How do I get rid of 50Hz mains interference in LabView

[Deke1955]

How do I get rid of 50Hz mains interference in LabView. I have around one hundred and twenty mV signals and some current signals connected to daq boards via SBC68 interface cards. Everything including the PC is housed within an Earthed metal cabinet within the attic of a house.
The interference seems to be coming from the mains as it is around 50Hz.
Does National Instruments have something built into the LabView software that can cancel it out?

Thanks in advance for any help with this.

[TCPlomp]

How have you connected your signal to the board?
Have you set RSE/Differential in software according to your connection?

Ton

[Deke1955]

Thanks Ton

I have posted this query on behalf of a colleague that is sitting in the attic of the house at this very moment. I had a brief conversation with him a short while ago, just after posting the query.
He has more or less cleared the problem by using a bias resistor to ground.
I thought he had done all this already but, apparently not.
He just has a slight offset now which he can live with and take account of later.

thanks for your reply. It will be noted for future.

Deke1955.

[johnsold]

It is always better to eliminate interference at the earliest point possible in the system. Using proper connection, signal conditioning, and shielding techniques is better than trying to remove interference later.

If it is necessary to try to remove interference rom a digitized signal, a variety of filtering and signal processing techniques may be tried. The selection will depend upon the nature of the desired signal as well as the type of interference. One critical point is to be sure that the sampling rate is fast enough that the interference is sampled at the Nyquist rate or faster. If the interference is aliased due to undersampling, it may be impossible to remove.

Lynn