Electronic Torricelli Barometer Circuit Diagram – Build Your Own!

Circuit diagram:

Description

This electronic replica of the Torricelli barometer, despite lacking the aesthetic appeal of traditional mercury barometers with their lengthy glass tubes mounted on carved and polished wood, functions as a practical equivalent. Instead of displaying atmospheric pressure on conventional digital screens, the design prioritizes a visual resemblance to earlier electronic barometers.

The mercury column is superseded by a simple LED indicator, a safer alternative in the event of damage, though perhaps less visually striking. The pressure sensor employed is a Motorola MPX2200AP. This circuit has been configured for the measurement of absolute pressure and possesses a suitable range for atmospheric readings. These sensors generate an output voltage which is proportional not just to the measured pressure, but unfortunately, also to the applied power supply voltage.

Therefore, it requires a consistent power source, which is assured through IC1. Due to the differential nature of the MPX2200’s output and its low signal level, operational amplifiers IC4.A to IC4.D, contained within an LM324, are utilized to amplify the signal. With potentiometer P1 correctly adjusted, this group of operational amplifiers delivers a voltage of 1 volt per 1,000 hPa to the LM3914.

Given that atmospheric pressure typically ranges from 950 to 1040 hPa at sea level, an expanded-scale voltmeter is incorporated using the LM3914 to maximize the utilization of its ten LED controls. Resistors R7 and R8 accomplish this by artificially elevating the minimum voltage that the chip can measure. Consequently, the LED scale can be ‘calibrated’ with one LED representing 10 hPa, allowing for a measurement range extending from 950 hPa to 1040 hPa. Generally, operation beyond this range is not necessary.

This circuit can be conveniently powered from a 9-volt battery but only if infrequently used. Typically, this is not the case for barometers, so a mains adapter supplying approximately 9 volts is recommended. Calibration involves adjusting potentiometer P1 to illuminate the LED corresponding to the atmospheric pressure of the location at the time. Comparison with an existing barometer, or ideally, contacting the nearest weather station, is advised. They will willingly provide the necessary information. After Evangelista Torricelli, 1608-1647, Italian physician who demonstrated the existence of atmospheric pressure and conceived the mercury barometer.

LM324 Operational Amplifier

The LM324 is a versatile and widely used integrated circuit (IC) that functions as a four-channel operational amplifier. This particular IC provides four independent amplifier stages, offering flexibility for various circuit applications. The LM324 is favored for its small size, low power consumption, and relatively high gain. Its construction utilizes a CMOS (Complementary Metal-Oxide-Semiconductor) technology, leading to excellent switching speeds and low power operation. It's frequently employed in circuits requiring amplification, signal conditioning, and voltage regulation. The four amplifier channels allow for multiple functionalities to be achieved with a single IC, simplifying circuit design and reducing component count.