AstroAI M4KOR Digital Multimeter

Precautions

To avoid electric shock, personal injury, or damage to the meter or equipment under test, follow these rules:

• Inspect the meter's exterior case before use. Do not use if damaged or if parts are missing. Check for cracks or missing plastic. Pay special attention to the insulation around the connectors.
• Do not use or store the meter in high temperatures, high humidity, or strong magnetic fields. Moisture can degrade performance.
• Ensure test leads have no insulation damage or exposed metal. Verify test lead continuity.
• Exercise extreme caution when selecting settings for current and voltage measurements. Incorrect settings can damage the meter.
• Do not apply voltage exceeding the meter's ratings between terminals or between a terminal and ground.
• Be cautious of electric shock when measuring voltages exceeding 60V DC or 30Vrms AC.
• Use the correct terminals, function, and range for the measurement.
• When using test leads, keep fingers behind the finger guards.
• Before testing resistance, continuity, or diodes, disconnect power to the circuit and discharge all high-voltage capacitors.
• Disconnect test leads and power before opening the meter case.
• When repairing the meter, use only replacement parts with the same model number or electrical specifications.
• Do not modify internal circuits to avoid damaging the meter.
• Clean the meter surface with a soft cloth and mild detergent. Do not use abrasive cleaners or solvents, as they can corrode or damage the surface.
• Turn off the meter when not in use. For long-term storage, remove the batteries. Batteries may leak over time, so inspect them periodically.
• Replace leaking batteries immediately, as they can damage the meter.
• Do not move the multimeter during measurement, as it may lead to inaccurate readings.

Package Contents

• User Manual: 1 pc
• Test Lead Pair: 1 pc
• AstroAI 4000 Count Digital Multimeter: 1 pc

Electrical Symbols

• ⚠ Caution
• = AC and DC
• ⌂ Ground (Earth)
• ⚡ Fuse
• ⏣ DC (Direct Current)
• ⏢ AC (Alternating Current)
• ☂ Double Insulation
• 🖳 Low Battery
• CE [CE Marked]

CAT III test instruments are suitable for testing and measuring circuits connected to the distribution part of the low-voltage power supply unit in buildings.

Dimensions

The multimeter measures approximately 5.9 inches in length and 2.8 inches in width.

Product Diagram

The multimeter features the following components:

• ① NCV Detector
• ② Indicator Light
• ③ HOLD Button
• ④ FUNC Button
• ⑤ Rotary Dial
• ⑥ COM Terminal
• ⑦ 10A Terminal
• ⑧ Flashlight
• ⑨ LCD Screen
• ⑩ MAX Button
• ⑪ Backlight/Flashlight Button
• ⑫ Input Terminals
• ⑬ Test Leads

Function Description

Button Functions

• ① HOLD Button: Press this button during measurement to freeze (hold) the reading for easy recording. The screen will display 'H' when the hold function is active. Press again to release data hold.
• ② FUNC Button: Use the rotary dial to select a function. If a rotary dial setting has multiple functions, use the 'FUNC' button to select the specific function (e.g., switching between AC voltage test and DC voltage test, or selecting diode test and continuity test). Caution: Pay close attention to function selection before performing tests.
• ③ MAX Button: Pressing this button displays and holds the maximum value recorded by the multimeter during a measurement test. The maximum value is cleared when the test function is changed or the meter is turned off.
• ④ Backlight/Flashlight Button: Press this button to turn the screen backlight on/off. Press to turn the flashlight on/off.

Settings (Rotary Dial Functions)

Note: If a rotary dial setting has multiple functions, use the 'FUNC' button to select the specific function.

• V=: AC/DC Voltage Test: 0.01 V ~ 600 V
• mV=: AC/DC Voltage Test: 0.01 mV ~ 400 mV
• Ω: Resistance Test: 0.1 Ω ~ 40 MΩ
• +: Capacitance Test: 0.01 nF ~ 4 MF
• ⚡: Audible Continuity Test
• →: Diode Test
• Battery Voltage Test: 1.5 V, 9 V, 12 V
• mA=: AC/DC Current Test: 0.01 mA ~ 400 mA
• A=: AC/DC Current Test: 400 mA ~ 10 A
• NCV Live: NCV Detection / Live Wire Detection

Test Lead Terminals

• ① For current from 400 mA to 10 mA: Connect the red test lead to this terminal.
• ② Connect the black test lead to this terminal (COM).
• ③ For current up to 400 mA: Connect the red test lead to this terminal.

Other Functions

• Auto Power Off: The meter automatically turns off after 15 minutes of inactivity. To turn it back on, rotate the range dial or press a button.
• Auto Power Off Cancel: With the multimeter off, press and hold the 'FUNC' button, then rotate the rotary dial until the meter beeps and the 'APO' icon disappears from the screen. This indicates the auto-shutoff function has been cancelled. It will reactivate upon restart.

How to Use the Multimeter

This digital multimeter is highly sensitive and can be affected by nearby magnetic fields. If you power it on without touching anything, readings may appear on the screen. This is normal behavior for a digital multimeter and does not affect measurement results.

Voltage Measurement

1. Insert the red test lead into the 'Input' (red) jack and the black test lead into the 'COM' (black) jack.
2. Set the rotary dial to 'V=' for voltage measurement. If the voltage is below 400 mV, set the dial to 'mV='. Press the 'FUNC' button to switch between AC and DC. 'DC' will be displayed for DC settings, and 'AC' for AC settings.
3. Connect the two test leads to the neutral and live wires, respectively (red to live, black to neutral).
4. Once the reading is stable, record it from the LCD screen.
5. Turn off the meter by rotating the rotary dial to the 'OFF' position.

Voltage Measurement Precautions:

• To avoid damaging the meter, do not measure voltages exceeding 600V DC or 600V AC.
• Pay close attention to the voltage setting on the multimeter. The LCD screen will indicate whether the setting is AC or DC. Use the 'FUNC' button to select the correct setting.
• Measuring DC with an AC setting, or vice versa, can damage the meter and the component being tested.

Resistance Measurement

1. Insert the red test lead into the 'Input' (red) jack and the black test lead into the 'COM' (black) jack.
2. Set the rotary dial to the 'Ω' setting.
3. Place the test leads across the terminals of the resistor being measured, ensuring firm contact.
4. The result will be displayed on the LCD screen.
5. If the measured value is equal to the resistor's nominal resistance within the specified tolerance, the resistor is functioning correctly. A large deviation between the nominal and measured resistance indicates a malfunction. If the measured resistance is infinite (open circuit), zero (short circuit), or unstable, the meter may be damaged or the component may be unusable.

Resistance Measurement Precautions:

• Do not change the resistance setting during measurement, as it may damage the meter and affect test results.
• Do not test parallel circuits, as it may affect measurement accuracy and yield incorrect results.
• Do not directly measure the internal resistance of components like micrometers, galvanometers, or batteries.

Capacitance Measurement

1. Insert the red test lead into the 'Input' (red) jack and the black test lead into the 'COM' (black) jack.
2. Set the rotary dial to the '+' setting. Press the 'FUNC' button to switch to Capacitance Test.
3. Connect the test leads firmly to both terminals of the capacitor.
4. The measurement result will be displayed on the LCD screen.

Continuity Test

1. Turn off the power to the circuit being tested.
2. Insert the red test lead into the 'Input' (red) jack and the black test lead into the 'COM' (black) jack.
3. Set the multimeter to the '⚡' setting and turn on the power. When the tips of the test leads touch, an audible beep will sound if the connection is normal.
4. When the circuit is connected, the buzzer will sound, and the indicator light will turn green. The resistance value will also be displayed. If there is no continuity, the buzzer will not sound, and 'OL' will be displayed, indicating infinite resistance.

Continuity Test Notes:

• An audible 'beep' indicates that the resistance of the circuit under test is less than 30Ω.
• Overload Protection: 250V.

Diode Test

1. Insert the red test lead into the 'Input' (red) jack and the black test lead into the 'COM' (black) jack.
2. Set the rotary dial to the '→' setting. Press the 'FUNC' button to switch to Diode Test.
3. Connect the red test lead to the positive terminal of the diode and the black test lead to the negative terminal. (Generally, the positive terminal of a diode is the longer lead).
4. The LCD will display the voltage drop across the diode. If the leads are not correctly connected to the diode's terminals, 'OL' will be displayed.

Diode Test Tips:

• Normal Diode Function: When the red test lead is connected to the positive terminal of the diode and the black lead to the negative terminal, the diode is in forward conduction. If connected correctly, the displayed value is the forward voltage drop. The forward voltage drop for typical silicon diodes is 0.5 ~ 0.7V, and for germanium diodes, it is 0.15 ~ 0.3V.
• If '000' is displayed, the diode is faulty. If 'OL' is displayed, check that the red test lead is connected to the negative terminal of the diode under test and the black test lead to the positive terminal.

Polarity Determination Method:

1. Switch the multimeter to resistance setting.
2. Connect the two test leads to the two terminals of the diode.
3. Measure one result, then swap the test leads and measure the second result.
4. The result with the larger resistance is the reverse bias, and the result with the smaller resistance is the forward bias. For lower resistance, the terminal connected to the black test lead is the positive terminal, and the terminal connected to the red test lead is the negative terminal.

Battery Test

1. Insert the red test lead into the 'Input' (red) jack and the black test lead into the 'COM' (black) jack.
2. Use the rotary dial to select the battery test setting for 1.5V, 9V, and 12V batteries.
3. Connect the red test lead to the positive terminal and the black test lead to the negative terminal.
4. Once the reading is stable, record it from the LCD screen. The indicator light will turn red if the battery voltage is low.

Battery Test Tips:

• Checking for a Degraded Car Battery:
  1. Set the multimeter to the appropriate battery test setting.
  2. Connect the test leads to the positive and negative terminals of the battery.
  3. Start the car and turn on the car's air conditioning. Check the voltage display.
  4. If the voltage drops significantly, the battery is degraded. If the battery voltage drops significantly below 12V during this test, it indicates the car battery needs replacement.
• Checking if the Battery is Supplying Power:
  1. Measure the battery voltage.
  2. If the displayed voltage is above the rated voltage, the battery is supplying power normally.
  3. If the measured voltage is lower than the rated voltage, the battery is degraded and needs replacement.
  4. If the reading is 0, it means the battery has high internal resistance or is damaged.
  Note: Do not test batteries directly with current or resistance settings.

Current Measurement

1. Set the rotary dial to 'mA=' or 'A~' depending on the current level.
2. Press the 'FUNC' button to switch between AC/DC. 'DC' will be displayed for DC function, and 'AC' for AC function.
3. For the 'mA=' setting, insert the red test lead into the 'mA' terminal and the black test lead into the 'COM' terminal.
4. For the 'A~' setting, insert the red test lead into the 10A terminal and the black test lead into the 'COM' terminal.
5. Turn off the power to the circuit being tested. Connect the meter in series with the circuit to be measured, then turn on the circuit power.
6. The reading will be displayed on the LCD screen.

Car Battery Standby Current Measurement

1. Confirm if the battery voltage and charging system are within the normal range. Battery voltage is typically around 12.7V, and charging voltage is around 14V.
2. Turn off all electrical devices inside and outside the car, and close the doors.
3. Remove the battery's negative terminal. Set the multimeter to the maximum current measurement range and connect it in series with the battery. Connect the red test lead to the wire disconnected from the negative terminal, and the black test lead to the battery terminal.
4. Adjust the meter to a lower range if necessary.
5. To accurately measure standby current (discharge current), wait approximately 30 minutes for all vehicle modules to enter sleep mode, then measure the current. Standby current is typically 0.02A (20mA), but varies by vehicle, generally not exceeding 50mA.
6. If the standby current (discharge current) is greater than 50mA, check which circuit has an excessive load by removing one fuse at a time.
7. If removing a fuse reduces the current to below 50mA, that circuit is identified as having an excessive discharge.

Current Measurement Precautions:

• If the red test lead was inserted into the 10A terminal, always return it to the 'input' terminal after testing. Failing to switch the terminals before the next operation can damage the multimeter.
• For safety, when measuring high currents, limit the measurement time to no more than 10 seconds. Also, ensure an interval of at least 15 minutes between measurements.
• A circuit must have a load when testing current. Do not connect the multimeter in series with a circuit that has no load, as this may damage the meter.
• Do not measure current exceeding the meter's range, as it may cause damage.

Non-Contact Voltage (NCV)

The NCV function detects AC voltage without using test leads.

1. Set the rotary dial to the NCV function (symbol often depicted as a lightning bolt or similar).
2. Move the NCV detector close to the point you want to test.
3. If the meter detects a weak AC signal, the green indicator light will illuminate, and the buzzer will emit a slow beep.
4. If the meter detects a strong AC signal, the red indicator light will illuminate, and the buzzer will emit a fast beep.

NCV Note: This function does not affect the meter's subsequent measurements after exiting the NCV setting. If the rotary switch is not in the NCV position, the meter operates normally.

Live Wire Detection

1. Insert the red test lead into the 'input' (red) terminal. Do not insert the black test lead into a terminal.
2. Set the rotary dial to the 'Live' setting (symbol often depicted as a lightning bolt or similar). Press the 'FUNC' button to switch to Live Wire detection; 'Live' will be displayed on the screen.
3. Touch the tip of the red test lead to the measurement point.
4. If the meter detects a weak AC signal, the green indicator light will illuminate, and the buzzer will emit a slow beep.
5. If the meter detects a strong AC signal, the red indicator light will illuminate, and the buzzer will emit a fast beep.

Maintenance

Battery Replacement

Replace the batteries when the low battery indicator appears on the LCD display. Remove the rubber cover and screws on the back, then replace the depleted batteries with new ones (4 x AAA, 1.5V x 2). Note: Replace batteries immediately to prevent inaccurate readings due to low power, which can also lead to potential safety issues.

Fuse Replacement

Fuses rarely need replacement and are typically blown due to operational errors. To replace a fuse:

• Remove the test leads.
• Remove the rubber sleeve and screws on the back cover of the meter.
• Open the back of the meter and replace with a fuse of the same rating.

It is important that the rating of the replacement fuse is the same:

• Fuse 1: F400mA/250V fuse, φ5mm×20mm.
• Fuse 2: F10A/250V fuse, φ5mm×20mm.

Troubleshooting

Measurement Value Unstable

• Check test leads for damage.
• Verify connection between test leads and the object under test.
• Verify connection between test leads and the meter.

Measurement Value Inaccurate

• Check test leads for damage.
• Check if battery replacement is needed.

Large Range Error

The shunt resistance may need adjustment or replacement.

No Measurement Value

• Check fuses for damage.
• Check test leads for damage.

Detailed Specifications

DC Voltage

• Input Impedance: 10MΩ.
• Maximum Input Voltage: 600V.
• Overload Protection: 600V.

AC Voltage

• Input Impedance: 10MΩ.
• Overload Protection: 600 V.
• Maximum Input Voltage: 600 V.
• Frequency Range: 40 Hz ~ 1KHz.
• Response: True RMS.

DC Current

Overload Protection: mA: F400 mA / 250 V fuse; A: F10 A / 250 V fuse. (For >5A measurement: limit <10 sec, interval >15 min)

AC Current

• Frequency Range: 40 Hz ~ 1KHz.
• Response: True RMS.

Resistance

Overload Protection: 250 V.

Battery

Capacitance

Overload Protection: 250V.

Warranty

AstroAI 3-Year Limited Warranty.

This product is manufactured under strict quality control. However, fuses, batteries, and damage caused by improper operation, normal wear and tear of mechanical parts, contamination, or modification are outside the warranty coverage. Furthermore, the warranty is void if the product is transferred to another party.

For any questions regarding this product, please contact AstroAI Customer Support at support@astroai.com.

Contact Information

Web: www.astroai.com

E-mail: support@astroai.com