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General => Technical support => Topic started by: DLUN on January 26, 2011, 01:56:17 PM

Title: ADC negative polarity
Post by: DLUN on January 26, 2011, 01:56:17 PM

Hello.

I have a voltage input from -10V to 10V on my F1616 PLC. I only care about reading 0 to 10V. Can I just connect the input to the ADC directly, or do i need to eliminate the negative voltage via diode prior to connection to the ADC. I am concerned that the negative polarity might damage the ADC.

Please advice.

Thanks. :)

Title: Re:ADC negative polarity
Post by: support on January 26, 2011, 04:59:19 PM

Negative voltage should not be applied to the PLC's analog inputs.

Although there are current-limiting resistors on the F1616-BA analog inputs to protect against temporary negative voltage spikes that could occur on the ADC inputs, prolong exposure may damage the ADC input.

If you add a diode to the input remember that there is a finite forward voltage drop across the diode and this should be compensated in your software.