KC868-A4 ,RS232 can not communicate with Max232

[Nantawit]

Good  afternoon ,I  met  the problem that  used  ADC (4-20 mA)  ,6  mA  pass through  but   reading  was 4.70 mA  (digital  value is 963 )  how  about  your  formular  ?.
                          For  0-5 V  it  ok  the formular  is ( read (adc)*5)/4096  .

Why  your   device  has  a small electric shock occurred.