Digital volt and Amp gauges

Discussion in 'General Electronics Chat' started by Edison, Jun 10, 2005.

  1. Edison

    Thread Starter Member

    Apr 13, 2005
    10
    0
    I was hooking up digital amp meter(0-30 amp DC/Shunt) Also a 0-200 volt digital meter. Both require 5 volt power supply.I have a 5 volt out-put regulator. So hooked up a 9 volt battery through a switch to 5 volt regulator, run shared positve wire and shared ground to both meters. So far so good, both lit up,switch activated both. Then installed 30 amp shunt in-line on positive side of incoming DC from Wind Turbine. Hooked amp meter, one lead to each end of shunt. Hooked Volt meter, positive wire to one end of shunt, negative wire to negative DC wire from turbine. I should back up a step I tried volt meter first, When hooked to battery string it showed 49.6 volts,so I knew that worked. I disconnected leads to battery bank, hooked amp meter leads to shunt, reconnected battery leads and poof! a spark, no amp meter and seconds later no volt meter! What happened? It was disconnected from Wind Turbine at the time so no incoming current, only current it could have read was from the batteries.So if I understand this right it should have showed no amps as no current was flowing. Do I need a diode to just read current going to batteries?..or does it matter?.. Lost again.. This is the wiring diagram I used http://www.lightobject.com/support/PMeter.htm Should the Amp gauge be on On negative side? Should both gauges be on separate 5 volt regulators?..Lots of questions
     
  2. David Bridgen

    Senior Member

    Feb 10, 2005
    278
    0
    For the ammeter to have been damaged it sounds as if you connected it across the battery (as you would the voltmeter.)
    I can't even guess why the voltmeter was damaged too.
     
  3. Brandon

    Senior Member

    Dec 14, 2004
    306
    0

    When in Ameter mode, the resistance is very low in the meter. So if you connect it across a battery, even a 9v can kill it very very easily. Check your fuses first.

    When checking current from the battery you connect the negative ameter probe to the + terminal then put the + ameter probe connect to circuit where the + terminal o the battery normally went. Now you are measuring the current in that particular wire, in this case, it happens to be the current from the battery. If you just connect an ameter between + and - terminal, its like putting a wire short, bam, there goes a fuse.

    If you want a constant current meter, your going to need to make a high resistance shunt off of the battery to permit a small portion of the current to flow into your meter. Based on your shunting ratio, you can find your current, i.e., if you go 100 to 1 on the resistance of the shunt, your current will be 100x what ever you read from the shunt. Just make sure the max current through the shunt won't kill the meter.

    Also, were you trying to measure up to 30 amps?? The meters I've used usually only can handle up to 5 amps from the ameter input, we're talking the nice Flukes. I usually have to make a 0-1amp shunt and do a little math to find high current.

    There is a good chance that if the meter had no internal current limiting diode, OR you made the mistake of forgetting to put the probe into the correct socket for Ameter mode and voltage mode, (VERY different. Ammetere input res is low, vmeter input res is very very high) If there was no limiting fuse or diode and you put it into the wrong socket, your meter is totally fried, buy a new one. If there is a fuse for the input, just swap it for a new one and you'll be good to go.
     
  4. Edison

    Thread Starter Member

    Apr 13, 2005
    10
    0
    I guess I should have clarified, these are permanet panel meters I was hooking up, not just a test meter. Everything was hooked up according to diagrams. Only thing I maybe should have changed was putting shunt on negative side?. Also I installed shunt in line, not parralell to line. Here is the meter I'm referring to http://cgi.ebay.com/ws/eBayISAPI.dll?ViewI...AMEWA%3AIT&rd=1 Thanks
     
  5. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6

    :( "Shunt" means "bypass" or "parralell."

    Fortunatley, that particular e-bay vendor has several of those meters.
     
  6. Edison

    Thread Starter Member

    Apr 13, 2005
    10
    0


    Ok, Lets get this straight.. In line for example an 'In-line fuse' all the current flows through that fuse. So thats how I installed that shunt,'In -line'. Is that the right way? I think of parralell as running alongside the main line.Which is right?..And also which line..negative or positive?.. Thanks
     
  7. David Bridgen

    Senior Member

    Feb 10, 2005
    278
    0
    This shows how they should be connected.
    The shunt is "in line", i.e. in series with the circuit, and it can be in either the positive lead, as shown, or in the negative lead. The voltmeter is in parallel with the load.

    Without seeing the diagram of the meters it is difficult to say with certainty but I am wondering if the problem may have been the fact that you used a common supply for them.
     
  8. Edison

    Thread Starter Member

    Apr 13, 2005
    10
    0
    I'm coming to the same conclusion. The hook-up was right according to your diagram. Only thing different is instead of going to a load, it was going to a 48 volt bank of batteries.As for the common supply, I presumed that was just for illumination . Thanks
     
Loading...