We've used the Coqui to get information about the salinity of water by measuring relative amounts of conductivity, and some folks have been wondering about ways to get accurate measurements. My question has a few parts:
At Barnraising, folks used a guitar tuning app to measure the frequency of the Coqui. I'm wondering if this is a method that could be calibrated against the specific gravity of a known sample (say, using a hydrometer to measure aquarium salt in distilled water) to get accurate quantitative information?
Is there any reason that a multimeter couldn't be used the same way that the coqui and tuning app are? By say, checking the resistance of a sample against a few different of levels of salinity with both a multimeter, comparing that to a hydrometer measurement, and figuring out how ohms translate into gravity?