> Temperature compensation is for the substance you are testing not for temperature induced instrument error which is negligible. 

Ok, good, that was my thought, which is why I didn't give it a second one.

> The refractive index of liquids is quite sensitive to temperature.  In the lab the instruments are hooked up to a constant temp water source  that brings the plates the sample sits on to 25 C thus bringing the sample itself to 25C.  Or 20C if you prefer.  Yes temp compensation is a big deal if you are interested in an accurate result.

Ok, now I'm confused. I understand how you can compensate in a lab with a defined sample temperature, but how do you do that with a portable refractometer that's not electronic? Per your link:

> ...record the refractive index with four decimal places i.e. 1.3945. Then push the "TEMPERATURE" button to get the temperature reading (on the built-in thermometer). Adjust the refractive index to the standard 20C using the formula:
nD(20) = nD(obs) + (T-20)^0.00045

So I have to know the temperature and run the calcs to adjust the refractive index and get to %water (or check a reference table and save a step). Manually with a thermometer, no problem. If the refractometer is electronic and has a chip and that could sense temp, do the calcs, and make the adjustment, nifty. I'm presuming those are the $300 versions. But what of our instrument? Incorporate a piece of temperature-sensitive material that deflects a defined amount for temperatures between 10 and 30C (the given range), thus altering the readout? Pretty cool for a $30 piece....

S

Skillman, NJ

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