Abstract: When a generator shuts down intentionally or un-intentionally the low frequency switch disconnects a load from a generator before the output frequency of the generator drops below a preset frequency. Without the low frequency switch on some loads, such as a motor, the current will rise to several times the running current of the motor before the generator coasts to a stop. If this load is switched over to a source with insufficient capability to handle the high current, caused by low frequency operation of the load, serious damage can take place to the new source.

Abstract: A liquid-level measuring device measures the liquid level in a tank. This invention measures liquid level by measuring the pressure at the bottom of the tank. A pressure sensor is placed in the top sealed end of a pipe extending from above the top of the tank down to and open into the bottom of the tank. When the tank is empty the pressure is zero (relative to atmospheric pressure). As the liquid level of the tank rises from empty to full, the pressure rises according to the weight of the liquid. An electronic pressure sensor is used to measure the pressure. The output of the pressure sensor is amplified and sent to an operator display device.