Internet PLC Forum

General => Technical support => Topic started by: Melin on June 08, 2004, 09:39:09 AM

Title: What I'm doing wrong?
Post by: Melin on June 08, 2004, 09:39:09 AM

I am testing the analogic inputs of the T100MD+ using regulated
pin 13 to 2,5 V and monitoring I see that the signal is fixes to
4092, although disconnects pin 13 of entrance 1. I do not understand
that it happens, because with a generator 0-5Vdc does the same.

Any idea?

Title: Re:What I'm doing wrong?
Post by: Melin on June 08, 2004, 10:20:43 AM

OK.

using  a potentiometer of 1K finally read the inputs but in the other inputs I have a residual signal.

Melin

Title: Re:What I'm doing wrong?
Post by: support on June 11, 2004, 10:29:07 AM

When an analog input is "floating" (i.e. not connected to any voltage) it tends to be "influenced"by its neighbouring pin voltage. So if you apply voltage to one of the analog pin and read the ADC( ) values of the other unconnected ADC pins you will see value changes as well. This is normal. As soon as you connect the other pin to proper analog voltages they will read correct values.