UEi Test Instruments M110A - Manual (Page 3)

Set the SELECTOR switch to the appropriate range. Connect one test
lead to the “COM” jack and the other test lead to the “ +VΩM” jack.
Touch the free ends of the test leads together. The pointer will swing to
the right hand side of the scale. Adjust the “Ω A D J” control until the
pointer is set on the green numeral 0. (Note: If this adjustment cannot
be made refer to the MAINTENANCE section). Rezero the M110A each
time the OHMS setting of the SELECTOR switch is changed. To make the
resistance measurement, connect the free ends of the test leads across
the element to be measured. The measured resistance value will be the
green numeral indicated on the OHMS scale times the multiplier on the
SELECTOR switch. For example, if the pointer is on the numeral 4, and
the SELECTOR switch is set on Rx10, the resistance is 40 ohms (4 Ω x 10
= 40 Ω).
Continuity tests are normally made to test a wire, or element, to see if it
is unbroken. Because continuity tests involve low values of resistance,
the SELECTOR switch should be set on the Rx1 position.
Testing Diodes / Transistors
A simple check of diode or transistor quality may be made with the
M 110A. Using the same test procedure as for measuring resistance,
connect one test lead to one end of the diode and the other test lead to
the other end of the diode. Note the resistance reading. Then reverse
the test leads and again note the reading. If the two readings differ by a
factor of ten then the diode, (or transistor junction) is probably good.
If the readings are approximately the same then the diode is shorted.
If a reading cannot be obtained in either direction, the diode is
probably between the base and emitter leads, or between the base
and collector leads.
Measuring AC Voltage
Set the SEL E C TO R switch to the appropriate range. Always start with the
600 V AC position if unsure of the magnitude of voltage present. Connect
the test leads to the “C OM” jack and the “+VΩM” jack and to the circuit
under test. Read the voltage on the red meter scale corresponding to the
SEL E C TOR switch setting. Use the lower red scale marked 6 V ONLY when
the SEL E C TOR switch is set on 6 V AC. For all other V AC measurements
use the upper red scale marked 30 V UP.
M a i n t e n a n c e
Periodic Service
WARNING!
Repair and service of this instrument is to be performed by qualified
personnel only. Improper repair or service could result in physical
degradation of the meter. This could alter the protection from
electrical shock and personal injury this meter provides to the
operator. Perform only those maintenance tasks that you are
qualified to do.
Operating Instructions
Color Coding
The meter scale plating and front panel are color coded. The DC Vo l t a g e
and DC Current meter scale and SEL E C TO R switch positions are in BLACK .
The OHMS meter scale and SEL E C TO R switch positions are in GREEN. The
AC Voltage meter scales and SEL E C TO R switch positions are in RED .
To provide an uncrowded easy-to-read meter scale plate a single meter
s cale may be used for more than one position of the SEL E C TOR switch.
For example, the meter scale numerals 0 - 30 are used for the follow i n g
positions of the SEL E C TO R switch: 300 V DC, 3 V DC, 300 mV DC, 0.03 mA
DC and 300 V AC. If the SEL E C TOR switch range is 300, divide the sca l e
n u m e rals by ten.
Measuring DC Voltage
Set the SEL E C TO R switch to the appropriate range. Always start with the
300 V DC position if unsure of the magnitude of voltage present. Connect
the black test lead to the “C OM” jack and to the negative side of the
circuit under test. Connect the red test lead to the “+VΩM” jack and to
the positive side of the circuit under test. Read the voltage on the black
meter scale corresponding to the SEL E C TOR switch setting. When
measuring DC voltage on the 1200 V DC range set the SEL E C TOR switch
to the 300 V Dc position and connect the red test lead to the 1200 V DC
jack. The black test lead is connected as before.
Measuring DC Current
Set the SEL E C TOR switch to the appropriate range. Always start with the
600 mA DC position if unsure of the magnitude of current present.
(Note: 0.03 mA DC = 30 µA DC and 0.06 mA DC = 60 µA). When
taking current measurements the meter must be connected in SERIES
with the circuit, or circuit element, under test. Break the connection at
the point at which current is to be measured. Place the M110A in series
with the circuit by connecting the black test lead to the “COM” jack
and to the lower voltage side of the circuit. Connect the red test lead
to the “+VΩM” jack and to the higher voltage side of the circuit. Read
the current on the black meter scale corresponding to the SELECTOR
switch setting.
Measuring Resistance
WARNING!
Remove all power to the circuit under test when making resistance
measurements. If any voltage is present in the test circuit an erroneous
reading will result ad the 6/10A fuse may open.
NOTE: When the M110A is set on the Rx1 OHM range, the accuracy
of the measurements can be degraded if there is dirt on the probe
tips. If the measurements are questionable, clean the tips and input
connections of the probes and the input jacks of the M110A.
M110A-MAN P. 2