PWM Protocol Support

Robotics & Industrial

Pulse Width Modulation

What is PWM?

PWM (Pulse Width Modulation) is a digital signaling technique where information is encoded in the duty cycle (ratio of high time to total period) of a rectangular waveform. PWM is universally used in embedded systems for motor speed control, LED brightness dimming, servo positioning, power converter regulation, and DAC emulation. While PWM is not a communication protocol in the traditional sense, analyzing PWM signals is essential for verifying correct duty cycle, frequency, dead time in H-bridge configurations, and timing accuracy. Engineers debugging motor controllers, LED drivers, switching power supplies, and servo systems routinely need to measure PWM parameters and verify that the actual output matches the intended control signal.

PWM Quick Reference

type Digital pulse
signals Single-wire
features Motor control, LED dimming, servo

Acute Instruments Supporting PWM

Recommended Solutions

Recommended for Decode

TB3016F

TB3016F

With Analog Channels

MSO2116E

MSO2116E

All Supporting Products

Protocol Decode
Hardware Trigger
Protocol Exerciser

LA4000 Series

LA4068B
LA4068B
LA4136B
LA4136B

MSO2000 Series

MSO2116B
MSO2116B
MSO2216B
MSO2216B

MSO3000 Series

MSO3124H
MSO3124H
MSO3124V
MSO3124V

TravelBus Series

TB3016B
TB3016B

TravelLogic Series

TL4134B
TL4134B
TL4234B
TL4234B

TravelScope Series

TS3124E
TS3124E
TS3124B
TS3124B
TS3124H
TS3124H
TS3124V
TS3124V

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How to Analyze PWM with Acute Instruments

1

Connect your Acute logic analyzer to the PWM output signal on the target board.

2

Attach a ground lead to the target board's ground reference.

3

In the Acute software, select the PWM analysis mode and assign the signal to the correct input channel.

4

Configure the expected frequency range and measurement parameters (duty cycle, frequency, period).

5

Capture and view PWM timing measurements including duty cycle percentage, frequency, high time, low time, and any deviations from the expected values.

Frequently Asked Questions

What sample rate do I need for PWM analysis?
The required sample rate depends on the PWM frequency and the measurement resolution you need. For a 25 kHz PWM signal (common for motor control), sampling at 2.5 MHz gives 1% duty cycle resolution, and 25 MHz gives 0.1% resolution. For servo PWM at 50 Hz, 500 kHz is sufficient for microsecond-level timing. Higher sample rates provide finer duty cycle measurement granularity.
Why does my PWM duty cycle measurement not match what I programmed?
Discrepancies between programmed and measured PWM duty cycle can result from timer prescaler rounding errors in the microcontroller, output driver propagation delays, or loading effects on the PWM output. Use the logic analyzer to measure the actual high and low times precisely. Compare the measured period to the expected period to identify any frequency error, then check whether the duty cycle error is consistent (systematic) or varies (jitter-related).
How many channels do I need for PWM analysis?
A single PWM signal requires 1 channel. For H-bridge motor control with complementary PWM and dead time, you need 2 channels (high-side and low-side). For 3-phase motor control (BLDC/PMSM), 6 channels cover all three phase pairs. Adding a channel for a direction or enable signal is often useful for correlating PWM with motor control commands.

Related Protocols

UART

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