electronics_101@yahoogroups.com, "Nick" wrote:
> Hi guys, I'm fairly new to electronics and have a question about an old
ammeter that I acquired. I know that it requires a shunt as the wires on the
posts are small and it is a 100 amp meter. In the lower right corner of the
meter face it shows [E.S.=50mv ]. What can I use for a shunt and does it go
in series with the + or in parallel with the + and -. Will it read full
scale with the shunt installed [not that I would ever need that much]. Thank
you in advance for any info.
An ammeter is actually a sensitive voltmeter.
It seems the full scale voltage of your ammeter is 50mV.
If the the shunt is 1 Ohm, the full sacle current would be 50mA If the the
shunt is 0.1 Ohm, the full sacle current would be 500mA.
If the the shunt is 0.01 Ohm, the full sacle current would be 5A.
If the the shunt is ?? Ohm, the full sacle current would be 100A ;)
Please trim excess when replyingYahoo! Groups Links
- In reading the thread, it sounds like you got the help you needed.
From: Electronics_101@yahoogroups.com [mailto:Electronics_101@yahoogroups.com] On Behalf Of james nicholson
Sent: Wednesday, March 20, 2013 1:45 PM
Subject: Re: [Electronics_101] Re: old ammeter
I have another question for you. The control board on our treadmill went out. I have done some tests and the motor is fine. It's a DC 120 volt brush type motor, it has a choke coil in series with the motor. I don't want to spend $120 for a new board unless I have too [ retired & fixed income].I ran the motor with a big ceramic ohmite pot of 68 ohms and then thru a bridge rectifier. The motor ran fine and I could control the speed but the pot got really hot which is understandable because of the iron coil. I found a router speed control on ebay that is good for 120 volt-15 amp--says it is good for any ac or dc motor brush type. What are your thoughts on using this as a speed control. Sent a pic of the motor data plate. Any help would be greatly appreciated Just remember I'm very elementary when it comes to electronics. By the way haven't got to my ammeter shunt yet but will get it.
Thank you, James