How to Check PWM Signal with FNIRSI 1014D Oscilloscope Malaysia
How to Check PWM Signal with FNIRSI 1014D Oscilloscope Malaysia
How do you know whether a PWM signal is working correctly?
A digital multimeter may show a voltage at the output, but that number alone does not tell you exactly what the pulse waveform looks like.
With an oscilloscope such as the FNIRSI 1014D, you can actually see the PWM waveform and examine its frequency, duty cycle, amplitude and stability.
This can be useful for electronics repair, motor controllers, LED drivers, Arduino projects and general PCB troubleshooting in Malaysia.
What Is PWM?
PWM means Pulse Width Modulation.
Instead of providing a continuously variable output voltage, a circuit rapidly switches a signal between different states.
By changing how long the signal remains ON compared with OFF, the circuit can control the effective output.
PWM is commonly used for:
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Motor speed control
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Fan speed control
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LED brightness control
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Power electronics
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Heater control
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Microcontroller outputs
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DC-DC converter control
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Electronic control boards
What Does a PWM Signal Look Like?
A typical PWM signal appears as a repeating series of pulses.
The waveform switches between a low level and a high level.
Two important parameters are:
Frequency – how often the switching cycle repeats.
Duty Cycle – how much of each cycle the signal remains ON.
For example, a signal with approximately 50% duty cycle remains high for roughly half of each cycle.
Why Use an Oscilloscope for PWM?
Suppose you measure a PWM-controlled output with a multimeter.
You get:
6V
Does that mean the circuit is supplying a steady 6V?
Not necessarily.
It could be a pulsed signal switching between approximately 0V and 12V.
The multimeter may only provide an averaged or otherwise processed reading.
An oscilloscope allows you to see the actual waveform.
Step 1: Identify the PWM Test Point
Before connecting the oscilloscope, identify the correct point in the circuit.
Depending on the equipment, this could be:
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Microcontroller PWM output
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Motor controller signal
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Fan control line
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LED driver control signal
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Driver input
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Driver output
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Suitable PCB test point
Do not probe unknown circuits without understanding the voltage and grounding arrangement.
Step 2: Check the Signal Voltage
Make sure the expected signal is within the limits of the oscilloscope and probe.
PWM signals in electronic circuits may operate at different voltage levels.
Examples could include low-voltage logic signals or higher-voltage switching signals.
The fact that a waveform is called “PWM” does not automatically mean it is safe to connect directly to an oscilloscope.
Step 3: Display the PWM Waveform
Connect the probe correctly and adjust the oscilloscope so several PWM cycles are visible.
You should be able to see the repeating pulse pattern.
From there, you can investigate whether the waveform is:
Present
Stable
Regular
At the expected voltage
At the expected frequency
Changing duty cycle correctly
Step 4: Check PWM Frequency
Frequency tells you how many cycles occur per second.
For example:
1kHz = 1,000 cycles per second
If the circuit specification calls for a particular PWM frequency, the oscilloscope can help confirm whether the measured signal is reasonably consistent with that requirement.
An incorrect frequency may indicate a control, configuration or circuit problem.
Step 5: Check Duty Cycle
Duty cycle is one of the most important PWM measurements.
If a controller changes its output command, the PWM duty cycle may also change.
For example:
Low command → Lower duty cycle
Higher command → Higher duty cycle
The exact relationship depends on the circuit.
By observing the waveform while changing the control input, you can determine whether the PWM signal responds as expected.
Example: DC Motor Controller
Suppose a DC motor controller has a speed adjustment.
At low speed, you observe one PWM waveform.
Increase the speed setting.
The duty cycle should change according to the controller design.
If the control input changes but the PWM waveform remains unchanged, the fault may be somewhere in the control system.
If the PWM control signal changes correctly but the motor does not respond, troubleshooting can continue further downstream.
Example: LED Dimming
PWM is commonly used for LED brightness control.
When the LED is dimmed, the duty cycle may decrease.
When brightness is increased, the duty cycle may increase.
Using an oscilloscope allows you to see whether the LED driver is actually changing its control waveform.
This can help separate a control-signal problem from an LED or driver-stage problem.
Example: Arduino and Microcontroller Projects
The FNIRSI 1014D can also be useful for Arduino, MCU and embedded-system development.
Suppose your program is supposed to generate a PWM output.
The software compiles successfully, but the hardware is not responding correctly.
An oscilloscope lets you check:
Is there actually a PWM signal at the pin?
Is the frequency correct?
Does the duty cycle change when commanded?
Is the signal stable?
This helps connect software debugging with real hardware behaviour.
Use Two Channels to Compare PWM Signals
The dual-channel capability of the FNIRSI 1014D can make PWM troubleshooting more useful.
For example:
CH1 → PWM control signal
CH2 → Circuit response
This allows you to observe whether changes in the PWM signal correspond with changes elsewhere in the circuit.
Another possibility is:
CH1 → Controller output
CH2 → Driver-stage output
If the PWM exists at CH1 but disappears at CH2, the driver stage becomes an area for further investigation.
What Does a Bad PWM Signal Look Like?
There is no single waveform that means “faulty.”
Depending on the circuit, possible symptoms may include:
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No PWM signal
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Incorrect frequency
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Incorrect duty cycle
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Unstable frequency
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Irregular pulses
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Unexpected missing pulses
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Incorrect amplitude
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Excessive noise
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Distorted waveform
Always compare the measurement with the circuit design, service information or a known-good unit where possible.
Can FNIRSI 1014D Test Motor Drives and Inverters?
This requires much more caution.
Motor drives, inverters and power-electronic systems may contain high voltage, floating switching nodes and high-energy circuits.
Do not connect a standard oscilloscope probe directly to a point simply because you want to see its PWM waveform.
Depending on the measurement, specialized equipment such as a suitable differential probe may be required.
The measurement method must be determined before connecting the oscilloscope.
PWM Testing: Multimeter or Oscilloscope?
For checking the actual PWM waveform, the oscilloscope provides much more useful information.
A multimeter may tell you:
There is some voltage here.
An oscilloscope can help show:
The pulse waveform
Frequency
Duty cycle
Amplitude
Timing
Signal stability
For PWM troubleshooting, that difference can be very important.
Who Can Use FNIRSI 1014D for PWM Testing?
The FNIRSI 1014D may be useful for suitable PWM measurements in:
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Electronics repair
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PCB troubleshooting
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Arduino projects
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MCU development
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LED control circuits
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Fan controllers
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Low-voltage motor control
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Electronics education
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Technical training
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General R&D
Its 100MHz dual-channel oscilloscope capability also allows users to compare related signals during troubleshooting.
Looking for FNIRSI 1014D in Malaysia?
If you need to check PWM signals, electronic waveforms, PCB signals or control circuits, the FNIRSI 1014D Oscilloscope with Signal Generator may be worth considering.
For FNIRSI 1014D enquiries in Malaysia, contact MTM Precision Sdn Bhd.
Not sure whether your PWM signal can be measured directly?
WhatsApp us a photo of the equipment, PCB or test point first.
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
Serving customers across Selangor, Kuala Lumpur, Johor, Penang, Melaka, Negeri Sembilan, Perak, Pahang, Kelantan, Terengganu, Kedah, Perlis, Sabah and Sarawak.
05 Oct 2026
