[Edited question as I've partially fixed my problem].
I'm running an ADC-24 and PT-104 from a laptop, and I've noticed really noisy readouts from when the laptops are on mains power. It's in the order of +/- 0.2mV.
Is there any way to reduce this noise? Unfortunately my experiments are going to be run over 48 hour periods in a laboratory, so desktops and laptops running off batteries are out of the question.