I-50S and I-50A (1948 to 1990) Previous
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The I-50 meter was a revolutionary advance in metering. Ever since the first meters were made, jewel bearings had been used which required periodic maintenance to keep the meter accurate. There had been a previous but unsuccessful attempt to use a magnetic bearing in meters in the late 1890s in the Stanley meters. GE had started research on an improved magnetic bearing in 1940, but this was interrupted by WWII. Development of this bearing quickly resumed following the war, and this magnetic bearing significantly reduced the maintenance required and allowed longer intervals between tests. Another major improvement was to incorporate the brake magnets and full-load adjustment into the frame, simplifying construction and adjustment of the meter. The self-contained version of this model was quickly replaced by the I-55 and I-60, but transformer-rated versions were made into the 1970s and special versions into the late 1980s. The I-50 family of meters is probably the only series of meters where the register and nameplate are one piece, but meters with S/N beyond #42,400,000 do have separate registers and nameplates.
 
I-50S
Photo by Austin International
I-50A
Pete Mallet collection