6
DC CURRENT MEASUREMENTS USING EXTERNAL SHUNT
An external shunt (not supplied)
is required. MCM’s .001 ohm LC shunt (5803) used in conjunction with
the 20mV range yields a range of 0-20A DC. This compact shunt has convenient banana plug potential
terminals which plug into the common (-) and (+) 20mV terminals. Other external shunts can also be used.
However they would require a pair of test leads to be connected between the common (-) and center (+)
meter terminals and the potential of the shunt. Depending on the particular shunt, the 20mv or 200mv range
would be employed.
RESITANCE MEASURMETS
Any resistance less than 200 ohms can be measured. The only precaution is to make sure that there is no
pre-existing voltage in the circuit being measured. If there is a pre-existing voltage, a noticeable error will be
produced. If the voltage is high enough, damage to the meter is likely. Always check for existing voltage
before measuring resistance.
The resistance range is very useful for checking resistance and continuity of test leads, test station wiring,
bond connections, etc. if the circuit is open (non-continuous), or if resistance exceeds 200 ohms, the display
will show “1” followed by blank digits. To measure resistance, place range switch in “200 ohms” position,
connect test leads to common (-
) and (+) center banana jack terminals, turn function switch to “ohms”
position.
AC POTENTIAL MEASUREMENTS
The use of the 600V AC rage will enable you to check line voltage of AC power source, to check AC output Voltage of
rectifier transformers, to check for hazardous induced voltages on structures near power lines, and to measure
structure-to-soil AC potentials which may have an effect on corrosion behavior of concentric copper neutrals of buried
cable.
To measure AC voltage, turn the range switch to “600V AC”, turn function switch to AC position, then connect the test
leads to the (-) left and (+) center input terminals of the meter.
The input resistance selector switch is functional on the 600V AC range and can be used to detect and eliminate errors
caused by high resistance in the external circuit (
see “use of Input Resistance Selector Switch”).
The voltage source, if over 500V, should not be energized at the time test leads are being connected. Do not touch
bare parts of the banana plugs or test clips when measuring line voltages. Make sure that the test leads have an
adequate insulation rated 600V or more.
The banana jack terminals on your meter are insulated from the panel, which in turn is an insulating material.
When measuring structure-to-soil AC voltages, contact to the soil may be with any metal rod or a copper sulfate
reference electrode can be employed.
If the soil is very dry, frozen, or consists of mostly gravel, it may be necessary to use the input resistance selector
switch (right side) to check for and eliminate contact resistance errors.
(See “Use of Input Sensitivity Switch”)
Caution
: Always disconnect test leads from AC voltage source before turning either the range switch or function switch
to another position. Failure to do so may result in damage to the meter.
