question about sensors that measure concentration of a solution?

Question

for my physics coursework, i had to build a simple sensor for measuring the voltage of a light dependent resistor (LDR) that was kept underneath a beaker full of water and a light source over the beaker of water. obviously, the light from the lamp passed through the water in the beaker, to the LDR, and according the voltmeter measured a certain voltage across the LDR.
to measure concentration, i had to add small amounts of about 0.01 grams of Copper sulphate salt each time. the solution turned pale blue to brilliant aqua blue and the light passing through the beaker of coloured solution to the LDR would vary, thereby making the voltage of the LDR vary.
now i have to draw a calibration curve of voltage (on the y axis) and concetration (on the x axis) and measure the sensitivty of my sensor.
my question is (if ur not tired reading all this!) is how would you put my sensor in context? how could it be used or developed? are concentratin sensors that use LDRs used in batteries?

Answer 1

I'm not sure what you mean when you ask to put it in context, but I can tell you that a similar technique to the one you're using is actually commonly used to measure concentrations in liquid. For example, UV detectors are widely used in chemical laboratories to measure the concentration of a chemical (e.g., a drug molecule, a protein, etc.) in a liquid solution. The UV detector measures the absorption of ultraviolet light at different wavelengths, and the absorption is compared against a standard solution to calculate the concentration. The ability to measure at different wavelengths makes the test more sensitive and more applicable to different compounds.

To develop your testing apparatus using a lamp and LDR, you'd have to devise an instrument that keeps several things constant. The lamp would have to have a constant output over its life, and the distance the light travels through the liquid would need to be constant as well. If you vary either of these variables, your voltage will vary as well and will become a source of error.