Pic16f877 Adc

A

Thread Starter

a_s_impressed

Joined Jul 1, 2008

8

Jul 2, 2008

• #1

What happens if the input to the A/D module has a negative range before the positive range in concern?

e.g, I have a signal conditioning circuit converting the reading of a sensor to a range of: -6 to 5V. I'm only concerned with the values 0-5V.

How will the negative range affect the A/D operation? or shall I eliminate the negative range. And how?

 

N

nanovate

Joined May 7, 2007

666

Jul 2, 2008

• #2

How will the negative range affect the A/D operation? or shall I eliminate the negative range. And how?

Click to expand...

You can damage the A/D on the PIC.

 

A

Thread Starter

a_s_impressed

Joined Jul 1, 2008

8

Jul 2, 2008

• #3

nanovate said:

You can damage the A/D on the PIC.

Click to expand...

That's what I thought of. so, do you have anu suggestions to eliminate that unwanted negative range?

 

N

nanovate

Joined May 7, 2007

666

Jul 2, 2008

• #4

diode in series with the output

 

A

Thread Starter

a_s_impressed

Joined Jul 1, 2008

8

Jul 2, 2008

• #5

I have tried this too but didn't work. The diode showed a strange response. When it's connected to -0.5 for example the output was around 2.5V . I have the 1N4007

 

Reshma

Joined Mar 11, 2007

54

Jul 4, 2008

• #6

Have you configured the ADC in the bipolar mode?

 

theamber

Joined Jun 13, 2008

325

Jul 8, 2008

• #7

You can try with Zener diodes or Schottky diodes but the dynamic range of the ADC may be reduced if you care.
I am sure that Reshma may have a better answer than this she is really cool.

 

C

calebsmyth

Joined Jul 15, 2008

1

Jul 15, 2008

• #8

I have 7 years experience with this part,...and 2 years experience with dsPIC33FJ256GP506, do you still require help with this problem ?