Be careful with some of the DMM's too. I did a study on the voltage produced at the leads for several brands of industry-standard meters at work. Here is one of them:
Resistance Range Voltage on the leads 0.2 ohms 12 volts 2 ohms 12 volts 20 ohms 12 volts 200 ohms 6 volts 2M ohms 6 volts 20M ohms 1 volt We found out why certain semiconductor devices were being destroyed after "meter checking". 73, John W2XS Generally it is not a problem, if you are checking resistors. The area you can get into trouble is when you have semiconductors connected to the circuit - Elecraft Rigs are loaded with them. The problem can come from most VOMs not being able to limit the current applied to the circuit under test. Even at low voltage you could apply a voltage with enough current to bias a transistor to a destructive level. Most DMMs use a high impedance amplifier on input to reduce current flow to/from the meter. The resistance circuitry can also be made to sample E/I data at low enough levels to provide resistance measurement at much lower current and voltage. IMO, with many DVM/DMMs on the market at low cost, it's probably not worth the risk. Al WA6VNN **************New MapQuest Local shows what's happening at your destination. Dining, Movies, Events, News & more. Try it out! (http://local.mapquest.com/?ncid=emlcntnew00000001) _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com -- View this message in context: http://n2.nabble.com/dmm-vs-vom-tp1307371p1314193.html Sent from the Elecraft mailing list archive at Nabble.com. _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
