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    Car Ammeter

    After a number of expreiments I gave up the torroid idea.
    Could not over come the zero problems ,it has to be the B/H curve the flux in the ferrite does not return to the same point ,so after the first current you get an offset which must remanence .
    I did think of a flux gate like you can have a compass ,a coil wound all the way around the coil and is energised, this might degauss the core but I dont know

    I had a request for help from abroad out of the blue ,so I had to dig out some info on elemental anlysis , I found my origonal notes from years ago I did on My Honda car measuring the voltage drop from battery to the earth point .My tests made the resistance to be 15 milliohms.
    Interstingly on My Citreon C3 there is awire connected to the negative post on the battery, there is a economy mode on the car wich switches off the power after a while when the engine is not running.
    I might look into this a bit later on and find out what it is.

    Barry

    #2
    Re: Car Ammeter

    That's too bad a Hall-effect current sensor did not work out. It's what the DC clamp-on ammeters use, some even go to mA level. I have had those get magnetized jaws and then the readings get "sticky" so it reads OK in one direction but the other direction reads way low because the ferrite is magentized in the opposite flux polarity. After I demagnetized them they work better. You could also try using more turns?
    15mV/A means 150mV for 10A with a gain of 10 should be good to use.

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      #3
      Re: Car Ammeter

      Originally posted by barry wilkins View Post
      After a number of expreiments I gave up the torroid idea.
      Could not over come the zero problems ,it has to be the B/H curve the flux in the ferrite does not return to the same point ,so after the first current you get an offset which must remanence .
      I did think of a flux gate like you can have a compass ,a coil wound all the way around the coil and is energised, this might degauss the core but I dont know

      I had a request for help from abroad out of the blue ,so I had to dig out some info on elemental anlysis , I found my origonal notes from years ago I did on My Honda car measuring the voltage drop from battery to the earth point .My tests made the resistance to be 15 milliohms.
      Interstingly on My Citreon C3 there is awire connected to the negative post on the battery, there is a economy mode on the car wich switches off the power after a while when the engine is not running.
      I might look into this a bit later on and find out what it is.

      Barry
      You might be interested in this product

      https://www.allegromicro.com/en/prod...sor-ics/acs772

      I have used this product in the past and the results are decent

      You do have to use a micro controller with this device to get best results

      You can use it with out the use of a micro controller but you would have to do the math

      100 amp version / 5 volt scale = 20 amp per volt output

      This is what I found when I used this device in a application that I was doing

      One note if your output voltage value reaches 4.5 volts and higher the accuracy is not quite as good the lower the output voltages the more accurate it is

      Also at voltage output less than 0.50 the accuracy is also less accurate

      But overall the accuracy of the device is decent for the price of the device

      This was at the time that I did this project
      Last edited by sam_sam_sam; 03-12-2020, 09:27 PM.
      9 PC LCD Monitor
      6 LCD Flat Screen TV
      30 Desk Top Switching Power Supply
      10 Battery Charger Switching Power Supply for Power Tool
      6 18v Lithium Battery Power Boards for Tool Battery Packs
      1 XBox 360 Switching Power Supply and M Board
      25 Servo Drives 220/460 3 Phase
      6 De-soldering Station Switching Power Supply 1 Power Supply
      1 Dell Mother Board
      15 Computer Power Supply
      1 HP Printer Supply & Control Board * lighting finished it *


      These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

      1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
      2 Hem Saw Computer Stack Board

      All of these had CAPs POOF
      All of the mosfet that are taken out by bad caps

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