Sonel MRU-200 User manual

USER MANUAL
EARTH RESISTANCE METER
MRU-200 ● MRU-200-GPS
SONEL S. A.
Wokulskiego 11
58-100 Świdnica
Version 2.0228.07.2021

MRU-200 ●MRU-200-GPS –USER MANUAL
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The MRU-200 / MRU-200-GPS 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.

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TABLE OF CONTENTS
1Safety ................................................................................................................5
2Menu..................................................................................................................6
2.1 Wireless transmission..............................................................................................6
2.2 GPS settings ............................................................................................. 6
2.3 Measurement settings.............................................................................................. 7
2.3.1 Mains frequency ............................................................................................................7
2.3.2 Calibration of the measurement clamp C-3 ....................................................................8
2.3.3 Earth resistivity settings...............................................................................................11
2.4 Meter settings.........................................................................................................12
2.4.1 LCD contrast................................................................................................................12
2.4.2 LCD Backlight..............................................................................................................12
2.4.3 AUTO-OFF settings.....................................................................................................12
2.4.4 Display settings............................................................................................................13
2.4.5 Date and time ..............................................................................................................13
2.4.6 Battery discharging......................................................................................................13
2.4.7 Programme update ......................................................................................................14
2.5 Language choice.................................................................................................... 14
2.6 Information on the manufacturer............................................................................14
3Measurements................................................................................................15
3.1 Measurement of resistance of earth connection and equipotential bonding (2P) ..15
3.2 Calibration of the test leads ...................................................................................16
3.2.1 Auto-zeroing on............................................................................................................16
3.2.2 Auto-zeroing off............................................................................................................17
3.3 Earth resistance measurement with 3-pole method (RE3P)................................... 18
3.4 Earth resistance measurement with 4-wire method (RE4P)...................................21
3.5 Earth resistance measurement with 3-pole method with additional clamp (RE3P+C)24
3.6 Earth resistance measurement with 3-pole method with ERP-1 adapter
(RE3P+ERP-1)........................................................................................................27
3.7 Earth resistance measurement with two-clamp method (2C).................................31
3.8 Earth impedance measurement with impulse method (RE4P ).............................33
3.9 Current measurement (I)........................................................................................37
3.10 Earth resistivity measurement (ρ) ..........................................................................38
4Memory ...........................................................................................................41
4.1 Saving of the measurement results in the memory................................................ 41
4.2 Memory erasing ..................................................................................................... 42
4.3 Memory browsing................................................................................................... 43
5Data transmission..........................................................................................44
5.1 Computer connection accessories.........................................................................44
5.2 Connection of the meter to a computer..................................................................44
5.3 Data transmission with Bluetooth module..............................................................44
6Power supply..................................................................................................46
6.1 Monitoring of the power supply voltage.................................................................. 46
6.2 Replacement of accumulators................................................................................ 46
6.3 Fuse replacement ..................................................................................................47
6.4 Charging of accumulators......................................................................................47
6.5 Discharging of accumulators..................................................................................49

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6.6 General principles regarding using Ni-MH accumulators .......................................49
7Cleaning and maintenance........................................................................... 50
8Storage........................................................................................................... 50
9Dismantling and disposal............................................................................. 50
10 Technical data................................................................................................ 51
10.1 Basic data...............................................................................................................51
10.2 Additional data........................................................................................................54
10.2.1 Influence of the serial interference voltage UZupon earth resistance measurements for
functions RE3P, RE4P, RE3P+C................................................................................... 54
10.2.2 Influence of the serial interference voltage UZupon earth resistance measurements for
earth resistivity function (ρ) ......................................................................................... 54
10.2.3 Influence of the auxiliary electrodes upon earth resistance measurements for
function RE3P, RE4P, RE3P+C .................................................................................... 54
10.2.4 Influence of the auxiliary electrodes upon earth resistance measurements for earth resistivity
function (ρ) ................................................................................................................... 55
10.2.5 Influence of the auxiliary electrodes upon earth resistance measurements by means of
the impulse method (RE4P )......................................................................................55
10.2.6 Influence of the interference current IZupon the result of the earth resistance
measurement for method RE3P+C .............................................................................. 55
10.2.7 Influence of interference current on the result of the earth resistance measurement for
two-clamp method (2C)...............................................................................................56
10.2.8 Influence of the relation of the resistance measured with clamp for the multiple earthing
branch to the resultant resistance (RE3P+C)...............................................................56
10.2.9 Additional uncertainties in accordance with IEC 61557-4 (2P)..................................... 56
10.2.10 Additional uncertainties in accordance with IEC 61557-5 (RE3P, RE4P, RE3P+C)....... 56
11 Accessories ................................................................................................... 57
11.1 Standard accessories.............................................................................................57
11.2 Optional accessories..............................................................................................58
12 Positions of the meter’s cover ..................................................................... 59
13 Manufacturer.................................................................................................. 59
14 Laboratory services ...................................................................................... 60

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The icon with the meter name is placed next to sections of the text that refer to specific
features of the device. All other parts of the text relate to all types of the instrument.
1 Safety
The MRU-200 / MRU-200-GPS meter has been designed to realize measurements whose re-
sults determine the safety conditions of the installation. Therefore, in order to provide conditions for
correct operation and the correctness of the obtained results, the following recommendations must be
observed:
Before you proceed to operate the meter, acquaint yourself thoroughly with the present manual
and observe the safety regulations and specifications determined by the producer.
The MRU-200 / MRU-200-GPS meter has been designed for the purpose of measurements of
earth connection and equipotential bonding, ground resistivity, as well as clamps current meas-
urements. 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 device must be operated solely by appropriately qualified personnel with relevant certificates
to realize measurements of electric installation. Operation of the meter realized by unauthorised
personnel may result in damage to the device and constitute a source of danger for the 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. exces-
sive humidity). If the meter has been transferred from a cool to a warm environment of
a high level of relative humidity, do not realize measurements until the meter has
been warmed up to the ambient temperature (approximately 30 minutes).
Before measurements may commence, make sure the test leads are connected to the appropri-
ate measurement sockets.
Do not operate a meter with an open or incorrectly closed battery (accumulator) compartment or
power it from other sources than those specified in the present manual.
The meter’s inputs are electronically protected from power surge, as a result for example, of ac-
cidental connection to the power supply source:
- for all input combinations –up to 276 V for 30 seconds.
Repairs may be realized solely by an authorized service point.
The device complies with the following norms; EN 61010-1 and EN 61557-1, -4, -5.
Note:
The manufacturer reserves the right to modify the appearance, accessories and
technical data of the meter.

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2 Menu
The menu is available at any position of the knob.
Press MENU.
Using buttons and highlight
the required position.
Press ENTER to select the option.
2.1 Wireless transmission
See chapter 5.3.
2.2 GPS settings
Using buttons , select GPS on
or off. Press ENTER to select the op-
tion.

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Note:
- Switching GPS on during the resistance (resistivity) measurement is signalling by the icon in the left
upper corner of the display. Searching GPS signal is indicated by the blinking icon. The icon stops
blinking and is displayed continuously, when the satellite signal is found.
2.3 Measurement settings
Using buttons and highlight
the required position.
Press ENTER to select the option.
2.3.1 Mains frequency
It is necessary to determine the frequency of the mains which is the source of potential interfer-
ence in order to select the appropriate frequency of the measurement signal. Solely measurements
based upon the correct frequency of the measurement signal will guarantee the optimum interference
filtering. The meter is adapted for filtering of interference from 16 2/3 Hz, 50 Hz, 60 Hz and 400 Hz
networks. It also has the function of automatic specification of the parameter in question (selection of
the mains frequency = AUTO), which is based upon the result of measurements of the interference
voltage realized before the earth resistance measurement. The function is active if the interference
voltage UN≥1 V. Otherwise the meter adopts the last frequency value selected from the MENU.

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Using buttons and select
the frequency and press ENTER to se-
lect the option.
2.3.2 Calibration of the measurement clamp C-3
The clamp bought apart for a meter that was purchased before must be calibrated before it is
used for the first time. It may be periodically calibrated in order to avoid the influence of the ageing
elements upon the resolution of measurements. The procedure of calibration must be realized also
after clamp has been replaced.
Calibration of hard clamps
Having read the preliminary infor-
mation ENTER.
Follow the displayed instructions.
Once the calibration has been successfully concluded, the following will be dis-
played.
The meter has determined the correction factor for connected clamp. The factor is saved in the
memory also when the power supply of the meter is off until the following successful calibration of the
clamp has been performed.

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Calibration of flexible clamps (using ERP-1 adapter)
After reading the intro-
ductory information
press ENTER.
Follow on-screen prompts displayed by the meter and short H and E sockets with
a wire.
Connect ERP-1 adapter to the terminal of the clamps.
Turn ERP-1 adapter ON.

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Connect flexible clamps to ERP-1 adapter.
Wrap the clamps around the wire referred to in sec. (up to 4 times).
Use FLEX and TURNS buttons on ERP-1 adapter to select the clamps
and number of wraps, according to the actual situation around the wire
referred to in sec. .
Press START button on MRU meter.
If the calibration is successful, you will see the following screen.
The meter has determined the correction factor for connected clamp. The factor is saved in the
memory also when the power supply of the meter is off until the following successful calibration of the
clamp has been performed.

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Note:
- Make sure the test lead passes centrally through the clamp.
Additional information displayed by the meter
Message
Cause
Procedure
ERROR: CLAMP NOT CONNECTED
OR NOT PUT ON WIRE
CONNECTED TO H AND E SOCKET!
The clamp is not
connected
Check whether the
clamp is connected
to the device or
whether it is placed
upon the test lead
used by the meter
to force the pas-
sage of current.
ERROR: WIRE NOT CONNECTED
TO H AND E TERMINAL!
CALIBRATION ABORTED. PRESS
ENTER
No wire
Revise the connec-
tions
ERROR: CALIBRATION
COEFFICIENT OUT OF RANGE.
CALIBRATION ABORTED. PRESS
ENTER
Incorrect calibra-
tion factor
Check the quality of
the connections
and/or replace the
clamp.
2.3.3 Earth resistivity settings
Using buttons , ,
and select the result and the
distance unit and press
ENTER to confirm.

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2.4 Meter settings
Use , to select an option.
Press ENTER to confirm.
2.4.1 LCD contrast
Using the buttons and set the contrast value and press ENTER.
2.4.2 LCD Backlight
Use , to set the time for LCD
backlight shut-off and press ENTER
to confirm.
2.4.3 AUTO-OFF settings
The setting determines the time before the automatic turning-off of the device when it is not in use.
Use buttons and to set the time or AUTO-OFF disable, press ENTER.

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2.4.4 Display settings
The setting permits to turn on/off the setting bar display. Use buttons and to set the dis-
play of the setting bar (measurement parameters), press ENTER.
Visible bar
Hidden bar
2.4.5 Date and time
Use buttons and to select
the value to be modified (Day,
month, hour, minute).
Use buttons and to set
the value. Once the date and
time have been set, press
ENTER.
2.4.6 Battery discharging
The procedure is fully described in chapter 6.5.

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2.4.7 Programme update
NOTE!
Before you proceed to programming, charge the accumulators.
During programming do not turn the meter off or disconnect the transmission ca-
ble.
Before you proceed to updating the programme, download from the manufacturer’s web page
(www.sonel.pl) the meter programming software, install it in the computer and connect the meter to
the computer.
Having chosen the Program update in the MENU, proceed in accordance with the instructions
displayed by the programme.
2.5 Language choice
Use buttons and to select **Language choice** in the main MENU and press ENTER.
Use buttons and to select the language and press ENTER.
2.6 Information on the manufacturer
Use buttons and in order to select Product info and press ENTER.

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3 Measurements
Note:
During measurements the status bar is displayed.
3.1 Measurement of resistance of earth connection and equipotential
bonding (2P)
Note:
The measurement complies with the requirements specified in the norm EN 61557-4
(U<24 V, I>200 mA for R≤10 Ω).
Turn the meter on.
Set the rotational
function selector at 2P.
Connect the object being measured to the terminals Sand Eof the meter.
The meter is ready for measurement.
The auxiliary display shows the value
of the interference voltage and its fre-
quency. The setting bat shows the
mains frequency set in the MENU.

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Press START In order for the test to
commence.
Read out the result.
The right side of the display
shows the date, time and GPS coordi-
nates.
The result is displayed for 20 s.
It may be displayed again when ENTER is pressed.
Additional information displayed by the meter
R>19,99kΩ
Measurement range exceeded.
UN>40V! and a con-
tinuous sonic signal

The voltage on the measurement points exceeds 40 V,
the measurement is blocked.
UN>24V!
The voltage on the measurement points exceeds 24 V
but lower than 40 V, the measurement is blocked.
NOISE!
The value of the interfering signal is too high,
the result may be distorted by additional uncertainty.
3.2 Calibration of the test leads
In order to eliminate the influence of the resistance of the test leads over the result of the meas-
urement, it is possible to realize its compensation (auto-zeroing). In order to do so the measurement
function 2P includes the AUTOZERO subfunction.
3.2.1 Auto-zeroing on
Turn the meter on.
Set the rotational
function selector at 2P.
Press F1.

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Follow the displayed instructions.
E S
CATI V 30 0V
Once the auto-reset function has concluded the following will be displayed:
Auto-zeroing is signalled by the legend AUTOZERO on the right-hand side of the display.
3.2.2 Auto-zeroing off
Turn the meter on.
Set the rotational
function selector at 2P.
Press F1.
Separate the test leads. Press START.
S
E
C AT I V 300 V
Once the auto-zeroing function has been turned off, the legend AUTOZERO will be no long-
er displayed.

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Note:
- It is sufficient to realize compensation once for the given test leads. It is also remembered once the
meter has been turned off, until the next successful auto-reset procedure.
3.3 Earth resistance measurement with 3-pole method (RE3P)
The basic kind of the earth resistance measurement is 3-pole measurement.
Disconnect the tested earth electrode for the object installation.
Turn the meter on.
Set the rotational
function selector at 3P.
E S H
CATIV 300V
Connect the current electrode driver into ground to the Hsocket of the meter.
Connect the voltage electrode driver into ground to the Ssocket of the meter.
Connect the tested earth electrode to the Esocket of the meter.
The tested earth electrode as well as the current electrode and voltage electrode
should be aligned.
The meter is ready for measurement.
The auxiliary display shows the value of
the interference voltage and its fre-
quency. The setting bar shows the
mains frequency set in the MENU.