Author Topic: Analog Input Voltage Range  (Read 10642 times)

Ben

  • Guest
Analog Input Voltage Range
« on: March 25, 2004, 08:13:46 AM »
I have an op amp circuit feeing the analog input on a T100MD-888+. Under normal conditions, the analog input would see 0 to +4.5 vdc, but if the sensor fails, or is removed, the opamp saturates to the negative rail of -5.0 vdc. Will any damage be done to the Analog input on the T100MD-888+

support

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 3174
    • View Profile
    • Internet Programmable PLCs
Re:Analog Input Voltage Range
« Reply #1 on: March 26, 2004, 03:27:20 PM »
The ADC should not be subjected to greater than -0.3V for long period of time. So if there is a danger of negative voltage, then use a reverse-biased diode across the opAmp output and 0V. That way when the OpAmp output goes negative the diode will clamp it to 0.3V for germanium diode and 0.7V for silicon diode.
Email: support@triplc.com
Tel: 1-877-TRI-PLCS

Ben

  • Guest
Re:Analog Input Voltage Range
« Reply #2 on: March 31, 2004, 01:02:24 PM »
Thanks.