Addition to Vol.3, chap.3, pg.2?

Discussion in 'Feedback and Suggestions' started by WillST, Oct 12, 2009.

  1. WillST

    Thread Starter New Member

    Oct 12, 2009
    1
    0
    I am new to electronics and am enjoying your website:D. On the "Meter Checking of Diodes" page, I couldn't make sense of meter testing of diodes with my analog volt/ohm meters. I found out that in both of my analog meters when in the ohms mode, they have opposite polarity to their meter leads colors (red is negative, black is positive), so they indicate diode polarity the opposite of actual diode polarity. My digital meters do indicate proper diode polarity, so I used them on the volt scale to measure the polarity of my analog meters when they are on the ohms scale and found this opposite analog meter polarity issue. It took me a while to figure this out:confused:, you might put in a note about analog meters ohms scales measuring with opposite polarity, if that is true for most/all analog VOMs.
     
  2. ELECTRONERD

    Senior Member

    May 26, 2009
    1,146
    16
    Will,

    When you use your ohm meter, resistance doesn't have polarity. That means whatever way you use the probes, you'll get the same reading. You must be reading the meter wrong, the "COM" input should go to the black probe, not the red one. Voltage does have a specific polarity reading, if you have it wrong, usually it will say -_V. So for example, it might be around -12V for some application. You should look in your manual for your multimeters and make sure you have the probes connected correctly. As for diodes, they block current flow one direction and let current flow pass the other direction. Therefore, if you took your ohm meter, you should get a high resistance one way and a low resistance the other way. This is how you can determine the polarity. The high resistance end should be the cathode.
     
Loading...