Matco Tools MD79 User manual

USER'S MANUAL
MD79 AC+DC
Clamp-on Multimeter

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1) SAFETY
This manual contains information and warnings that must be followed
for operating the instrument safely and maintaining the instrument in a
safe operating condition. If the instrument is used in a manner not
specified by the manufacturer, the protection provided by the
instrument may be impaired.
The meter protection rating, against the users, is double insulation per
UL/IEC/EN61010-1 Ed. 3.0, IEC/EN61010-2-033 Ed. 1.0, CAN/CSA
C22.2 No. 61010-1 Ed. 3.0, IEC/EN61010-2-032 Ed. 3.0 &
IEC/EN61010-031 Ed. 1.1:
Measurement Category III 600V & Category IV 300V AC & DC.
Per IEC61010-1 (2010) OVERVOLTAGE CATEGORY
OVERVOLTAGE CATEGORY ll (CAT II) is for equipment intended to
be supplied from the building wiring. It applies both to plug-connected
equipment and to PERMANENTLY CONNECTED EQUIPMENT.
OVERVOLTAGE CATEGORY lll (CAT III) is for equipment intended to
form part of a building wiring installation. Such equipment includes
socket outlets, fuse panels, and some MAINS installation control
equipment.
OVERVOLTAGE CATEGORY lV (CAT IV) is for equipment installed at
or near the origin of the electrical supply to a building, between the
building entrance and the main distribution board. Such equipment may
include electricity tariff meters and primary overcurrent protection
devices.
TERMS IN THIS MANUAL
WARNING identifies conditions and actions that could result in
serious injury or even death to the user.
CAUTION identifies conditions and actions that could cause damage
or malfunction in the instrument.

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WARNING
To reduce the risk of fire or electric shock, do not expose this product to
rain or moisture. The meter is intended only for indoor use.
To avoid electrical shock hazard, observe the proper safety precautions
when working with voltages above 60 VDC or 30 VAC rms. These
voltage levels pose a potential shock hazard to the user. Before and
after hazardous voltage measurements, test the voltage function on a
known source such as line voltage to determine proper meter
functioning.
Keep your hands/fingers behind the hand/finger barriers (of the meter
and the test leads) that indicate the limits of safe access of the hand-
held part during measurement. Inspect test leads, connectors, and
probes for damaged insulation or exposed metal before using the
instrument. If any defects are found, replace them immediately. Only
use the test lead provided with the equipment or UL Listed Probe
Assembly rated CAT III 600V or better.
This Clamp-on meter is designed to apply around or remove from
uninsulated hazardous live conductors. But still, individual protective
equipment must be used if hazardous live parts in the installation where
measurement is to be carried out could be accessible.
CAUTION
Disconnect the test leads from the test points before changing meter
functions.
INTERNATIONAL ELECTRICAL SYMBOLS
!
Caution ! Refer to the explanation in this Manual
Caution ! Risk of electric shock
Earth (Ground)
Double Insulation or Reinforced insulation
Fuse
AC--Alternating Current
DC--Direct Current
Application around and removal from hazardous live conductors
is permitted
2) CENELEC Directives
The instruments conform to CENELEC Low-voltage directive

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2006/95/EC and Electromagnetic compatibility directive 2004/108/EC
3) PRODUCT DESCRIPTION
This user's manual uses only representative model(s) for illustrations.
Please refer specification details for function availability to each model.
1) Antenna area for Non-Contact
EF-Detection
2) Jaw center indicator (with DCA
polarity for Models 079, 078 &
077), at where best current
accuracy is specified
3) Rotary Selector to turn the
power ON/OFF and Select a
function
4) 3-5/6 digits 6000 counts numeric
LCD display
5) Additional input Jack for Phase
Rotation function only
6) Input Jack for all functions
EXCEPT non-invasive DCA,
DC+ACA, or ACA current
functions
7) Common (Ground reference)
Input Jack for all functions
EXCEPT non-invasive DCA,
DC+ACA, or ACA current functions
8) Push-buttons for special
functions & features.
9) Jaw trigger for opening the
clamp jaw
10) Hand/Finger Barrier to indicate
the limits of safe access of the
meter
11) Clamp Jaw for DC or AC
current magnetic field pick up
12) Additional center indicator for
AmpTipTM Low-current function,
at where best AmpTipTM current
accuracy is specified

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4) OPERATION
WARNING: Before and after hazardous voltage measurements, test
the voltage function on a known source such as line voltage to
determine proper meter functioning.
ACV, DCV, DC+ACV Line-level Hz, & EF (NCV) functions
Inputs, other than that of EF as described below, are made through the
test lead terminals COM/+. Defaults at ACV* Function. Press SELECT
button momentarily to select DCV, DC+ACV, Line-level Hz or EF**
(NCV) function in sequence.
Note:
*ACV (and hence AC+DCV & Line-level Hz) function is equipped with
digital low-pass filter, and is capable of dealing with VFD (Variable
Frequency Drives) signals. It also improves ACV reading stability in
noisy electrical environments.

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Electric Field EF-Detection
The meter displays “EF” when it is ready. Signal strength is indicated
as a series of bar-graph segments on the display together with variable
beep tones.
• Non-Contact EF-Detection: An antenna is located along the top-right end of the
stationary clamp jaw, which detects electric field surrounds energized conductors. It is
ideal for tracing live wiring connections, locating wiring breakage and to distinguish
between live or earth connections.
• Probe-Contact EF-Detection: For more precise indication of live wires, such as
distinguishing between Live and Ground connections, use one single probe to test via
terminal COM for direct contact EF-Detection with best sensitivity.

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CAUTION & WARNING for Non-Invasive (Clamp-on) Current
Measurements:
CAUTION
(Application and Removal of the Clamp-on Jaws) For non-invasive
current measurements, press the jaw trigger and clamp the jaws
around conductor(s) of only one single pole of a circuit for load current
measurement. Make sure the jaws are completely closed, or else it will
introduce measurement errors. Enclosing conductor(s) of more than
one pole of a circuit may result in differential current (like identifying
leakage current) measurement. Align the conductor(s) to the Jaws
center indicators (Regular or AmpTip™ indicators where applicable) as
much as possible to get the best measuring accuracy. For removal,
press the jaw trigger and remove the jaws from the conductor(s).
Adjacent current-carrying devices such as transformers, motors and
conductor wires may affect measurement accuracy. Keep the jaws
away from them as much as possible to minimize influence.
WARNING
Do not use the meter to measure currents above the rated frequency
(400Hz). Circulating currents may cause the magnetic circuits of the
Jaws reach a hazardous temperature.

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Non-Invasive AmpTipTM Low-Current Functions:
ACA, DCA, DC+ACA & Hz
Input is made via the clamp jaws with best accuracy specified near the
jaw tip area for small conductors low-current measurements. Defaults
at ACA function. Press SELECT button momentarily to select the
subject functions in sequence.

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Non-Invasive Regular Current Funtions:
ACA, DCA, DC+ACA & Hz
Input is made via the clamp jaws with best accuracy specified at the
jaw center for regular current measurements. Press SELECT button
momentarily to select the subject functions in sequence.

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Resistance, Continuity, & Diode functions
Inputs are made through the test lead terminals COM/+. Defaults at 
Resistance. Press SELECT button momentarily to select the subject
functions in sequence.
Note
When using Diode test function, normal forward voltage drop (forward biased) for a
good silicon diode is between 0.400V to 0.900V. A reading higher than that indicates a
leaky diode (defective). A zero reading indicates a shorted diode (defective). An OL
indicates an open diode (defective). Reverse the test leads connections (reverse
biased) across the diode. The digital display shows OL if the diode is good. Any other
readings indicate the diode is resistive or shorted (defective).
CAUTION
Using Resistance, Continuity or Diode function in a live circuit will produce false results
and may damage the meter. In many cases, the suspected component(s) must be
disconnected from the circuit to obtain an accurate measurement reading.

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Capacitance & Temperature functions
Inputs are made through the test lead terminals COM/+. Defaults at
Capacitance. Press SELECT button momentarily to select oC(Celsius)
or oF(Fahrenheit) in sequence.
Note
Be sure to insert the banana plug type-K temperature bead probe
Bkp60 with correct polarities. You can also use a plug adapter
Bkb32 (Optional purchase) with banana pins to type-K socket to adapt
other type-K standard mini plug temperature probes.
CAUTION
1) Using Capacitance function in a live circuit will produce false results
and may damage the meter. In many cases the suspected
component(s) must be disconnected from the circuit to obtain an
accurate measurement reading.

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2) When using Capacitance function, discharge capacitor(s) before
making any measurements. Large value capacitors should be
discharged through an appropriate resistance load
DCA Current function
Inputs are made through the test lead terminals COM/+.
Application notes:
The DCAfunction is designed especially for HVAC/R flame sensor
applications. The 0.1A resolution is useful for identifying the minute
current changes in flame detector applications. Flame signal current
check should indicate steady flame signal of at least 2A for a
rectification type, or 1.5A for an ultraviolet type (8A for self checking
systems). If a flame signal current with inadequate strength or
fluctuation beyond 10%, check the following to avoid the risk of
unwanted flame relay dropout :
For gas or oil flames (Minipeeper):
•Low supply voltage
•Detector location
•Defective detector wiring
•Dirty viewing windows
•Faulty Minipeeper
For oil flames (Photocell):
•Detector location & wiring
•Smoky flame or poorly adjusted air shutter
•Faulty Photocell
•Temperature over 165 oF (74 oC) at photocell
For gas flames (Flame Rod):
•Ignition interference (A flame signal current difference with the
ignition both on and off greater than 0.5A indicates the presence
of ignition interference)
•Insufficient ground (must be at least 4 times the detector area)
•Flame lifting off burner head (ground), or not continuously in
contact with the flame rod
•Temperature in excess of 600 oF (316 oC) at the flame electrode
insulator causing short to ground.

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& 3-Phase Rotation function
Inputs are made through the test lead terminals L1/L2/L3. Phase
Rotation directions are indicated as symbolic movements by the LCD
segments. Defaults at . Press SELECT button momentarily toggles
between and modes.
: Hi-sensitivity mode, which detects relatively low signal outputs
generated from motor spinning, for checking phase connections
of Motors.
: Normal-sensitivity mode for identifying phase sequence of
MAINS (electricity supply).
CAUTION
Proper Rotation detection relies on solid signal connection to all three
test lead terminals simultaneously. Any single disconnection will lead to
detection failure and may produce false indication. To verify signal
connection and hence proper meter indication, swap any two connects
(between the meter and the test points) to check for indication of
reverse movement

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Using the Hi-sensitivity mode for Motors:
Connect to the Motor as illustrated. Be sure the electricity supply is
removed. From the perspective of looking down the shaft of the motor,
speed-spin it clockwise to generate sufficient signal strength for proper
meter detection. If the meter indicates a clockwise movement, the
motor leads connected to L1, L2 and L3 of the meter are L1, L2 and L3
(also known as R, S and T), respectively. If the meter indicates a
counter-clockwise movement, swap any two connects between the
meter and motor. Then retest.
Using the Normal mode for MAINS (electricity supply):
Connect to the MAINS as illustrated. If the meter indicates a clockwise
movement, the phases connected to L1, L2 and L3 of the meter are L1,
L2 and L3 (also known as R, S and T), respectively. If the meter
indicates a counter-clockwise movement, swap any two connects
between the meter and phases. Then retest. Connect the above
mentioned L1, L2 and L3 of a Motor and that of the MAINS respectively
should get a clockwise motor movement.
Using the Complementary Beeper feature:
The Complementary Beeper feature is selected in Power-up option.
Press and hold the REC button while turning the meter on to enable. If
the segments indicate a clockwise movement, the beeper sounds a
single long beep per segment cycle. If the segments indicate a counter
clockwise movement, the beeper sounds 3 short beeps per segment
cycle.
Hold
Hold feature freezes the display for later view. LCD “ ” turns on. Press
the HOLD button momentarily to toggle the hold feature.
Record mode
Press REC button momentarily to activate MAX/MIN/AVG recording
mode. LCD “ ” & “MAX MIN AVG”turn on. The meter beeps when
new MAX (maximum) or MIN (minimum) reading is updated. AVG
(Average) reading is calculated over time. Press the button
momentarily to read the MAX, MIN and AVG readings in sequence.
Press the button for 1 second or more to exit this mode. Auto-Power-

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Off is disabled automatically in this mode.
Relative-Zero ( ZERO) mode
Relative-Zero allows the user to offset the meter consecutive
measurements with the main display displaying reading as the
reference value. LCD “ ” turns on. Press the
ZERO (HOLD) button for one second or more to toggle Relative-Zero
mode.
DC-Zero mode is set instead of Relative-Zero mode, however, to only
offset the non-zero DCA residuals caused by magnetic hysteresis of
the jaws as in DCA & DC+ACA functions. Press the ZERO (HOLD)
button for one second or more to activate/ re-activate this mode. Apply
this mode before making any single DCA or DC+ACA measurement for
best measuring accuracy. The meter shows “dc_0” shortly to confirm
activation before continuing measurements. The beeper will sound 3
short beeps, however, to warn for null activation if the residual is
beyond a reasonable hysteresis reading of -5 to 5 DCA.
80ms PEAK-RMS mode
Press PEAK-RMS button for one second or more to toggle PEAK-RMS
mode to capture inrush current or voltage RMS values in duration as
short as 80ms. LCD turns on. Auto-Power-Off is disabled
automatically in this mode.
Backlighted LCD display
Press the SELECT button for 1 second or more to toggle the LCD
backlight. The backlight will also be turned off automatically after 32
seconds to extend battery life.
Intelligent Auto-Power-Off (APO)
The Auto-Power-off (APO) mode turns the meter off automatically to
extend battery life after approximately 32 minutes of no specified
activities, where applicable:
1) Rotary switch or push button operations
2) Significant measuring readings of above 8.5% of ranges
3) Non-OL readings for Resistance, Continuity or Diode function
4) Non-zero readings for Hz function
5) Significant movement indication as in Phase Rotation functions

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In other words, the meter will intelligently avoid entering the APO
mode when it is under normal measurements. To wake up the meter
from APO, press the SELECT button momentarily and release, or turn
the rotary switch OFF and then back on. Always turn the rotary switch
to the OFF position when the meter is not in use
5) MAINTENANCE
WARNING
To avoid electrical shock, disconnect the meter from any circuit,
remove the test leads from the input jacks and turn OFF the meter
before opening the case. Do not operate with open case.
Trouble Shooting
If the instrument fails to operate, check batteries and test leads etc.,
and replace as necessary. Double check operating procedure as
described in this user’s manual.
If the instrument voltage-resistance input terminal has subjected to high
voltage transient (caused by lightning or switching surge to the system
under test) by accident or abnormal conditions of operation, the
protective impedance components in series might be blown off
(become high impedance) like open fuses to protect the user and the
instrument. Most measuring functions through this terminal might then
be open circuit. Such components should only be replaced by qualified
technician.
Cleaning and Storage
Periodically wipe the case with a damp cloth and mild detergent; do not
use abrasives or solvents. If the meter is not to be used for periods of
longer than 60 days, remove the batteries and store them separately.
Battery replacement
The meter uses standard 1.5V AAA Size (IEC R03) battery X 2
Loosen the 2 captive screws from the battery cover case. Lift the
battery cover case. Replace the batteries. Replace battery cover case.
Re-fasten the screws.

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GENERAL SPECIFICATIONS
Display: 3-5/6 digits 6000 counts.
Polarity: Automatic
Update Rate: 5 per second nominal;
Operating Temperature: 0C to 40C
Relative Humidity: Maximum relative humidity 80% for temperature up
to 31C decreasing linearly to 50% relative humidity at 40C
Pollution degree: 2
Storage Temperature: -20C to 60C, < 80% R.H. (with battery
removed)
Altitude: Operating below 2000m
Temperature Coefficient: nominal 0.15 x (specified accuracy)/ C
@(0C -- 18C or 28C -- 40C), or otherwise specified
Sensing: True RMS
Safety: Double insulation per UL/IEC/EN61010-1 Ed. 3.0,
IEC/EN61010-2-033 Ed. 1.0, CAN/CSA C22.2 No. 61010-1 Ed. 3.0,

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IEC/EN61010-2-032 Ed. 3.0 & IEC/EN61010-031 Ed. 1.1 to CAT III
600V and CAT IV 300V AC & DC
Transient Protection: 6.0kV (1.2/50s surge)
Overload Protections:
Current & Hz functions via jaws: 600ADC/AAC rms at <400Hz
Voltage & 3-Phase Rotation functions via terminals: 660VDC /
920VAC rms
Other functions via terminals: 600VDC/VAC rms
E.M.C.: Meets EN61326-1:2006 (EN55022, EN61000-3-2, EN61000-3-
3, EN61000-4-2, EN61000-4-3, EN61000-4-4, , EN61000-4-5,
EN61000-4-6, EN61000-4-8, EN61000-4-11):
DCA and DC+ACA Functions, in an RF field of 1V/m:
Total Accuracy = Specified Accuracy + 20 digits at around
405MHz
DCA and Ohm Functions, in an RF field of 1V/m:
Total Accuracy = Specified Accuracy + 25 digits
Other Functions, in an RF field of 3V/m:
Total Accuracy = Specified Accuracy + 20 digits
Power Supply: 1.5V AAA Size battery X 2
Power Consumption: Typical 13mA
Low Battery:
Below approx. 2.85V for Capacitance & Hz
Below approx. 2.5V for other functions
APO Timing: Idle for 32 minutes
APO Consumption: 5A typical
Dimension (LxWxH): 223 x 76 x 37mm
Weight: 234gm
Jaw opening & Conductor diameter : 35mm max
Accessories: Test lead set, User's manual, Soft carrying pouch,
Bkp60 banana plug K-type thermocouple Alligator Clip set
Optional purchase accessories: BKB32 banana plug to type-K socket
plug adaptor
Special Features: AmpTipTM low-current range; MAX/MIN/AVG
Recording mode; Display Hold; EF-Detection (NCV); Backlighted LCD;
80ms Peak-RMS mode for inrush current; Relative-Zero; 3-Phase
Rotation detection

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Electrical Specifications
Accuracy is (% reading digits + number of digits) or otherwise
specified, at 23C 5C.
Maximum Crest Factor < 2.5 : 1 at full scale & < 5 : 1 at half scale or
otherwise specified, and with frequency spectrum not exceeding the
specified frequency bandwidth for non-sinusoidal waveforms.
DC Voltage
RANGE
Accuracy
600.0V
1.0% + 5d
Input Impedance: 10M, 100 pF nominal
AC Voltage (with Digital Low-Pass Filter)
RANGE
Accuracy
50Hz ~ 60Hz
600.0V
1.0% + 5d
Input Impedance: 10M, 100 pF nominal
DC+AC Voltage (with Digital Low-Pass Filter) (Models 079 & 078
Only)
RANGE
Accuracy
DC, 50Hz ~ 60Hz
600.0V
1.2% + 7d
Input Impedance: 10M, 100 pF nominal
PEAK-rms (ACV & ACA)
Response: 80ms to > 90%
Audible Continuity Tester
Audible Threshold: At between 10and 250
Response time: 32ms approx.
Ohm
RANGE
Accuracy
600.0, 6.000K, 60.00K
1.0% + 5d
Open Circuit Voltage: 1.0VDC typical

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Capacitance
RANGE
Accuracy1)
200.0F, 2500F
2.0% + 4d
1)Accuracies with film capacitor or better
Diode Tester
RANGE
Accuracy
2.000V
1.5% + 5d
Test Current: 0.3mA typically
Open Circuit Voltage: < 3.5VDC typically
DCA
RANGE
Accuracy
Burden Voltage
200.0A, 2000A
1.0% + 5d
3.5mV/A
Temperature
RANGE
Accuracy
-40.0oC ~ 99.9oC
1.0% + 0.8oC
100oC ~ 400oC
1.0% + 1oC
-40.0oF ~ 211.8oF
1.0% + 1.5oF
212oF ~752oF
1.0% + 2oF
K-type thermocouple range & accuracy not included
AmpTipTM clamp-on ACA
RANGE
Accuracy1) 2) 3) 4)
50Hz ~ 60Hz
60.00A
1.5% + 5d
1) Induced error from adjacent current-carrying conductor: <0.01A/A
2) Specified with Relative Zero mode applied to offset the non-zero
residual readings, if any
3) Add 10d to the specified accuracy @ < 4A