Sonel MRU-20 Manuel utilisateur
OPERATING MANUAL
EARTH RESISTANCE METER
MRU-20
SONEL SA
ul. Wokulskiego 11
58-100 Świdnica
Version 3.1 24/02/2017
OPERATING MANUAL MRU-20 version 3.1
2
The MRU-20 meter is a modern, easy and safe measuring device. Please acquaint yourself with the
present manual in order to avoid measuring errors and prevent possible problems related to operation
of the meter.
OPERATING MANUAL MRU-20 version 3.1
3
CONTENTS
1SAFETY......................................................................................................5
2MEASUREMENTS....................................................................................6
2.1 MEASUREMENT OF RESISTANCE USING THREE-POLE METHOD ....................... 6
2.2 MEASUREMENT OF RESISTANCE USING DOUBLE-POLE METHOD, .................... 9
2.3 MEASUREMENT OF THE RESISTANCE OF PROTECTIVE CONDUCTORS AND
EQUIPOTENTIAL BONDINGS .......................................................................... 11
2.4 CALIBRATION OF TEST LEADS...................................................................... 13
2.4.1 Activation of Autozeroing ........................................................................... 13
2.4.2 Switching-off Autozeroing ..........................................................................14
3POWER SUPPLY OF THE METER.....................................................16
3.1 MONITORING OF THE POWER SUPPLY VOLTAGE ...........................................16
3.2 REPLACEMENT OF BATTERIES (RECHARGEABLE BATTERIES ) ...................... 16
3.3 GENERAL PRINCIPLES REGARDING USING NI-MH RECHARGEABLE
BATTERIES...................................................................................................18
4CLEANING AND MAINTENANCE...................................................... 20
5STORAGE ................................................................................................20
6DISMANTLING AND UTILIZATION..................................................20
7TECHNICAL DATA................................................................................ 21
7.1 BASIC DATA................................................................................................. 21
7.2 SUPPLEMENTARY DATA............................................................................... 23
7.2.1 RE Measurement.......................................................................................... 23
7.2.2 Measurement of RCONT ................................................................................ 24
8EQUIPMENT ........................................................................................... 24
8.1 STANDARD EQUIPMENT............................................................................... 24
8.2 OPTIONAL EQUIPMENT................................................................................ 24
9MANUFACTURER...................................................................................26
OPERATING MANUAL MRU-20 version 3.1
4
OPERATING MANUAL MRU-20 version 3.1
5
1 Safety
MRU-20 meter is designed for measuring parameters important for safety of electrical installa-
tions. Therefore in order to provide conditions for correct operation and the correctness of the obta-
ined results, the following recommendations must be observed:
Before you proceed to operate the meter, acquaint yourself thoroughly with this manual and ob-
serve the safety regulations and specifications defined by the producer.
MRU-20 meter is designed to measure earth resistance and the resistance of protective conduc-
tors and equipotential bondings. Any application that differs from those specified in the present
manual may result in a damage to the device and constitute a source of danger for the user.
The meter must be operated solely by appropriately qualified personnel members holding re-
quired certificates for carrying measurements in electric installations. Unauthorized use of the me-
ter may result in its damage and may seriously endanger unauthorized user.
Using this manual does not exclude the need to comply with occupational health and safety regu-
lations and with other relevant fire regulations required during the performance of a particular type
of work. Before starting the work with the device in special environments, e.g. potentially fire-
risk/explosive environment, it is necessary to consult it with the person responsible for health and
safety.
It is unacceptable to operate the following:
a damaged meter which is completely or partially out of order,
a meter with damaged test leads insulation,
a meter stored for an excessive period of time in disadvantageous conditions (e.g. excessive
humidity).If the meter has been transferred from a cool to a warm environment of a high level
of relative humidity, do not carry out measurements until the meter is warmed up to the am-
bient temperature (approximately30 minutes).
Before commencing measurements, make sure the test leads are connected to the appropriate
measurement sockets.
Do not operate a meter with an open or incorrectly closed battery compartment or power it from
sources other than those specified in this manual.
The inputs of the meter are protected electronically against overload e.g. due to having been con-
nected to a live circuit:
- for all combinations of inputs - up to 276V for 30 seconds.
Repairs may be carried out only by an authorized service point.
The device meets the requirements of standards EN 61010-1 and EN 61557-1, -4, -5.
Attention:
The manufacturer reserves the right to introduce changes in appearance, equi-
pment and technical data of the meter.
Note:
An attempt to install drivers in 64-bit Windows 8 may result in displaying "In-
stallation failed" message.
Cause: Windows 8 by default blocks drivers without a digital signature.
Solution: Disable the driver signature enforcement in Windows.
OPERATING MANUAL MRU-20 version 3.1
6
2 Measurements
2.1 Measurement of resistance using three-pole method
The three-pole measuring method is the basic type of resistance-to-earth measurement.
Disconnect earth
electrode being
tested from the
installation of
the building.
Turn on the meter.
Set the rotational func-
tion selector
set at RE3p position.
Using Unbutton
set test voltage
on 25V or 50V.
After 5 sec. the
meter returns to
the measure-
ment mode.
You can also
confirm the
choice by
pressing the
START push-
button.
ESH
2,2m
The current electrode (driven into earth) should be connected to Hsocket of the meter.
The voltage electrode (driven into earth) should be connected to Ssocket of the meter.
The earth electrode being tested should be connected to Esocket of the meter.
The earth electrode being tested and the current electrode and the voltage electrode should
be located one line
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