Fieldpiece SMG5 - Megohmmeter 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.

International Electrical Symbols

	DANGEROUS VOLTAGE		SEE EXPLANATION IN MANUAL
	AC-ALTERNATING CURRENT		DOUBLE INSULATION (Protection ClassII)
	DC-DIRECT CURRENT		GROUND

Do not measure when compressor motor is in a vacuum.

To avoid electrical shock remove test leads before opening case or battery cover. Do not operate with battery cover open.

Remove power from circuit under test.

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.

Insulation Resistance

How to use

1. Disconnect all wires from the winding tobe tested. Test each winding in three-phase system separately.
2. Connect the E terminal to ground andinsert probe tip in L.
3. Select ON (middle slide switch).
4. Touch test point, and press MEAS, andhold until you get a stable reading.
5. Release MEAS. The reading will remainon 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.

Temperature 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.

To insure consistent measurements, the system should be run for at least an hour and shut off. Take 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.

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.

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 (@20Μ Ω range test 10Μ Ω resistor).

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

Weight: 160g including batteries.

ELECTRICAL
Range: 20ΜΩ,2000ΜΩ.

Resolution:
10KΩ on 20ΜΩ range.
1 ΜΩ 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)

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 INCIDENTAL 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