Products > Test Equipment
IET LOM-501A Micro Ohm meter
SeanB:
Nice, but i will stick with my bridge, where I can watch resistors heating up if I touch them. 4 D cells for power, but now is using 4 alkaline C cells and a spacer to fit, much cheaper to buy and use. Life will still be shelf life. At least i di make a zero reference shunt, using a copper foil to short the terminals, wire had an offset of about 10 milliohms.
robrenz:
--- Quote from: SeanB on March 10, 2012, 10:31:14 am ---Nice, but i will stick with my bridge, where I can watch resistors heating up if I touch them. 4 D cells for power, but now is using 4 alkaline C cells and a spacer to fit, much cheaper to buy and use. Life will still be shelf life. At least i di make a zero reference shunt, using a copper foil to short the terminals, wire had an offset of about 10 milliohms.
--- End quote ---
I didn't get the correct din plug yet to make up a set of kelvin clips and kelvin probes so I just used 4 short jumper clips to make sure the unit worked. I was measuring a 3" length of 22AWG wire and I could breath on it and see the resistance rise and then fall as it cooled. Touching the wire gets an instant jump in resistance that takes longer to return to the original reading. I got this to calibrate the low ranges of decade boxes I am making so a manual bridge would not be practical for me from a time per measurement perspective.
SeanB:
Takes 2 minutes per measurement, but I do it so infrequently it is no problem.
robrenz:
Can you tell me a little about your bridge? (I am sincerely interested, not trying to start a battle which is better). What level of traceable accuracy can you achieve at 20m Ohm? I would need +/- .04% just to match the accuracy of the unit to use for calibrating it. It has separate trims for each range. I only realy care about the 20m Ohm and 200m Ohm ranges.
SeanB:
Itt is a Yokogawa bridge I got from a flea market, a little rat nibbled case wise, a few hundred roach droppings to clean out from the carry case but basically clean and sound inside. Tested with the few precision resistors i have around, and was pretty much within 1 digit on all of them. New batteries and it worked ( after a little googling to get the manual to replace the rat eaten scraps inside) for me.
See for detail
http://tmi.yokogawa.com/products/portable-and-bench-instruments/dc-precision-measuring/2755-precision-wheatstone-bridge/
0.6% accuracy at the ranges you need, but it is within this spec. Most due probably due to contact resistance, even after cleaning all the switches with cleaner and general clean up. Checked the Zero with a copper foil shunt I made to fit the terminals, pretty close to zero as I can get without a 4 wire ability. Mostly meant to find cable faults, have used it to check windings for shorts on motors.
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