Problem of pick up

[ShBa_282106]

I am using PSoC CY8C001 kit for counting pulses in window 1V to 2.5V. When the pin is ground it dsnt pik up..but when left stray counts go beyond 20000! what could be the issue?

   

i have changed many pins and checked, even decreased and increased time of counting.

[ETRO_SSN583 · Accepted solution]

The input Z of an analog input is very high, therefore when left

   

floating very susceptable to picking up noise, power line induced

   

frequency, etc.. via start C coupling to pin.

       

Either terminate with a R to lower input Z when not connected to

   

anything, or ground input to comparators with a mux.

       

Regards, Dana.