A simple device for testing the accuracy of x-ray timers.
A simple device for testing the accuracy of x-ray timers uses a portable record player whose turntable spins the film cassette beneath the lid on which lead shielding protects the film except for a tiny pin-hole through which the exposures  are made. Multiple exposures of different times of the reproducibility of one time setting can all be made on one film.
D011859:Radiography / Q000295:instrumentation*; D013997:Time Factors