Circutor MI-10KV User manual

MI-10KV

ELECTRONIC

MEGOHMMETER

•TECHNICAL SPECIFICATION

•OPERATING INSTRUCTIONS

WARNING

Hazardous voltages exist on the terminals during operation.

Although output current of the megohmmeter is limited,

external capacities are charged to very high potentials and there

is no protection against them. So, this equipment should only be

used by a suitably trained and competent person, strictly

applying corresponding security standards.

MI-10KV

DESCRIPTION

The CIRCUTOR MI-10KV electronic megohmmeter is a versatile,

portable, user friendly, rugged instrument. It uses an efficient, well

experienced technology providing reliable, safe and accurate insulation

resistance measurements up to 2.000.000MΩ, with four test voltages:

1.000, 2.000, 5.000 and 10.000 V.

Due to its compact size and reduced weight, mechanical strength, self-

contained battery supply, this apparatus is particularly suitable for field

tests under severe environments. It is easily to be carried, very simple

to be operated and stands severe handling conditions including

frequent shocks, extreme temperatures, vibrations during transportation

through hard roads, long direct exposure to solar radiation, dust, sand

and other air-borne impurities, etc. Accuracy is not affected by all these

adverse conditions and it is still comparable with that of the best

laboratory instruments.

IMMUNITY AGAINST ELECTRIC AND MAGNETIC FIELDS

CIRCUTOR megohmmeters feature an effective filtering system that

improves immunity against electromagnetic disturbances and prevents

variations induced by industrial frequency fields.

OPERATOR’S SAFETY

Due to the high voltages involved, operator’s safety is a must.

CIRCUTOR megohmmeters were designed considering this

outstanding aspect:

•ENCLOSURE: Molded in high dielectric strength plastic. There are no

conductive parts accessible to the operator with the exception of the

output terminals. This terminals are located in a hidden and protected

position on the enclosure.

MI-10KV

•HIGH-VOLTAGE INDICATOR LIGHT: An indicator light (LED) is

warning the presence of high voltage at the output terminal during a

measurement and remains lit until the discharge process is completed.

MI-10KV

TECHNICAL SPECIFICATIONS

MEASURING INTERVALS, TEST VOLTAGES

MEASURING INTERVALS (MΩ)

Test

Voltage

(volts) ^ _ ` `=ñ=NM

Scale

Multiplier

Output.

Resistance

NKMMM MJ=OM =OM=J=QMM OMM=J=OMKMMM OKMMM=J=OMMKMMM =ñ=O ==O=jΩK

OKMMM MJ=QM =QM=J=UMM QMM=J=QMKMMM QKMMM=J=QMMKMMM ñ=R Q=jΩ

RKMMM MJNMM NMM=J=OKMMM NKMMM=JNMMKMMM NMKMMM=JNKMMMKMMM ñ=NM NM==jΩ

NMKMMM MJOMM OMM=J=QKMMM OKMMM=JOMMKMMM OMKMMM=J=OKMMMKMMM =u=OM OM==jΩ

TEST VOLTAGE STABILITY

1 % during full battery service life.

SHORT-CIRCUIT CURRENT

500 µA.

CLASS

Class 2 (related scale size) @ 30 º C.

BATTERY TEST

Allows checking battery status under real consumption conditions

without interrupting the generation of test voltages.

GUARD TERMINAL

Allows the measurement of very high resistance values, avoiding the

effect of stray resistances.

MI-10KV

CARRYING CASE

A strong synthetic leather carrying case provides easy transportation for

the instrument and attachments. The megohmmeter may operate

without being removed from the carrying case.

DIMENSIONS AND WEIGHT

290 x 155 x130 mm (outside dimensions without carrying case)

8 kg. (including apparatus, carrying case, battery and test probes)

ENVIRONMENTAL OPERATING CONDITIONS

This apparatus is designed to be used in outdoors field work under very

unfavorable weather conditions. Room temperature may vary between

0°C and +50°C, with relative humidity close to saturation point without

affecting the instrument operation.

ATTACHMENTS SUPPLIED

Every megohmmeter is supplied with a full set of test leads,

rechargeable battery, charger, carrying and operating manual.

MI-10KV

KEYBOARD

Low resistance range. Read values at scaleA

Higher resistance range. Read values at scale,

then multiply it by 10.

Read values at scaleB

Read values at scaleC

When pressed, the battery test is performed under

actual consumption conditions

ON/OFF Switch

High voltage Terminals

Return

Terminal

Guard

Terminal

MI-10KV

OPERATING INSTRUCTIONS

1) Be sure that there are no voltage differences between the points at

which the megohmmeter will be connected, nor between them and

ground.

2) Determine the value of test voltage to be used in the insulation

resistance measurement.

3) Connect the red banana pin of the red cable to the 1.000, 2.000,

5.000 or 10.000 V terminal in accordance with the selected test voltage.

4) Connect the black cable to the -R megohmmeter terminal and the

yellow terminal to terminal G.

5) The green GUARD terminal is not always used. Technical Note #32

explains the use of GUARD terminal in order to minimizing the effect of

stray resistances. When measurement is carried out between parts

which none of them is grounded, (like between high-side and low-side

windings of a transformer), GUARD terminal must be connected to

ground in order to fix the apparatus potential. At any time a

measurement is performed, either the “-R " or GUARD terminals

must be connected to ground but never both simultaneously. If

none of these terminals are connected to ground, the megohmmeter

can reach a high potential that may result in an unstable non-reliable

reading. If both terminals are simultaneously connected to ground,

there is a short-circuit between them and consequently the

megohmmeter will measure with error.

6) Connect the free ends of cables (alligator clips) to the element to be

measured.

MI-10KV

7) Before turning on the apparatus, be sure that the key corresponding

to Ascale is pressed. Turn on the apparatus by pressing the ON/OFF

key. Then the high-voltage generator starts operating and the

corresponding indication light turns on at the front panel. The meter

pointer will indicate the value of the unknown resistance. If the element

to be measured is strongly capacitive it will initially indicate a low

resistance value, which will be gradually increased while the charging of

that capacitance takes place.

8) When the measured resistance exceeds the maximum value in range

A, press range Bkey, and if still the value is not achieved, press keys of

ranges Cor Cx10, as required.

9) Always remember to multiply the reading by the factor stated in the

following table, depending on selected test voltage:

10) When key C x 10 is used, reading shall be carried out in range C

and shall be multiplied by 10, in addition to the factor corresponding to

the test voltage.

11) To finish measurement press again and release ON/OFF key. The

megohmmeter will start discharging the potentials accumulated in the

apparatus internal capacitances and in those of the element under test

as well. When this discharging process is over (up to 60 seconds after

turn off) the high-voltage indicator will turn off automatically. Then, test

leads may be disconnected.

12) In certain instances, when the apparatus is disconnected the pointer

exceeds the infinite position to the right side. This is a normal behavior.

1.000 V x 2

2.000 V x 4

5.000 V x 10

10.000 V x 20

MI-10KV

13) Checking battery status. Battery measurement can be performed

without interrupting high-voltage generation, which will provide a better

evaluation of the battery status, by pressing the BATTERY key during

the measurement. So, the battery test is performed under actual

consumption conditions and, for long lasting measurements, (i.e.

Polarization Index), the evolution of battery status can be checked

without affecting the measurement.

The meter pointer should stop over the blue zone. If the pointer stop

over the red zone this means that the battery is discharged and shall be

charged

14) Infinite setting. The mechanical zero of galvanometer must be

periodically checked. In order perform this checking, be sure that the

megohmmeter is off. The pointer should stay on the right end of the

scale just over the infinite mark on scale C. In other case, the plastic

screw at the bottom of the galvanometer acrylic cover shall be adjusted.

MI-10KV

TECHNICAL NOTE # 32

USE OF GUARD TERMINAL IN MEGOHMMETERS

When insulation resistance measurements are performed

with megohmmeters, specially with high-sensitivity

instruments measuring high resistance values, the use of

the GUARD terminal avoids the harmful influence of stray

resistances.

In order to better explain the function of this terminal, let us

start reviewing the megohmmeter basic circuit diagram of

Fig. 1.

-R

Guard

Fig. 1

Where:

V : DC high-voltage generator

Ri: Generator internal resistance

A: Indicator meter (microammeter)

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