Most techs use a hand-held volt / ohm meter for all of their diagnostics work. They repair stuff all day long! These hand-held digital multimeters are cheap and reliable and get the job done. I use my old (1995) Fluke 79 series II from my iron worker / overhead crane field service electrician days when I need to use diode mode or continuity beep laziness. Some more common diagnostics problems cannot be solved with a cheap hand-held digital multimeter. Above is a 7 1/2 digit Keithley 2001 bench meter. It doesn’t time out and turn itself off during use to save battery. It just sits there warming up, stabilizing and becoming more accurate.
4-wire Kelvin probe 7 1/2 digit resistance measurements read accurately down into the tens of nano-ohms. My hand-held DMM won’t do THAT. What do I need a $5,800 bench meter for? Who needs all that accuracy? A common problem: a capacitor is DEAD-shorted to ground on a power rail. pumping more amps into the rail still won’t make this particular short heat up and show itself to your thermal camera. It won’t evaporate your 99% isopropyl alcohol any quicker than the surrounding board. Freeze spray won’t show it. Believe it, or not: the very component causing this short of that power rail will read individually lowest resistance of all components on that power rail…IF only you had good enough resolution, stability, speed and accuracy to read that! (all features that cost!) Finding a bench meter that excels in all of those specs = $$$$! It doesn’t even have a continuity beep or diode mode!
This is a FET VOM. It replaces and out-performs the VTVM in most cases. One of the reasons for using an FET VOM is that the ohm meter could operate at a voltage that would not
forward-bias germanium or silicon junctions, allowing measurements of resistance in these circuits.
The FET also could protect the meter movement from over current by separating the input circuitry
from the meter movement.
The meter movement is NOT driven by the circuit under test, like with normal VOM’s. Instead – the movement is driven by the batteries in the FET VOM and is only lightly *triggered*
by the circuit under test.
Analog meters are the king of showing trends and naturally normalize/average fast moving readings. A FET meter has highest input impedance (10, 12 Mohm!) – where at BEST – any other meter is ~ 10kohm. Not to say that the lower input impedance meters have no use! SOMETIMES: their lower input impedance is needed! The way they load a circuit – only THEN – will a problem become evident. My preference in the shop is my bench meter then. In the field: either my old Fluke 79 DMM or this beauty!:
Aaah. The Triplett 630. Look at the guts inside of a Simpson model 260 and compare with the meat n taters build of this brute!
Sorry ’bout that. The Triplett 630 just does something to me. What was I trying to say here, anyway!? Oh yeah. Good tools, good education, decades of experience = We’re ready to fix some electronics stuff over here.