An Automatic Field-Analog Plotting Device

A device is described which samples the potentials of a 90-node resistance-grid analog computer and turns on lamps whenever it finds a potential higher than a set value. The resulting lamp pattern displays to watching students the approximate location of a given line of equal potential; a series of such lines can be successively illuminated by progressively increasing the voltage across the resistance-grid model. Application of the device to various teaching situations is briefly considered.