The 7800 Visual Patching and Imaging Chamber consists of an aluminium heat exchanger plate heated by a thin heating element. The heat exchanger supplies concentric heat to the chamber itself and in-line heat to the incoming perfusate ensuring both are heated uniformly. A thermistor embedded in the plate gives temperature feedback to the control system. In its upper surface the plate has a series of annular grooves to carry up to four perfusate tubes. The perfusate tubes carry perfusate to the central chamber at very low level encouraging laminar flow across the chamber.
A gas inlet port allows gas to be introduced for hypoxia studies. Gas flows around the grooves and is heated, eventually exhausting into the central chamber through radial grooves. The heat exchanger plate is coated on all surfaces with p.t.f.e. to discourage drug adhesion. Considerable attention in the design stage has resulted in a chamber with a very low profile reducing the likelihood of the unit interfering with the objective lens and instrumentation probes, electrodes, etc. Because the unit is very compact, the heater output has been closely balanced to the thermal mass of the heat exchanger and the likely demands of perfusate / gas flow. The unit should therefore be protected as much as possible from outside influences such as cold draughts, open doors and windows that may cause unexpected and unwanted variations in temperature.