Have you ever wandered how effective are cooling fans when compared to each other. Some of them are noisy, other quieter. But with more silence there comes a question – are they effective enough. Instead of probing with bare fingers, nop head decided build his own coolometer which would give some objective results. He surfed through various methods and instead of anemometer he decided to use a 12V 0.8W light bulb and measure the cooling effect – measure how fast bulb filament is cooled. Knowing that when bulb is cold, resistance is about 15 Ohms, when hot – resistance is ten times higher. He constructed Wheatstone bridge circuit where one resistor is replaced with bulb.
To make it digital, he has chosen MicroView module which comes with Arduino and OLED 64×48 Lcd display. He soldered all components on prototyping board and put in to 3D printed enclosure with display, bulb sensor connector, power plug and control button. With his meter he was able to take pretty interesting measurements including cooling maps taken from cooling fan area with 2mm resolution.