Originally posted by Infalable
How often do you calibrate? If it is only once in a while then it would be about $20 cheaper.
IMO, it should be calibrated before every use...and it should be used often. Salinity should be checked quite often, IMO. If you don't want to do a calibration before each use, then there is no real point in buying one, because they can be off just as much as any cheaper model hydrometer. The key to having equipment like a refractometer is to use it as accurately as possible, and that means zeroing it before every use....even if it is just checking that it has stayed at zero.
I think you can 'get by' without one, but it is a pretty darn good piece of equipment to invest in for something that is pretty darn important. Also, if using a swing arm, remember to clean those out (they can be soaked in white vinegar) to remove any buildup that might cause errors in reading.