Abstract: A slit for selectively allowing the transmission of emitted light from a light-emitting portion that has been diffracted through passing through a pipe wherein there is no fluid is provided on the slit side of the pipe, between a slit of the light-emitting portion and a slit of a detecting portion. The emitted light from the light-emitting portion, which is diffracted by passing through the pipe wherein there is a fluid, is blocked by the plate member wherein the slit is formed, so as to not arrive at the detecting portion.

Abstract: A dial type indicator in which the zero point on a scale fixed to a rotatable tubular outer frame can be set to the position of the pointer by rotating the outer frame around a circular inner frame. An elastic element at one side of the inner frame is pressed against the inner peripheral face of the outer frame by compressing the element in the thickness direction of the inner frame, using a manually adjustable arrangement to compress the element and cause it to extend laterally. In this manner the inner and outer frames can be reliably fastened together without damage to the outer frame and the operability of the outer frame is improved.

Abstract: A measuring instrument with digital display including a relatively elongate caliper body formed with a measuring part adapted to make measuring engagement with an article to be measured and a slider freely slidable in a longitudinal direction of the caliper body and formed with a measuring part disposed opposite to the measuring part of the caliper body. In the measuring instrument a transparent linear scale is fixedly disposed on the caliper body with its axis extending in the longitudinal direction of the caliper body and a transparent index scale is mounted on the slider with its calibrated face disposed opposite to the calibrated face of the linear scale and slightly spaced apart relationship. A measuring circuit including a digital display element is mounted in the slider and is electrically connected to a light emitting element and a light receiving element mounted in the slider.