FNIRSI USB tester - A budget 5-digit BT voltmeter?

• FNIRSI USB tester - A budget 5-digit BT voltmeter?
  Posted by Cliff Matthews on 16 Feb, 2023 13:59
• Could this new product really have such a high-resolution ADC as its 6-digit display would seem to indicate? I suppose if the BT protocol was hacked and it was powered externally by a variable 5 to 15 volt reference, one could double its functionality as a quasi 10,000 count voltmeter and portable logging device (without ever opening it...)
  
  DiodeGoneWild opened one at about the 9 minute mark (maybe the ADC is the SSOIC-10 above the current shunt?)
  

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• #1 Reply
  Posted by ledtester on 16 Feb, 2023 15:39
• TheHWCave did a video on using a USB tester (a TC66) that employs an TI INA226 as a 5.5 digit DC meter:
  
  Using the TC66 USB tester as a $30 5½ digit precision multi-meter -- TheHWCave
  https://youtu.be/iZ5JjA6DoZg
  
  And his teardown/review of the TC66:
  
  Ruideng TC66 / TC66C USB Type-C Tester - Way too good for just USB!
  https://youtu.be/rOlhibDUJgs
• #2 Reply
  Posted by Gyro on 16 Feb, 2023 19:30
• That really does seem like an excessive number of decimal places for a simple USB tester. I think I would have gone for a faster update rate instead.
  
  
  Edit: It does look like it might have potential for other uses though.
• #3 Reply
  Posted by Cliff Matthews on 16 Feb, 2023 22:39
• Quote from: ledtester on 16 Feb, 2023 15:39

  TheHWCave did a video on using a USB tester (a TC66) that employs an TI INA226 as a 5.5 digit DC meter:
  
  Using the TC66 USB tester as a $30 5½ digit precision multi-meter -- TheHWCave
  https://youtu.be/iZ5JjA6DoZg
  
  And his teardown/review of the TC66:
  
  Ruideng TC66 / TC66C USB Type-C Tester - Way too good for just USB!
  https://youtu.be/rOlhibDUJgs
  

  Thanks! That TC66C seems like it would also work, but I overlooked negative voltages (it would take some work!)
  TheHWCave provided a good reference:  https://sigrok.org/wiki/RDTech_TC66C
  
  I think it would require an isolated outboard front-end with a stable 15v reference, along with a summing amp capable of a linear 20v swing. A basic BT app would offset displayed readings as -10.0v=5.0v, 0.0v=15.0v, and +10.0v=25.0v together with a 10x and 100x decimal shift for good measure, pardon the humour
  
  I'd bet Joe Smith could make this look easy, like a Sunday walk in the park with his dog.
  
• #4 Reply
  Posted by thm_w on 17 Feb, 2023 00:04
• 24V / 0.0001V = 240,000. So it would seem to be an 18-bit+ ADC.
  Could be MAX11212, or some China clone equivalent. Or they are oversampling on a 12/14-bit converter.
  
  Look at the internal reference spec for these, they are OK, but not great compared to an external reference.
  
  
  
• #5 Reply
  Posted by Vovk_Z on 17 Feb, 2023 20:33
• In theory it may have 16-bit or less ADC and a good wiring design and fast averaging.