Ohm Meter to the 100th

[Mooch]

No they don't, they read to 100th
1 Ohm coil displays 1.00
0.1 Ohm displays 100
0.01 Ohm displays .010
USA are saying their Ohm meters are accurate to 0.018 so on a 0.1 Ohm coil this means 18% error! How is that good?

Yea, there's something not right there...
The photo they show of a comparison between the readings from a BK Precision meter and a USA Ohm Meter show that the USA meter was off by 0.018 ohms when reading a 0.175 ohm build. That is a 10% error. That would mean that a 1 ohm build would could read anywhere from 0.9 ohms to 1.1 ohms. Not terrible, but not what I personally would say was very accurate. And we have no idea if the accuracy is the same for all build resistances, ambient temperatures, etc.

But that Japanese video shows about 1.7% accuracy so I just don't know. I would really like to see a proper accuracy spec on those or, at least, a good third party test of its accuracy. It involves so much more than taking a measurement or two!

 

[yo han]

Yeah, something's not right indeed.
It's almost as if they have no clue about it themselves.
When talking about accuracy you're talking percentages, not hard values.
Yet with every meter on the website they claim an accuracy of 0.018 Ohm.
It totally makes no sense.

 

[K_Tech]

USA are saying their Ohm meters are accurate to 0.018 so on a 0.1 Ohm coil this means 18% error! How is that good?

Yea, there's something not right there...
The photo they show of a comparison between the readings from a BK Precision meter and a USA Ohm Meter show that the USA meter was off by 0.018 ohms when reading a 0.175 ohm build. That is a 10% error. That would mean that a 1 ohm build would could read anywhere from 0.9 ohms to 1.1 ohms. Not terrible, but not what I personally would say was very accurate. And we have no idea if the accuracy is the same for all build resistances, ambient temperatures, etc.

But that Japanese video shows about 1.7% accuracy so I just don't know. I would really like to see a proper accuracy spec on those or, at least, a good third party test of its accuracy. It involves so much more than taking a measurement or two!

I don't like the way they calculate their error. Having been directly involved in measuring equipment calibration in the past, a single-point reading comparison is really useless. You have to do a multi-point calibration over the entire range of the meter being tested in order to see what's going on.

All we know from that particular reading is that at 0.175 ohms, it reads 0.157 ohms. Without more data, that really tells you nothing about the meter's accuracy.

However, I will say that if it reads off by 0.018 ohms across its entire resistance range, that's really not bad for a cheap meter, and that's something that you can work with.

For example, I've tested (and re-tested) my el-cheapo black box tester, and it reads consistently 0.03 ohms high from a dead short to 2.5 ohms (I didn't go any higher because I don't build above 1.5 anyway), and I take that into account when testing my coils.

 

[yo han]

Already sent them a message to clarify.
Normal accuracy would be given as x% (+x counts)
I don't know what you compared your el-cheapo to but if it's only off by 3 counts then that's very good indeed (assuming the meter you've compared it to is spot on).
Have you opened it up to see if perhaps there's a trim potentiometer inside that let's you zero it out? (short the 510 and then turn the potentiometer until it reads zero)

 

[K_Tech]

Already sent them a message to clarify.
Normal accuracy would be given as x% (+x counts)
I don't know what you compared your el-cheapo to but if it's only off by 3 counts then that's very good indeed (assuming the meter you've compared it to is spot on).

I tested it against a calibrated micro-ohm meter. What I did was put a strand of Kanthal on an rda and measure it on the ohm meter, then on the atomizer tester. I did that for about ten different resistances by varying the length of the kanthal wire. I also used a Fluke 754 to double check, and the readings were still in line with my readings.

Have you opened it up to see if perhaps there's a trim potentiometer inside that let's you zero it out? (short the 510 and then turn the potentiometer until it reads zero)

Yes, I opened it up, there's no adjustments, but I really wasn't expecting any at the price I paid (I think it was around $10USD).