timer(redirected from hand timer)
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A device for measuring, signaling, recording, or otherwise indicating elapsed time. Various forms of timers are used in radiographic, surgical, and laboratory work.
n radiographic timing device that functions as an automatic exposure timer and a switch to control the current to the high-tension transformer and filament transformer. The face of the timer is calibrated in seconds and fractions of seconds. The timer controls the total time that the current passes through the radiographic tube and thus the time during which the roentgen rays are emitted. The timer activates a switch or contractor that closes and opens the low-voltage circuit of the high voltage.
n an electronic vacuum tube device, with no moving parts, that covers a time range of 1/20 to 10 seconds. It automatically sets itself, is more accurate than mechanical timers, and meets all the needs of modern high-speed dental techniques.
n a timer with an attachment that permits the timing device to be activated by foot pressure. This is the preferred type of timer.
n an attachment to or part of a timer that requires thumb or finger pressure to activate the timing device.
n a timer using a spring mechanism for determination of length of exposure. Accuracy of timing is not assumed in exposures of less than 1 second with a mechanical timer.
the device on the x-ray machine that controls the period of exposure to the beam. It may be a simple clockwork, wind-back timer, or one of two electronic timers which are capable of fast and repeated exposures. Only electronic timers are allowed on modern machines.