Abstract: A Weathering apparatus having a light source which irradiates onto specimens located in a specimen supporting wall which is located on a side of a test chamber. The output of the light source is controlled by independently adjustable control channels. Each of the control channels include a light source detector inserted into the test chamber, control circuitry, and ballasts connected to the light sources. The light sources are controlled by the control channels to deliver an output equivalent to a desired set-point. In order to disperse light in an even manner to the specimens, a barrier is provided which interferes in a predetermined pattern with the passage of light produced by the light sources. The apparatus includes a calibrating device which automatically transfers an irradiance signal from a reference detector selectively positioned immediately adjacent the light source detector. The calibration signal is sent to the controller where the re-calibration of a selected control channel is accomplished.

Abstract: An easel having a tripod stand each of whose legs are telescopically mounted in tubular sleeves. A traveller unit is mounted on one of the sleeves and it has attached thereto cross brace members whose opposite ends are connected to the other respective sleeves. The traveller unit has a pair of legs extending angularly downwardly from the sides of a platform to form a channel between the legs. A cross member connects the tips of the legs and forms an opening into which a middle sleeve is received and which acts as a guide for the traveller unit as it slides upwardly and downwardly when setting up or collapsing the easel. A pair of pad holder units are attached to the other sleeves and are positionable on the sleeves at an infinite number of heights due to the frictional clamping nature of their structure when a load is supported thereon. Cooperating structure is formed on the sleeves and leg members which allow the length of the legs to be varied by utilizing resiliently biased leaf springs.