Comparison of SKB EP milli-ohmmeters

Measurement of active resistance of windings is an important stage of maintenance, as well as part of the acceptance test program at the factory.  Transformers, electric motors, electromagnets, etc. are subject to vibration, overload and the influence of large temperature drops, which in time leads to the disruption of the connections and requires constant testing with special instruments - milli-ohmmeters.

	MIKO-9А	MIKO-8M(A)	MIKO-7М(А)	MIKO-2.3
Application area
Windings of power transformers				windings of small size transformers
Non-demountable estimation of transformers' OLTCs
Windings of current and voltage measuring transformers	with winding resistance up to 30 kΩ	with winding resistance up to 10 kΩ	with winding resistance up to 2 kΩ	with winding resistance up to 1 kΩ
Windings of electromagnets, electric motors and compensators
Windings of high frequency filters
Compensatory, current limiting and other resistors of high-voltage circuit breakers
Contacts and connections of power and signal circuits
Cables
Temperature measurement of water, air, oil (non-aggressive environments)
General characteristics
Measurement range	1 μΩ ÷ 30 kΩ	1 μΩ ÷ 10 kΩ	1 μΩ ÷ 2 kΩ	100 μΩ ÷ 1 kΩ in milli-ohmmeter mode 0,1 μΩ ÷ 0,1 Ω in micro-ohmmeter mode
Test current range	0,0005 ÷ 10А	0,001 ÷ 10А	0,01 ÷ 10А	0,5 ÷ 5А in milli-ohmmeter mode 10 ÷  1000А in micro-ohmmeter mode
Accuracy	±(0,1%+0,5 μΩ)	±(0,1%+0,5 μΩ)	±(0,1%+0,5 μΩ)	±0,2%
Resolution capability	0,1 μΩ	0,1 μΩ	0,1 μΩ	0,1 μΩ
The instrument has protection against: EMF of self-induction; excess of test current; overheat of the test block.
Built-in memory	up to 1,000 measurements	up to 1,000 measurements	up to 200 measurements	up to 100 measurements
Display	color graphic TFT touch, 800 x 480 pixels	color graphic TFT touch, 800 x 480 pixels	monochrome graphic display, 128 x 64 pix	monochrome, alphanumeric, 6 х 2,5 сm
PC connection	By cloud server on PC and through mobile app	By cloud server on PC and through mobile app	By cloud server on PC and through mobile app	RS-232 and USB (when using adapter)
Instrument control from mobile app (smartphone)	Bluetooth	Bluetooth	Bluetooth
Power supply by built-in battery	Li-ion battery	Li-ion battery MIKO-8MA modification	Li-ion battery MIKO-7MA modification	Condenser battery is in development. Power supply by an external li-ion battery
Mains power supply
Operating temperature range, ºC	-20 ÷ +55 °С	-20 ÷ +55 °С	-20 ÷ +55 °С	-20 ÷ +40 °С
Dimensions, mm	270х250х130	270х250х130	270х250х130	150х190х75
Instrument weight with battery, kg	4,0	4,0 MIKO-8MA modification	4,0 MIKO-7MA modification	-
Instrument weight without battery, kg	-	2,7	2,7	2,7
Functions
High precision measurement modes for different objects, taking into account their specific features	10 objects	10 objects	5 objects
Automatic or manual measuring current setting
High precision measurement modes in non-inductive circuits
Connection directly to the three phases of the transformer and measurement with automatic switching
Simultaneous resistance measurements across 2 windings, in particular for high-power transformers with secondary windings delta connected when the use of traditional methods does not give a stable result
Automatic load inductance meter. The instrument automatically detects the moment of setting the resistance and stops the measurement
Automatic inductance discharge after measurement
Electric resistance measurement mode of power transformer windings with OLTC device. When switching OLTC devices, the instrument can stay connected
Winding electrical resistance measurement mode during the cooling test. The test procedure is in accordance with paragraph 2. GOST 3484.2-88 "Power tramsformers. Heating Tests"
AUTO demagnetization mode of the magnetic transformers system
Non-demountable estimation of the OLTCs (DRM test) with generating oscillograms
Automatic recalculations
Automatic calculation of the relative deviations of the electrical resistance at the three-phase windings between each other
Automatic recalculation of linear electrical resistance of windings delta or star connected into electrical resistance of phase windings
Automatic recalculation of the electrical resistance of the winding measured at the current temperature into electrical resistance at the passport temperature	taking into account the winding material	taking into account the winding material		taking into account the winding material
Automatic calculation of deviations of the measured and passport temperature electrical resistance of the windings compared to the passport resistance values
Automatic calculation of the winding temperature according to its measured and passport value of electrical resistance and passport temperature	in the cooling test (heat run test) mode