By the way, I tried streaming mode and set
sampleInterval = ctypes.c_int32(50) #50 us
sampleUnits = ps.PS4000A_TIME_UNITS['PS4000A_US'] # unis is us
It got correct sine waveform.

You are correct a timebase of 3999 should give a sampling speed of 20000Samples/sec for a 4425A I am not in the office and don't have that device to hand so can't check. I would suggest trying to set this up in PicoScope 7 and see what you get, the rule of thumb is that if it works in PicoScope the...

@Martyn
Hi Martyn，
Could you please help me to comfirm the timebase value?
if use 20000Hz sampling frequency, What the value of the timebase should be? by using picoscope 4425A.
Or I need to adjust some parameters else?

Now I have a picoscope 4425A device, I copied the code by following the python example of github and want to run block mode. As the equation of sampling rate in picoscope-4000-series-a-api-programmers-guide.pdf, Sampling frequency (fS) = 80 MHz / (timebase+1), I want to set frequency as 20000Hz, so ...

@Neil
I am tring to set resolution enhancement of channel B as 16bits by using Python,
Could please give me an example code to set it?
I tried to use ps4000aOpenUnitWithResolution, but I can not figure out how to define PS4000A_DEVICE_RESOLUTION.