Problem with My A/D readings. Any suggestions? - Electronic Circuits Projects Diagrams Free

cubdh23 · 23rd September 2004, 10:49 PM

Ok, I developed a data aquisition project and i finished it like a month ago. Now the guy that is hooking up the lines to the A/D pins of the controller i programmed, says that the readings is always 0.
When you hook a variable voltage to the A/D pins it works fine. I believe the problem arises because the device that he is trying to get A/D readings is in a different room.
Ok maybe it didnt come out right. What i am trying to say is, could it be that because the wires, which are carrying the voltages, are too long. Would this high capacitance cause the A/D readings to be 0? The A/D pins does work when i hook it to a variable voltage from close range. In any case, lets say this is the problem. The wire is too long. How can i remedy this problem. Because the device that we are measuring has to be far away.
The wire cannot be shortened. Is there someway to lower the capacitance somehow? Please help would be greatly appreciated as i have to go there tomarrow and fix this.

cubdh23 · 23rd September 2004, 11:02 PM

Also could someone explain to me how the capacitance of the wire affects the micro pins. Or if you have a link that i could check out. I am confused about this.

williB · 23rd September 2004, 11:12 PM

as long as the signal is getting to the A/D it should work.
is it possible that he hooked something else up wrong?
say you are measuring music from the stereo in the other room, even if you are using crappy wires it will still get to the A/D..
maybe the signal isnt getting to the A/d converter.

Oznog · 24th September 2004, 03:37 AM

Capacitance doesn't help or hurt really. On the other hand, resistance hurts, but there's no way your wire has the thousands of ohms needed to make it less accurate, much less lose the reading.

Long wires can pick up noise, but for the most part, it's not going to affect the PIC's ADC stage.

Are you sure the signal he's reading is grounded in the same place as the PIC's gnd?

cubdh23 · 24th September 2004, 05:22 AM

"Are you sure the signal he's reading is grounded in the same place as the PIC's gnd?"

Probably not. That could be the problem. I dont know, i never tested his part of it, i guess i will find out tomarrow. I just thought maybe the wire was too long but i guess i was wrong about that. thanks.

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23rd September 2004, 10:49 PM	(permalink)
cubdh23	Problem with My A/D readings. Any suggestions? Ok, I developed a data aquisition project and i finished it like a month ago. Now the guy that is hooking up the lines to the A/D pins of the controller i programmed, says that the readings is always 0. When you hook a variable voltage to the A/D pins it works fine. I believe the problem arises because the device that he is trying to get A/D readings is in a different room. Ok maybe it didnt come out right. What i am trying to say is, could it be that because the wires, which are carrying the voltages, are too long. Would this high capacitance cause the A/D readings to be 0? The A/D pins does work when i hook it to a variable voltage from close range. In any case, lets say this is the problem. The wire is too long. How can i remedy this problem. Because the device that we are measuring has to be far away. The wire cannot be shortened. Is there someway to lower the capacitance somehow? Please help would be greatly appreciated as i have to go there tomarrow and fix this.

23rd September 2004, 11:02 PM	(permalink)
cubdh23	Also could someone explain to me how the capacitance of the wire affects the micro pins. Or if you have a link that i could check out. I am confused about this.

23rd September 2004, 11:12 PM	(permalink)
williB	as long as the signal is getting to the A/D it should work. is it possible that he hooked something else up wrong? say you are measuring music from the stereo in the other room, even if you are using crappy wires it will still get to the A/D.. maybe the signal isnt getting to the A/d converter.

24th September 2004, 03:37 AM	(permalink)
Oznog	Capacitance doesn't help or hurt really. On the other hand, resistance hurts, but there's no way your wire has the thousands of ohms needed to make it less accurate, much less lose the reading. Long wires can pick up noise, but for the most part, it's not going to affect the PIC's ADC stage. Are you sure the signal he's reading is grounded in the same place as the PIC's gnd?

24th September 2004, 05:22 AM	(permalink)
cubdh23	"Are you sure the signal he's reading is grounded in the same place as the PIC's gnd?" Probably not. That could be the problem. I dont know, i never tested his part of it, i guess i will find out tomarrow. I just thought maybe the wire was too long but i guess i was wrong about that. thanks.