Patent ID: 6385554
Filing Date: 2002-05-07
Classification: G01L

Abstract:
A digital tire gauge for measuring an air pressure of a tire comprising:a housing; a valve stem fitting mounted at one end of the housing for receiving and guiding the air pressure of the tire into the housing; a pressure transducer for measuring the air pressure value of the tire and outputting an analog output signal at an output end; a first switching unit having a first end connected to the output end of the pressure transducer and a second end; a second switching unit having a first end connected to a positive voltage and a second end connected to the second end of the first switching unit; an integrator having an input terminal connected to the second ends of the first switching unit and the second switching unit, for receiving the analog output signal of the pressure transducer and then generating a triangular waveform signal with an increasing ramp section and a decreasing ramp section under control of the first and second switching units; a comparator having a first input terminal receiving the triangular waveform signal of the integrator and a second input terminal connected to a reference signal generating circuit, generating an output signal with a wave width corresponding to the increasing ramp section of the output signal of the integrator; a register for storing the output signal of the comparator; a peak value detector to measure the peak value of the output signal stored in the register; a holding circuit to hold the peak value of the output signal measured by the peak value detector; a counting pulse generating circuit providing a series of counting pulse signals; a counting circuit for calculating a counting value of the output signal held in the holding circuit with respect to the counting pulse signal of the counting pulse generating circuit, and then generating a pressure value signal representing the air pressure of the tire; a pressure value output buffer storing the pressure value signal; a display for displaying the pressure value signal stored in the pressure value output buffer; a speech processing circuit receiving the pressure value signal of the pressure value output buffer and generating a speech signal accompanying with the display of the visual pressure value signal displayed on the display; and, a timer circuit coupled to the speech processing circuit for generating an actuating signal at preset regular intervals for triggering the speech processing circuit to play a predetermined reminding speech.