Abstract: An electronic tire pressure gauge has a tire valve stem receiver, a thin silicon square diaphragm with four diffused resistors configured in a full Wheatstone bridge as a pressure transducer, a voltage controlled oscillator, a comparator, a clock, a microprocessor with program memory, and a display. The comparator compares the stable transducer output for a given pressure with the voltage-controlled oscillator output, to yield a comparator pulse which goes high while the transducer signal is greater than the oscillator signal. The clock provides bus cycles used by the microprocessor for counting the duration of the high comparator pulse. Multiple high comparator pulses are compared, and the longest duration is selected and converted to a pressure value and displayed. Battery power is conserved by a power on/off algorithm.

Abstract: A light sensor 10 includes two parallel, spaced mask plates 12, 14. A first mask plate 12 has nine, small, spaced holes 38a-i which are in alignment with corresponding holes 36a-i in the second mask plate 14. The light sensor 10 includes a base plate 18 having nine holes 22a-i into which photosensitive devices 26a-i are positioned and the base plate 18 is secured to the outer surface of the second mask plate 14. The photodiodes 26a-i are connected to an indicating means 32 which provides an indication of the light falling upon each photodiode 26a-i individually or upon all of the photodiodes 26a-i collectively.