This is a 1 wire barometer using MPX4115 circuit. Feature : Simple circuitry, more reliable, output voltage ranges from about 4.17 to 3.72 volts at sea level, about 3.5 to 3.04 volts at 5000 feet, gain of 4.4. Component : MPX4115, 7805 regulator, DS2438, 1N4001 diode, resistor, capacitor, 2N4403 transistor, LM358 op amp, variable resistor. [davidbray.org]
