Chuck, KI4DGH, wrote: I would like to see some recommendations for a Digital Multimeter. The Fluke 187 is a little out of my range but something between my Walmart $29.95 special and the Fluke would be nice.
---------------------------------- I have cheap meters and expensive meters. On the high end, a Bel Merit probe type meter and a Fluke DMM. On the low end, A Radio Shack and a freebie DMM that came with an order from Mouser a while back. Curious, I compared all of them closely, using a variety of voltages and resistances. They are ALL produce readings within 1% or one digit of each other. There are three significant differences though. 1) Speed. The RS and cheapie meter take about 2 or 3 seconds to produce a reading. The Fluke and Bel Merit are virtually instantaneous. Reading about the design of these meters, it seems that they all tend to use the same divider chain for the ranges, and that modern manufacturing technologies ensure that the accuracy of these dividers are very good. That also determines the accuracy of the readings. The highest priced items in the meter are the chip that takes the analog input from the range divider and drives the digital display and the digital display itself. The cheaper I.C.s are slow. That's why the RS meter takes 2 or 3 seconds to produce a display while the more expensive meters look almost instantaneous. 2) Resolution. To hold down costs, many cheaper meters have only 3 or 3-1/2 digit displays. That is usually adequate for just about anything you might do. My RS, Fluke and Bel Merit all have four digit displays, typical of better meters. Also, some meters have a little row of dots or bars that vary with the reading. That's handy when making an adjustment when peaking a voltage, but it's pretty useless in a slower meter where you have to wait for a couple of seconds after making a change to see the results! 3) Durability. Robust packaging helps keep a meter working after hard physical use. Cheaper meters tend to skimp here. Still, one can be careful. I have an old d'Arsonval movement VOM (common wiggly-needle type of meter from the 1960's) that I still prefer when the oscilloscope isn't handy for peaking a circuit adjustment. It's a nice Radio Shack meter, but it is absolutely fragile, I'm sure. Still, I've had it for 40 years and it's still working FB. I just don't take it up a tower or other dangerous places. It stays on the bench or packed away in its box <G>. I do use my Fluke more than most. The Bel Merit, which fits easily in my shirt pocket, goes up masts or towers with me and generally anywhere where I want to travel "light" because it's small. Its disadvantage, being a "pen" or "probe" type instrument in which the display is an integral part of the probe, is that it's sometimes hard to see the display when holding the tip on the circuit. Also it doesn't do current measurements. In spite of its slower speed, the RS meter gets LOTS of use because it analyzes transistors showing the correct pinout along with an hFE reading directly and measures capacitor values from a few pF to many microfarads - as well as doing the common voltage/current/resistance checks. Neither my Fluke or Bel Merit offer all of those features. Frankly, if I had to take only one meter, I'd take the Radio Shack for its versatility. The model I have isn't made any longer, but I think the replacement is RS 22-812 (http://tinyurl.com/58fmn). The web page doesn't mention capacitance measurements in the features list, but the instruction manual says it does. This one has added a PC interface and a protective boot. It's about $70. If you're on a real tight budget, a cheaper meter will suffice. The only ones to really avoid at all costs are the older d'Arsonval meters built for use before solid state, like the venerable Simpson 260's and the like that many OT's use. They are FB meters, but load the circuit they test much more than modern DMM's and, more importantly, they drive the Ohms measurements with far more voltage and current than is safe for most solid state electronics. You can destroy a lot of modern circuitry by simply making a resistance check with one of those. Any of the modern DMM's are quite safe in that respect. Even the cheap ones. Ron AC7AC _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
