Phenix Technologies MRM10E User manual

1
MRM10E
User’s Guide
MRM10E
Digital Micro-Ohmmeter
GU-1522
Copyright © Phenix Technologies. All rights reserved.
Rev 6/22/2018

2
MRM10E
WARNING !!
Complete Grounding of this unit is necessary for the safe operation of this
equipment. Disconnect inputs before ungrounding this equipment.

3
MRM10E
SAFETY PRECAUTIONS
•This equipment should be operated only by qualified and trained personnel, closely observing the
corresponding safety regulations and instructions contained in the User guide.
•Check that the item to be measured is voltage free.
•Before starting with the measurements, be sure that the battery is well charged and that the line voltage is
between specified limits.
•DO NOT connect or disconnect the test leads during the measurement.
•There are no adjustable parts or parts that can be replaced by the user within the equipment. Taking out the
Control Panel to have access to the internal parts is dangerous as there are high voltages inside
•capable of causing fatal accidents.
•Cleaning of this instrument should be carried out using a soft cloth and cleaning liquid, after verifying that it
doesn't attack the plastic parts used in the case and in the Control Panel of this equipment.
This equipment should be used only by a trained and competent person, strictly applying suitable safety rules.
Used symbols
Caution, refer to User Guide.
Equipment complies with current EU Directives.
The rubbish bin with a line through it means that in the European Union,
the product must undergo selective disposal for the recycling of electric
and electronic material, in compliance with Directive WEEE 2002/96/EC.

4
MRM10E
Table of Contents
1. Description...............................................................................5
1.1. Operating principle .............................................................5
2. Control panel............................................................................6
3. Power supply............................................................................7
3.1. Battery condition................................................................. 7
3.2. Battery charger...................................................................7
4. Measurement...........................................................................8
5. Messages.................................................................................9
6. Some notes about accuracy.....................................................9
7. RS232 output......................................................................... 10
8. Cleaning.................................................................................10
9. Replacement fuse ..................................................................10
10. Technical specifications........................................................ 11

5
MRM10E
1. Description
The MRM-10E micro-ohmmeter is a portable, microprocessor-controlled instrument, used to accurately
measure very low contact resistances of breakers and switches, busbars, transformers, and engine windings,
etc, with test currents from 1mA to 10A.
•Kelvin architecture (four-terminal method).
•Digital reading, alphanumeric display.
•Up to 4½ digits readings.
•Powered by rechargeable battery or mains supply.
•0.1µΩ resolution.
•200Ω maximum reading.
1.1. Operating Principle
This device uses the Kelvin Bridge architecture, with four terminals, avoiding testing leads resistance to cause
error during measurement. The operator may choose test current and the reading is obtained by comparison
through internal high-stability standards. The result appears in the alphanumeric display that is very easy to
read.

6
MRM10E
2. Control Panel
1. RS-232 Data Output 13. Test Current Control
2. Fuse 14. Battery Key (measures battery charge condition)
3. Power Cord Connector 15. STOP Key
4. Ground 16. START Key
5. Current Terminal (C+) 17. Hold Key (retains last measurement in display)
6. Potential Terminals (P+ / P-)
7. Current Terminal (C-)
8. ON / OFF Switch
9. Displays both measured resistance value
& messages for operator
10. ON Indicator LED
11. Battery Charge Iindicator
12. Range & Test Current Selector
1
2
3
4
8
5
6
7
9
10
11
12
13
14
15
16
17

7
MRM10E
3. Power Supply
Mains supply or internal battery powered
Battery: rechargeable, 12 V –7 Ah.
Mains: 220 –240 V~ 50 Hz
At the end of the useful life, the battery must be recycled or disposed of properly
to protect the environment.
3.1. Battery Condition
The charge condition of the battery can be verified before or during the resistance measurement. To achieve
that, the operator has to press the battery key while the equipment is turned on. The bar graph shows remaining
charge as a percentile value. If during measurement the charge of the battery achieves a critical level, the display
will show the BAT message notifying that the charge level is low. After a few minutes the measurement will be
automatically interrupted to preserve the battery from a deep discharge that is prejudicial for its expected useful
life.
3.2. Battery Charger
The built-in battery charger is always active when the equipment is connected to the mains supply, even if the
On/Off switch is turned off.
Charging Procedure:
•Check that the On/Off switch is in Off position.
•Connect the equipment to the mains supply.
•The battery charge indicator will keep on lighting with a red light up to completing the charge. At that point,
it will change to a green light, and remain until the equipment is disconnected from the mains supply.

8
MRM10E
4. Measurement
CAUTION: Check that the item to be measured is voltage free.
1. Before turning the equipment On, connect the test leads to the item to be measured and to the front panel
terminals.
(The alligator clamps in the drawing are only for illustration.)
2. Using the test current selector, choose the range and the current to be used.
3. Choose the power supply to use. If you are going to use the battery, advance to the following point. If you
are going to use the mains supply, plug the power cord into the connector.
4. Switch the equipment On using the On/Off switch.
5. The PRESS START message will appear showing that measurement can be started. Press the Start key.
Depending on the position of the test current control, the LOW CURRENT message will turn up.
6. Turning the test current control clockwise increases the current. Adjust this control until obtaining the
desired value or until the current indicator (bar graph) indicates 100%. The bar graph will show the test
current value as a percentage of the nominal value selected by using the test current selector.
7. The lowest current for measuring is 10% of the nominal value. It is important to consider that the
measurement errors increase while test current decreases. The equipment accuracy is specified for test
currents higher than 80%.
8. The display will show the resistance value measured and the corresponding unit (Ω [ohms], mΩ [milli-
ohms] or µΩ [micro-ohms]).
9. The value can be retained in the display by pressing the hold key. Pressing this key again, the value will
be released.
10. Press the Stop key to finish the measurement. Do not turn Off the equipment without pressing the Stop
key.
11. Finally, when finishing measurements, turn the equipment Off using the On/Off switch.
CAUTION: Do not connect or disconnect the test leads during the measurement.
Power Cord Connector

9
MRM10E
5. Messages
MRM-10E
When turning the equipment On using the On/Off switch, this introductory message appears briefly. During
that time, the equipment carries out functional checking.
WAIT...
This message appears each time the equipment needs to adjust any parameter to optimize the readings.
PRESS START
The equipment is ready to start a measurement, thus the operator has to press the Start key.
LOW CURRENT
It shows that the test current is not enough to carry out the reading. It appears at the beginning of each test
and it keeps on being there up to the operator rotates the test current control clockwise, as necessary for the
test current to be higher than 10 % of the nominal current in the scale. The inappropriate connection of the
cables may cause a difficult circulation of test current. If this message keeps on being displayed, please check
that the current cables are connected appropriately.
OVERRANGE
It indicates that the measured resistance is higher than the maximum value readable in the selected range.
H
Indicates that the value is the one retained in the memory when pressing the hold key.
BAT
It shows that the battery is discharged. It is necessary to recharge the battery.
6. Some Notes About Accuracy
To obtain the specified accuracy, the operator has to adjust the test current to a value higher than the 80% of
the nominal value. If it is necessary, it is possible to use a lower current, but by doing this the accuracy will be
affected.
MRM-10E has an auto-compensation system that automatically eliminates the error produced by internal
offset. Thus, it is not necessary to carry out measurements by reversing the polarity to compute the average
value. Nevertheless, if the operator suspects that there is a difference of temperature between the contact
points that may generate thermoelectric voltages, it is necessary to carry out two measurements by reversing
the current cables and so, the circulation sense of the current through the resistance under measurement. The
resistance value to be measured will be the average between the values in one sense and in the contrary
(direct and inverse current).

10
MRM10E
7. RS-232 Output
The RS-232 data porton the control panel can be used to register measurements in a serial printer or data
collector. The outputs are the following ones:
Pin 2: Rx ; Pin 3: Tx ; Pin 5: Gnd;
Rate: 4800 bps
8 bits - no parity - 1 stop bit (8,n,1)
Note: To assure the compatibility with most printers available in the market, the resistance units are shown
with the following symbols:
uR = micro-ohm
mR = milli-ohm
R = ohm
8. Cleaning
CAUTION: Before cleaning, ensure that the unit is Off and removed from power
connection.
The panel, terminals, and connectors of the equipment must stay dry and clean. Clean using a damp cloth in
water and a soft detergent or isopropyl alcohol (be sure that the products to be used for cleaning do not affect
plastic goods).
9. Replacement Fuse
To check the instrument fuse, remove it with a screw driver. If the fuse is ruptured, replace it by another with
the following specifications:
Fuse Schurter, model SPT 5x20 (Time-lag) 5A/250V. High breaking capacity.