ITTSB.EU Blog Forum
Electrical Metrology | Measurement Tips & Products | Calibration standards => Electrical Metrology for enthusiast => Topic started by: Kiriakos GR on March 21, 2017, 09:03:53 PM
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Quality made multi-meters by HIOKI, BRYMEN, Keysight and FLUKE, all offer the range of conductance function and measuring unit this is nanoSiemens (nS)
Conductance function this is about measuring very high resistance.
Most Digital multimeter they have limit at measuring lower resistance at NS range and not higher ones.
For example:
60nS=16.6 meg ohms ( This is Fluke 28II limit down)
300nS= 3.33 meg ohms ( This is Keysight U1272A limit down)
The conversion of nS to Mega Ohm is simple by dividing by 1000 your NS measured value.
Example : 1000 / nano-Siemens (measurement) = resistance
ITTSB Blog begging of 2017 added in it testing devices one special resistances box this for evaluation of insulation testers.
http://www.ittsb.eu/POWERTRON%20GST4020%20ITTSB%20Project%202017.html (http://www.ittsb.eu/POWERTRON%20GST4020%20ITTSB%20Project%202017.html)
This translates that now I am able to test also regular multimeter conductance function speaking of quality of calibration and its DMM true potentials.
It is known that conductance function this is not of high accuracy and at best could be 2%, from the other hand it is useful at understanding the magnitude of high resistance element under test.
Bellow it is my fresh made ITTSB Blog conversion chart, this including examples so to help you at easy identification of Ohms measuring range. 8)
0.055 ns = 18.0 G
0.06 nS = 16.0 G
0.38 nS = 2.6 G
2.5 nS = 400 M
5 nS = 200 M
10 nS = 100 M
20 nS = 50 M
25.66 nS = 39M
90.9 nS = 11M
100 nS = 10M
I took those measurements by using HIOKI DT2872, and if there is one conclusion to be made this is that resistance measurements above 5 GigaOhm starts to become a challenge because we getting in measurement made by what is called as less significant digits range.
At this point differences as for example 0.055 ns VS 0.05 or VS 0.06 nS are huge and measurement accuracy gets extremely questionable.
Now few tips for reliable measurements at conductance function:
a) Test lead probe this must be not touched by hands, use of alligators clip this is required, we are talking here for No-hands measurement.
b) Test lead wires them should not cross its other or be near to its other, five centimeter clearance between two cables all the way until measuring point this is safe.
c) When cables and multimeter both are set correctly, keep a distance of 30 centimeter away of multimeter until measurement this settle down (stabilizes).
Measurements of high resistance values it is a very tricky business for a multimeter, but not impossible if you are aware of all details and this ( By ITTSB made) How-To guide.