Abstract: A fluid handling apparatus, such as a viscometer of the falling piston type, wherein at least a portion of the fluid in a main conduit is diverted into a secondary conduit system which includes a measurement channel having a filter at the entrance to prevent entry of undesired material. When the flow of fluid into the measurement channel is stopped, the fluid flows past the filter, removes the undesired material which has been retained thereat, and carries it back into the main stream. The viscometer can further provide means for producing an external visual indication of the piston movement within the channel. Further, the fluid can be permitted to flow continuously in a second channel, thermally coupled to the measurement channel, so as to maintain the temperature of the measurement channel at or substantially near that of the main stream. Further means can be provided in the second channel to permit adjustment of the fluid flow in the measurement channel to assure adequate operation of the device.

Abstract: A recording device using a circular chart wherein the major portion of the chart containing the central portion thereof is driven so as to rotate in a first plane, the lesser portion thereof being folded so as to rotate in a second plane angularly disposed, and preferably orthogonal, to the drive plane. A writing means, such as a stylus, is in writing contact with the chart on its major portion so that the recordal of information thereon occurs in the drive plane. The folded lesser portion of the chart is retained in place during rotation by the inner surface of one side of the case in which it is enclosed.