Abstract: A force that causes tensile stress in a thread must be measured, for example in the textile industry, to avoid overstretching of the thread. Thus, small thread tensions must be maintained for many threads moving at high speeds. For this purpose a device for measuring thread tensions up to about 0.1 N (Newton) has a rod type metal component, one end of which forms a mounting member while the other end forms a thread engaging lever arm connected to the mounting member by a flat leaf spring carrying at least one strain gage. The lever arm is, e.g., conically tapering away from the leaf spring and carrying a thread engaging cylinder or extension at its end remote from the leaf spring. The signal provided by the strain gage is proportional to the force. The device forms a thread tension sensor having an eigenfrequency of about 3 kHz for measuring tensile stress on threads travelling at high speeds.