1. Introduction
The Brother HD-390D is a high-precision analog multimeter designed for electricians, hobbyists, and home maintenance tasks. It provides accurate measurements for AC/DC voltage, AC/DC current, resistance, and battery levels. This manual provides essential information for safe and effective operation of your device.
2. Safety Information
WARNING: READ AND UNDERSTAND THIS MANUAL BEFORE USING THE INSTRUMENT. Failure to understand and comply with the WARNING and operating instructions can result in serious or fatal injuries and/or property damage.
- Always ensure the multimeter is set to the correct function and range before connecting to a circuit.
- Do not exceed the maximum input ratings for any function.
- Use caution when working with live circuits. High voltages can be dangerous.
- Inspect test leads for damage before each use. Replace if insulation is cracked or wires are exposed.
- Ensure the battery cover is securely closed before operation.
- For continued protection against fire, replace fuses only with specified types: 0.5A/250V and 10A/250V.
3. Package Contents
Verify that all items are present in your package:
- Brother HD-390D Analog Multimeter
- Test Leads (Red and Black)
- Operator's Instruction Manual
- Protective Carrying Case (may be included depending on variant)
Figure 3.1: Multimeter with test leads and optional carrying case.
Video 3.1: Unboxing and initial overview of the Brother HD-390D Analog Multimeter.
4. Product Overview
The HD-390D features a clear analog display, a central rotary switch for function and range selection, and input jacks for test leads. An Ohm adjustment knob is provided for resistance measurements.
Figure 4.1: Front panel of the HD-390D Multimeter.
Key Components:
- Analog Display: Large, easy-to-read scale for measurement readings.
- Rotary Switch: Selects measurement function (Voltage, Current, Resistance, Battery) and range.
- Input Jacks: Connect test leads. 'COM' for common (black lead), 'VΩmA+' for positive (red lead) for most measurements, '+10A' for high current measurements.
- Ω ADJ Knob: Used to zero the meter for resistance measurements.
- Transistor/Diode Test Sockets: Dedicated sockets for testing transistors (NPN/PNP hFE) and diodes.
5. Setup
5.1 Battery Installation
The multimeter requires two 1.5V AAA batteries and one 9V battery for operation. These are not included.
- Locate the battery cover on the back of the multimeter.
- Slide the cover down and open as indicated by the 'PULL DOWN' and 'OPEN' markings.
- Insert the two 1.5V AAA batteries and one 9V battery, observing correct polarity.
- Close the battery cover securely.
Figure 5.1: Back panel with battery and fuse access.
5.2 Connecting Test Leads
Always connect the test leads correctly for accurate and safe measurements.
- Insert the black test lead into the 'COM' (Common) jack.
- For most measurements (Voltage, Resistance, low Current), insert the red test lead into the 'VΩmA+' jack.
- For high current measurements (up to 10A), insert the red test lead into the '+10A' jack.
Figure 5.2: Multimeter with test leads connected.
6. Operating Instructions
Before taking any measurement, ensure the test leads are properly connected and the rotary switch is set to the desired function and range.
6.1 DC Voltage Measurement (DC V)
- Connect the red lead to 'VΩmA+' and the black lead to 'COM'.
- Set the rotary switch to the desired DC V range (e.g., 0.1V, 0.5V, 2.5V, 10V, 50V, 250V, 1000V). Start with the highest range if the voltage is unknown.
- Connect the test probes in parallel across the component or circuit to be measured.
- Read the voltage value from the appropriate DC V scale on the analog display.
6.2 AC Voltage Measurement (AC V)
- Connect the red lead to 'VΩmA+' and the black lead to 'COM'.
- Set the rotary switch to the desired AC V range (e.g., 10V, 50V, 250V, 1000V). Start with the highest range if the voltage is unknown.
- Connect the test probes in parallel across the component or circuit to be measured.
- Read the voltage value from the appropriate AC V scale on the analog display.
6.3 DC Current Measurement (DC A)
- For currents up to 250mA, connect the red lead to 'VΩmA+' and the black lead to 'COM'. For currents up to 10A, connect the red lead to '+10A' and the black lead to 'COM'.
- Set the rotary switch to the desired DC A range (e.g., 0.05mA, 0.25mA, 2.5mA, 25mA, 250mA, 10A). Start with the highest range if the current is unknown.
- Important: Connect the multimeter in series with the circuit to be measured. Break the circuit and insert the meter.
- Read the current value from the appropriate DC A scale.
6.4 AC Current Measurement (AC A)
- For currents up to 250mA, connect the red lead to 'VΩmA+' and the black lead to 'COM'. For currents up to 10A, connect the red lead to '+10A' and the black lead to 'COM'.
- Set the rotary switch to the desired AC A range (e.g., 0.05mA, 0.25mA, 2.5mA, 25mA, 250mA, 10A). Start with the highest range if the current is unknown.
- Important: Connect the multimeter in series with the circuit to be measured. Break the circuit and insert the meter.
- Read the current value from the appropriate AC A scale.
6.5 Resistance Measurement (Ω)
- Connect the red lead to 'VΩmA+' and the black lead to 'COM'.
- Set the rotary switch to the desired Resistance range (e.g., X1, X10, X1K, X10K, X100K).
- Zero Adjustment: Short the test leads together. While shorted, adjust the 'Ω ADJ' knob until the needle points to '0' on the Ohm scale. This must be done for each resistance range.
- Connect the test probes across the component to be measured (ensure the component is de-energized).
- Read the resistance value from the Ohm scale and multiply by the selected range multiplier.
6.6 Battery Test (BATT)
- Connect the red lead to 'VΩmA+' and the black lead to 'COM'.
- Set the rotary switch to the 'BATT' function (1.5V or 9V).
- Connect the test probes to the battery terminals, observing polarity.
- Read the battery voltage from the appropriate battery scale.
6.7 Diode and Transistor Check
- Set the rotary switch to the 'Ω X 10' range for transistor and diode checks.
- For transistor hFE measurement, insert the transistor leads into the appropriate NPN or PNP sockets.
- For diode check, use the extra jack as indicated in the specifications.
6.8 Continuity Check
- Set the rotary switch to the 'Continuity Check' position (often indicated by a speaker icon).
- Connect the test probes across the circuit or component.
- If the resistance is less than 200 Ohms, the beeper will sound, indicating continuity.
7. Specifications
The following table details the technical specifications of the Brother HD-390D Analog Multimeter:
Figure 7.1: DC Voltage Specifications.
Figure 7.2: AC Voltage, Current, Resistance, and other Specifications.
| Feature | Specification |
|---|---|
| AC Voltage Ranges | 0.1V, 0.5V, 2.5V, 10V, 50V, 250V, 1000V |
| DC Voltage Ranges | 0.1V, 0.5V, 2.5V, 10V, 50V, 250V, 1000V |
| AC Current Ranges | 0.05mA, 0.25mA, 2.5mA, 25mA, 250mA, 10A |
| DC Current Ranges | 0.05mA, 0.25mA, 2.5mA, 25mA, 250mA, 10A |
| Resistance Ranges | X1 (0.2 ~ 2KΩ), X10 (2 ~ 20KΩ), X1K (200 ~ 2MΩ), X10K (2K ~ 20MΩ), X100K (20K ~ 200MΩ) |
| Battery Test | 1.5V, 9V |
| Transistor Check | hFE: 0-1000 (via extra jack, at Ω X 10 Range) |
| Diode Check | IF, IR, LI, LV (at Ω X 10 Range) |
| Continuity Check | Beeper sounding (<200 Ohm) |
| Power Supply | 2 x 1.5V AAA batteries, 1 x 9V battery |
| Operating Mode | Manual Range |
| Certification | CE |
| Standard Environmental Conditions | 23°C ± 5°C, humidity <75% RH |
| Working Environment Range | 0°C ~ 40°C, humidity <90% RH |
| Dimensions | 160mm x 105mm x 40mm |
8. Maintenance
8.1 Cleaning
To clean the multimeter, wipe the case with a damp cloth and a mild detergent. Do not use abrasives or solvents. Ensure the device is powered off and disconnected from any circuits before cleaning.
8.2 Battery Replacement
When the battery indicator shows low power, replace the batteries promptly to ensure accurate readings. Refer to Section 5.1 for battery installation instructions.
8.3 Fuse Replacement
If the current measurement function stops working, the fuse may be blown. To replace the fuse:
- Ensure the multimeter is powered off and disconnected from all circuits.
- Open the battery cover on the back of the unit (refer to Figure 5.1).
- Carefully remove the old fuse(s).
- Replace with new fuses of the specified ratings: 0.5A/250V for mA ranges and 10A/250V for the 10A range.
- Close the battery cover securely.
9. Troubleshooting
- No reading or unstable reading: Check battery levels and replace if necessary. Ensure test leads are securely connected and not damaged. Verify the rotary switch is set to the correct function and range.
- Incorrect resistance reading: Perform Ohm adjustment (zeroing) as described in Section 6.5. Ensure the component being tested is de-energized.
- Current measurement not working: Check the fuse(s) and replace if blown (refer to Section 8.3). Ensure the meter is connected in series with the circuit.
- Needle not moving: Ensure the meter is powered on (if applicable for specific functions) and the test leads are making good contact.
10. User Tips
- Always start with the highest range: When measuring an unknown voltage or current, always start with the highest range setting and then decrease it until you get a suitable reading. This prevents overloading the meter.
- Zero Ohm adjustment: Remember to perform the Ohm adjustment (zeroing) every time you change the resistance range for accurate readings.
- Observe polarity: For DC measurements, observing polarity is important. If the needle deflects backward, reverse the test leads.
- Analog vs. Digital: Analog multimeters are great for observing trends and fluctuating signals, as the needle movement can show changes more dynamically than a digital display.
11. Warranty and Support
For warranty information or technical support, please refer to the documentation provided at the point of purchase or contact your vendor. Keep your purchase receipt as proof of purchase.
