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Guard Ring Diode


Creator: UoD_Museums on 18 Sep 2011, 3:36 p.m.

According to the accompanying instruction booklet, Ferranti’s GRD7 valve (introduced in 1961) is “a directly heated diode with cylindrical coaxial electrodes and a tungsten filament. The guard rings ensure a homogeneous anode-cathode field and eliminate 'fringe' effect. Although primarily designed for educational purposes it is equally suitable in applications requiring a saturated diode of high stability, such as in stabilised AC supply circuits… The anode and guard ring are of non-magnetic material. A hole in the anode allows the filament to be sighted for the approximate assessment of temperature by optical method.”