As a novice in the area, I want to buy one refractometer but I’m really in doubt about what I should do. I have seen many analogue models (American, European and Asian) and few digital, ranging considerably in cost and quality.
My questions:
How to decide between analogue and digital?
What factors should I consider during this process of evaluation to have the right instrument?
Day in day out, what are the advantages and disadvantages you have encountered?
Have you regretted with a purchase of an analogue or digital model/manufacturer?
I stick with an analogue because without spending big money, digital refractometers have a limited ability to identify stones. I think the Presidium is 57
Analog refractometers are limited to a R.I. of 1.81 and that is with the use of a hazardous fluid, toxic even.
Digital refractometers have a range of 1.30 to 3.00, and use NO HAZARDOUS FLUIDS, and can read stones as small as 2mm, diamonds, CZ, Moissianite , anything you want to check, cabs are an occasional problem if mounted.
I have 3 digital units and check one against the other two if a spurious reading does occur. My oldest is a Gemeter 90 and it is the workhorse and is seldom in error, and it is 30 years old. I just change the battery every 6 months.
As a trained Metrologist (science of measurement) I would like to state a philosophical point about refractometers. The purpose of a refractometer is to measure the Refractive Index of a material and not to identify gems. It is your measurements, observations, separation efforts, and your Mind that Identifies the Gems. For example: You have a Red gem and a Green gem, both measure the same Refractive Index … Did the Refractometer Identify the Gems? Of course not, but the observation of Red or Green went towards the separation effort. Not many gems are above 1.81 so the first choice should be the critical angle refractometer utilizing RI fluid. I use a Gem-N-Eye Digital to confirm an OTL measurement and to see how high above 1.81 the gem under test might be. The standard refractometer utilizing RI fluid can give you information that the gem is doubly refractive or singly refractive, where the Digital units can’t readily provide that information. I hope this discussion was useful.
