Noise in hardware timed sampling sequence USB 6212 Multifunction DAQ

[Linkster]

I am using a 6212 USB Multifunction DAQ Board to sample 2 analog inputs and 1 counter.  I pull single samples using DAQMX read single channel single sample for each of the analog inputs and they are not noisy.  But when I switch to a task that reads both the inputs and 1 counter, I get a noisy signal on the analog input.
 
 The task is timed out by the other counter set to output at a certain clocking frequency.  I have the clocking frequency set to the same value as the sampling frequency I'm using to take measurements.
 
Any ideas on why the signal becomes noisy when I switch to a task?

[Linkster]

*Correction:  I meant to say it is the internal timer is clocking the other functions.

[Paul C.]

Hi Linkster, I'm afraid this could be due to a number of reasons.&nbsp; Can you provide me a little more information about what type of Noise you are seeing?&nbsp; Perhaps if you could take a screenshot that would be helpful. There is a knowledgebase <a href="http://digital.ni.com/public.nsf/websearch/B9BCDFD960C06B9186256A37007490CD?OpenDocument" target="_blank">here</a> that has some great information you might find useful.&nbsp; Also, the field wiring and noise considerations article, found <a href="http://zone.ni.com/devzone/cda/tut/p/id/3344" target="_blank">here</a>, is very useful for reducing noise.&nbsp; It is likely that the noise is due to the fact that we use a multiplexer to switch between channels on the USB 6212.&nbsp; This can sometimes cause something called "ghosting" to occur.&nbsp; If what you are seeing is indeed ghosting, I would take a look at the article <a href="http://digital.ni.com/public.nsf/allkb/73CB0FB296814E2286256FFD00028DDF" target="_blank">here</a> for some ideas on reducing the effect. I hope this helps,Paul C.