Abstract: The invention includes a direct current energy source monitor which automatically detects the nominal voltage of the direct current energy source to which it is attached. The invention further includes a direct current energy source monitor which is self-powered from the direct current energy source being monitored. The multiple nominal voltage direct current energy source monitor includes an analog-to-digital converter configured to measure voltage from a direct current energy source being monitored and generate a digital output corresponding thereto. The apparatus includes a programmable control device configured to receive the digital output from the analog-to-digital converter and to look up a nominal voltage corresponding to the digital output, and is further configured to calculate a relative charge of the direct current energy source as compared to a full charge on the direct current energy source.

Abstract: An event counter is disclosed which, in one embodiment, provides a reaction timer to time a user's response time to an event. In a second embodiment, the event counter provides a counting device to count the number of occurrences of events or the magnitude of an event. The invention uses a commercially available stopwatch to time the response time. The start/stop switch of the stopwatch is connected to a signal generator such as a piezoelectric element. In one variation, the internal piezoelectric element used as a beeper in the stopwatch is used as the signal generator. In a second variation, the event timer is further provided with a circuit to allow a higher voltage LED to be driven by a lower voltage of the system battery. In yet another variation, the event timer further includes a random delay circuit to randomly delay the start time of the stopwatch. Random delay is provided without a microprocessor by using a variable current switch and two RC circuits having different tau values.