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DC current resistance measurement in inductive and noninductive circuits in the range from 10 µOhm ÷ 30 kOhm for the currents of up to 10А
Automatic measurement of three-phase transformers
There is also a mode for resistance measurement across two windings simultaneously
Demagnetization mode of transformer’s magnetic circuit
OLTC in-place check mode (DRM-test method)
"Heat test" mode (cooling test)
Full automation of measurements and an archive of results in the analyzer itself
High level of protection and safety conformance in regard to
Independent power supply, interactive control and communication with PC

Modern milliohmmeter MIKO-9

DC current resistance measurement in inductive and noninductive circuits in the range from 10 µOhm ÷ 30 kOhm for the currents of up to 10А

  • Windings of power transformers, instrument current transformers, electromagnets and electric motors;
  • Compensatory, current-limiting and other resistors of high-voltage circuit breakers;
  • Contacts and contact connections of power and signal circuits;
  • Cables.

Measurement ranges and currents are specified both for automatic and manual modes. The analyzer ensures fully automated measurement of highly inductive load resistance and balancing the thermal EMF in the external circuit.

Automatic measurement of three-phase transformers

The instrument's peculiarity is the ability to connect to three phases of a transformer and to perform measurements at automatic switch-over. Measurements are automatically stored in the non-volatile memory and later can be processed by PC with the help of special software or downloaded via Bluetooth interface to a mobile telephone or tablet.

High output capacity (up to 60W on the load) of the in-built battery allows saturation of a magnetic conduit of power transformers and thus guarantees reliable measurement of transformer windings resistance.

Furthermore, there a special mode for measuring the transformer windings resistance using switch-over devices of OLTC and PBV (off-circuit tap changer) types.

There is also a mode for resistance measurement across two windings simultaneously

This mode guarantees fast and accurate measurement of DC electric resistance of power transformers, particularly, by triangular-form connection of the secondary winding, should conventional methods do not produce reliable results.

Demagnetization mode of transformer’s magnetic circuit

Demagnetization mode is intended for eliminating the residual magnetization of transformer's magnetic conduit after DС tests prior to other tests such as idle run, short circuit, measurement of a transformation factor, etc.

Demagnetization mode of power transformer’s core follows requirements of GOST 3484.1 and is operated either fully automatically or manually by specifying the demagnetization current increment and limit.

OLTC in-place check mode (DRM-test method)

OLTC "in-place" check mode allows carrying out of in-place check and diagnostics of OLTC with current-limiting resistors without removing the contactor tank covers. This mode involves measuring of instantaneous current passing at first through the transformer cover and then through OLTC contracts at switching from one tap to another.

A graph of current variance at contacts switching is drawn up and the time of switching as well as the general technical condition of the instrument is checked on its basis. Analysis of the acquired graphs provides not only for sorting out of elements by fault-free/faulty criteria but also for defining the nature of the defect allowing eliminating of fault-free OLTCs opening.

Measurements in milliohmeter mode and in in-place check mode complement each other and provide a comprehensive picture of the state of transformer.

"Heat test" mode (cooling test)

The instrument has a special ‘heat test’ mode (cooling test).  The testing procedure and results interpretation technique follow the requirements set forth in Item 2 of GOST 3484.2-88 "Power Transformers. Heat Tests".

Full automation of measurements and an archive of results in the analyzer itself

The history of measurements stored in the instrument is designed for viewing, copying and deleting measurement results, stored in the non-volatile memory of the instrument as well as for performing various calculations:

  • Automatic calculation of relative deviations of winding resistance at three phases against each other;
  • Automatic recalculation of linear resistance of windings connected with delta or star connection to the phase winding resistance;
  • Automatic recalculation of winding resistance measured at current temperature to resistance at the certified temperature (with due regard to winding material);
  • Automatic calculation of deviations measured and normalized to the certified temperature of winding resistance in relation to the certified values of resistance;
  • Automatic calculation of winding temperature based on its measured and certified value of resistance and certified temperature.
High level of protection and safety conformance in regard to
  • exceeding of measuring current;
  • polarity reversal of cable ends in accumulator storage battery;
  • electromotive force (emf) of self-induction. 

At disconnection of the measuring cable from transformer bushings or from the instrument as well as at disconnection of the mains cable from the mains or accumulator battery in the course of measurement, emf of self-induction of up to several kV is generated in the disconnected circuit and the electric arc appears in the break point.

MIKO-9 is characterized by the redundant protection against emf of self-induction in case of involuntary disconnection of the measuring cable or power cable protecting users from electric shock and the instrument from being damaged.

  • a set of required protective means against superheat of the measuring unit;
  • protection grounding contact in the mains plug and safety earthing terminal on the case of the measuring unit.
Independent power supply, interactive control and communication with PC

The instrument can be powered from the mains (110÷220, 330V) or from an in-built battery.

Color graphic display of high brightness ensures easy reading on a sunny day, whereas intuitively understandable interface with a sensor display facilitates the instrument use.

The Instrument can be manipulated either from the film keyboard or from the sensor display, as suits.

The instrument can be built into the testing systems under control of software complexes of test laboratories and equipment manufacturers. It is supported by Modbus RTU Protocol.

Personal computer connection through USB or Bluetooth allows for:

  • controlling the instrument with the help of PC;
  • systematizing and storing the results on computer;
  • drawing up of measurement reports.

Data transmission to the computer and filing of measurement results is performed with the help of a special program developed by the manufacturer.


Specifications Value
Resistance range 10µOhm ÷ 30kOhm
Maximum permissible intrinsic error of resistance measurement ±(0.1%+0.5µOhm)
Measuring current intensity, А 0.00075 ÷ 10
Relative drift of measuring current intensity, %/s ±0.002
Maximum output capacity: when powered from the battery 20W
Maximum output capacity: when powered from the mains 60W
Mains voltage: AC (valid value) 90 ÷ 253V
Mains voltage: DC 127 ÷ 354V
Maximum consumed power 120W
Type of data transmission channel USB, Bluetooth
IP rating in operating state IP40
IP for transportation IP64
Operating temperature range, ºС -20 ÷ +50
Maximum measuring unit weight, kg 4.0
Dimensions, mm 270х250х130
Interface language English
User manuals language English
Calibration interval, year 3
Standard complete set
Photo Item, Index Application
MIKO-9 measuring unit MIKO-9 measuring unit The instrument and accompanying documents: calibration certificate, operation manual and record book.
Measuring cables <br><b>on order</b> Measuring cables
on order
As a matter of convenience for the user, measuring cables are not included in the standard complete set. Each user can select a cable to his/her own requirements.
Select at least one measuring cable (see "additional complete set on order" below).
Mains cable Mains cable SKB018.09.00.000 For connecting the instrument to the power line. Temperature range -25°С ÷ +120°С. Rubber insulation (length – 2 m).
Ground wire Ground wire СКБ010.01.00.000 For instrument case grounding. Equipped with a ground clamp and screw end cap. Rated current – 50А.
Zero resistance equivalent Zero resistance equivalent СКБ023.15.00.000 Resistance zero point accuracy check. Value – 0.000 µOhm.
Shunt 75ШСММ3 Shunt 75ШСММ3 Performance check. Value – 1 MOhm ± 0.5%.
VP2B-1V-2А cut-out (2 pcs.) VP2B-1V-2А cut-out (2 pcs.) For power source protection.
Cable USB 2.0 A-B Cable USB 2.0 A-B For connecting the instrument to the computer and its control from PC (length – 1.8 m).
Additional complete set (on order)
Photo Item, Index Application
Measuring cable <br> (set of 2 PCs.) Measuring cable
(set of 2 PCs.)
СКБ041.18.00.000
СКБ041.18.00.000-01
Cable for connection to transformer leads. The cable is made in the form of elastic silicone tube resistant to low and high temperatures and corrosive media. Alligator type clamps with the jaw of up to 80 mm. Length – 8.5 m
Measuring cable Measuring cable СКБ041.19.00.000 Cable for measuring the transient resistance of contacts; measurement of CT and VT windings resistance. Length: 3 m.

Clamps: current and potential contacts: ‘crocodile’ clamps with 25mm jaws (2 pcs.), and removable probes with a 3mm diameter plug 70mm long (2 pcs.).
Measuring cable <br> (set of 2 pcs.) Measuring cable
(set of 2 pcs.)
СКБ041.26.00.000
СКБ041.26.00.000-01
Cable for connection to transformer leads as an alternative to cables available СКБ041.18.00.000 and СКБ041.18.00.000-01. Clamp jaw of up to 103 mm. Length - 8.5 m.
Test cables for CT and VT Test cables for CT and VT СКБ041.21.00.000 For measuring the resistance of CT and VT windings of both in-built and stand-alone transformers / circuit-breakers. Alligator type clamps with the jaw of 25 mm. Length – 4 m
Measuring cable extension (set of 2 pcs.) Measuring cable extension (set of 2 pcs.) СКБ031.20.00.000 Recommended for application together with measuring cables СКБ041.18.00.000/СКБ041.18.00.000-01 (throat of up to 80 mm) and СКБ041.26.00.000/СКБ041.26.00.000-01 (throat of up to 103 mm).
The extension is made in the form of elastic silicone tube resistant to low and high temperatures and corrosive media. Length - 6.5 m.
Short-circuiting cable (set of 3 pcs.) Short-circuiting cable (set of 3 pcs.) СКБ041.23.00.000 For applying the DRM-test one of the short circuiting cable sets for closing secondary circuits shall be ordered. This set consists of thee short-circuiting wires 3m long each. Both ends of the wire are furnished with welded ‘crocodile’ clamps with 80 mm jaws.

This cable is for OLTC devices of power transformers.

Furthermore, this cable is needed for connecting the high-voltage and low-voltage windings when performing measurements in the ‘two consecutive windings’ mode.
Short-circuiting cable (set of 3 pcs.) Short-circuiting cable (set of 3 pcs.) СКБ035.31.00.000 For applying the DRM-test one of the short circuiting cable sets for closing secondary circuits shall be ordered. This set consists of thee short-circuiting wires 12m long each. Both ends of the wire are furnished with welded ‘crocodile’.

This cable is for OLTC devices of auto transformers. It is to be applied for all the single- and three-phase transformers and for three-phase transformers with Yn/Yn and Y/Yn winding connections.

KMDLAX-6P plug KMDLAX-6P plug An adapter for the RS-485 cable for the analyzer communication with the SCADA-controlled measurement system.
Reference inductor adaptor Reference inductor adaptor СКБ023.12.00.000 For verification laboratories: inspection / calibration of the instrument.
Cable and documentation bag Cable and documentation bag СКБ126.06.00.000 Handy, sturdy and wear-resistant bag for carrying cables, documents and other additional component parts to MIKO-9.
Manipulating rod Manipulating rod СКБ010.41.00.000
СКБ010.41.00.000-01
СКБ010.41.00.000-02
The rod is designed to ensure convenient connection to contacts of a transformer inputs.

The rod is completed with a clamp with current and potential contacts connected by wires with the measurement platform. Test cables are connected to the measurement platform from the ground.

  • Manipulating rod for equipment of up to 35kV (2.2 m);
  • Manipulating rod for equipment of up to 110kV (3.7 m);
  • Manipulating rod for equipment of up to 220kV (5.1 m);
Articles (2)
Present-Day Market of Instruments for Electric Resistance Measurements
Present-Day Market of Instruments for Electric Resistance Measurements
The Company moves forward and continuously updates its products, that is evidenced by three new milliohmmeters to be manufactured in 2018: MIKO-7M, MIKO-8M, and MIKO-9.
A Method for Determining the HV Windings Faults Locations in Power Transformers
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One of the methods of finding the fault in the electric circuit is its division into separate sections followed by measurement of electric resistance of each section.
Reviews (2)
Comparison of milliohmmeters MIKO-7 and MIKO-8 with the new modifications
Comparison of milliohmmeters MIKO-7 and MIKO-8 with the new modifications
The SKB EP Company moves forward and continuously updates its products that is evidenced by two new versions of milliohmmeters to be manufactured in 2018: MIKO-7M and MIKO-8M.
Comparison of new milliohmmeters produced by SKB EP
Comparison of new milliohmmeters produced by SKB EP
SKB EP Company sells three types of instruments for measurement of DC electric resistance of windings of transformers, electric motors, electric magnets, cables and of other inductance and inductance-free circuits: the MIKO-7M, the MIKO-8M and the MIKO-9.