A new electric telemeter

The recording of strains produced in bridges by trains or motor trucks passing over them has been made possible by a new electric telemeter or strain gage developed at the Bureau of Standards. The gage has two points which are clamped to the part of the bridge truss on which the measurements are to be made, and two stacks of carbon disks. A change of load on the truss causes a change in the distance between these points, and this is arranged to cause a change in the pressure on the carbon stacks and a consequent change in their resistance. The electrical apparatus can be made to record very rapid changes. The recording apparatus can be used with several gages at once.