RavensFan,
Thanks for the suggestion. Find attached the signal charts and the vi used to produce them. The signal does flustuate a ltittle, but never enough to go positive and then negative. At start up oand shut down there is no spike in the signal either.
To produce this chart i started with the potentiometer set to give a negative signal, then increased it to positive, held it positive and then changed to a negative value. the second half of the samples was when there was no change of the potentiometer position, thus giving an idea of the level of signal fluctuation.
Does any one have any further ideas?