H

HA coating - Photomultiplier tube

HA coating - Photomultiplier tube

A conductive coating placed on the bulb of photomulitiplier tubes to prevent noise generation by the proximity of grounded objects. It is only necessary for negative high voltage operation.

Hysteresis

A phenomenon in which the output level of a device measured while the input level is increased does not equal the output level measured while the input level is decreased, even if at the same input level. Because of this phenomenon, noise within the hysteresis width does not cause chattering. Hysteresis circuits used in a comparator make use of this effect by feeding back part of the output to the non-inverted input terminal.