Week10 | Output Devices

Group members

Group assignment

  • Measure the power consumption of an output device.
  • Document your work on the group work page and reflect on your individual page what you learned.

OLED display – Power consumption

This week in the group assignment, we measured the power consumption of an OLED display as an output device.

The current consumption of the OLED display was tested using four different power meters.

Hardware and Software used

  • USB‑C cable
  • QPAD XIAO board
  • OLED Display
  • RP2040
  • Arduino
  • Power meter: Multicomp MP780426
  • Power meter: Keweisi
  • Power meter: MODE:U96P USB
  • Power meter: USB Safety Tester

We used the same Arduino code that Omid used in Week 04 of the individual assignment.

First, we connected each power meter to the laptop and checked the voltage and current without the OLED. Then we connected the OLED and recorded the differences.

Power Measurement

Each power meter was connected between the laptop’s USB port and the RP2040, which powered the OLED display. The measured values are shown below.

Power Measurement: Multicomp MP780426

Since the OLED was soldered to the board, the measured power consumption includes both the OLED and the board itself.
With the OLED disconnected, the reading was: 0.0 A, 5.17 V.

After connecting the OLED, the meter still showed 0.0 A, 5.17 V, resulting in:
Power = 5.17 V × 0.0 A = 0.0 W

Power Measurement: Keweisi USB

Using the same setup, with the OLED disconnected the reading was: 0.0 A, 5.18 V.

After connecting the OLED, the reading was: 0.07 A, 5.18 V, resulting in:
Power = 5.18 V × 0.07 A = 362.6 mW

Power Measurement: MODE:U96P USB

With the OLED disconnected, the reading was again: 0.0 A, 5.18 V.

After connecting the OLED, the reading was: 0.031 A, 5.18 V, resulting in:
Power = 5.188 V × 0.031 A = 160.8 mW

Power Measurement: USB Safety Tester

This meter was unable to measure current.
With the OLED disconnected: 0.0 A, 5.17 V.

After connecting the OLED, the reading remained 0.0 A, 5.17 V, giving:
Power = 5.17 V × 0.0 A = 0.0 W

Additional Test

We connected the power meter to the laptop and placed the Keweisi meter after it.
The Keweisi readings matched the earlier measurements, while the first meter’s current increased from 0.031 A to 0.040 A.
This means the Keweisi meter itself consumes approximately:

5.188 V × (0.040 A – 0.031 A) = 46.6 mW

Comparison

The four power meters produced noticeably different results. Two meters were unable to detect the OLED’s current draw and consistently showed 0.0 A, while the Keweisi meters provided more realistic values between 31–40 mA. This demonstrates how measurement accuracy depends heavily on the sensitivity and quality of the power meter. The additional test also showed that the Keweisi meter introduces its own small power consumption when placed in series.

Summary

We measured the power consumption of an OLED display using several USB power meters and observed significant variation between devices. Only the Keweisi meters provided reliable current readings. This assignment highlighted the importance of selecting appropriate measurement tools and understanding their limitations when working with low‑power electronic components.