Thanks to the Sensor, Switch, Smart Camera, and Machine Vision device OEM's who've helped us compile our listing here.


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Hermetic seal - An air-tight seal. In photoelectrics, the lens assemblies of some sensors have hermetic seals to exclude the entrance of air and water behind the lens, thereby preventing fogging of the inner surface of the lens. In limit switches are hermetic seal contacts prevent contact surface contamination.

Hertz (Hz) - The international unit of frequency, equal to one cycle per second.

Holding current - The current drawn by a load while it is energized. Also called “sealed current” of a load.

Hysteresis - The difference between the nominal sensing distance ("On" point) and reset point (sensor switch "Off") when a target moves away from the sensor’s face. See illustration below. Hysteresis is sometimes specified by sensor and switch manufacturers as a percentage (%). Without sufficient hysteresis a proximity sensor will “chatter” (continuously switch on and off) when there is significant vibration applied to the target or sensor.

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