A light table apparatus and inspection methods are provided for detecting fluid-transmitting defects in heat exchanger plates using light. The method includes positioning the heat exchanger plate on top of a support frame of the apparatus, and covering peripheral portions of the heat exchanger plate with at least one light-shielding element. In some examples, the light-shielding element may be edge mats that cover peripheral portions of the plate, or alternatively, may be a gasket-like template that engages a resilient light seal with profiles of the heat exchanger plate surrounding a central portion thereof. The ambient environment is darkened and illumination units in the support frame are activated, and light energy can only be transmitted through defects in the central portion. Thus, a quick manual inspection process is provided for such plates, and defects as small as 15 microns are accurately detected when using the light table apparatus and inspection methods.

A motion detector (1) for a security system includes a primary sensing system including a PIR sensor (5) configured to detect movement of a person within a monitored environment (2), and an ancillary sensing system including a first emitter (7), a second emitter (8) and a receiver (9) configured to detect masking of the primary sensing system. Masking by an object (10) in the monitored environment (2) is determined using the first emitter (7) and the receiver (9) based on a time-of-flight of an optical signal emitted into the monitored environment (2) and reflected by the object (10). Masking by obscuring of a window (4) of the motion detector (1) is determined using the second emitter (8) and the receiver (9) based on the intensity of light transmission from the second emitter (8) through the window (4) to the receiver (9).

A light table apparatus and inspection methods are provided for detecting fluid-transmitting defects in heat exchanger plates using light. The method includes positioning the heat exchanger plate on top of a support frame of the apparatus, and covering peripheral portions of the heat exchanger plate with at least one light-shielding element. In some examples, the light-shielding element may be edge mats that cover peripheral portions of the plate, or alternatively, may be a gasket-like template that engages a resilient light seal with profiles of the heat exchanger plate surrounding a central portion thereof. The ambient environment is darkened and illumination units in the support frame are activated, and light energy can only be transmitted through defects in the central portion. Thus, a quick manual inspection process is provided for such plates, and defects as small as 15 microns are accurately detected when using the light table apparatus and inspection methods.