FNIRSI FNAC-28 USB Charger Voltage and Current Testing Guide Malaysia

FNIRSI FNAC-28 USB Charger Voltage and Current Testing Guide Malaysia

Introduction

USB chargers are essential for smartphones, tablets, power banks, wireless accessories and many portable electronic devices. However, charging performance can vary significantly depending on the charger, USB cable, connected device and supported charging protocol.

A charger advertised as 18W, 30W or 65W does not necessarily deliver its maximum rated power every time a device is connected.

To understand actual charging behaviour, technicians need to measure USB voltage, charging current and electrical power under suitable operating conditions.

The FNIRSI FNAC-28 USB Tester is a compact measuring instrument designed to monitor these parameters during compatible USB charging applications.

This guide explains how to use the FNIRSI FNAC-28 USB Charger Tester Malaysia for practical voltage, current and power measurements, including common troubleshooting examples.

1. Why Measure USB Charger Voltage and Current?

USB charging involves electrical power transfer between a charger and a connected device.

Three important electrical parameters are:

Voltage (V): The electrical potential supplied by the charger.

Current (A): The amount of electrical current flowing to the connected load.

Power (W): The rate of electrical energy transfer.

These parameters are related by the formula:

Power (W) = Voltage (V) x Current (A)

For example, a charger operating at 9V and delivering 2A provides approximately 18W.

However, actual charging power depends on the connected device, cable, charging protocol and operating conditions.

The FNIRSI FNAC-28 USB Power Meter allows users to observe these values instead of relying only on the charger's advertised specifications.

2. FNIRSI FNAC-28 Measurement Specifications

The following table summarises important measurement characteristics.

ParameterFNIRSI FNAC-28Instrument TypeUSB Digital TesterVoltage Measurement Range4V to 24VCurrent Measurement Range0A to 6.5AMaximum Rated Power156WUSB ConnectionsUSB-A and USB Type-CMain MeasurementsVoltage, Current and PowerAdditional FunctionsCharging Monitoring and Cable Resistance TestingFast ChargingSelected Protocol Detection and TriggeringTypical ApplicationsUSB Charger and Cable Testing

Important: These ratings describe the instrument's specified measurement limits. They do not mean that every USB charging protocol or voltage-current combination is supported.

Before testing, users should confirm the charger's operating voltage and the tester's compatibility.

3. How to Connect the FNIRSI FNAC-28 USB Tester

For a basic USB charging measurement, the tester is installed between the USB charger and the connected device.

**Typical USB Charging Measurement Connection**

USB Charger → FNIRSI FNAC-28 → USB Cable → Smartphone or Compatible Load

The FNAC-28 monitors electrical parameters while current flows through the charging connection.

Step 1 - Prepare the USB Charger

Select a compatible USB charger within the FNIRSI FNAC-28 operating limits.

Inspect the charger and connectors for visible damage.

Do not use equipment with damaged cables, exposed conductors or loose electrical connections.

Step 2 - Connect the USB Tester

Insert the FNIRSI FNAC-28 into the appropriate USB output connection according to the manufacturer's instructions.

Ensure that the USB-A or Type-C connection is compatible with the intended measurement.

Step 3 - Connect the Device

Connect a smartphone, power bank charging input or suitable electronic load to the tester's output.

The connected device should begin charging if the connections and charging conditions are correct.

Step 4 - Read the Measurements

Observe the displayed values:

Voltage (V)

Current (A)

Power (W)

Depending on the selected display mode, additional charging information may also be available.

Step 5 - Observe Changes

Allow the device to charge while monitoring the measurements.

Charging current may change as the battery level increases or as the device adjusts its charging conditions.

Important: Do not assume that a lower charging current indicates a faulty charger. Battery state, temperature and device charging controls can all affect the result.

4. Understanding USB Voltage Measurements

USB voltage measurement helps users check the voltage supplied during charging.

Different charging systems may use different operating voltages.

Nominal VoltageExample Application5VConventional USB Charging9VSelected Fast-Charging Modes12VSelected Fast-Charging Modes15VSelected USB Power Delivery Modes20VSelected Higher-Power Charging Modes

The table illustrates common USB charging voltages. It does not indicate that the FNAC-28 can actively negotiate or trigger every listed mode.

For example, if a conventional 5V charger supplies approximately 5V under an appropriate load, the measured voltage is consistent with normal USB operation.

If the voltage decreases significantly when current increases, possible causes include:

Excessive USB cable resistance

Poor connector contact

Charger current limitations

Overloaded USB output

Damaged charging accessories

Further testing may be required to identify the actual cause.

5. Understanding USB Charging Current

USB charging current is measured in amperes.

A smartphone may draw different current levels depending on battery condition, charging protocol and device temperature.

For example:

Measured VoltageMeasured CurrentCalculated Power5.0V0.5A2.5W5.0V1.0A5.0W5.0V2.0A10.0W9.0V1.5A13.5W9.0V2.0A18.0W

These are example readings for educational purposes, not guaranteed FNAC-28 test results.

When using the FNIRSI FNAC-28 USB Current Tester, it is important to observe current over time rather than relying on a single measurement.

For example, a smartphone battery approaching full charge may draw considerably less current than it did earlier in the charging session.

This is normal behaviour for many battery charging systems.

6. How to Calculate USB Charging Power

Charging power is an important parameter when evaluating charger performance.

The formula is:

P = V x I

Where:

P = Power in watts

V = Voltage in volts

I = Current in amperes

Example 1 - Standard USB Charger

Measured voltage: 5.1V

Measured current: 1.8A

Calculated power:

5.1 x 1.8 = 9.18W

The charger is delivering approximately 9.18W at the measurement point.

Example 2 - Fast Charging

Measured voltage: 9.0V

Measured current: 2.1A

Calculated power:

9.0 x 2.1 = 18.9W

The measured power is approximately 18.9W.

Example 3 - Lower Charging Power

Measured voltage: 5.0V

Measured current: 0.4A

Calculated power:

5.0 x 0.4 = 2.0W

This lower reading does not automatically indicate a charger problem.

The device may be nearly fully charged, limiting current because of temperature or operating without a compatible fast-charging mode.

7. Why Does a 65W Charger Not Always Deliver 65W?

A common question among USB charger users is why a high-power charger sometimes displays much lower wattage.

For example, a charger labelled 65W may supply only 10W or 18W to a particular smartphone.

This can occur for several reasons.

Device Charging Limitations

The connected device determines how much charging power it can accept under its current operating conditions.

A smartphone designed for lower-power charging will not necessarily draw the full output capacity of a 65W charger.

Charging Protocol Compatibility

The charger and device must support compatible charging protocols.

Some higher-power modes require USB Power Delivery negotiation or other proprietary charging methods.

The FNIRSI FNAC-28 is not a full USB PD protocol analyser and does not support PD active triggering.

USB Cable Limitations

Some charging cables are not designed for higher current levels.

Cable resistance and supported cable capabilities can influence charging performance.

Battery Charge Level

Many devices reduce charging current as their batteries approach full charge.

Temperature Protection

Smartphones and other battery-powered devices may reduce charging power when their internal temperature becomes too high or too low.

Therefore, USB charger wattage testing should always consider the entire charging system.

8. Troubleshooting Slow USB Charging

The FNIRSI FNAC-28 USB Tester can help technicians investigate slow charging complaints.

A practical troubleshooting procedure is shown below.

ObservationPossible CauseRecommended CheckLow Voltage Under LoadCable Loss or Charger LimitationCompare with a Known-Good CableLow Charging CurrentDevice Limitation or Charging ModeCheck Battery State and ProtocolUnstable CurrentConnection or Load ChangesInspect Connectors and Repeat TestCharging Stops IntermittentlyPoor Contact or Protection CircuitCheck Charger, Cable and DeviceLower Than Advertised WattageCharging Negotiation or Device DemandVerify Supported Charging Modes

Important: A USB tester provides measurement evidence but cannot independently diagnose every charger or smartphone fault.

For reliable troubleshooting, compare results using a known-good charger, compatible cable and suitable test load.

9. How to Compare Two USB Chargers

Suppose a technician wants to compare two chargers used with the same smartphone.

The following results are hypothetical.

Test ParameterCharger ACharger BVoltage5.0V9.0VCurrent1.5A2.0ACalculated Power7.5W18.0W

Under these particular test conditions, Charger B is delivering more electrical power.

However, this does not automatically prove that Charger B is more efficient or better in every application.

A meaningful comparison should consider:

Same Device: Use the same device for both tests.

Similar Battery Level: Compare results under similar battery conditions.

Same Cable: Use a suitable cable consistently.

Similar Temperature: Avoid comparing tests performed under significantly different temperature conditions.

Compatible Charging Protocols: Verify that both chargers support the device's charging requirements.

These steps improve the usefulness of USB charger performance testing.

10. Can FNIRSI FNAC-28 Test USB-C Fast Charging?

The FNIRSI FNAC-28 includes USB Type-C connectivity and supports selected charging measurement functions.

However, USB-C is a connector type, while USB Power Delivery is a communication and power negotiation standard.

These terms should not be confused.

A tester may measure voltage and current on a compatible USB-C charging connection without providing full USB Power Delivery protocol analysis.

The FNAC-28 supports selected non-PD fast-charging protocol functions, but PD active triggering and PD packet capture are not supported.

For applications requiring detailed USB-C PD negotiation analysis, a dedicated USB PD analyser is more appropriate.

11. Applications for Electronics Technicians in Malaysia

The FNIRSI FNAC-28 USB Charger Tester Malaysia can be useful in several working environments.

Mobile Phone Repair Workshops

Technicians can compare charging current and voltage when investigating slow or inconsistent charging.

Computer Service Centres

Service personnel can test compatible USB chargers, accessories and portable electronics.

Electronics Retailers

Retailers can demonstrate charger output characteristics and compare charging accessories.

Electronics Training Centres

Students can learn practical relationships between voltage, current, power and resistance.

DIY Electronics Projects

Electronics hobbyists can monitor USB power consumption in compatible low-voltage projects.

12. Where to Buy FNIRSI FNAC-28 USB Tester in Malaysia?

MTM Precision Sdn Bhd supplies electronic testing and measuring instruments for professional and general technical applications.

Customers looking for a FNIRSI FNAC-28 USB Tester Malaysia can contact MTM Precision to enquire about pricing, stock availability and suitable applications.

Our team can also assist customers in selecting other electronics measuring instruments according to their testing requirements.

We serve customers throughout Kuala Lumpur, Selangor, Johor, Penang, Melaka, Negeri Sembilan, Perak, Pahang, Kedah, Kelantan, Terengganu, Perlis, Sabah and Sarawak.

Please contact us to confirm current stock and delivery arrangements.

Frequently Asked Questions

Q1. Can the FNIRSI FNAC-28 measure USB charger voltage?

Yes. It measures voltage within its specified operating range of 4V to 24V.

Q2. Can the FNIRSI FNAC-28 measure charging current?

Yes. It measures charging current within its specified range of 0A to 6.5A.

Q3. Can it measure USB charging wattage?

Yes. USB charging power can be determined from the measured voltage and current.

Q4. Why does charging current change during testing?

Charging current may vary because of battery level, device temperature, charging protocol negotiation and internal charging controls.

Q5. Can it confirm whether a 65W USB charger is working correctly?

It can help measure charging power under compatible conditions. However, confirming the full rated output of a charger requires an appropriate load and a test setup that supports the required charging mode.

Q6. Does FNIRSI FNAC-28 support USB PD active triggering?

No. The FNAC-28 does not support USB PD active triggering or PD packet capture.

Q7. Is the FNIRSI FNAC-28 suitable for electronics repair shops?

Yes. It can assist with routine USB charging measurements, cable comparisons and preliminary troubleshooting.

Contact MTM Precision Sdn Bhd

For FNIRSI FNAC-28 USB Tester Malaysia, USB charger testing equipment and electronics measuring instrument enquiries, contact:

MTM Precision Sdn Bhd

Showroom & Service Centre

No. 29-1 & 29-2, Jalan Bandar 18,

Pusat Bandar Puchong,

47160 Puchong, Selangor, Malaysia.

Tel: 03-8080 7172

WhatsApp: +6016-660 7346

Email: mtmpre@yahoo.com

Website: www.mtmpre.com.my

Contact MTM Precision for FNIRSI FNAC-28 pricing, availability and USB testing instrument recommendations in Malaysia.

Conclusion

Measuring USB charger voltage, current and power is an effective way to understand charging performance and investigate common USB charging problems.

The FNIRSI FNAC-28 USB Tester provides useful measurement functions for electronics technicians, repair workshops, training centres and DIY users.

By comparing measurements under consistent test conditions, users can better evaluate charger performance, investigate cable-related voltage drops and identify situations that require further testing.

For customers searching for a USB Charger Voltage Tester Malaysia, USB Current Tester Malaysia or FNIRSI FNAC-28 USB Power Meter Malaysia, MTM Precision Sdn Bhd can assist with product enquiries and suitable testing equipment selection.