Multimeter range

Discussion in 'The Projects Forum' started by noteleks, May 10, 2009.

  1. noteleks

    Thread Starter New Member

    May 10, 2009
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    I am getting into working on old radios and need to get an analog and digital multimeter. Not sure what ranges I need to make sure the multimeter coveres. Help please. Thank you.
     
  2. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
    99
    If your going to be buying a new DMM then any one of them will cover the ranges that you need. ;)
     
  3. CDRIVE

    Senior Member

    Jul 1, 2008
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    Since your endeavor is to trouble shoot and restore old radios I think this is a good time to bring up a pet peeve of mine.

    Before the DMM came along every test bench was equipped with a VTVM. I still own a few. All VTVMs (that I know of) had a DC input resistance of 11MΩ, with the exception of the HP410B, which boasted a phenomenal 100MΩ input. The standard VTVM's input resistance was actually 10MΩ, just like the DMM is today. So where was the 11th Megohm? Well, it was in the DC probe, soldered directly to the lead end of the probe. It was put there for a darn good reason!

    That's all I'm going to say about this now because I'm anxious to read what others think of the why of this. I will say that I keep a second probe for my DMMs that has a 100KΩ soldered in there.
     
  4. noteleks

    Thread Starter New Member

    May 10, 2009
    5
    0
    Thank you for the input. Hope I get half the knowledge that you have. Any other bits of advice would be great. Thank you again.
     
  5. DonQ

    Active Member

    May 6, 2009
    320
    11
    Keeps the capacitance/inductance of the lead/meter from affecting the circuit you are measuring (it's at least some help). I have often dangled a MΩ or multi-MΩ resistor off the end of my test leads.

    Lots of times, while looking for a problem, I would touch a point while trying to troubleshoot a problem. Problem is, when I touch the point, the problem stops! Good luck finding the problem! Other times, it would cause new problems because of the effect on the circuit.

    This is somewhat like the X10 scope probe. The standard scope has a 1MΩ resistive impedance. The X10 probe has a 9MΩ resistive impedance to divide the signal by 10. Since it is also used for AC signals, often high freq., there is also a capacitor to do a X10 on the AC components of the signal, balanced against the (non-standard) capacitive impedance of whatever scope you are using. Thus the ability to tune the capacitor in the X10 probes to match the particular scope.
     
  6. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
    99
     
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