When using this to test % PG in water, is it possible to get a false positive at low levels (e.g., 0.1, 0.2)? Does the turbidity of the sample have any effect?
The uncertainty of the Palm Abbe digital refractometer PA203X with a propylene glycol (PG) scale is +/-0.1%. So, if you are testing pure water there is always the possibility of receiving a reading of either -0.1% or +0.1% concentration. To minimize the possibility of an erroneous reading, you can take multiple readings and average them together. Generally, turbidity caused by suspended solids will have little effect on refractive index measurement.