Measurement
Cardiophone
The human heartbeat can be made audible by using this cardiophone circuit. It is basically an audio circuit coupled to a probe made specially for the purpose of picking up electric signal from the human heart.
To get the best signal, place the probe’s electrodes to a point close to the heart. The preferred point is [...]
Digital bike tachometer
This digital tachometer for bikes uses two reed switches to get the speed information of the bicycle. The reed switches are installed near the rim of the wheel where permanent magnets pass by. The permanent magnets are attached to the wheelspokes and activate the reed switches everytime they pass by it. The speed is digitally [...]
Diode electronic thermometer
This thermometer circuit uses a common 1N4148 diode as the temperature sensor. The temperature coefficient of the diode, -2 mV / 0C is exploited for this application to create an accurate electronic thermometer. To display the measured temperature, a digital multimeter is used and so we can measure temperature values from -9.990C up to +99.90C.
