GVDA GD188 3-in-1 Digital Oscilloscope, Multimeter, and Signal Source

1. Introduction

Thank you for choosing the GVDA GD188 digital storage wave multimeter. This innovative product combines the functions of a digital oscilloscope, a smart multimeter, and a signal source, designed to provide great convenience for field testing and various electrical measurements. Please read this manual carefully before use, especially the safety instructions, and keep it for future reference.

Product Overview

The GVDA GD188 is a versatile tool featuring a 2.4-inch HD color screen, offering clear display and intuitive operation. It integrates a 12MHz bandwidth oscilloscope, a 6000-count auto-ranging multimeter, and a signal source capable of outputting sine, square, and triangular waveforms.

Figure 1: GVDA GD188 Device

Key Features

• 50Msps high-speed sampling chip with 12MHz analog bandwidth.
• 6000-count digital multimeter with auto-ranging.
• Three waveform scanning modes: automatic, conventional, and single.
• Signal source output for sine, triangle, and square waveforms with adjustable range, frequency, and duty cycle.
• Configured with replaceable 18650 lithium batteries for environmental friendliness.
• Data waveform hold function, capable of storing 100 sets of DMM data and 10 OSC waveforms.
• Waveform range up to 200V/grid, with a maximum measurement of 1600Vpp.
• Relative value measurement to eliminate lead resistance, distributed capacitance, or interference signals.
• Multimeter functions include voltage, current, resistance, capacitance, frequency, duty cycle, diode, and on/off testing.
• Automatic/manual range switching, displaying real-time and stored data on the screen.
• Overload protection with 750mA and 10A double fuses.
• 15-minute no-operation auto-sleep function.
• 2.4-inch color screen for clear display.
• Panel calibration without potentiometer adjustment for higher reliability.

Product Video Overview

2. Safety Instructions

The technical design of this digital storage visual wave multimeter complies with IEC1010-1 safety specifications, overvoltage measurement category II CAT II - 1000V, and pollution protection level: 1.

1. Check the case before use. Do not use the meter with a damaged case, or if there are cracks or missing plastic parts. Pay special attention to the meter probes and their connecting wire insulation layer. Keep fingers away from the metal part of the meter pen probe when in use.
2. Do not operate in hot, humid, rainy, or flammable environments, or when the instrument is wet.
3. Never apply more voltage/current to the instrument than its maximum withstand limit.
4. Be sure to disengage the probe from the test point before changing the measuring gear, unplugging the probe, and switching the machine on/off.
5. Attention to safety sound and light warning: If measurement voltage exceeds "safety voltage" (24V), a red warning message "⚠" is displayed, accompanied by 3 beeps and flashing red light to indicate attention to safety.
6. Do not perform voltage measurements when the voltage to ground on the reference input "COM" of the instrument reaches 500 V.
7. Do not perform current measurements on circuits with voltages above 250V.
8. Never connect the meter probe across both ends of the voltage source when the measurement function selects current, resistance, on/off test, diode, capacitance, and other gears.
9. Before conducting resistance and diode/on/off tests, the power to the equipment under test must be turned off, and the discharge of capacitors in the power circuit must be confirmed to be exhausted.
10. Before opening the back cover of the instrument to replace the fuse and battery, the instrument must be powered off, and the meter probe must be removed from the circuit under test. Use fuses of the same specifications for replacement.
11. Do not modify, disassemble, or use the product and accessories for purposes other than their functional design. All accessories and attachments are not to be substituted at will.
12. Do not allow children to use this equipment or as a toy.

Measurement Function Limits

Safety Signs

3. Setup

Unboxing and Components

Upon opening the package, ensure all components are present and undamaged. The standard accessories include:

• 1x GVDA GD188 Oscilloscope Multimeter
• 1x Test Pen (probes)
• 1x Charging Cable (Type-C)
• 1x Cloth Bag
• 1x User Manual (this document)
• 1x Gift Box

Figure 2: Product Accessories (1. Gift box, 2. Charging cable, 3. Original pen, 4. Bag, 5. Oscilloscope Multimeter, 6. Manual)

Battery and Charging

The device is powered by one replaceable 18650 lithium battery (1500mAH).

• When the screen displays a red battery prompt, charge the device immediately to avoid affecting the accuracy of oscillometric measurements or the output range of the signal source.
• To charge, select the OFF gear. Use a charger with a Type-C interface, output DC5V, and current ≥ 1A.
• The red light indicates charging in progress, and the blue light indicates a full charge.

Figure 3: Rechargeable Battery Installation

4. Operating Instructions

Power On/Off and Auto Sleep

• Power On: Turn the knob to select the desired measuring position.
• Power Off: Turn the knob to the OFF position.
• Auto Sleep: If there is no key or knob operation within the set time (15 minutes), the meter will automatically sleep. To disable auto-sleep, hold down the "F1" key and rotate the knob; the device will then run continuously.

Key Functions

The multi-functional keys (F1-F4) change their function based on the current range and operating mode. The LCD screen displays the current function of each key.

Figure 4: Product Introduction with Labeled Parts (Charging indicator light, Charging interface, Multi-Function Buttons, One click oscillogram, Backlight/signal output, Data retention/storage, Functional range knob, Oscillographic/voltage/resistance/current input port, Signal output/current input terminal, 10A current input terminal, COM input)

Oscilloscope Operation

The oscilloscope mode allows for visual analysis of waveforms. The device features a 2.4-inch HD color screen for clear waveform display.

Figure 5: 2.4 Inch HD Color Screen Oscilloscope Display

Entering Oscilloscope Mode

Press the "AUTO" button for 2 seconds to enter the oscilloscope (OSC) mode from the voltage section of the multimeter mode (DMM). To return to DMM mode from OSC mode, press the "AUTO" key for 2 seconds again.

• OSC mode (mV range): Amplitude range is 50mV/div ~ 200mV/div, measurable amplitude 0 ~ 1.6Vpp.
• OSC mode (V range): Amplitude range is 500mV/div ~ 200V/div, measurable amplitude 0 ~ 1600Vpp.

Basic Display in Oscilloscope Mode

The oscilloscope screen displays various parameters including Amplitude, Time base, Trigger method, Trigger mode, Trigger state, Direct current, Power, Trigger level, Test Data, and DOS menu.

Function Keys in Oscilloscope Mode

The F1-F4 keys at the bottom of the LCD screen provide various functions:

• F1 (TIME): Enters the time base adjustment sub-menu to adjust scan time base and trigger position.
• F2 (VOLT): Enters the range adjustment sub-menu to adjust vertical range and waveform position.
• F3 (TRIG): Enters the trigger control sub-menu to adjust trigger edge, trigger mode, and trigger level.
• F4 (AC/DC): Switches DC/AC coupling mode.

Time Base Adjustment

From the main menu, press F1 (TIME) to enter the time base adjustment sub-menu.

• Press F1 (EXIT) to exit and return to the main menu.
• Press F2 (◄) and F3 (►) to adjust the time base (t/div).

Range Adjustment

From the main menu, press F2 (VOLT) to enter the range adjustment sub-menu.

• Press F1 (EXIT) to exit and return to the main menu.
• Press F2 (▲) and F3 (▼) to adjust the vertical range (V/div).

Trigger Control

From the main menu, press F3 (TRIG) to enter the trigger control sub-menu.

• Press F1 (EXIT) to exit and return to the main menu.
• Press F2 (⊙ or ⊗) to select rising or falling edge trigger.
• Press F3 (MODE) to select the trigger mode.
• Press F4 (LEVEL) to enter the Trigger Level Adjustment sub-menu.

Trigger Level Adjustment

From the trigger setting sub-menu, press F4 (LEVEL) to enter the trigger level adjustment sub-menu.

• Press F1 (EXIT) to exit and return to the Trigger Control sub-menu.
• Press F2 (▲) and F3 (▼) to decrease or increase the trigger level. The display will mark the position of the current trigger level.
• Press F4 (RESET) to reset the trigger level to zero.

About Trigger Mode

• Auto: The oscilloscope can acquire waveforms even if no trigger condition is detected. If no trigger condition, it will trigger itself and start collecting data after a certain period. Without a correct trigger, the waveform scrolls. Useful for monitoring irregular signals or observing signal ranges.
• Normal: Starts collecting waveform data only after a trigger signal is detected. If no trigger occurs, no new waveform is acquired, and the display content is not refreshed.
• Single: Starts waveform data acquisition once the trigger condition is detected. The latest waveform is automatically held when new data is acquired.

Prompt Message for Scan Status

Trigger Operation for Single Scan

To perform a single-trigger data acquisition:

1. Adjust the vertical range V/div and horizontal range s/div to fit the waveform.
2. Select the appropriate trigger level, trigger edge, and choose the "Single" trigger mode.
3. Once the signal is present, the oscilloscope will trigger and capture it.

Holding of Signal Waveforms

Stopping data collection will keep the display content. This is useful for closer inspection. You can hold a waveform by pressing the "SAVE" key or using the single-trigger scan mode.

• Pressing "SAVE" starts/stops waveform data acquisition. The last waveform is kept immediately after pressing "SAVE".
• Once the oscilloscope stops collecting data, the display is held.

Multimeter Operation

The multimeter mode provides various measurement functions. The basic display shows high voltage tips, auto range, current gear, real-time data, AC/DC indication, unit, MAX/MIN values, and P-H menu.

Figure 6: Multimeter Measurement Icons (AC/DC Voltage, AC/DC Current, Resistance Test, Frequency Test, Capacitance Test, Diode Test, Continuity Test)

Entering Multimeter Mode

The device powers on in default multimeter mode (DMM). Long press the "AUTO" key to switch between DMM and OSC modes.

Warning! When changing the measurement function, always detach the probe from the test point first.

Switching Measurement Functions

Turn the knob to select the test function. Functions cycle in the following order: DC/ACV → DC/ACmV → Resistance/Diode/On-Off Test → Capacitance → Hz/% → DC/ACµA current → DC/ACmA current → DC/AC10A current. Press F3 (SEL) to switch functions within a gear.

Manual/Automatic Range Selection

The device starts in auto-range mode. To fix a range:

1. Press F4 (RNG). The "AUTO" mark disappears, and the meter enters manual range.
2. Each press of F4 (RNG) switches to the next range.
3. Press the AUTO key to return to auto-range.

Relative Measurement Mode

This mode displays the difference between the measured value and a reference value.

1. Press F1 (REL) to store the current display as a reference and activate relative value mode.
2. The screen shows the difference.
3. Press F1 (REL) again to exit.
4. The meter switches to manual range in this mode.
5. Changing the measurement function automatically exits relative value mode.

Peak Hold (P-H) Mode

This mode displays maximum and minimum measured values, updated with each new measurement. Activate by pressing F2 (P-H). The LCD shows max/min peak values.

• Press F1 (EXIT) to exit.
• Press F2 (RUN) for peak hold measurement.
• Press F3 (STOP) to stop refreshing max/min values.
• Press F4 (REST) to reset the measured peak.

Tips! Peak hold mode is automatically released when the measurement function, gear, or range is changed, or when relative value mode is selected midway.

AC and DC Voltage Measurement

Tips! If measured voltage exceeds 24V, a warning message "⚠" will be displayed with beeps and flashing red light.

Warning! Do not apply 700V AC or 1000V DC for more than 10 seconds to the measurement terminal to avoid damage.

1. Insert the black test lead into the "COM" socket and the red test lead into the "VOCx" socket.
2. Turn the knob to select the "V" or "mV" function. "VOLTAGE" appears on screen.
3. Press F3 (SEL) to switch between DC/AC/Hz/% measurement (Hz/% not available in mV gear).
4. Touch the test point with the probe and read the voltage.

AC and DC Current (µA, mA, 10A) Measurement

Warning! To avoid electric shock, do not perform current measurements on circuits with voltages above 250V. When using the 10A gear for high current, measurement time should not exceed 30 seconds in every 15 minutes, otherwise the meter and probes may be damaged.

1. Insert the black test lead into "COM" and the red test lead into "mA" or "10A" socket.
2. Turn the knob to select the "µA", "mA", or "10A" function. "CURRENT" appears on screen.
3. Press F3 (SEL) to switch between DC and AC measurement.
4. Insert the meter probe in series with the circuit under test and read the current.

Frequency Measurement and Duty Cycle Measurement

1. Insert the black test lead into "COM" and the red test lead into "VOCx" socket.
2. Turn the knob to select the "Hz%" gear.
3. Press F3 (SEL) to select between frequency and duty cycle.

Attention! The signal frequency measurement range is proportional to the signal range. For 1Hz-5MHz, requires >500mVpp; for 5MHz-10MHz, requires >1Vpp; for 10MHz-20MHz, requires >3Vpp. Above 20MHz is for reference only.

Resistance Measurement

Warning! To avoid electric shock, disconnect power to the device under test and discharge capacitors before resistance measurements.

1. Insert the black test lead into "COM" and the red test lead into "VOCx" socket.
2. Turn the knob to select the resistance (Ω) function. "RESISTANCE" appears on screen.
3. Connect the probes across the circuit or component. Disconnect the part under test from the circuit for accurate readings.
4. Read the resistance value.

Diode Detection

1. Insert the black test lead into "COM" and the red test lead into "VOCx" socket.
2. Turn the knob to select the resistance (Ω) function.
3. Press F3 (SEL) to select the diode detection function. "DIODE" appears on screen.
4. Use the probes across the diode or semiconductor PN junction. (Silicon tube: 0.5-0.7V, Germanium tube: 0.15-0.25V).

On/Off Test (Continuity)

Warning! Do not test diodes containing voltage or perform on-off tests on lines containing voltage.

1. Insert the black test lead into "COM" and the red test lead into "VOCx" socket.
2. Turn the knob to select the resistance (Ω) function. "CONTINUITY" appears on screen.
3. Press F3 (SEL) to select the on-off test function.
4. Contact the circuit under test with probes. If resistance is less than 50Ω, the buzzer will sound.

Capacitance Measurement

Warning! To avoid electric shock, capacitors containing voltage should not be tested. Capacitance measurement cannot be used with manual ranges.

1. Insert the black test lead into "COM" and the red test lead into "VOCx" socket.
2. Turn the knob to select the "Cx" function. "CAPACITANCE" appears on screen.
3. Touch the probes to the capacitor under test and read the capacity.

Signal Source Output Function

The device can output various signals for testing purposes. Waveform parameters can be set individually.

Figure 7: Signal Source Output Function (Sine wave, Square wave, Triangular wave)

To use the signal source function:

1. Plug the black test lead into "COM" and the red test lead into the "mA" socket.
2. Turn the knob to select the "V" measurement function.
3. Press and hold the ☀️ key for 2 seconds to enter/exit the signal setting interface.
4. Use F1 (WAVE) to select Sine, Triangle, or Square wave.
5. Use F2 (FREQ) to select the frequency.
6. Use F3 (DUTY) to select the duty ratio (only for square waveform).
7. Use F4 (VOLT) to select the amplitude.
8. Press the AUTO key to turn the signal output on or off.

5. Data Storage and Readout

The instrument can store up to 100 DMM measurement data records and 10 OSC waveform data records.

Figure 8: Storage Function (100 records of DMM data, 10 records of OSC waveforms)

Measurement Data Hold

Pressing the "SAVE" key will hold the current reading, and "STOP" will appear on the LCD. Press "SAVE" again to resume normal operation.

• In data hold state, a small window shows dynamic data, which remains refreshed.
• The meter switches to manual range in data hold state.
• The meter automatically exits data hold when switching ranges or changing measurement functions.

Storage and Readout of Signal Waveforms

1. Press the "SAVE" key to hold the current waveform.
2. Press "SAVE" again and hold for 2 seconds to enter the database.
3. Use F1 (◄) / F2 (►) to select the save location. Press F4 (SAVE) to save the current waveform.
4. Press "SAVE" again and hold for 2 seconds to exit the database.

Database Operations:

Tips! Saving a new waveform to an existing memory location will replace the old one. Be careful to avoid losing useful data.

After reading a stored waveform, the waveform and related parameters (peak-to-peak, average, RMS values) are displayed.

6. Technical Specifications

General Parameters

Figure 9: Device Dimensions (153mm height, 30mm depth, 75mm width)

Oscilloscope Parameters

Signal Source Parameters

Multimeter Parameters

Display Symbols and Icons

7. Daily Maintenance

Keep Dry

If the meter gets wet, dry it as soon as possible and do not use it until you are sure it is completely dry.

Use and Storage at Room Temperature

Extreme ambient temperatures can shorten the life of electronic components, deform plastic parts, and render the meter unusable. Store and use the device at room temperature.

Handle with Care

Drops or impacts may damage the LCD, internal electronic components, or the casing.

Keep Clean

Wipe the instrument's housing frequently with a damp cloth moistened with a tiny amount of detergent. Do not use rough objects, chemical solvents, or alcohol.

Replacement of Fuse

1. Remove the probes from the test point and turn off the power. Loosen the set screw, remove the back cover. The fuse is located on the back of the test socket.
2. Remove the burnt fuse and replace it with a new fuse of the same specification: 750mA/250V fused fuse for 600mA, 10A/250V fused fuse for 10A. Install the back cover and secure it with screws.

8. Troubleshooting

If your instrument is malfunctioning, check the following points before concluding that it needs repair:

No Screen Display, No Key Response

1. Check for power supply. Charge the machine if the battery is low.
2. Turn the knob to the OFF position and then back to a measurement position.

Unable to Measure

Check the condition of the meter probes (e.g., short-connect the probes in the on/off gear to test continuity).

Current Cannot Be Measured

The fuse may have melted. Replace the fuse as described in the Maintenance section.

Note: The content of this manual is subject to change without notice.

Disclaimer: All man-made damage, customer's own dismantling, revision, upgrade, or improper use resulting in damage will not be covered by the company's responsibility.

9. User Tips

• Always ensure the device is fully charged before critical measurements to avoid interruptions.
• For precise resistance or capacitance measurements, always disconnect the component from the circuit and discharge any capacitors.
• When using the oscilloscope function, experiment with different time base and vertical range settings to get a stable and clear waveform display.
• Utilize the data storage function to record important measurements for later analysis or comparison.

10. Warranty and Support

This product is a precision instrument. Unauthorized modification of wiring, replacement of components, or product calibration and repair work are not allowed without authorization from the manufacturer's Product Service Center.

For technical support, service, or warranty inquiries, please contact the GVDA Tools Store directly or refer to the contact information provided with your purchase documentation.

11. Additional Resources

A detailed PDF version of the user manual is available for download. You can access it via the following link: GVDA GD188 User Manual (PDF)