Fieldpiece SMG5 User Manual

Model SMG5

MEGOHMMETER

HOLD

OPERA TOR'S MANUAL

Description

The SMG5 Megohmmeter is for fast, easy, and
safe testing of insulation resistance. It provides
1000V voltage source, monitors current, and
displays the resistance between the test points.
Maximum current output is <1.5mA. To extend
battery life, it automatically turns itself off in 15
seconds.

Applications

The SMG5 can be used to determine the
condition of insulation from winding to ground in
a motor, compressor, or transformer. Disconnect
the windings and measure the resistance between
the windings and ground through the insulation.
Determine what a "good" reading is by comparing
your reading to values supplied by the
manufacturer of the equipment or from your own
experience. Make sure that all measurements are
compared to readings at the same temperature.
Insulation resistance can vary dramatically with
temperature.

Megohm readings can work best when the
same equipment is measured over time.
Decreasing insulation resistance levels can
forecast failure before catastrophic failure.

WARNING

Do not measure when compressor

motor is in a vacuum.

WARNING

T o avoid electrical shock remove test

leads before opening case or battery cover.

Do not operate with battery cover open.

WARNING

Remove power from circuit under test.

WARNING

Do not touch test lead tips, test points,

or terminals when pressing MEAS.

For your safety ...

1. Connect the E terminal to ground using

the alligator clip (included).

2. Use one hand to conduct test.

3. Make sure to turn meter OFF to avoid
accidentally pressing MEAS and creating a
1000V voltage source. If the switch is ON
and MEAS is depressed, 1000V will appear
on the terminals.

Specifications

Display:

3 1/2 digit liquid crystal display (LCD)

with maximum reading of 1999.

Overrange: (OL) or (-OL) is displayed.
Low battery indication: The " " is

displayed when the battery voltage
drops below the operating level.

Measurement rate: 2.5 times per

second, nominal.

Operating Environment: 0°C to 40°C at

< 70% relative humidity.

Storage Temperature: -20°C to 60°C, 0

to 80% R.H. with battery removed from
meter.

Auto power off: 15 seconds approx.
Standby consume current: <10μA
Battery:

4 pcs 1.5V (AAA size) UM-4 R03.

Battery Life:

4 hours (continuity) typical with alkaline

battery (@20ΜΩ range test 10ΜΩ
resistor).

Dimensions:

170mm(H) x 44mm(W) x 40mm(D).

Weight: 160g including batteries.

ELECTRICAL
Range: 20ΜΩ,2000ΜΩ.
Resolution: 10KΩ on 20ΜΩ range.

1ΜΩ on 2000ΜΩ range.

Accuracy:

20ΜΩ range: ±(2%rdg + 2dgts)
2000ΜΩ range: <500ΜΩ ±(4%rdg + 2dgts)
>500ΜΩ ±(5%rdg + 2dgts)
Rated voltage: DC-DC converter to

1000VDC

Accuracy temperature: 23°C ± 5°C less

than 70%RH

Temperature Coefficient: 0.1X (specified

accuracy)/°C (<18°C or >28°C)

DANGEROUS
VOLTAGE

AC-ALTERNATING
CURRENT
DC-DIRECT
CURRENT

International Electrical Symbols

SEE EXPLANATION
IN MANUAL

DOUBLE INSULATION
(Protection ClassII)

GROUND

Insulation Resistance
Measurement Terminal
Voltage

Terminal voltage(V)

ΩΩ

Rx(

Ω )

ΩΩ

How to use

1. Disconnect all wires from the winding to
be tested. Test each winding in three-phase
system separately.

2. Connect the E terminal to ground and
insert probe tip in L.

3. Select ON (middle slide switch).

4. Touch test point, and press MEAS, and
hold until you get a stable reading.

5. Release MEAS. The reading will remain
on the display for approximately in 15
seconds.

6. Select OFF.

Range select

If the meter is on the 20MΩ setting and
reads OL during the test, select the 2000MΩ
setting and try again. If the meter is on the
2000MΩ setting and the display reads 19 or
less, select 20MΩ for better resolution. The
range selected will be displayed on the bottom
of the LCD.

Display back-light switch ( )

Select to turn on backlight. Backlight
will remain on only when the LCD is on.

Battery test

1. Slide the middle switch to power on.

2. Press the MEAS button.

3. If the " " in the display lights, the
batteries are near the end of their life and should
be replaced immediately.

The low battery indicator

The low battery indicator " " is displayed
when measuring very low values of resistance
(below 500KΩ). This is due to the large amount
of current power consumed when measuring such
small resistances. Replace the batteries if
subsequent resistance measurements of high
values result in the display " " appearing.

T emperature effects

For accurate measurements, when comparing
readings over time or when comparing readings
to other similar equipment or to the
recommended values, the temperatures must be
the same. Insulation resistance can change by a
factor of two with a change in temperature from
70 deg F to 100 deg F .

Equipment manufacturers publish acceptable
limits that vary with temperature.

Refrigeration and A/C systems

A megger can be particularly effective with
compressors. Contaminants (moisture,
microscopic metal filings, and acids) can get in
the refrigerant and destroy the insulation in the
windings of the compressor. With a megger, you
can see the degradation over time and may be
able to replace the compressor before it
catastrophically fails and spews contaminants
into the refrigeration system, possibly requiring a
much more expensive repair.

T o insure consistent measurements, the system
should be run for at least an hour and shut off.
T ake the megohmmeter reading immediately. This
way temperatures and the exact condition of the
refrigerant will be the same from test to test.

Guidelines

The following are general guidelines. The
numbers recommended by the equipment
manufacturer may be different, depending on
the equipment tested and conditions. Results
can vary significantly as the temperature
varies.

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How does it relate to a
milliohmmeter?

A megger such as the Fieldpiece SMG5
measures the insulation resistance between
the coil and ground by supplying a very high
voltage to break down the insulation and
measuring the very low resultant current. The
resistance measured is very high. Fifty million
ohms is typical. A milliohmmeter such as the
Fieldpiece AMR1 supplies a higher current
(50mA) but at a very low voltage. The
resistance measured is very low (thousandths
of an ohm).

You may be able to determine insulation
problems with either a megger or a milliohm
meter. The megger will tell you the condition
of the insulation between the winding and
ground by forcing a small current though it
with a high voltage. The milliohm meter will
determine if the test current supplied between
the ends of the windings takes a "shortcut" at
a point where the insulation has failed.

Both measurements can be used to
determine the health of the insulation, but in
different ways.

Why a DMM often won’t work

To test resistance, a DMM supplies low
voltage (<1V) to the test points and is capable of
delivering only a few milliamps. It's not a high
enough voltage to detect high resistance
problems that might indicate moisture and other
contaminants and it's not enough current to
measure real low values of resistance.

Cleaning

Periodically wipe the case with a damp cloth
and detergent. Do not use abrasives or solvents.

Limited warranty

This meter is warranted against defects in
material or workmanship for one year from date
of purchase. Fieldpiece will replace or repair the
defective unit, at its option, subject to verification
of the defect.

This warranty does not apply to defects
resulting from abuse, neglect, accident,
unauthorized repair, alteration, or unreasonable
use of the instrument.

ANY IMPLIED WARRANTIES ARISING
OUT OF THE SALE OF A FIELDPIECE
INSTRUMENT’S PRODUCT, INCLUDING
BUT NOT LIMITED TO IMPLIED
WARRANTIES OF MERCHANTABILITY AND
FITNESS FOR A PARTICULAR PURPOSE,
ARE LIMITED TO THE ABOVE. FIELDPIECE
SHALL NOT BE LIABLE FOR LOSS OF USE
OF THE INSTRUMENT OR OTHER
INCIDENT AL OR CONSEQUENTIAL
DAMAGES, EXPENSES, OR ECONOMIC
LOSS, OR FOR ANY CLAIM FOR SUCH
DAMAGE, EXPENSES, OR ECONOMIC
LOSS.

State laws vary. The above limitations or
exclusions may not apply to you. This warranty
gives you specific legal rights, and you may also
have other rights which vary from state to state.

Service

Return any defective SMG5 to Fieldpiece
for warranty service along with proof of
purchase. Contact Fieldpiece for out of
warranty repair charges.

Fieldpiece Instruments, Inc.

California,U.S.A.

www.fieldpiece.com

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