+ Post New Thread
Results 1 to 8 of 8
  1. #1
    Advanced Member level 2
    Points: 3,794, Level: 14
    Achievements:
    7 years registered
    imranahmed's Avatar
    Join Date
    Dec 2011
    Location
    Karachi,Pakistan
    Posts
    613
    Helped
    3 / 3
    Points
    3,794
    Level
    14

    Shunt in DC ammeter circuit

    I have DC ammeter and shunt for sending current.
    Shunt is 30A@60mA and ammeter also have same rating @24VDC supply.

    But I connected 24VDC line from 2 series batteries with shunt 1st main terminal and load connected to shunt 2nd main terminal.And Ammeter connected with 2 small screws in shunt but when I energised power ammeter was burned and on-off switch for ammeter also burnt.

    I tested negative terminal of ammeter and most left terminal was showing continuity.

    Please try to understand.
    Click image for larger version. 

Name:	IMG_20190910_002858.jpg 
Views:	8 
Size:	476.4 KB 
ID:	155420
    Click image for larger version. 

Name:	IMG_20190910_003011.jpg 
Views:	3 
Size:	467.8 KB 
ID:	155421
    IMRAN

    •   AltAdvertisement

        
       

  2. #2
    Advanced Member level 3
    Points: 5,825, Level: 18

    Join Date
    Feb 2014
    Posts
    828
    Helped
    273 / 273
    Points
    5,825
    Level
    18

    Re: Shunt in DC ammeter circuit

    I assume you mean 30A->60mV not mA. Shunts convert current to voltage.

    Use a volt-meter to measure the shunt.


    1 members found this post helpful.

  3. #3
    Advanced Member level 2
    Points: 5,164, Level: 17
    Achievements:
    7 years registered
    ZASto's Avatar
    Join Date
    Jan 2008
    Location
    Messy Corner, 44°47'31.56"N, 20°28'9.16"E
    Posts
    617
    Helped
    126 / 126
    Points
    5,164
    Level
    17

    Re: Shunt in DC ammeter circuit

    Did you connect it this way?

    Click image for larger version. 

Name:	EDAB.jpg 
Views:	7 
Size:	144.5 KB 
ID:	155422

    Green rectangle is LOAD,
    Make no mistake between my personality and my attitude.
    My personality is who I am.
    My attitude depends on who you are.



    •   AltAdvertisement

        
       

  4. #4
    Advanced Member level 3
    Points: 5,825, Level: 18

    Join Date
    Feb 2014
    Posts
    828
    Helped
    273 / 273
    Points
    5,825
    Level
    18

    Re: Shunt in DC ammeter circuit

    Unfortunately I don't know that the 'digital panel meter' does exactly.

    The marking on it for 30A/60mV indicate it may be configured to scale the signal for your shunt but if that's true you probably wouldn't have blown it.

    One thing to test: Before you connect a black box to the shunt measure the R of the two pins you're about to connect. They should be high R. If they're a short then current will bypass your shunt and flow into the back box, probably blowing it (unless it's a 30A meter in which case you don't need a shunt at all).



  5. #5
    Full Member level 6
    Points: 2,014, Level: 10

    Join Date
    Jan 2019
    Posts
    374
    Helped
    93 / 93
    Points
    2,014
    Level
    10

    Re: Shunt in DC ammeter circuit

    Quote Originally Posted by imranahmed View Post
    But I connected 24VDC line from 2 series batteries with shunt 1st main terminal and load connected to shunt 2nd main terminal.And Ammeter connected with 2 small screws in shunt
    As asdf44 said, a voltmeter goes across the small terminals of the shunt.
    Read the voltage and calculate the current using the resistance of the shunt.
    Voltmeters have a very high input impedance so they do not carry any current, compared to whatever you're measuring

    When you connected the ammeter across the small terminals of the shunt,
    you connected a low impedance across the shunt, maybe less than the shunt,
    the current went through the ammeter, not the shunt
    since it was more current than the meter was designed for, it burned up.


    1 members found this post helpful.

    •   AltAdvertisement

        
       

  6. #6
    Advanced Member level 5
    Points: 14,943, Level: 29
    schmitt trigger's Avatar
    Join Date
    Apr 2013
    Posts
    2,483
    Helped
    804 / 804
    Points
    14,943
    Level
    29

    Re: Shunt in DC ammeter circuit

    Also, put a small value fuse, 1or 2 amps.
    My batteries are recharged by "Helpful Post" ratings.
    If you feel that I've helped you, please indicate it as a Helpful Post


    1 members found this post helpful.

  7. #7
    Super Moderator
    Points: 77,731, Level: 67
    Achievements:
    7 years registered
    Awards:
    Most Frequent Poster 3rd Helpful Member

    Join Date
    Apr 2014
    Posts
    15,750
    Helped
    3587 / 3587
    Points
    77,731
    Level
    67

    Re: Shunt in DC ammeter circuit

    Hi,

    From the explanation it seems you connected the load on the terminals of the voltmeter....and not directly to the shunt.
    This is not the same since the wires between shunt and voltmeter have resistance that causes additional voltage drop and thus measurement errors.
    In worst case the resistance is much higher than the shunt resistance ( 60mV / 30A= 0.002 Ohms) causing too high voltage at the voltmeter inputs destroying the voltmeter.

    Thus the correct wiring is shown in post#3 ... with galvanically isolated power supply.

    Klaus
    Please don´t contact me via PM, because there is no time to respond to them. No friend requests. Thank you.



  8. #8
    Advanced Member level 2
    Points: 3,794, Level: 14
    Achievements:
    7 years registered
    imranahmed's Avatar
    Join Date
    Dec 2011
    Location
    Karachi,Pakistan
    Posts
    613
    Helped
    3 / 3
    Points
    3,794
    Level
    14

    Re: Shunt in DC ammeter circuit

    Sorry yes 30A@60mV
    IMRAN



--[[ ]]--