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What is it?

A power meter. My summary so far: my goal is to measure power consumption of my Thinkpad, and be able to read the consumption details from Linux. Right now, I can only supply the Thinkpad with 5V@2A when the CT-3 is used, while the Thinkpad would also support 20V@3A. (Forum thread) Also have not yet succeeded in reading the values from Linux.

Kernel messages

[17217.725904] usb 1-2: USB disconnect, device number 19
[17222.280704] usb 1-2: new full-speed USB device number 20 using xhci_hcd
[17222.409132] usb 1-2: New USB device found, idVendor=0483, idProduct=ffff, bcdDevice= 2.00
[17222.409151] usb 1-2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[17222.409158] usb 1-2: Product: Shizuku in Application Mode
[17222.409163] usb 1-2: Manufacturer: YK Lab
[17222.409168] usb 1-2: SerialNumber: 5A5AA5A6004E00473439510838363239
[17222.414835] cdc_acm 1-2:1.0: ttyACM0: USB ACM device
[17222.415891] usb-storage 1-2:1.2: USB Mass Storage device detected
[17222.416310] scsi host0: usb-storage 1-2:1.2
[17223.440649] scsi 0:0:0:0: Direct-Access     YK-Lab   Shizuku Platform      PQ: 0 ANSI: 2
[17223.441393] sd 0:0:0:0: Attached scsi generic sg0 type 0
[17223.455133] sd 0:0:0:0: [sda] Attached SCSI removable disk


  • firmware update, works from Linux
  • power consumption of some devices, measured with the Satechi metering device:
    • Google pixel 4a:
      • rapidly: 9V0.8A (power supply PD), 4.8V1.6A (thinkpad usb-c out)
      • charging: 4.6V0.7A (thinkpad usb-A out left side)
      • charging slowly: 4.7V0.5A (thinkpad usb-A out right side)
    • Thinkpad L480:
      • 20V@0.8A
  • devices with CT-3
    • input thinkpad usb-A left: PD3 5V
      • out right side usb-A, red cable: 5V@0.7A (pixel4a load)
    • input thinkpad usb-C: PD3 5V@3A
      • out right side usb-A, black cable: 5V@0.5A
    • input power supply: PD3 5V@3A, 9V@3A, 15V@3A, 20V@3.25A
      • out right side usb-A, red cable: 5V@0.4A (pixel4a load), 5V@1.7A (thinkpad load)
      • out right side usb-A, black cable: 5V@1.3A (pixel4a load), 5V@2A (thinkpad load)
      • out up side usb-C, white cable:
        • 9V@0.7A (pixel4a load)
        • 20V@0A, “A correct CC attachment is detected, but no source_cap is received in time.”, Thinkpad load


I want to see how much power for example the Thinkpad uses, and how accurate the internal computation from powertop is.

  • Right now, I just managed to get the CT-3 to supply 5V to the Thinkpad, and with no load the Thinkpad then uses 3 or 4W.
  • Powertop shows a bit more, 5W, but correct scale.
  • Powertop supports direct interaction with a power meter, Extech* Power Analyzer/Datalogger (model number 380803), but these clock at $1000. The CT-3 just costs ~$60.
  • Unfortunately, I did not yet manage to digitally read the CT-3 values from Linux.
  • power measure software:
    • powertop: the default. much c++, measures consumption also if power supply connected
    • ubuntu powerstat (project vanished in late 2021?)
      • leaner, measures only if on battery by default, 'total consumed power' readings are then very much in line with power top. Also has a mode to read RAPL, that works also with power supply connected.
  • What metrics would I want from a pmda-denki/pmda-power?
    • overall consumption (on power supply, as well as when on battery)
      • sources: powertops 'base power', upower -d's “energy-rate” if the battery is fully charged, RAPL (i.e. from powerstat)
    • power consumption by single components: RAPL, plus other components
hardwarerelated/avhzy_ct-3.txt · Last modified: 2021/12/31 01:57 by chris