Ohmmeter that is accurate below 10 ohms?

[steveu]

I once had to deal with very high resistance. Now that was tricky. Did you know that probe cables and a mains outlets have measurable leakage resistance? Like a 4 wire Ohmmeter, you have to deliver the test voltage to the Unit-Under-Test with separate cable from the sense cable.
https://www.keysight.com/us/en/assets/7018-02332/product-fact-sheets-archived/5990-4780.pdf

 

[egellings]

Agree. Read my post (#15) above, in this thread.

 

[jlinkels]

I once had to deal with very high resistance. Now that was tricky. Did you know that probe cables and a mains outlets have measurable leakage resistance?

Yes, in power generation the test equipment is called a "Megger". In Dutch that is, obviously derived from Mega ohm meter. Even the best insulators on medium voltage generators (~11kV and such) measure a few hundred MOhms.
That is not as much as the meter you mentioned. 16 x 10e15! That is an awful high resistance. I did not know those existed. But then again, in the late 1980-ies I worked for a company where one of the wizards designed a meter which was able to measure in the femto Ampere range.
Thanks for sharing that information.

 

[cocolino]

There are also meters for checking battery impedance which can work and maybe an ESR checker could work but my experience with the cheap Asian knock offs have not been good.
This may be a good option https://www.ebay.com/itm/4051422960...HeY4O9x/bGR5XPbSIrnq4tXoo=|tkp:Bk9SR-ab787sZQ The price is right and it seems to have accuracy. The controls are all in Chinese but I'm sure Google can help.

I`ll throw in something similar in this price-range: FNIRSI HRM-10 "Internal-Resistance-Tester".
Bought one last year (ALI).
4-wire Kelvin probes (GX12 jack for the probe, so You can easily also make own probes).
Nice display (could be somewhat brighter for my taste).
Accuracy: +/- 0,5%
Resolution: 10µOhm = 0,01 Milliohm

NOTE: it measures with ~1kHz AC! Good enough for resistor measurements.
Can test internal resistance of batteries as well (+ voltage).

I measured:
# 100mOhm / 0.1% precision 4-wire resistor (= ±0,1 Milliohm = ±100µOhm = 99.9 - 100.1 Milliohm).
FIRSNI measured: 100.34 Milliohm. Above resistor specs but inside instrument specs (+/-0.5%).

# 10mOhm / 1% precision 4-wire resistor (= ±0,1 Milliohm = 9.9 - 10.1 Milliohm).
FIRSNI measured: 9.99 - 10.01 Milliohm.

Repeatability of measurements is also very good.

Voltage measurements as well, two different batteries:
# FLUKE 87 III (4.5 digit): 12.524V vs. FNIRSI HRM-10: 12.523V
# FLUKE 87 III (4.5 digit): 12.380V vs. FNIRSI HRM-10: 12.379V

Amazing for the price and reasonable well built. I like it.

BTW: measured 5m AWG16 silicon cable. Rolled off in a straight line: 72 Milliohm (good).
The 5m coiled up the FNRISI did not like that...and measured crap (always good to know the limitations).

 

[lcsaszar]

Yes, in power generation the test equipment is called a "Megger". In Dutch that is, obviously derived from Mega ohm meter.

Megger is a Swedish company for manufacturing test and measuring equipment. I frequently encounter with their electricity supervision gear (last time I measured a 5000 A current source).

 

[jean-paul]

Yes, in power generation the test equipment is called a "Megger". In Dutch that is, obviously derived from Mega ohm meter

No it is a brand of equipment but the mistake is often made. Using such a device is called "meggeren" ("meggering") in electro-babble/jargon which does not make stuff more clear either 🙂 Officially "testing insulation resistance"

 

[jlinkels]

Then the brand name became a type name. We had them from ABB, Gossen and others. Everyone referred to the device as "a megger".

 

[jean-paul]

Like Luxaflex.

You probably also know the single brand that made one clamp 3 phase current meters (very unprecise as one could expect). Also called by their brand name (which I happily forgot, terrible instruments).