A device including a chain strand where a contact point of a pivoting arm rests and slides on the chain of the chain strand. The pivoting arm is mounted on the shaft. The pivoting arm is coupled with the source of a compressive force in a form of a weight or a torsion spring. The pivoting arm is coupled with the shaft and therefore with the indicator of tension of the chain strand. The compressive force compensates for the change in resistance and lengthening of the chain when the chain conveyor is running, wherein its chain strand has been pre-tensioned by the basic pre-tensioning force induced by the tensioning device. The co-acting of the pre-tensioning force and the compressive force creates the operating tension which is not only indicated but also optimized by the device of the invention depending on a change in resistance in the chain strand.

Provided are an abnormality detection system, an abnormality detection device, an abnormality detection method, a computer program, and a chain that enable detecting of an abnormality not only in a chain but also in equipment using the chain while distinguishing the location at which the abnormality occurs. The abnormality detecting system comprises a sensor unit comprising a sensor, to be fixed to a chain that is to be attached to equipment, and transmitting an output from the sensor, a detection section which detects an abnormality of the chain or the equipment based on the output, and a determining section which determines a location of the abnormality in the equipment, based on a position of a part fixed with the sensor unit in the equipment, the position changes in each time point with moving of the chain.

Provided are an abnormality detection system, an abnormality detection device, an abnormality detection method, a computer program, and a chain that enable detecting of an abnormality not only in a chain but also in equipment using the chain while distinguishing the location at which the abnormality occurs. The abnormality detecting system comprises a sensor unit comprising a sensor, to be fixed to a chain that is to be attached to equipment, and transmitting an output from the sensor, a detection section which detects an abnormality of the chain or the equipment based on the output, and a determining section which determines a location of the abnormality in the equipment, based on a position of a part fixed with the sensor unit in the equipment, the position changes in each time point with moving of the chain.