Abstract: A calipering tool for use in a pipe and having a body and feeler means mounted with the body for engaging the surfaces of the pipe being calipered and with feelers moving in response to variations in the surface of the pipe, the improvement residing in mechanisms with the body for permitting the body of the calipering tool to be pumped in response to fluid pressure thereon into and out of the pipe for operation of the calipering tool.

Abstract: A calipering tool for use in a pipe and having a body and feeler means mounted with the body for engaging the surfaces of the pipe being calipered and with feelers moving in response to variations in the surface of the pipe, improvements residing in pairs of stylus members, including active and base-line styli, each active stylus adapted to engage a chart and move relative thereto in response to movements of a feeler and with each base-line stylus adapted to engage the chart adjacent the active stylus for providing an individual base-line for the respective active stylus for providing accurate dimensional recording and continuing thermal calibration of the calipering tool in response to temperature variations encountered within the pipe and a new removable stylus assembly capable of being removed from the calipering tool as a unit for repair and/or replacement as is necessary without requiring replacement of the entire calipering tool.

Abstract: A new and improved signal-producing pipe caliper adapted to be moved through a section of pipe to detect internal variations in the inside surface of the pipe, and to transmit analog signals corresponding to such variations for suitable recording at a location which is remote from the caliper; such caliper having individual caliper feelers which are separately removable and replaceable without disturbing the electrical signal system, whereby replacement, including size changes of the caliper feelers for accommodating different inside diameters of the pipe being calipered, and/or repair may be accomplished in the field rather than requiring the return of the caliper to the shop.