a configuration the rollers 16 could be initially formed with a non electrically conductive surface such as being rubber coated painted anodized or powder coated however with use over time such a non electrically conductive coating tends to wear away and the electrically conductive portions of the probes 16 may be exposed and come into contact with the volume 14 while this is acceptable it is appreciated that the exterior surface of the probes 16 that contact the volume 14 need not be electrically conductive and non electrically conductive surfaces tend to have some advantages such as resistance to corrosion the probes 16 preferably contact just a single surface face of the volume 14 or in other words are disposed so that they contact only one side of a cotton bale 14 as it rolls along the track 18 however in alternate embodiments one or more of the probes 16 can be disposed on adjacent opposite or other such sides of the volume 14 depending upon the shape of the volume 14 or other factors there are most preferably two probes 16 however in various embodiments a greater number of probes 16 can be used which additional probes 16 can be disposed in the same track.