PCE Instruments PCE-MO 3001 Users guide

PCE-MO 3001

MICROOHM METER

INSTRUCTION MANUAL

Index

Page

1. Safety Rules..........................................................

2. Safety Check.........................................................

3. General Description..............................................

4. Operating Instructions...........................................

5. Display .................................................................

6. Specications........................................................

7. Cleaning................................................................

8. Inside LID Instructions Label.................................

9. 4 Terminals Measurement.....................................

10. 3 Terminals Measurement.....................................

11. 2 Terminals Measurement.....................................

12. Typical Applications...............................................

13. Working Principle of The Instrument.....................

14. Charging The Battery............................................

15. Fuse Replacement................................................

16. The Storage and Maintenance of Batteries...........

17. Limited Warranty...................................................

1

2

3-4

5-8

9

10-11

11

12

13

14

15

16

17

18

19

19

20

REMEMBER TO CHARGE THE BATTERY!

ALWAYS recharge the battery when the Low Battery info appears on
the display. Leaving the battery uncharged for a long period of time
may affect the lifespan of the battery.

Charging interval: Every 3 months

1. Safety Rules

CAUTION RISK OF ELECTRIC

SHOCK

This tester has been designed with your safety in mind. However,
no design can completely protect against incorrect use. Electrical
circuits can be dangerous and/or lethal when lack of caution or poor
safety practices are used.

Do not carry out eld measurements on either the power system

grounding or anything connected to it, without ensuring the contact
or circuit under test is fully isolated.

Take all the necessary precautions. Do not exceed the limits of
this instrument. The circuit to be tested must be de-energized and
isolated before connections are made to it.

Do not use test leads, probes or crocodiles/alligators clips that
are dirty, damaged or have broken or cracked insulation. Such
accessories should be removed and repaired Immediately.

Always disconnect the test leads before replacing any fuse. Always

replace the fuse with the type specied and ensure that they are
correctly tted.

Double check your settings and leads connections before
measuring. Make a sketch to ensure proper operation and the
principle of measurement is correct and well understood.

Do not touch any exposed wiring, connections or other "live" parts of

an electrical circuit. If in doubt, check the circuit for no voltage rst

before testing it.

Disconnect the tester from any external circuit when charging the
battery.

CAUTION READ THE MANUAL

Follow the instructions in the Manual for every measurement. Read
and understand the general instructions before attempting to use
this tester.

-1-

2. Safety Check

Before using the tester check the condition of the battery. This is
done by switching the tester ON.

If the BAT LOW symbol appears the battery needs charging.

When charging the battery, changing a fuse, or removing the cover
to access the internal circuitry, always disconnect the test leads.

When replacing the fuse use only the type specied and insert

correctly in the fuse holder.

Double check the settings, and lead connections before making
measurements.

DON'T TOUCH

Don't touch exposed wiring, connections or other "Live" parts of an

electrical circuit. If in doubt, check the circuit rst for voltage before

touching or connecting to it.

Do not use cracked of broken test leads.

THIS INSTRUMENT SHOULD ONLY BE USED BY A COMPETENT,

SUITABLY TRAINED PERSON.

REMEMBER

SAFETY IS NO ACCIDENT

CAUTION RISK OF ELECTRIC SHOCK

CAUTION READ THE MANUAL

-2-

3. General Description

The Digital Low Resistance Ohm and Contact Meter is a battery
(rechargeable) operated instrument which supply a constant current
to the circuit under test, with which, stable, accurate measurements
of very low resistance (down the micro ohm) can be made, still, over
a wide range of values.

Resolution on the lowest range is 1µohm and on the highest range,
100 milli-ohm.

The meter has 6 measuring ranges, from 2000 micro-ohm to 200.0
ohms.

Measurements are displayed on a large 3½ digit custom liquid
crystal display.

This instrument is powered from it's internal rechargeable battery.

It has a regulated DC constant current source with current of 10mA
100mA and 1A.

During recharge of the battery, the instrument is disconnected from
the battery. Measurements can only be made while not charging.

The instrument supply the current to the resistance being measured
through the C1 and C2 terminals (C1 being +, C2 being -).

The voltage drop across the resistance under test is measured by
the potential terminals P1 and P2 (P1 being +, P2 being -).

Should the current regulation drops out, the RC Led will lit, indicating
that the resistance in the current circuit is too high. (Lowering
the current by selecting a higher resistance range can solve the
regulation.)

Should the RP Led lights up, it mean that the voltage measured on
the resistance is too high, and therefore over-range.

(Lowering the current by selecting a higher resistance range can
solve the over voltage on RP)

The resistance can only be measured precisely when the RP and
RC LEDs do not lit. If anyone of these LEDs lights up, then the
measurement will be inaccurate.

-3-

The I

LED is the LED indicating the Constant Current Source

CCS

being OFF. When this led lights up, it means that the current
injection has been switched OFF (could be over-temperature).

The METER has a built-in custom 3½ digit liquid crystal display
which can be viewed in most lightning conditions.

This display indicates the conditions (Hold, m, buzzer, polarity
condition of load, + or -, automatic decimal point change with range
selection).

The ranges are selected by the 'SCROLL / RANGE' push button.

A test is initiated by pressing the TEST/STOP push-button.

The instrument takes measurements for 10 seconds if the TEST/
STOP push-button is depressed for less than 3 seconds (EnerSave
mode).

If the TEST/STOP push button is depressed for more than 3
seconds, the test will carry on for 60 seconds.

The tester switch "OFF" completely when the OFF push button is
pressed, but The METER has also an auto-off feature

The tester "Hold" the last reading before stopping the test.

The tester is fuse protected and has a crowbar between C1 and C2.

This crowbar is activated by voltage. If the voltage is too high, that
crowbar will blow the CF fuse automatically to interrupt the circuit.

The voltage between P1 and P2 is also protected for over voltage.
If that voltage is too high, the crowbar will blow the PF fuse
automatically to interrupt the circuit.

The tester has a temperature shut down.

The temperature sensing is done on the current regulation transistor.

Should this over-temperature alarm be activated, the I

OFF LED

CCS

will lit, indicating the current has been shut down.

Allow the instrument to cool down for a while before proceeding
further.

-4-

4. Operating Instructions

The connector for the Battery charger can
accept AC or DC signals up to a maximum of

22Vdc. There is a full bridge rectier inside

the tester, as well as a regulated battery
charger. The battery is charged to 13.8V.
We recommend the use of the power supply
(step down transformer) which is supplied
with this tester. The light on the power supply
transformer will lights up when the battery
charger is working.

Depressing the ON key will switch the tester
"ON" . At switch "ON", the tester retrieve the
last settings utilized. These are the current/
range settings which were last utilized by the
Instrument. At Switch ON, the buzzer sounds

to conrm the "ON" status.

Depressing the OFF key will switch the
instrument "OFF". This "OFF" switch is
software operated. At switch OFF, the buzzer

will sound to conrm the "OFF" condition is

processed by the micro. Next, the tester will
be switched OFF completely.

Depressing the SCROLL/RANGE key will
stop the test, if in progress, then will change
the scale, to the higher ohmic scale (going
down on the tester). Depressing the key again
will move to the next range etc... Each range
illuminate it's cores-ponding led.

-5-

Provided, the TESTER is ON, when the
TEST Start/Stop is depressed, the selected
TEST will start (if stopped) or stop (if in
progress). The TEST Start/Stop also has the
EnerSave features. What that mean, is that
if you depress the TEST Start/Stop key for
more than 3 second, while starting the test,
then, the test will be carried up to a duration
of 1 minute (long Test). But, if you depress
the TEST Start/Stop Key for less than 3
second, or just depress it, than the instrument
will enter the EnerSave mode, and the test
duration is limited to about 10 seconds. In
both cases, the Test is stopped automatically
by the instrument, but the user can always
override the auto-stop, by depressing the
TEST Start/Stop key at any time, in any mode.

Range Indication by LED:
Test Current 1A

Resistance 0-2.000mΩ (2000uΩ)

When this LED lights up, the instrument

will measure up to 1999uΩ and will display

it as milli ohms. The resistance which can
be measured using this scale/range is from

0.000m to 1.999mΩ.

Range Indication by LED:
Test Current 1A

Resistance 0-20.00mΩ

When this LED lights up, the instrument will

measure up to 19.99mΩ and will display it as

milli ohms.
The resistance which can be measured using

this scale/range is from 00.00m to 19.99mΩ.

-6-

Range Indication by LED:
Test Current 1A

Resistance 0-200.0mΩ

When this LED lights up, the instrument will

measure up to 199.9mΩ and will dis and will

display it as milli ohms. The resistance which
can be measured using this scale/range is

from 000.0m to 199.9mΩ.

Range Indication by LED:
Test Current 100mA

Resistance 0-2000mΩ

When this LED lights up, the instrument will

measure up to 1999mΩ and will display it as

milli ohms.
The resistance which can be measured using

this scale/range is from 0000m to 1999mΩ.

Range Indication by LED:
Test Current 100mA

Resistance 0-20.00Ω

When this LED lights up, the instrument will

measure up to 19.99Ω and will display it as

ohms.
The resistance which can be measured using

this scale/range is from 00.00 to 19.99Ω.

Range Indication by LED:
Test Current 10mA

Resistance 0-200.0Ω

When this LED lights up, the instrument will

measure up to 199.9Ω and will display it as

ohms. The resistance which can be measured
using this scale/range is from 000.0 to

199.9Ω.

-7-

Main Status Indicators by LED:

Constant Current Source Indicator.
When this LED lights up, the Constant Current
Source is shut down.
The Constant Current Source is shut down
when the test is not in progress.
While in progress, the Constant current
Source LED does not light up.
After Switching the Instrument ON, the I
OFF led will lights up.
When a test has stopped, the I

OFF led will

CCS

lights up.
In case of Over-Temperature, the I

OFF led

CCS

will lights up.

The RC indicator LED lights up, when the
resistance between the current terminals is
too high for the constant current source to

regulate. This indicator is only signicant while

the test is in progress. You can try to lower the
test current if it comes on while testing.

The RP indicator LED lights up, when the
potential between the potential terminals is too
high. This also can be due to the resistance
under test being too high for that current
range. Try to lower the current or increase the

resistance range. (only signicant while the

test is progress).

CCS

-8-

5. Display

The HOLD Sign indicator comes on when the
readings are held.
This happens:

At switch "ON", as no reading has been done yet,
so the display is on Hold with whatever value when
TEST stops. When Scroll/Range is depressed while
a test is in progress.

The Sound Sign indicator is shown
while the buzzer is working. That mean that when
the buzzer sound, the sign is ON

The Low Battery Sign indicator is showing when the
battery need charging.

The negative sign is shown when the test leads are
reversed. This instrument is calibrated while the Test
leads are in the Correct polarity.

-9-

6. Specications

ELECTRICAL

Range:

0 to 2.000mΩ in steps of 1uΩ
0 to 20.00mΩ in steps of 10uΩ
0 to 200.0mΩ in steps of 100uΩ
0 to 2.000Ω in steps of 1mΩ
0 to 20.00Ω in steps of 10mΩ
0 to 200.0Ω in steps of 100mΩ

Accuracy:

Resistance Ranges

Maximum Output Voltage 10V

Response Time 1secs nominal

Voltage Withstand 6V AC between any two terminals

Battery Low Indication
point

0 to 2.000mΩ => ± (5%rdg + 5 dgt)
0 to 20.00mΩ => ± (4%rdg + 4 dgt)
0 to 200.0mΩ => ± (4%rdg + 4 dgt)
0 to 2.000Ω => ± (3%rdg + 4 dgt)
0 to 20.00Ω => ± (2%rdg + 4 dgt)
0 to 200.0Ω => ± (2%rdg + 4 dgt)

Test Current:

2.000mΩ to 200.0mΩ : 1A ± 3%

200.0mΩ to 20.0Ω : 100mA ± 2%

200.0Ω : 10mA ± 1.5%

10V nominal

MECHANICAL

Size 330 x 260 x 160 mm

Material Polycarbonate/ABS

Weight (less carrying case)

Display Custom Liquid Crystal

ENVIRONMENTAL

Operating temperature Range

Storage Temperature -20°C to +70°C

Approx. 3200 g (with battery)

-15°C to +55°C

-10-

GENERAL

Safety

Battery 12V rechargeable 12V 2.3Ah

Fuses

SPARES AND ACCESSORIES

Accessories

EN 61010-1
EN 61326-1

1 X 500mA (Potential Fuse)
1 X 2A (Current Fuse)
Slow Blow, 250V type

Test Leads
Fuses 1: 500mA / 250V
Fuses 2: 2A / 250V
Battery: 12V Rechargeable
Instruction Manual

7. Cleaning

Clean the instrument case with an anti-static cleaner and wipe with
dry cloth.

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8. Inside LID Instruction Label

-12-

9. 4 Terminals Measurement

Using the 4T method, R

the readings R

and R

P1L

, R

C1L

P2L

does not affect

C2L

are negligeable as no

current goes into P1 and P2.

For measuring low to very low resistance (contact resistance), this
is the preferred measuring method because the resistance of the
test leads does not have an effect (negligeable) on the measuring
results.

R

is the Resistance of the Current Lead going to C1

C1L

R

is the Resistance of the Current Lead going to C2

C2L

R

is the Resistance of the Current Lead going to P1

P1L

R

is the Resistance of the Current Lead going to P2

P2L

The input impedance between P1 & P2 is 10M ohms, so because
the current being drawn by these pins is so small, the voltage loss
on R

P1L

+ R

is very small too.

P2L

So the loss in these potential wires is not even inuencing the

voltage measured on P1 P2.

Due to the fact that the tester has a constant current source,

the current owing between C1 to C2 is constant. Provided the

resistance of the current leads are reasonably low (low enough
for the current regulation to still be able to regulate properly), the
measurement using this method will give the bet results of all the
methods.

-13-

10. 3 Terminals Measurement

Using the 3T method, R

the readings R

are negligeable as no

P2L

current goes into P2 but R

does not affect

C2L

is added to RX.

P1L

For measuring low resistance, this measuring method can be utilized
C1 and P1 terminals are shorted at the tester.

R

is the Resistance of the Current Lead going to C2

C2L

R

is the Resistance of the Current Lead going to P1

P1L

R

is the Resistance of the Current Lead going to P2

P2L

In this case, R

is not negligeable anymore, because the current

P1L

going into this lead is the constant current, which is high. So the
error of R

exist and in reality, this error is added to Rx. So, if the

P1L

resistance under test is much higher than the test lead, than this
method could be accepted.

This method is a simplied method of measurement.

Always, keep in mind, that R

is your error resistance.

P1L

-14-

11. 2 Terminals Measurement

Using the 2T method, the resistance of the test

leads are added to the readings. This is not

recommended for low resistance and long leads.

For measuring resistance, this measuring method can be utilized C1
and P1 terminals are shorted, P2 and C2 are shorted at the tester.
R

is the Resistance of the Current Lead going to P1

P1L

R

is the Resistance of the Current Lead going to P2

P2L

In this case, R
current going into these leads is the constant current, which is high.
So the error of R
to Rx. So, if the resistance under test is much higher than the test
leads, than this method could be accepted.

and R

P1L

P1L

are not negligeable anymore, because the

P2L

+ R

exist and in reality, this error is added

P2L

This method is a simplied method of measurement.

Always, keep in mind, that R

and R

P1L

are your error resistance.

P2L

This is not an accurate method and is not recommended, unless the
resistance is above 10 ohms.

-15-

12. Typical Applications

Measuring the contact resistance of circuit breakers.

Measuring Circuit breaker resistance is very important. If the
resistance of a circuit breaker become too large, than, the current
going through will warm up the circuit breaker (RxI2) and it could

start a re. If the resistance is too high, the power transferred to the

load could be too low and the load could malfunction.

Measuring the bonding of welding points.

Welding point or good connections are the basic of good earthing
and continuity in electrical wiring. This is specially true for protection
conductors. For example lightning protection conductors requires
extremely low resistance to conduct the lighting into the earth.
On aircrafts, the lightning must be conducted from one side to the
other side of the wings by low resistance conductors, instead of
going through the frame of the plane.
These resistance can be checked with this instrument.

Measuring the contact resistance of bolted conductors.

Similarly to bonding of welding points, some times, connections are
done using bolted conductors or using bolted lugs. These contact
resistance can be tested and measured with this instrument.

Measuring the copper resistance fo transformers.

The low resistance of transformer winding can be measured with this
instrument, to ascertain the ohmic component of the winding.
Measuring the earthing conductor resistance.
Earthing conductor Resistance is one of the most important
component of an electrical protection system. The measurement of
its value can be done using this instrument.

Measuring the earth conductor resistance.

Earthing conductor Resistance is one of the most important
component of an electrical protection system. The measurement of
its value can be done using this instrument.

Measuring the earth mat connections resistance.

The Earth mat connections resistance is done using the 4 wires
method, to ensure accuracy of these low resistance.
The earth mat is connected using very low resistance connections to
ensure fault current are passed without or very little resistance.

-16-

It is very important to measure these connections, using the 4 wires
methods, to ensure added accuracy and remove errors from the
test leads. Earth mat rely completely on good connections and low
resistance for their effectiveness. Their regular testing and correct
measurement will ensure proper working of the protection systems.

13. Working Principle of The Instrument

This Test Instrument has a regulated current source which injects its
regulated DC current into the low resistance to measure.

The current is injected into the resistance under test through the
terminals C1 and C2.

This Test Instrument has a DC voltmeter which measure the DC
voltage across the resistance to be measured.

The Voltmeter connections are on P1 and P2.

The display shows a number proportional to the ratio of the current

injected and the voltage measured. R=U/I

When the user change the range of the instrument, the current
regulation change, from 10mA to 1A, according to the user selection.

The current selected is shown on its corresponding LED, on the left
of the facia.

When selecting a current, the range is automatically selected by the
processor.

So, selecting a current and a range has the same function and is
using one push button.

The Instrument is processor driven and the software takes care of
the different switching elements inside the circuit.

The product has protection against over-voltage and over­temperature.

-17-

14. Charging The Battery

This instrument has an internal rechargeable battery.

Only use the supplied battery charger to charge it.

To avoid safety issues, do not connect to a device to test or use
while re-charging the battery.

However, the internal circuitry will disconnect the measuring and
testing circuitry while charging, it is recommended to make sure that
no test leads are connected while charging the internal battery.

Do not try to by pass that circuit, or warranty will be void.

The battery has a maximum life of about one or 2 years, depending
of its maintenance.

Only replace with the same type of battery.

REMEMBER TO CHARGE THE BATTERY!

ALWAYS recharge the battery when the Low Battery info appears on
the display. Leaving the battery uncharged for a long period of time
may affect the lifespan of the battery.
Charging interval: Every 3 months

-18-

15. Fuse Replacement

REPLACING THE POTENTIAL FUSE

The PF fuse mean it's the Potential Fuse.
The Potential Measurement Circuit of this instrument is fuse
protected.
Only replace with the same type as the original fuse.
The Potential Fuse is 500mA Slow Blow type.

EPLACING THE CURRENT FUSE

The CF fuse mean it's the Current Fuse.
The Current Injection Circuit of this instrument is fuse protected.
Only replace with the same type as the original fuse.
The Current Fuse is 2A Slow Blow type.

16. The Storage and Maintenance of the rechargeable
battery

● The storage temperature range : -15°C~40°C

● Fully charge the rechargeable battery before storage ; if not, the

battery life will be shorter.

● The rechargeable battery under storage at ambient temperature

of 25°C should be recharged every six months to maintain their
quality, performance and reliability.

Charge Retention (shelf life) at 20°C

1 month 92%
3 month 90%
6 month 80%

-19-

17. Limited Warranty

We warrant the product manufactured by us to be free from defective
material or factory workmanship and agree to repair or replace this
product which, under normal use and service, disclose the defect
to be the fault of our manufacturing, with no charge for parts and
service. If we are unable to repair or replace this product, we will
make a full refund of the purchase price.

Consult the user's manual for proper instruction regarding use of this
instrument.

Our obligation under this warranty is limited to repairing, replacing
or making refund of this test equipment which proves to be defective
within twelve months from the date of original purchase.

This warranty does not apply to any of our products which have
been repaired or altered by unauthorized persons in any way so as,
in our sole judgement, to injure their stability or reliability, or which
have been subject to misuse, abuse, misapplication, negligence or
accident or which have had the serial numbers altered, defaced or
removed.

Accessories, not of our manufacture used with this product, are not
covered by this warranty.

All warranties implied by law are hereby limited to a period of twelve
months, and the provisions of the warranty are expressly in lieu of
any other warranties expressed or implied.

The purchaser agrees to assume all liability for any damages or
bodily injury which may result from the use or misuse of the product
by the purchaser, or it's user, his employees, or others, and the
remedies provided for in this warranty are expressly in lieu of any
other liability we may have including incidental or consequential
damages.

We reserve the right to discontinue models at any time, or change

specication, price or design, without notice and without incurring

any obligation.

-20-