ALIENTEK DM40C Digital Multimeter, Oscilloscope, and Signal Generator User Manual

1. Introduction

Thank you for choosing the ALIENTEK DM40C. This device is a professional 4.5-digit digital multimeter, oscilloscope, and signal generator integrated into a single handheld unit. It offers high precision measurements, a 50M sample rate oscilloscope, and various waveform generation capabilities, making it suitable for a wide range of electrical testing and diagnostic applications.

This manual provides essential information for the safe and effective operation, maintenance, and troubleshooting of your DM40C device. Please read it thoroughly before use.

2. Safety Information

Always observe safety precautions when using electrical testing equipment to prevent personal injury or damage to the device.

• General Safety: Ensure the device is in good working condition before use. Do not operate if damaged.
• Voltage Measurement: For DC-DC or high voltage measurements above 36V, it is recommended to use the AUTO+ mode. This mode skips the millivolt (mV) range to prevent mismeasurement, sparking, and potential damage. The default AUTO mode includes the mV range, which may not be suitable for higher voltages.
• MCX Connector Usage: The MCX pin sizes for the alligator clip and oscilloscope probe differ. The alligator clip's inner pin is larger. Do not attach the alligator clip to the CHA/CHB (oscilloscope analog channels). The alligator clip is intended only for the OUT channel (waveform output) to avoid poor contact or damage to the oscilloscope's analog channels.
• Current Measurement: Ensure the circuit is de-energized before connecting the device for current measurements.
• Fuses: The unit is fused. If a fuse blows, replace it with one of the specified type and rating.
• Test Leads: Use only the provided or equivalent high-quality test leads. The included leads are fine-tipped, suitable for small electronics. For higher-current or heavier work, consider investing in more robust leads.

3. Product Overview

The ALIENTEK DM40C combines three essential tools into one compact device: a digital multimeter, an oscilloscope, and a signal generator. It features a high-resolution IPS touchscreen for clear data display and intuitive control.

Figure 3.1: The ALIENTEK DM40C unit shown with its standard accessories, including test leads, probe leads, and a USB-C cable.

Figure 3.2: This image illustrates the core capabilities of the DM40C: a high-precision multimeter, a 10-bit ADC oscilloscope with 50M sampling rate, and a signal generator.

Key Features:

• Multimeter: 4.5-digit (59999 count) with high precision and 5ppm reference source.
• Oscilloscope: 10-bit ADC, 50MHz sampling rate, 10MHz bandwidth, 64kpts memory.
• Signal Generator: Generates various waveforms (Sine, Sawtooth, Triangular, Square).
• Display: 3.5-inch IPS touchscreen (480x320 resolution).
• Power: Rechargeable battery providing over 10 hours of operation.

Figure 3.3: The device features a 3.5-inch IPS touchscreen (480x320 resolution) for clear display and intuitive interaction.

4. Setup

4.1. Charging the Battery

The DM40C is powered by an internal rechargeable battery. Before first use, fully charge the device using the provided USB-C cable and a compatible USB power adapter (not included). The charging indicator on the device will show the charging status.

4.2. Connecting Test Leads

Connect the test leads to the appropriate input jacks on the right side of the device. The common (COM) jack is typically used for the black lead. The VΩHz°C jack is for voltage, resistance, frequency, and temperature measurements. The A mA uA jack is for current measurements. Ensure connections are secure.

4.3. Initial Power-On

Press and hold the power button to turn on the device. The IPS touchscreen will illuminate, displaying the main interface. Follow any on-screen prompts for initial setup or calibration if presented.

5. Operating Instructions

5.1. General Operation

• Power On/Off: Press and hold the power button.
• Menu Navigation: Use the touchscreen to navigate through menus and select functions.
• Data Hold: Freeze the current reading on the display.
• Relative Measurement (RLE): Measure the difference between a stored reference value and the current reading.
• Data Logging: Record measurement data over time.
• Trend Graph: Visualize measurement data trends graphically.

5.2. Multimeter Mode

The DM40C offers a comprehensive range of multimeter functions. Select the desired measurement mode from the main interface.

Figure 5.1: The automatic measurement feature simplifies operation by automatically selecting the correct range for voltage (0.01mV-1000V DC, 0.01mV-750V AC) and current (0.01uA-10A) without manual mode switching.

• Automatic Measurement: The device can automatically detect and select the appropriate range for voltage (DC: 0.01mV-1000V, AC: 0.01mV-750V) and current (0.01uA-10A).
• Voltage Measurement (AC/DC): Connect leads to COM and VΩHz°C. Select AC or DC voltage mode. Remember to use AUTO+ for high voltage measurements (refer to Safety Information).
• Current Measurement (AC/DC): Connect leads to COM and A mA uA. Ensure the circuit is open and the device is connected in series. The innovative 3-hole design allows fully automatic current measurement across μA/mA/A ranges.
• Resistance Measurement: Connect leads to COM and VΩHz°C.
• Capacitance Measurement: Connect leads to COM and VΩHz°C.
• Diode Test: Connect leads to COM and VΩHz°C. The device provides a 4-stage voltage drop measurement with distinct audible indicators.


Figure 5.2: This screen capture details the diode measurement function with multiple voltage drop indications and the fast continuity test feature, including resistor measurement capabilities.

• Continuity Test: Connect leads to COM and VΩHz°C. An ultra-fast test with an audible indicator.
• Frequency Measurement: Connect leads to COM and VΩHz°C.
• Temperature Measurement: Requires a compatible temperature probe (not included). Connect the probe to the VΩHz°C and COM jacks.
• AC+DC Mixed Measurement: The DM40C supports simultaneous display of both AC and DC components for complex signals.


Figure 5.3: The display demonstrates the device's ability to perform True RMS measurements, simultaneously display AC and DC components, and visualize data trends over time with adjustable time bases.

5.3. Oscilloscope Mode

The integrated oscilloscope provides waveform visualization and analysis. Connect the oscilloscope probe to the CHA/CHB input.

• Basic Setup: Select oscilloscope mode from the main menu. Adjust vertical scale (V/div) and horizontal time base (s/div) as needed.
• Triggering: Set trigger level and type (edge, pulse, etc.) to stabilize waveforms.
• Measurements: The oscilloscope can display various waveform parameters such as peak-to-peak voltage, frequency, and duty cycle.

5.4. Signal Generator Mode

The DM40C can generate various test signals. Connect the output to the OUT channel using the alligator clip (refer to Safety Information regarding MCX connector usage).

• Waveform Selection: Choose from Sine wave, Sawtooth wave, Triangular wave, or Square wave.
• Frequency Adjustment: Set the desired output frequency (1Hz to 50KHz for most waveforms, up to 10MHz for square wave).
• Amplitude Adjustment: Adjust the peak-to-peak voltage (0.5Vpp to 3.0Vpp).
• Duty Cycle: Adjustable for Square wave (0-100%).

6. Maintenance

6.1. Cleaning

Clean the device regularly with a soft, damp cloth. Do not use abrasive cleaners or solvents. Ensure the device is powered off and disconnected from any power source before cleaning.

6.2. Battery Care

To prolong battery life, avoid fully discharging the battery frequently. If storing the device for an extended period, charge it to approximately 50% and store in a cool, dry place.

Figure 6.1: The DM40C incorporates safety isolation for multimeter communication and is powered by a rechargeable battery providing over 10 hours of operation.

6.3. Firmware Updates

ALIENTEK may release firmware updates to add features or fix bugs. Check the official ALIENTEK website for the latest firmware and instructions on how to update your device. Exercise caution when installing third-party applications or firmware not directly from the manufacturer.

7. Troubleshooting

• Device does not power on: Ensure the battery is charged. Connect the USB-C cable and attempt to power on while charging.
• Inaccurate readings: Check test lead connections. Ensure the correct measurement mode is selected. Verify the battery level.
• No oscilloscope waveform: Check probe connection to CHA/CHB. Adjust vertical scale and time base. Verify trigger settings.
• Sparking during voltage measurement: Immediately switch to AUTO+ mode for high voltage measurements (above 36V) to prevent this. Refer to Safety Information.
• Damage to oscilloscope input: Ensure alligator clips are not connected to CHA/CHB. Alligator clips are for the OUT channel only. Refer to Safety Information.
• Bluetooth connectivity issues: Ensure your device has the latest firmware (version 2.2 or higher for Bluetooth functionality, if available for your model). Note that Bluetooth may only support multimeter functions.

8. Specifications

The following table outlines the key specifications for the ALIENTEK DM40C.

Figure 8.1: A comprehensive table outlining the technical specifications, measurement ranges, and accuracy for the DM40A, DM40B, and DM40C models across various functions including voltage, current, resistance, capacitance, frequency, and temperature.

9. Warranty and Support

ALIENTEK products are designed for reliability and performance. For warranty information, please refer to the documentation included with your purchase or visit the official ALIENTEK website. For technical support, troubleshooting assistance, or inquiries about replacement parts, please contact ALIENTEK customer service through their official channels.