PURPOSE: To enable recording the history of date and time, count etc., of load generation exceeding a set value by providing a memory for storing the magnitude, generation date and time and count of the load.

CONSTITUTION: When a load is added on a load detector 3, strain is caused and a voltage proportional to the load is generated from an output terminal of a load detection element 1. This output signal is amplified with an amplifier 12 and converted with an A/D converter after eliminating high frequency component with LPF13. This digital output is input to MPU15 as load data. This digital output is input to MPU15 as load data. And the time signal from a timer 18 is also input to MPU15. The MPU15 compares the input load data with a threshold value set in advance and outputs a detection signal based on the relation between the load data and the threshold value. Each data of load value exceeding the threshold value, generation data and time and count are stored in a memory 16. The count of load exceeding the threshold is indicated on a display 20.