Refractometer TDS% Error Message When Testing Espresso

(Julian Colman) #1

I recently acquired a Reichert R2 Mini Coffee Refractometer. It is the version developed by Vince Fedele when he was with Howell, in collaboration with Reichert. I calibrated it and tested it with a defined sucrose solution. It has decent accuracy. However I get an “Error 12” when testing espresso when in TDS% mode. Now I am currently not filtering the coffee, as I read articles that said this did not make a difference in results. I’m not for or against filtering; just wanted to give it a try. Anyway, Error 1 is “no sample present” and Error 2 is “insufficient sample”. Any ideas on the cause, or solutions?


Interesting / curious that I do get refractive index mode (Nd) results, in both standard and temp adjusted mode. But Error 12 for TDS%. Any idea why? Solutions? See initial post above.


Apparently I could convert to Nd to TDS%, if I had V2 of MojoToGo or associated Iphone app. VST Coffee Tools does not seem to have that utility. Can I obtain that v2 software / app anywhere?)

(Julian Colman) #2

For those that are interested, the VST Technical Support team was most helpful, and solved my issue.

The short answer is that there were three versions of this device: one for poured coffee, one for coffee/espresso (weak espresso) and one for espresso. Each had a TDS% limit. Mine is a coffee/espresso device with a 9.9% TDS limit.

The solution is to dilute my sample shot with distilled water by a specifIed proportion, best using a scale accurate to 0.01g, then test and then adjust the resultant TDS% using the following formula: Mass(i) * %(i) = Mass (f) * %(f) and solve the equation for %(f), where Mass(i) is the weight of the diluted sample and %(i) is the TDS% of the diluted sample.

For example, weigh the shot and add an equal amount of distilled water. Then test the TDS% and multiply that x 2.