Ring dynamometer
A ring dynamometer is a mechanical measuring device for measuring compressive or tensile forces .
Mechanical ring dynamometer
The ring dynamometer , also ring dynamometer , is a mechanical force measuring device . It consists of a steel ring to which two opposing force absorbers are attached. If a tensile force is applied to this, the ring deforms minimally and becomes longer and narrower. When a compressive force is applied, the ring becomes shorter and wider. The ring is constructed in such a way that the deformation recedes elastically after the load is removed. Accordingly, ring dynamometers are designed for specific measuring ranges that must not be exceeded, not even for a short time.
The deformation in width is measured with a dial gauge and converted into tensile or compressive forces using a calibration table. Or a digital dial gauge is used that has saved the calibration curves and displays the force directly. With some ring dynamometers, the dial indicator can be set so that it shows the maximum or minimum force in one measuring process. The ring deforms a maximum of 1.5 mm. The relationship between change in load and change in length is almost linear when pulled, and slightly curved when pushed. With the same load steps, the lever arm changes in the ring, which results in a 3rd degree polynomial relationship . The measurement accuracy is around 0.5%.
A ring dynamometer is always used where only minimal differences in length may occur due to the measuring process, for example when measuring rope tension on rope bridges , because lengthening the rope would increase the sag, thereby changing the angle at the anchor points and the rope tension would decrease. They are a very robust measuring device and do not require any external power sources or amplifiers.
Electronic ring dynamometer
Ring dynamometers are also built with an electronic display. The elastic deformation is measured using either a digital dial gauge, see Sect. o. Or strain gauges in a bridge circuit converted into an electrical voltage, which is digitized and displayed. The zero setting takes place via a rotary or push button. So z. B. the packaging weight ( tare ) can also be set as a negative value and thus deducted. Power is supplied by the notebook via an internal battery or USB cable. Internal storage of the measurement data, storage on the notebook or radio transmission is also possible, for example on a notebook or goods and storage system.