Problems in differential acquisition

[Ashish_Naik_NIUK]

Dear Jorge,

I have read your issue regarding grounding issues within your industrial process.I would like to show you a Developer Zone article on Field Wiring and Noise Considerations which should help answer a few of your queries. Please refer to Section 3 - Measuring Floating (Nonreferenced) Sources .

The disadvantage of differential is that it halves the channel count of the device, however the measurement taken is of significant advantage as it rejects common mode noise.

I hope this helps.

Message Edited by Ashish N on 09-25-2008 07:41 AM

[jorgelopes]

Well, this solution is better than the COM, but needs aditional 10 k resistors for each differential channel. Is there a way of solving this problem without using the 10 k resistor with this scheme? An additional option, perhaps...

My best regards, Jorge Lopes

[Ashish_Naik_NIUK]

Dear Jorge,

If you are using a floating signal source then you need resistors to provide a return path to ground for the bias current.

However if you are using a grounded signal source then there is no need for resistors.

This is explained in Table 1 of Section 3 of Table 1 of Section 3 of Field Wiring and Noise Considerations.