Sense touch not working for plastic

[espsense]

Hi
i am having application for touch with plastic surface with mutiple pins connected in a straight line. I am measuring using filtered read with following options and read every 50ms

Code: Select all

  #define TOUCHPAD_FILTER_TOUCH_PERIOD 25
   ESP_ERROR_CHECK(touch_pad_init());
   touch_pad_set_fsm_mode(TOUCH_FSM_MODE_TIMER);
   touch_pad_set_voltage(TOUCH_HVOLT_2V7, TOUCH_LVOLT_0V5, TOUCH_HVOLT_ATTEN_1V);
   touch_pad_filter_start(TOUCHPAD_FILTER_TOUCH_PERIOD);

The variations between signal and noise is very low ie low SNR, also the range between touched and not touched is also between 700 and 800. Please help me increase this range and also help identify the correct

• reading time
• HVOLT
• LVOLT
• Measurement time
• FILTER Period
• SLOPE

to get more range, I tried to calibrate a threshold by generating the following chart in serial plotter. but the readings are inconsistent and vary dynamically. The is only touch scenario in the following image plotting the raw and filtered values. Please any help highly appreciated

Screenshot touch button.png (73.66 KiB) Viewed 820 times