Circuit-test DMR-2400 User manual

USER'S MANUAL
DIGITAL MULTIMETER
DMR-2400
CIRCUIT-TEST ELECTRONICS
www.circuittest.com

– 1 –
TABLE OF CONTENTS
SAFETY
Safety Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Safety Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
INTRODUCTION
Front Panel Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
SPECIFICATIONS
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Ranges and Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
OPERATING INSTRUCTIONS
1. DC Voltage Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2. AC Voltage Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7
3. DC Current Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-8
a) less than 200mA DC current
b) 200mA or more DC current
4. Resistance Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5. Continuity Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-9
6. Diode Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
7. Signal Injection Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
8. Battery Replacement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
9. Fuse Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10-11
MAINTENANCE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
ACCESSORIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
WARRANTY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

– 2 –
SAFETY INFORMATION
This meter is CUL and UL approved. This meter is designed to be safe un-
der the following conditions: indoor use, altitude up to 2000m, temperature
5°C to 40°C, maximum relative humidity 80% for temperatures up to 31°C
decreasing linearly to 50% relative humidity at 40°C and rated pollution
degree 2. Caution and proper guidelines must be followed for personal
and product safety. Read this instruction manual carefully and completely
before using the meter. Lack of caution or poor safety practices can result
in serious injury or death.
• This meter is not recommended for high voltage industrial use; for
example, do not use for measurement on 440VAC or 600VAC industrial
power mains. The unit is intended for use with low energy circuits up to
600VDC / 600VAC or high energy circuits up to 250VAC / 250VDC only.
• Use caution when working above 60VDC or 30VAC RMS as these volt-
ages pose a shock hazard.
• Always consider circuits to be energized. Never assume any equipment
to be de-energized.
• Always start with power off. Set the function switch to the correct setting
before making any measurements and do not change position of the
function switch during measurements.
• Never connect unit to AC or DC powered circuits when the function
switch is set to resistance, diode check or continuity ranges.
• Always disconnect the power when performing resistance, diode or
capacitance tests. Discharge capacitor before testing.
• Disconnect the live/positive test lead (red) prior to disconnecting the
common/negative test lead (black).
• When ʻLO BATʼ appears on the display, change both batteries to
achieve more accurate readings.
• Disconnect test leads from the meter before removing the batteries or
the fuse.
• Do not operate the unit unless the case is completely closed.
• When using the test probes always keep fingers behind the finger
guards. Never touch the exposed probe tip.
• Always inspect the instrument, test leads and other accessories for
damage prior to use.
• Use only UL recognized test leads (included with this meter).

– 3 –
SAFETY SYMBOLS
Safety symbols and special annunciators on the meter and in this manual
indicate cautions and warnings of important operational procedures that must
be followed to ensure personal and product safety.
This symbol indicates a General Warning. When adjacent to a termi-
nal or operating device indicates that the operator must refer to an
explanation in the Operating Instructions.
500V
MAX
This symbol indicates that the terminal(s) so marked must not be con-
nected to a circuit point at which the voltage with respect to ground
exceeds 500V AC/DC.
This symbol adjacent to one or more terminals indicates them as
being associated with ranges that may in normal use, be subjected
to particularly hazardous voltages. For maximum safety, the meter
and its test leads should not be handled when these terminals are
energized.
INTRODUCTION
DMR-2400 is a manual ranging compact digital multimeter with a 2000 count
LCD display. This meter can measure/test the following:
– Voltage – DC Current
– Resistance – Continuity
– Diode – Audio Devices (Signal Injection)
FRONT PANEL DESCRIPTION
NO. ITEM DESCRIPTION
1LCD Display 3-1/2 digit 2000 count LCD Display
2Function Switch Function switch to select measurement mode
310A Jack Positive input jack to plug in red test lead for 10A measurement
only
4V/ /mA/ Jack Positive input jack to plug in red test lead for voltage, resistor,
current up to 200mA and signal injection
5 Jack Plug in black test lead in all measurement modes, common ground

– 4 –
SPECIFICATIONS
GENERAL
Display: 3 1/2 digit 2000 count LCD
Maximum Display: 1999
Ranging: Manual
Polarity: Automatic, minus (-) sign indicates negative polar-
ity, no sign for positive polarity
Input impedance: 1M DCV / 452K ACV
Diode Test: Test current of 1.5mA maximum
Signal Injection: 2VAC Peak Approx., 30 to 40Hz Square Wave
Over range indication: ʻIʼ is displayed
Operating Temp: 0 to 50°C (32 to 122°F)
Power Source: 2 x AA 1.5V Batteries
Fuse: 0.8A/250V (5x20mm Fast Acting),
10A/250V (6.3x32mm Fast Acting)
Dimensions: 145(H) x 70(W) x 32(D) mm
(511/16 x 23/4 x 11/4")
Weight: 216g (7.6oz)
Accessories included: One pair of test leads, 2 x AA batteries,
Userʼs manual

– 5 –
RANGES AND ACCURACY
FUNCTION RANGE RESOLUTION ACCURACY
DC VOLTAGE
(DC V)
200mV
2000mV
20V
200V
1000V
100µV
1mV
10mV
100mV
1V
±(1% reading + 6 digits)
±(1.5% reading + 8 digits)
AC VOLTAGE
(AC V)
200V
750V
100mV
1V
±(1.2% reading + 20 digits)
DC CURRENT
(DC A)
200µA
2000µA
20mA
200mA
10A
100nA
1µA
10µA
100µA
10mA
±(1.2% reading + 8 digits)
±(1.2% reading + 10 digits)
RESISTANCE 200
2000
20k
200k
2000k
20M
100m
1
10
100
1k
10k
±(1.2% reading + 8 digits)
±(2% reading + 10 digits)
NOTE: Accuracy consists of: (% reading i.e. accuracy of the measurement circuit +
digits i.e. accuracy of the analog to digital converter)

– 6 –
OPERATING INSTRUCTIONS
1. DC VOLTAGE MEASUREMENT
WARNING: MAXIMUM INPUT IS 1000V DC. USE EXTREME CAUTION WHEN WORKING
WITH HIGH VOLTAGES. NEVER APPLY THE TEST LEAD TO THE MEASURING CIRCUIT WHEN
CHANGING THE POSITION OF THE FUNCTION SWITCH. IF YOU ARE UNSURE OF THE VOLTAGE
BEING MEASURED, SELECT THE HIGHEST RANGE AND REDUCE UNTIL A SATISFACTORY
READING IS OBTAINED.
➔ Set the function switch to 1000 on the DC VOLTS scale.
➔ Plug the red test lead in V/ /mA/ jack and the black test lead in
jack.
➔ Apply the test leads to the circuit to be measured. Ensure that the black
lead is connected to the negative side of the circuit and red lead to the
positive.
➔ Read the displayed voltage.
➔ If the reading displayed does not have a sufficient number of digits i.e.
00.2 Instead of 1.786, set the function switch to the next lower range.
Repeat until you have maximum digits possible without displaying ʻIʼ.
➔ If the minus (-) sign appears it means the voltage is negative at the
point being measured.
➔ If ʻIʼ appears on the display, it indicates over-range. Immediately remove
test leads from the measuring circuit to avoid any damage to the meter.
The input voltage should not exceed the measurement capability of this
meter.
2. AC VOLTAGE MEASUREMENT
WARNING: MAXIMUM INPUT IS 750V AC. USE EXTREME CAUTION WHEN WORKING
WITH HIGH VOLTAGES. NEVER APPLY TEST LEADS TO THE MEASURING CIRCUIT WHEN
CHANGING THE POSITION OF THE FUNCTION SWITCH. IF YOU ARE UNSURE OF THE VOLTAGE
BEING MEASURED, SELECT THE HIGHEST RANGE AND REDUCE UNTIL A SATISFACTORY
READING IS OBTAINED.
➔ Set the function switch to 750 on the AC VOLTS scale.
➔ Plug the red test lead in V/ /mA/ jack and the black test lead in
jack.
➔ Apply the test leads to the circuit to be measured.
➔ Read the displayed voltage.

– 7 –
➔ If the reading displayed does not have a sufficient number of digits, i.e.
115 instead of 115.4, set the function switch to the lower range.
➔ If ʻIʼ appears on the display, it indicates over-range. Immediately remove
test leads from the measuring circuit to avoid any damage to the meter.
The input voltage should not exceed the measurement capability of this
meter.
3. DC CURRENT MEASUREMENT
WARNING: WHEN MEASURING CURRENT REMOVE ALL POWER FROM THE CIRCUIT
BEING TESTED. NEVER APPLY THE TEST LEAD TO THE MEASURING CIRCUIT WHEN CHANG-
ING THE POSITION OF THE FUNCTION SWITCH. IF YOU ARE UNSURE OF THE CURRENT
BEING MEASURED, SELECT THE HIGHEST RANGE AND REDUCE UNTIL A SATISFACTORY
READING IS OBTAINED.
a) Less than 200mA DC Current Measurement
➔ Set the function switch to 200m on the DC AMPS scale.
➔ Plug the red test lead in V/ /mA/ jack and the black test lead in
jack.
➔ Remove power from the circuit that is to be measured. Open up the
circuit and connect the black lead to the negative side and the red lead
to the positive side of the circuit so that the test leads are in series with
the load to be measured.
➔ Apply power to the circuit.
➔ Read the displayed current.
➔ If the numeric value in the display is too small, change the function
switch to next lower range. Repeat until you have maximum digits pos-
sible without displaying ʻIʼ.
➔ If ʻIʼ appears on the display, it indicates over-range. Immediately remove
test leads from the measuring circuit to avoid any damage to the meter.
b) 200mA or more DC Current Measurement
CAUTION! Do not exceed 10 seconds when measuring the 10A range and
wait for 30 minutes between each measurement.
➔ Set the function switch to 10A on the DC AMPS scale.
➔ Plug the red test lead in 10A jack and the black test lead in jack.

– 8 –
➔ Remove power from the circuit that is to be measured. Open up the
circuit and connect the black lead to the negative side and the red lead
to the positive side of the circuit so that the test leads are in series with
the load to be measured.
➔ Apply power to the circuit.
➔ Read the displayed current.
➔ If ʻIʼ appears on the display, it indicates over-range. Immediately remove
test leads from the measuring circuit to avoid any damage to the meter.
4. RESISTANCE MEASUREMENT
WARNING: NEVER CONNECT THE TEST LEAD TO ANY VOLTAGE WHEN THE FUNC-
TION SWITCH IS SET TO . REMOVE ALL POWER FROM THE CIRCUIT BEING TESTED WHEN
CHECKING RESISTANCE. DISCHARGE ANY CHARGED CAPACITORS. NEVER APPLY THE TEST
LEAD TO THE MEASURING CIRCUIT WHEN CHANGING THE POSITION OF THE FUNCTION
SWITCH. IF YOU ARE UNSURE OF THE RESISTANCE BEING MEASURED, SELECT THE HIGH-
EST RANGE AND REDUCE UNTIL A SATISFACTORY READING IS OBTAINED.
➔ Set the function switch to the desired OHMS scale.
➔ Plug the red test lead in V/ /mA/ jack and the black test lead in
jack.
➔ Apply the test leads to the resistor being measured. If the resistor is part
of a circuit, it is necessary to disconnect one end of the resistor to avoid
any unwanted interference from the rest of the circuit.
➔ Read the displayed resistance.
NOTE:
• ‘I’ is also displayed when the inputs are not connected.
• When measuring resistance above 1M , the meter may take a few seconds to get
a stable reading.
• Never measure a resistor that has voltage on it.
5. CONTINUITY TEST
WARNING: NEVER CONNECT THE TEST LEADS TO ANY VOLTAGE WHEN THE FUNC-
TION SWITCH IS SET TO 200 . REMOVE ALL POWER FROM THE CIRCUIT BEING TESTED
WHEN CHECKING RESISTANCE. DISCHARGE ANY CHARGED CAPACITORS.
➔ Set the function switch to 200 on the OHMS scale.
➔ Plug the red test lead in V/ /mA/ jack and the black test lead in
jack.

– 9 –
➔ Apply the test leads to the circuit.
➔ If there is continuity, the display will read about 0.5 Ohms. If there is an
open circuit, the display will read ʻIʼ.
6. DIODE TEST
WARNING: NEVER CONNECT THE TEST LEAD TO ANY VOLTAGE WHEN THE FUNC-
TION SWITCH IS SET TO . REMOVE ALL POWER FROM THE CIRCUIT BEING TESTED WHEN
PERFORMING THE DIODE TEST. DISCHARGE ANY CHARGED CAPACITORS.
Note: If the diode is part of a circuit, it is necessary to disconnect one end of the diode
to avoid any unwanted interference from the rest of the circuit. The value indicated in
the display during the diode check is the forward bias voltage.
➔ Set the function switch to 2000 on the OHMS scale.
➔ Plug the red test lead in V/ /mA/ jack and the black test lead in
jack.
➔ Apply the test leads across the diode terminals and note the
meter reading.
➔ Reverse the diode and note this reading. Based on the readings the
result can be evaluated as follows:
– If one reading is around 0.5 and the other reading is ʻIʼ, the
diode is good
– If both readings are ʻIʼ, the diode is open (defective)
– If both readings are very small or 0 (zero), the diode is shorted
(defective)
7. SIGNAL INJECTION FUNCTION
This function allows the injection of square wave of about 2V peak at a
frequency of 30 to 40 Hz into an audio device.
➔ Set the function switch to .
➔ Plug the red test lead in V/ /mA/ jack and the black test lead in
jack.
➔ Apply the black test probe tip to the circuit ground and the red test probe
tip to the point in the circuit where you wish to inject the test signal.

– 10 –
8. BATTERY REPLACEMENT
WARNING: DISCONNECT BOTH TEST LEADS FROM ANY SOURCE OF VOLTAGE
BEFORE REMOVING THE BACK COVER. DO NOT OPERATE THE METER UNTIL THE BACK
COVER IS IN PLACE AND FASTENED SECURELY.
ʻLO BATʼ will appear in the display when the battery drops below the operating
voltage and requires replacing.
➔ Turn off the meter and disconnect both test leads.
➔ Remove the single screw securing the battery/fuse cover and lift to
open.
➔ Replace both AA batteries observing the correct polarity.
➔ Replace the cover and tighten the screw.
9. FUSE REPLACEMENT
WARNING: DISCONNECT BOTH TEST LEADS FROM ANY SOURCE OF VOLTAGE
BEFORE REMOVING THE BACK COVER. DO NOT OPERATE THE METER UNTIL THE BACK
COVER IS IN PLACE AND FASTENED SECURELY.
a) 0.8 Amp Fast acting 5x20mm Fuse
➔ Turn off the meter and disconnect both test leads.
➔ Remove the single screw securing the battery/fuse cover and lift to
open.
➔ Remove the batteries.
➔ Gently pull the fuse from its holder by pulling gently on the ribbon.
➔ Replace the blown fuse with a CSA/UL listed fast acting fuse rated at
0.8A/250V only (GMA-0.8A, with the same ribbon ring around the fuse).
Do not use a fuse which has higher rated value than specified or try to
bypass the fuse.
➔ Replace the batteries and cover and tighten the screw.

– 11 –
b) 10 Amp Fast acting 6.3x32mm Fuse (by a professional person
only)
➔ Turn off the meter and disconnect both test leads.
➔ Remove the two screws at the back of the case.
➔ Remove the single screw securing the battery/fuse cover and lift to
open.
➔ Remove the batteries.
➔ Carefully lift the top of the case away from the bottom.
➔ The 10 amp fuse is the larger fuse on the bottom of the PC board,
which should now be in full view. Carefully remove the old fuse and
replace it with a new CSA/UL listed fast acting 10A/250V fuse only
(AGC-10A).
MAINTENANCE
a) Always keep the meter dry.
b) Keep the meter clean. Wipe the case occasionally with a damp cloth.
Do not use chemicals, cleaning solvents or detergents.
c) Use and store the meter in recommended normal environmental
conditions. Extreme temperatures can shorten the life of the electronic
components.
d) Use only fresh batteries.
e) Remove the batteries when the meter is not being used for a long
period of time.

– 12 –
ACCESSORIES
Test Leads (TL-107)
Fuses: 5x20mm Fast 0.8A/250V, 6.3x32mm Fast 10A/250V
Batteries: 2 x AA
OPTIONAL:
Test Leads with Screw-on Alligator Clips (TL-222)
LIMITED WARRANTY
Circuit-Test Electronics warrants to the original purchaser that this product
be free of defect in material or workmanship for a period of 2 years from the
date of purchase. Visit our website (www.circuittest.com) for information on
warranty service.
Any product which has been subjected to misuse or accidental damage is
excluded from the warranty. Except as stated above, Circuit-Test Electronics
makes no promises or warranties either expressed or implied including war-
ranties of merchantability or the fitness for any particular purpose.
Register your product online at www.circuittest.com
CIRCUIT-TEST
ELECTRONICS
A division of R.P. Electronic Components Ltd.
www.circuittest.com