General DMM30 User Manual

8-FUNCTION

DIGITAL MULTIMETER

WITH NCV DETECTION

USER’S MANUAL

DMM30

Please read this manual carefully and thoroughly before using this product.

TABLE OF CONTENTS

Key Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

What’s in the Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Product Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 –4

Safety Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 –6

Setup Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Install Battery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Operating Instructions . . . . . . . . . . . . . . . . . . . . . . . . 7 – 11

General Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Holding Readings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Measuring AC or DC Voltage . . . . . . . . . . . . . . . . . 7 –8

Measuring DC Current . . . . . . . . . . . . . . . . . . . . . . 8 –9

Measuring Resistance . . . . . . . . . . . . . . . . . . . . . . . . . 9

Checking for Continuity . . . . . . . . . . . . . . . . . . . . 9 – 10

Checking the Integrity of a Diode . . . . . . . . . . . . . . . . 10

Checking Battery Voltage . . . . . . . . . . . . . . . . . . 10 – 11

Using the NCV Detector . . . . . . . . . . . . . . . . . . . . . . . 11

Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11 – 12

Operating & Maintenance Tips . . . . . . . . . . . . . . . . . . . . 13

Warranty Information . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Return for Repair Policy . . . . . . . . . . . . . . . . . . . . . . . . . 15

2

KEY FEATURES

• 8 functions, 22 ranges

• Measures AC/DC voltage, DC current and resistance

• Also checks continuity, diode integrity and battery voltage

• Non-contact voltage (NCV) detection

• ETL certified safe for CAT II 600V use

• Jumbo 3-1/2 digit (2000 count) LCD with 7/8 in. (22mm) high digits

• Powered by “9V” battery (included)

• Low battery indication • 1-year limited warranty

WHAT’S IN THE PACKAGE

The meter is supplied in a blister pack. A cavity on the blister card
contains a pair of double-insulated test leads. A “9V” battery is
pre-installed in a compartment in the back of the unit.

PRODUCT OVERVIEW

Fig. 1 shows the labels and positions of the controls, LCD and physical
structures of the DMM30. Fig. 2 shows all possible indications on the
LCD. Familiarize yourself with the functions and meanings of all
controls, indications and connectors
before moving on to the Setup
Instructions and Operating Instructions.

1) LCD 2) HOLD button

3) Rotary function switch

4) 10A input jack

5) COM jack

6) jack (for all inputs except
currents >200mADC)

7)

NCV

button

8) NCV detector and visual indication

9) Battery compartment (on back)

10) Flip-up stand (on back)

3

Fig. 1. The controls, display and
physical features of the DMM30

1) Low battery indicator

2) Indicates that the displayed
value is a held reading

3) Measured value

4) Negative polarity indicator

SAFETY INSTRUCTIONS



Warning



To avoid possible electric shock or personal injury, and to avoid
damaging the meter or the equipment under test:

• Do not use the meter in any way not detailed in this manual or the

meter's safety features may be compromised.

• Before using the meter, inspect the case. Do not use the meter if it is

damaged. Look for cracks or missing plastic. Pay particular attention
to the insulation around the connectors.

• 

WARNING

Inspect the test leads for damaged insulation or
exposed metal. Check the test leads for continuity. Replace damaged
test leads before using the meter.

• Verify the meter’s operation by measuring a known voltage. Do not
use the meter if it operates abnormally. Protection may be impaired.
When in doubt, have the meter serviced.

• 

WARNING

Do not apply more than the rated voltage, as marked

on the meter, between the and

COM

jacks or between any jack
and ground. Also do not input more than the rated current, as
marked on the meter, through the

10A

jack.

• 

WARNING

Do not measure voltages above 600V in Category II

installations.

• 

WARNING

Do not attempt to measure voltage with the rotary
function switch in any or Ω position. Never attempt to measure
current with the rotary function switch in any , or Ω position.

4

Fig. 2. All possible
display indications

• Use caution when working with voltages above
42VAC

RMS

, or 60VDC. These voltages pose a shock hazard.

• Use the proper terminals, function and range for all measurements.

• 

WARNING

Do not operate the meter around explosive gas, vapor,

or dust.

• 

WARNING

When using the probes, keep your fingers behind the
finger guards. Do not touch the metal probes of the test leads when
making a measurement.

• When making connections, connect the black (–) test lead before
connecting the red (+) test lead; when disconnecting, disconnect the
red (+) test lead before disconnecting the black (–) test lead.

• Disconnect circuit power and discharge all high-voltage capacitors
before measuring/testing resistance, continuity, diodes, or
capacitance.

• For all DC functions in both auto and manual ranging mode, to avoid
the risk of shock due to possible improper reading verify the
presence of any AC voltages by first using the AC function. Then
select a DC voltage range equal to or greater than the AC range.

• Before measuring current, turn off power to the circuit before
connecting the meter.

• Do not operate the meter with the case (or part of the case)
removed.

• Use only (1) “9V” battery, properly installed in the battery
compartment, to power the meter. Do not use rechargeable
batteries.

• Replace the battery as soon as the low battery indicator “ ”
appears. Operated with a weak battery, the meter might produce
false readings that could lead to electric shock and personal injury.

• Remove the test leads from the meter before opening the meter
case or battery compartment.

5

Electrical Symbols Used On the Meter and
In This Manual

Symbol Description Symbol Description

AC (Alternating Fuse
Current)

DC Double
(Direct Current) Insulated

Caution, risk of electric Risk of danger. Important
shock. Hazardous information. Refer to the
voltage. manual.

Low battery indication
(when shown Earth ground
on LCD)

Diode Continuity

Beeper

AC or DC Ω Resistance

CAT II For measurements

made on household
appliances, portable tools
and similar devices plugged
into standard wall outlets
(110 VAC in the U.S. and
220 VAC in Europe)

6

SETUP INSTRUCTIONS

INSTALL BATTERY

Turn the meter over to gain access to the battery compartment.

To open the compartment:

1)

Use a small Phillips-head screwdriver to remove the single screw near
the top of the one-piece battery compartment cover/flip-up stand.

2) Remove the cover/stand and set it aside.

3) After removing the plastic wrap from the “9V” battery in the

compartment, plug the battery into the wired socket inside the
compartment. The terminals of the battery and the socket mate in
only one way, with the smaller male terminal plugging into the
larger female terminal.

4) Secure the battery compartment by replacing the cover/stand and

reinstalling and tightening the Phillips-head screw.

OPERATING INSTRUCTIONS

GENERAL INSTRUCTIONS

All parameters are measured through the included test leads. Unless
you are measuring DC currents larger than 200 mA, plug the red test
lead into the jack and the black test lead into the COM jack.
To measure currents larger than 200 mA, plug the red lead into the
10A jack (Fig. 1, Callout 4) and the black lead into the COM jack.

HOLDING READINGS

Pressing the HOLD button “freezes” any measurement on the LCD and
causes the symbol to appear at its left. Pressing the button again
releases the hold, removes the symbol and resumes real-time
measurements.

MEASURING AC OR DC VOLTAGE



Warning



Do not measure any AC or DC voltage higher than 600V. Doing so may
damage the meter’s internal circuitry.

(1) Turn the rotary switch to one of the or positions, depending on

the type (AC or DC) and amplitude of voltage you expect to

7

encounter. If you are unsure of the type, select one of the
positions. If you are unsure of the amplitude, select either
600 position.

(2) Plug the black test lead into the front-panel COM jack and the

red test lead into the jack.

(3) Touch the black test lead to the lower-potential point of the circuit

under test, and the red test lead to the higher-potential point.

(4) Read the measured voltage on the display. If the readout is .OL, the

voltage level is beyond the currently selected range. If that is the
case, move the rotary switch to the next-widest position. When
measuring DC voltage, if the test leads are reversed a minus sign
will appear at the left of the readout.

MEASURING DC CURRENT



Warning



Do not attempt to measure: 1) currents larger than 200mA through the

jack; 2) currents larger than 10A through the 10A jack; or

3) currents larger than 5A through the 10A jack for more than

10 seconds at a time or for more than 30 seconds every 15 minutes;
pause 1 minute after each measurement of such a large current.

(1) Remove power from the circuit to be tested and discharge all high-

voltage capacitors.

(2) Turn the rotary switch to one of the positions, depending on the

amplitude of the current you expect to encounter. If you are unsure
of the amplitude, select the 10A position.

(3) Plug the black test lead into the black COM jack at the bottom left

of the front panel.

(4) Plug the red test lead into the or 10A jack. Choose the 10A

jack if you have set the rotary switch to the 10A position, and the

jack if you have set the rotary switch to any other position.

(5) Break the circuit and touch the red lead to the higher-voltage side

of the break and the black lead to the lower-voltage side.

(6) Re-apply power to the circuit and observe the display. If it shows

O.L, the current amplitude is beyond the selected current range. If
that is the case, move the rotary switch to the next-widest position.

8

RED TEST LEAD

BLACK TEST LEAD

If the readout is a negative value, the leads are reversed but the
absolute value represents a valid measurement of current
amplitude.

(7) Remove power from the circuit and discharge all high-voltage

capacitors.

(8) Remove the test leads and restore the circuit to its original

condition by eliminating the break you made in Step 5.

MEASURING RESISTANCE



Warning



To avoid electrical shock or damage to the meter when measuring
resistance, turn off all power to the circuit and discharge all high­voltage capacitors.

(1) Turn the rotary switch to one of the Ω positions. If you are unsure

how much resistance you expect to encounter, select the 200
position.

(2) Plug the black test lead into the front-panel COM jack and the red

test lead into the jack.

(3) Measure the resistance by touching the test leads to the desired

test points of the circuit or to the terminals of a component, as
shown below.

(4) Read the measured resistance on the display. If the readout is .OL,

the resistance value is beyond the currently selected range. If that
is the case, move the rotary switch to the next-widest position.

CHECKING FOR CONTINUITY



Warning



To avoid possible damage to the meter or other equipment, turn off the
power source and discharge all high-voltage capacitors.

(1) Turn the rotary switch to the (200 Ω) position.
(2) Plug the black test lead into the COM jack and the red test lead into

the jack.

9

(3) Touch the test leads to any two points of the circuit. The resistance

between those two points will be displayed. If the resistance is
<40Ω, the beeper will sound continuously. If there is no continuity
(an open circuit or a resistance >40Ω) between the two points,
OL. will appear on the readout.

CHECKING THE INTEGRITY OF A DIODE



Warning



To avoid possible damage to the meter or other equipment, turn off the
power source and discharge all high-voltage capacitors.

(1) Turn the function switch to the (2kΩ) position.
(2) Plug the black test lead into the front-panel COM jack and the red

test lead into the jack.

(3) Touch the red test lead to the anode (positive terminal) of the diode

to be tested and the black test lead to its cathode (negative
terminal), as shown below.

(4) Read the diode’s forward bias voltage drop on the display. A silicon

diode typically has a forward voltage drop of 0.7V. A germanium
diode typically has a forward voltage drop of 0.3V. A 0V reading in
both directions indicates a shorted diode. A readout of .OL means
either of two things: the leads are reversed, or the diode is
defective. Reverse the leads. If this still produces a readout of .OL,
the diode is defective and should be replaced.

CHECKING BATTERY VOLTAGE



Warning



To avoid possible electrical shock or damage to the meter, do not
apply a voltage greater than 250V between the meter’s and
COM jacks.

(1) Turn the rotary switch to the position corresponding to the

nominal voltage of the battery to be tested (12V, 9V or 1.5V).

10

RED TEST LEAD BLACK TEST LEAD

(2) Plug the black test lead into the COM jack and the red test lead into

the jack.

(3) Touch the red test lead to the battery’s anode (+ terminal) and the

black test lead to its cathode (– terminal). The battery’s voltage will
appear on the display.

USING THE NCV DETECTOR

To check whether a line, cable or AC outlet is “hot”

(energized), touch
it with the top of the meter or bring the top within 1/4 inch of it while
pressing and holding the

NCV

button (Fig. 1, Callout 7) . If the beeper
sounds repeatedly and the red LED at the top of the meter (Callout 8)
flashes rapidly, the line or outlet is carrying at least 110VAC

RMS

.

The NCV detector works with the rotary function switch in any
position.

SPECIFICATIONS

Pa

rameter or

Feature/Function

Attribute Specification

AC voltage Measurement ranges 0 to 200V/600V

Measurement accuracy ±(1% of reading + 5 digits)

Maximum resolution 0.1V

DC voltage Measurement ranges 0 to 200mV/2V/20V/200V/600V

Measurement accuracy ±(0.8% of reading + 5 digits)

in 600V range;

±(0.5% of reading + 2 digits)

in other ranges

Maximum resolution 0.1mV

DC current Measurement ranges 0 to 2mA/20mA/200mA/10A

Measurement accuracy ±(1.2% of reading + 3 digits) in

10A range; ±(0.8% of reading

+ 3 digits) in other ranges

Maximum resolution 1␮A

Resistance Measurement ranges 0 to 200Ω/2kΩ/20kΩ/

200kΩ/2MΩ

Measurement accuracy ±(0.8% of reading + 4 digits)

Maximum resolution 0.1Ω

11

Continuity Open circuit voltage 2.9V

Threshold <40Ω

Diode integrity Forward DC current 1mA

Reverse DC voltage 2.9V

Battery voltage Measurement ranges 12V, 9V, 1.5V

Measurement accuracy ±(0.8% of reading

+ 7 digits) in

12V

and

9V

positions; ±(3% of reading

+ 5 digits) in

1.5V

position

Max resolution 1mV
Safety rating CAT II 600V
NCV detection voltage & distance >110VAC

RMS

@ <1/4 in. (6mm)

Maximum input voltage 600VDC/AC

RMS

Overvoltage protection 250VDC/AC

RMS

Fuse protection 250mA/250V fuse for jack;

10A/250V fuse for

10A

jack
Sampling time 3X/sec
Display No. of digits 3-1/2

Maximum count 2000
Low battery indication threshold <6.7VDC
Operating temperature 32° to 104°F (0° to 40°C)

@<80%RH
Power source (1) “9V” battery (not included)
Dimensions 7.40 x 3.66 x 1.97 in.

(188 x 93 x 50mm)

Weight (including battery) 13.4 oz. (380g)

Note: Accuracy values are stated for an operating temperature between

64° and 82°F (18° and 28°C) with RH<80%. Accuracies are
lower outside this range, in proportion to the actual operating
temperature's distance from the “sweet spot.”

12

OPERATING & MAINTENANCE TIPS

When the icon appears in the upper left corner of the LCD,
immediately replace the “9V” battery that powers the meter. Before
following the instructions on p. 7, power off the meter and unplug the
test leads.

To replace a blown fuse:

1. Power off the meter.

2. Unplug the test leads.

3. Remove the meter's outer holster by using both hands to spread it
apart.

4. Loosen the screw that secures the meter’s back cover.

5. Remove the four Phillips-head screws that secure the two halves of
the housing and pull the two halves apart.

6. Locate the blown fuse on the circuit board. The DMM30 uses two
different ceramic fuses. The jack is protected by an
F250mA/250V fuse. The 10A jack is protected by an F10A/250V
fuse. Each fuse is located directly behind the jack it protects.

7. Using another multimeter or a continuity checker, verify that the
suspected blown fuse produces a resistance reading consistent
with an open circuit.

8. Replace the blown fuse by a fuse with the same current and voltage
ratings.

9. Rejoin both halves of the housing by replacing and tightening its
four screws.

10. Replace the back cover and tighten its screw.

11. Replace the outer holster.

Do not operate the DMM30 in the presence of a flammable or
explosive gas or near an arc welder or induction heater.

After subjecting the meter to a large change in ambient temperature,
wait at least 30 minutes before making measurements to guarantee
the accuracy of readings.

Remove the battery when storing the meter or when you do not expect
to use it for an extended period of time (months rather than weeks).

Do not disassemble the meter or immerse it in water.

13

WARRANTY INFORMATION

General Tools & Instruments’ (General’s) DMM30 8-Function Digital
Multimeter with NCV Detection is warranted to the original purchaser
to be free from defects in material and workmanship for a period of
one year. Subject to certain restrictions, General will repair or replace
this instrument if, after examination, the company determines it to be
defective in material or workmanship. The warranty period begins on
the date of purchase. You are encouraged to register your product
online. General will extend your warranty an additional
60 days if you register at www.generaltools.com/ProductRegistry.

This warranty does not apply to damages that General determines to
be from an attempted repair by non-authorized personnel or misuse,
alterations, normal wear and tear, or accidental damage. The defective
unit must be returned to General Tools & Instruments or to a General­authorized service center, freight prepaid and insured.

Acceptance of the exclusive repair and replacement remedies
described herein is a condition of the contract for purchase of this
product. In no event shall General be liable for any incidental, special,
consequential or punitive damages, or for any cost, attorneys’ fees,
expenses, or losses alleged to be a consequence of damage due to
failure of, or defect in any product including, but not limited to, any
claims for loss of profits.

Register now at www.generaltools.com/ProductRegistry to receive a
60-day extension to your warranty.

14

RETURN FOR REPAIR POLICY

Every effort has been made to provide you with a reliable product of
superior quality. However, in the event your instrument requires repair,
please contact our Customer Service to obtain an RGA (Return Goods
Authorization) number before forwarding the unit via prepaid freight to
the attention of our Service Center at this address:

General Tools & Instruments
80 White Street
New York, NY 10013

212-431-6100
Remember to include a copy of your proof of purchase, your return
address, and your phone number and/or e-mail address.

15

GENERAL TOOLS & INSTRUMENTS

80 White Street

New York, NY 10013-3567

PHONE [phone]

FAX [phone]

TOLL FREE [phone]

e-mail: [e-mail]

www.generaltools.com

DMM30 User’s Manual

Specifications subject to change without notice

NOTICE - NOT RESPONSIBLE FOR TYPOGRAPHICAL ERRORS.

©2015 GENERAL TOOLS & INSTRUMENTS

MAN# DMM30

1/28/15

General Tools & Instruments

GeneralToolsNYC