A seek control unit moves a head to the vicinity of a target track of a storage medium by coarse control, then switches it to fine control, and positions the head to the target track. The panel also includes multiple spaced-apart vertical members extending between and interconnecting the upper and lower horizontal rails. The mounting can move to different positions facing respective processing stations. The excess H2S returns to the scrubber and filtration unit, while the sulfide solution passes into a photoreactor containing a semiconductor photocatalyst such as Cadmium Sulfide, Platinized Cadmium Sulfide, PtCdS, Zinc Sulfide, ZnS, Zinc Ferrate, ZnFe2O4, Indium Sulfide, In2S3, along with a 450-500 nm light source. In addition, a temperature compensating current source provides an adjustment current to at least one of a pair of resistive sensor elements to compensate for differences between temperature change upon the pair of resistive sensor elements, thereby facilitating nullifying temperature effects upon the resistive sensor elements.