Sonel MRU-200-GPS User manual

OPERATING MANUAL
EARTH/GROUND RESISTANCE METER
MRU-200-GPS
SONEL TEST & MEASUREMENT, Inc.
Santa Clara, Ca. USA
SONEL S. A.
Świdnica, Poland
Version 1.06 Apr 12, 2017

Please acquaint yourself with this manual in order to avoid measuring errors and problems related to
operation of the meter.
This device complies with part 15 of the FCC Rules. Operation is subject to the following two
conditions: (1) This device may not cause harmful interference, and (2) this device must ac-
cept any interference received, including interference that may cause undesired operation.
This equipment has been tested and found to comply with the limits for a Class A digital de-
vice, pursuant to part 15 of the FCC Rules. These limits are designed to provide reasonable
protection against harmful interference when the equipment is operated in a commercial envi-
ronment. This equipment generates, uses, and can radiate radio frequency energy and, if not
installed and used in accordance with the instruction manual, may cause harmful interference
to radio communications. Operation of this equipment in a residential area is likely to cause
harmful interference in which case the user will be required to correct the interference at his
own expense.
Responsible for conformity:
Sonel Test and Measurement, Inc.
3350 Scott Blvd, Bldg 55, Unit 1
Santa Clara, CA 95054
USA
www.SonelTest.com
[email protected]om
tel. [phone]
CAUTION:
Equipment changes or modifications not expressly approved by SONEL TEST &
MEASUREMENT Inc., the party responsible for FCC compliance, could void the user’s au-
thority to operate the equipment, and could create a hazardous condition.

MRU-200-GPS OPERATING MANUAL Version 1.06
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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 current clamps ................................................................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 ..........................................................................................12
2.4.5 Date and time .............................................................................................13
2.4.6 Battery discharge procedure......................................................................13
2.4.7 Software upgrade .......................................................................................13
2.5 LANGUAGE CHOICE ...............................................................................................14
2.6 INFORMATION ON THE MANUFACTURER................................................................14
3MEASUREMENTS...............................................................................................14
3.1 MEASUREMENT OF EARTH CONNECTION AND EQUIPOTENTIAL BONDING (2P) .......14
3.2 CALIBRATION OF THE TEST LEADS.........................................................................16
3.2.1 Auto-zeroing on..........................................................................................16
3.2.2 Auto-zeroing off..........................................................................................17
3.3 MEASUREMENT 3P................................................................................................17
3.4 MEASUREMENT 4P................................................................................................21
3.5 MEASUREMENT 3P +CLAMP .................................................................................24
3.6 MEASUREMENT 3P +ERP-1 ADAPTER ..................................................................28
3.7 TWO-CLAMP MEASUREMENT.................................................................................31
3.8 MEASUREMENT 4P (IMPULSE METHOD)..............................................................33
3.9 CURRENT MEASUREMENT .....................................................................................37
3.10 EARTH RESISTIVITY MEASUREMENTS.................................................................38
4MEMORY..............................................................................................................41
4.1 SAVING MEASUREMENT RESULTS IN THE MEMORY................................................42
4.2 ERASING MEMORY................................................................................................43
4.3 MEMORY BROWSING.............................................................................................44
5DATA TRANSMISSION......................................................................................45
5.1 COMPUTER CONNECTION ACCESSORIES.................................................................45
5.2 CONNECTION OF THE METER TO A COMPUTER.......................................................45
5.3 DATA TRANSMISSION WITH BLUETOOTH MODULE.................................................45

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6POWER SUPPLY..................................................................................................47
6.1 MONITORING OF THE POWER SUPPLY VOLTAGE .....................................................47
6.2 REPLACEMENT OF BATTERIES................................................................................47
6.3 FUSE REPLACEMENT..............................................................................................48
6.4 CHARGING OF BATTERIES ......................................................................................48
6.5 DISCHARGING OF BATTERIES .................................................................................49
6.6 GENERAL PRINCIPLES REGARDING USING NI-MH BATTERIES.................................50
7CLEANING AND MAINTENANCE...................................................................51
8STORAGE..............................................................................................................51
9DISMANTLING AND DISPOSAL......................................................................51
10 TECHNICAL DATA.............................................................................................51
10.1 BASIC DATA........................................................................................................51
10.2 ADDITIONAL DATA..............................................................................................55
10.2.1 Influence of the serial interference voltage UZupon earth resistance
measurements for functions 3P, 4P, 3P + clamp........................................55
10.2.2 Influence of the serial interference voltage VZupon earth resistance
measurements for function ρ.......................................................................55
10.2.3 Influence of the auxiliary electrodes upon earth resistance measurements
for function 3P, 4P, 3P + clamp.................................................................55
10.2.4 Influence of the auxiliary electrodes upon earth resistance measurements
for function ρ...............................................................................................56
10.2.5 Influence of the auxiliary electrodes upon earth resistance measurements
by means of the percussive method.............................................................56
10.2.6 Influence of the interference current IZupon the result of the earth
resistance measurement 3P+clamp ............................................................56
10.2.7 Influence of interference current upon the result of the earth resistance
measurement using double clamps .............................................................57
10.2.8 Influence of the relation of the resistance measured with clamp for the
multiple earthing branch to the resultant resistance (3P + clamp)............57
10.2.9 Additional uncertainties in accordance with IEC 61557-4 (2P) ................57
10.2.10 Additional uncertainties in accordance with IEC 61557-5 (3P, 4P,
3P + clamp)................................................................................................57
11 ACCESSORIES .....................................................................................................58
11.1 BASIC ACCESSORIES ...........................................................................................58
11.2 ADDITIONAL ACCESSORIES .................................................................................58
12 POSITIONS OF THE METER’S COVER .........................................................60
13 MANUFACTURER...............................................................................................60

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1 Safety
Electrical systems depend upon effective grounding for safety. The MRU-200-GPS meter has been
designed to perform earth ground resistance measurements to determine whether the grounding of
electrical systems meets electrical safety code requirements. For correct operation, and to ensure
the accuracy of test results, observe the following instructions:
•Before operating the meter, acquaint yourself thoroughly with this manual and adhere to all safe-
ty regulations and specifications.
•The MRU-200-GPS meter has been designed to test and measure the resistance of earth/ground
connections and equipotential bonding, measure ground resistivity, as well as measure current.
Any application that differs from those specified in this manual may result in damage to the de-
vice and injury to the user.
•The device must be operated only by appropriately qualified personnel trained in the safety of
electric installations. Operation of the meter by unauthorized personnel may result in damage to
the device and injury to the user.
•Using this manual does not exclude the need to comply with occupational health and safety regu-
lations and with relevant fire regulations. Before starting work in special environments, e.g. with
fire risks, explosive environments etc., always consult first with the person responsible for health
and safety.
•Do not operate the meter:
If the meter is completely or partially malfunctioning.
If the meter has damaged test leads or insulation.
If the meter has been stored in adverse conditions (e.g. excessive humidity or heat).
If the meter is transferred from a cold to a warmer environment with high relative humidity
do not perform measurements until the meter has been warmed up to the ambient temper-
ature (approximately 30 minutes).
•Before starting any measurements make sure the test leads are connected to the appropriate
measurement sockets and are fully inserted.
•Do not operate a meter with an open or partially closed battery compartment or power it from
sources other than those specified.
•The meter’s inputs are electronically protected from power surges, for example in the case of ac-
cidental connection to a power source, up to 276V for 30 seconds for all input combinations.
•Repairs must only be performed by Sonel or an authorized Sonel service center.
•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.
Note:
An attempt to install drivers in 64-bit Windows 8 and Windows 10 may result in
displaying "Installation failed" message.
Cause: Windows 8 and Windows 10 by default blocks drivers without a digital
signature.
Solution: Disable the driver signature enforcement in Windows.

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2 Menu
The menu is available at any position of the knob.
Press MENU.
Using and buttons 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:
- Enabling GPS during resistance (resistivity) measurement is indicated by the icon in the left up-
per corner of the display. Searching GPS signal is indicated by the blinking icon. The icon stops blink-
ing and is displayed continuously, when the satellite signal is found.
2.3 Measurement settings
Using and buttons highlight
the required position.
Press ENTER to select the option.
2.3.1 Mains frequency
Before making any ground resistance measurements, the local mains frequency must be set in
the meter since it is the source of potential interference with resistance measurements due to stray
electrical fields. The meter will pick the appropriate frequency of its measurement signal to guarantee
the optimum interference filtering. The meter is adapted for filtering of interference at 16 2/3Hz, 50Hz,
60Hz and 400Hz. The meter can automatically select the filtering parameter (selection of the mains
frequency = AUTO), by running a series of measurements to determine the level of local interference
prior to performing the earth resistance measurement. The AUTO function is active if the interference
voltage is ≥ 1V. Otherwise the meter adopts the last frequency value selected from the MENU.

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Using and buttons select
the desired frequency and press ENTER.
2.3.2 Calibration of the current clamps
Current measurement is made using a rigid current clamp or flexible Rogowski current probe.
The clamp or probe must be calibrated before using for the first time. It is advisable to periodically
calibrate the clamp or probe so age effects will not influence the resolution of measurements. Re-
calibrate again after a clamp or probe has been replaced.
Calibration of hard clamps
Select Clamp calibration in 2.3 above
and press ENTER.
Follow the instructions.
When calibration completes the display shows:

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The meter has determined the calibration coefficients for the connected clamp or probe. This da-
ta is saved in the memory and is retained when the meter is switched off. In any subsequent calibra-
tion of a clamp or probe the calibration data will be updated.
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.
Connect flexible clamps to ERP-1 adapter.

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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 E –H passes through the center of the clamp or probe.
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 Ground resistivity settings
Using , , and
buttons select the desired op-
tions for distance units and
press ENTER.

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2.4 Meter settings
2.4.1 LCD contrast
Using and buttons set the contrast and press ENTER.
2.4.2 LCD Backlight
Use , buttons to set the time for
LCD backlight to remain on (Always)
or shut-off time, and press ENTER.
2.4.3 AUTO-OFF settings
To set the automatic turn-off of the device use and buttons to set the display ON time, or
AUTO-OFF disable, then press ENTER.
2.4.4 Display settings
To turn the Settings bar display that shows measurement parameters on or off use and but-
tons to select Yes or No, press ENTER.

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Visible Settings bar
Hidden Settings bar
2.4.5 Date and time
Use and buttons to
change day, month, hour, or
minute settings.
Use and buttons to set
values. Once the date and time
have been set press ENTER.
2.4.6 Battery discharge procedure
The procedure is fully described in chapter 6.5.
2.4.7 Software upgrade
NOTE!
Before updating the firmware charge the batteries.
Do not turn the meter off or disconnect the USB cable during the firmware update.
Before updating the meter firmware download the latest meter software version from
www.sonel.pl or www.soneltest.com. Save the file in the computer in a known folder or location, and

MRU-200-GPS OPERATING MANUAL Version 1.06
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then connect the meter to the computer. Select Software upgrade in the MENU and follow the on-
screen instructions.
2.5 Language choice
Use and buttons to select **Language choice** in the main MENU and press ENTER.
Use and buttons to select the language and press ENTER.
2.6 Information on the manufacturer
Use and buttons in order to select Product info and press ENTER.
3 Measurements
Note:
During measurements the status bar is displayed.
3.1 Measurement of earth connection and equipotential bonding
(2P)
Note:
The measurement complies with the requirements specified in the norm
EN 61557-4 (U<24V, I>200mA or R≤10Ω).
Turn the meter on.
Set the rotary
function selector switch at 2P.
Connect the earth ground system to be measured to the terminals Sand Eof the
meter.

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The meter is ready for measurement.
The auxiliary display shows the value
of the interference voltage and its fre-
quency. The settings bar shows the
mains frequency previously set in the
MENU in 2.3.1 above.
Press START to begin the test.
View the result.
The right side of the display shows the
date, time, and GPS coordinates.
The result is displayed for 20s.
It may be displayed again by pressing ENTER.
Additional information displayed by the meter
R>19,99kΩ
Measurement range exceeded.
VN>40V! and a con-
tinuous audio tone

The voltage on the measurement points exceeds 40V,
the measurement is cancelled.
VN>24V!
The voltage on the measurement points exceeds 24V
but lower than 40V, the measurement is cancelled.
NOISE!
The value of the interfering signal is too high,
the result may be distorted by additional uncertainty.

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3.2 Calibration of the test leads
In order to eliminate the resistance of the test leads, use the auto-zeroing function to compensate
for test lead resistance. The measurement function 2P includes the AUTOZERO sub-function.
3.2.1 Auto-zeroing on
Turn the meter on.
Set the rotary
function selector switch at 2P.
Press F1.
Follow the displayed instructions.
E S
CAT IV 30 0V
Once the auto-zero compensation has concluded the following will be displayed:
Auto-zeroing enabled is indicated by AUTOZERO shown on the right-hand side of the
display.

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3.2.2 Auto-zeroing off
Turn the meter on.
Set the rotary
function selector switch at 2P.
Press F1.
Separate the test leads. Press START.
S
E
C AT I V 300V
If auto-zero compensation is disabled, AUTOZERO will be not be displayed on the right-
hand side of the display.
Note:
- Auto-zero compensation needs only be enabled once for a given set of test leads. The last compen-
sation values are remembered when the meter is turned off, until the next successful auto-reset pro-
cedure.
3.3 Measurement 3P
The basic kind of the earth resistance measurement is three-pole measurement.
Disconnect the earth ground electrode for the installation that is to be tested.

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Turn the meter on.
Set the rotary
function selector switch at 3P.
E S H
CAT IV 300V
Drive the current probe into the ground and connect to the Hsocket of the meter.
Drive the voltage probe into the ground and connect to the Ssocket of the meter.
Connect the earth ground electrode under test to the E socket of the meter.
Align all electrodes in a straight line.
The meter is ready for measurement.
The auxiliary display shows the value of
the interference voltage and its fre-
quency. The settings bar shows the
mains frequency set in the MENU.
Press F1 to select the measuring
voltage.