I have a big box ohm meter that has a usb cable for power, my question is, there are 2 510 connection slots and one of them is either higher/lower than the other one by .05 ohms. Anyone came across this problem before?
ohm meter question
- Thread starter Cloud boy
- Start date
- th_trl_thread_readers 0
- Status
I would guess the one that reads higher has longer wires on the back side of it going to the electronics. Probably totally normal especially if it always reads .05 higher than the other one.
That's too much to be the wire itself, it's more than a foot of any half-decent-sized wire, but it is probably still some systematic hardware feature such as connection resistance.
50 milli-ohms is rather a small amount to measure accurately. Digital displays give us an unwarranted confidence in their numbers. I would be mildly surprised if either of the numbers you were seeing was within 0.1 ohms of the real value. When did you last have the meter calibrated?
50 milli-ohms is rather a small amount to measure accurately. Digital displays give us an unwarranted confidence in their numbers. I would be mildly surprised if either of the numbers you were seeing was within 0.1 ohms of the real value. When did you last have the meter calibrated?
That was my point ;-)
I've just been checking up, and the weak link is the panel meter. I can get a 0.1% current reference built for well under £10, but a 0.1% panel meter starts at £17. That's one-off prices, but these things are not mass-market and there will be a significant mark-up. Unless you bought an especially high-accuracy meter, you almost certainly have something accurate to around 1% of full-scale. Assuming it reads to 19.99 ohms (because it's got to be at least 3, and the rest is free) that's 0.2 ohms. If there's a 1.999 ohm range, then it will be accurate to 0.02 ohms.
That's assuming all components except the meter are more accurate, so the meter accuracy predominates. Murphy's Law states "In an instrument or device characterized by a number of plus-or-minus errors, the total error will be the sum of all the errors adding in the same direction." That would at least triple the inaccuracy, but it isn't generally that bad.
I've just been checking up, and the weak link is the panel meter. I can get a 0.1% current reference built for well under £10, but a 0.1% panel meter starts at £17. That's one-off prices, but these things are not mass-market and there will be a significant mark-up. Unless you bought an especially high-accuracy meter, you almost certainly have something accurate to around 1% of full-scale. Assuming it reads to 19.99 ohms (because it's got to be at least 3, and the rest is free) that's 0.2 ohms. If there's a 1.999 ohm range, then it will be accurate to 0.02 ohms.
That's assuming all components except the meter are more accurate, so the meter accuracy predominates. Murphy's Law states "In an instrument or device characterized by a number of plus-or-minus errors, the total error will be the sum of all the errors adding in the same direction." That would at least triple the inaccuracy, but it isn't generally that bad.
- Status
Similar threads
