Here we collect some links about low cost pH sensors that we can build into projects.
Another approach is to build a low cost Voltage-controlled-oscillator. This can be done with 1980s era analog IC electronics, very cheap and common, and no software - DIYBio
Connect each sensor (for example, photodetector) to the VCO IC (such as LM555 wired for it, or more specific model) through a simple transistor buffer, and send the output to a tabletop audio mixer to get stereo out's. Done.
An easier method would be to use a 300 baud modem to transmit the xray crystallography animated video and just record that modem audio, play back use a notch filter on the mixing console to get rid of the carrier, ta da, the music of chemical reactions.
# Cheap sensors for aquaponics tanks
There are (of course) electronic pH sensors, but the cheapest I have seen in a quick Google search were about $45 (which includes the microprocessor and the LCD readout and all the plastic), and they have to be calibrated every time they are used. - DIYBio