I have had a little bit of time to do some tests and there have been some interesting things happening but I need time to do more tests to double check things.
First of all this tablet has a pen reading height of 25 mm above the tablet case. The sensor doesn’t sit as deeply into the case as the Wacom but still that is an impressive reading.
Now the bad news is that the tablet gets a bad case of jitters when the operating LCD is placed on top of it. It starts randomly doing right and left click and other funky stuff. First I thought it must be the inverter so I tried various positions, having the controller/inverter boards on a different plane did seem to help but in this configuration I still get jittering and random clicking/moving. So I started unplugging things to see what was causing the problem:
– disconnecting back lights had no effect
– disconnecting inverter board from main controller had no effect
– putting the controller about a meter away from the LCD/Tablet had no effect
– Rotating the row column drivers perpendicular didn’t have very significant effect but could look into this some more
– unifying the grounds on the controller -> inverter -> column drivers -> row drivers didn’t have any effect
– some shielding material with plastic backing came with the monitor, I tried putting this between the tablet and the column drivers, no effect
– removing the whole backlight slab/unit and letting the LCD sit on the sensor(with paper in between for insulation) made it worse!
It seems the actual LCD is interfering with my tablet and not the backlight unit (or maybe that interferes as well but not as much). So I put the sensor back in its case and that actually helped a bit. All this time I was worried about things getting too thick but actually having the LCD too close to the sensor seems to cause some problems. Please note that these results are only for my tablet and my LCD, I think Wacoms use a different technology so I don’t think we can uniformly apply rules between different tablets or even LCDs.
After this I thought maybe increasing the distance between the LCD and sensor might help even more but it wasn’t to be… it helps a little but I still get the random clicking problem.
So now I am trying different monitor frequencies, resolutions, colour depths, so far without success. I have tried 60, 70, 72 and 75Hz, I will get the specs for this monitor so see what the range is and test them all.
A tip for other people doing tests, it’s handy to have a second monitor connected and have the stripped LCD sitting on the tablet, then you can move and disconnect things and still assess the result by drawing and seeing the result on the second monitor.