a month ago, I bought the oscilloscope 2D42 (SN: CN19030071002307) on aliexpress.Updated Firmware (HantekHTX2019022001) and everything works normally except for AC voltage measurement.More precisely, when I connect it to a computer I do not measure In the display instead of 0.00 it varies voltage from 3 to 4 volts?When I turn off the USB cable, everything is ok?
What is the problem?
Please connect the red and black pens, if the measurement result become zero, that's normal.
The measurement results of red and black pens when they are disconnected cannot be used as a standard.