Type OB (1924 to 1934) Previous
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In 1924, Westinghouse came out with the OB which was a radical departure from the OA's design. This meter was much smaller than the OA (and present-day meters) and in order to accomplish the size reduction, a special stator was used with both the voltage and current coils mounted above the disk. Unlike the OA's cast iron base, the base of the OB is of punched steel. Just like the Type C and OA meters, there are several styles of OB meters. The first picture is of the original version of the OB with metal cover and small nameplate. The second picture is of an OB with the original base and the 2nd generation nameplate. With S/N 9,000,000 Westinghouse changed the base (see third picture), possibly to make it fit better to meter service cabinets coming into use at that time. The fourth picture is of a high-capacity OB (25A, 50A, and 75A ratings). Over the next few years, various improvements were added to the OB's design to compensate for temperature and load variations. The last picture is of the FIRST socket-type meter, the OB 'detachable'. Note the rear view of the meter and the socket used with this meter.
 
Early OB
David Turner collection
Early OB, glass cover
David Dahle collection
OB
David Dahle collection
High capacity OB
Mark Zavislan collection
 
OB socket
Don Price collection