Load measuring apparatus

Abstract

Apparatus which measures loads imposed on load carrying members, and particularly such members in presses, to indicate the peak load reached during a press cycle, has circuits for amplifying the electrical signal from a sensing device such as a strain gage bridge, a peak detector which provides an output representing the peak load, and a digital indicator. Zero setting is achieved by integrating and holding an offset voltage derived by an integrating circuit in negative feedback relationship with the circuit which amplifies the signals from the sensing device. Calibration of the apparatus for press factor is obtained by adjusting the gain of a variable gain stage in the amplifier. The peak detector is reset each press cycle when the load sensed bears a predetermined ratio to rated or full capacity load. Overloads are indicated by comparing the peak load detector output with an output representing rated or full capacity load and enabling an oscillator to flash the decimal point indicator of the display when the overload condition is sensed. The different modes of operation of the apparatus (press factor calibration, zero setting and operating) are selectively obtained by switching means including solid state switches connected separately to each circuit of the apparatus in response to control voltages obtained from a front panel switch. The apparatus provides a compact device for measuring loading.