D4S (1968 to 1983) Previous
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The D4S meter was a complete redesign of the D3S meter for a lower profile and lighter weight. This was accomplished by using a smaller disk and mounting the voltage and current coil assemblies separately on the frame. Unlike the previous models, the light-load adjustment on the D4S is accessible from the front. Some of the last examples of this model (produced alongside the succeeding D5S meter) did have issues with the disk bearings, causing accuracy concerns on light loads. Westinghouse D4S
Photo by David Dahle