Maintaining the integrity of an analog signal

[van4]

Hi,

I am measuring an analog voltage with an Arduino analog in. The analog voltage comes from a cable which also contains digital signal wires. Do I need to separate the analog and digital signals using separate cables? If so, does the analog voltage signal cable need shielding? And if so, how do I ground the shield?

Thanks

 

[analogdesign]

Hi,

I am measuring an analog voltage with an Arduino analog in. The analog voltage comes from a cable which also contains digital signal wires. Do I need to separate the analog and digital signals using separate cables? If so, does the analog voltage signal cable need shielding? And if so, how do I ground the shield?

Thanks

You only need to shield or separate the analog and digital signals if you are having problems with crosstalk. If it isn't broken, don't fix it.

Are you doing DC measurements with the analog or AC? If AC, look at an FFT and see if the peaks at the digital clock frequency and its harmonics are high enough to cause you problems. If not, don't worry about it.

 

[van4]

You only need to shield or separate the analog and digital signals if you are having problems with crosstalk. If it isn't broken, don't fix it.

Are you doing DC measurements with the analog or AC? If AC, look at an FFT and see if the peaks at the digital clock frequency and its harmonics are high enough to cause you problems. If not, don't worry about it.

Ok, thanks for your advice.

The DC signal is from an encoder, so I'm only measuring the DC pulses on the digital pins of the Arduino. I haven't made the cable yet, so I will combine the digital and analog signals as planned, and see what happens. If I do get interference, would shielding on the cable help? If so, where should I terminate the shield? As far as I understand, shields are terminated at a ground terminal, but the Arduino isn't connected to ground. Should I terminate it to a 0V on the analog inputs?