Spinner (ca. 1950s)
The quality of radiograph (X-ray picture) depends on several parameters: the high voltage, the tube current, the exposure time, the film, etc. Unfortunately, the mechanical timer used by the early X-ray units were particularly unreliable.
These X-ray units used a transformer to obtain the high voltage required by X-ray tubes. Since the input current was 110 volts AC, the X-ray beam would consist of 60 pulses per second if half-wave rectification was employed and 120 pulses if full-wave rectification was used. This provided a convenient method for calibrating the X-ray unit’s timer.
The spinner, with a single hole (ca. 1 mm diameter) at its edge, was placed on a piece of X-ray film and spun gently. The X-ray unit was then operated with the timer set for a particular exposure. If the timer was set for one second, 60-120 spots should appear on the processed film depending on the rectification (in reality, one second is a bit long because you would want to avoid a complete rotation of the top). If a different number of spots appeared, the timer was faulty.
Size: 2.5" diameter, 1.25" tall