Triplett MG420 User manual

User Manual
MG420
Analog Megohmeter/Insulation Tester
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Introduction
Congratulations on your purchase of the Triplett MG420 Analog
Megohmmeter/Insulation Tester. The MG420 features three Insulation
test ranges with a live circuit indicator, as well as low resistance and AC
voltage measurements. The Power Lock On feature allows hands-free
operation.
Safety
International Safety Symbols
This symbol, adjacent to another symbol or terminal, indicates
the user must refer to the manual for further information.
This symbol, adjacent to a terminal, indicates that, under
normal use, hazardous voltages may be present
Double insulation
Safety Notes
Do not exceed the maximum allowable
input range of any function. Set the
function switch OFF when the meter is
not in use.
Remove the battery if meter is to be stored for longer than 60 days.
Circuits under test must be de-energized and isolated before
connections are made (except for voltage measurements).
Circuit connections must not be touched during a test. Use extreme
caution when working near bare conductors and bus bars.
Accidental contact with conductor could result in electrical shock.
After insulation tests, capacitors must be discharged.
Warnings
Set function switch to the appropriate position before measuring.
When changing ranges always disconnect the test leads from the circuit
under test.

Cautions
Improper use of this meter can cause damage, shock, injury or
death. Read and understand this user manual before operating
the meter.
Always remove the test leads before replacing the battery.
Inspect the condition of the test leads and the meter itself for any
damage before operating the meter. Repair or replace any damage
before use.
Use great care when making measurements if the voltages are
greater than 25VAC rms or 35VDC. These voltages are
considered a shock hazard.
Voltage checks on electrical outlets can be difficult and misleading
because of the uncertainty of connection to the recessed electrical
contacts. Other means should be used to ensure that the terminals
are not "live".
If the equipment is used in a manner not specified by the manufacturer,
the protection provided by the equipment may be impaired
Description
1. Analog display –See Display Description below
2. Batt Check key –Checks battery level (with
TEST key)
3. 0 ADJ key –Adjusts Zero point for
Analog display
4. Backlight key –Turns on Backlight
5. TEST/LOCK key –Enables Battery
Check, Resistance, and Megohmmeter
functions (can be locked by rotating
clockwise)
6. Function Selector knob –Selects desired
range and function

Top View
1. V Test Lead Input
2. COM Test Lead Input
Display Description
1. Red: Megohmmeter Scale: Multiply reading by 0.5 (for 250V
range), 1 (500V), 2 (1000V)
2. Green: Low Resistance Scale (0 to 3 )
3. Green: Resistance Scale (0 to 500
4. Blue: AC Voltage
Measurement Scale (0 to
600V)
5. BATT GOOD Indicator
6. Live Circuit Indicator LED

Operation
CAUTIONS
Observe all safety precautions when the FUNCTION switch is set to
the 250V, 500V or 1000V positions.
Connect the meter test leads to the circuit under test before operating
the TEST key.
Do not touch the clip ends of the test leads when the TEST key is
pressed.
Some electrical equipment, especially cables, may retain an
electrical charge when disconnected from the line. It is good practice
to discharge such equipment with grounding straps, or other suitable
devices, before touching or making connections. The meter
automatically discharges the test circuits when the spring loaded
TEST key is released.
IMPORTANT NOTE
Remove all power to the circuit under test when making
resistance measurements. If any voltage is present in the test
circuit the red on the meter scale plate will light. Immediately
disconnect test leads and turn off power to test circuit.
Live Circuit Indicator LED
If the Live Indicator status LED is lit, voltage is present on the device
under test. DO NOT proceed to test with voltage present. Shock to the
user and damage to the meter or device under test can result if testing is
done with voltage present. Proceed with testing only when the voltage is
removed from the device under test.
Connecting Test Leads
For all measurements, connect the red test lead to the V input terminal
and the black test lead to the COM input terminal.
Battery Check
1. Set the range selector switch to the BATT.CHECK position
2. Press and hold the TEST key.