I was having some issues with mine and had a lengthy convo with man guy with tech support. To make sure that your unit is spot on accurate you need to be sure it is starting at true zero – ( zero is 1.000 SG )
First clean the base lens with Windex using a heavy Windex soaked Q-Tip or cotton ball – Then flush the Windex out of the pan by using the pipette we provide using “Steam Distilled Water” & do 2 or 3 loads of the pan and dump out or extract the distilled water using the pipette [ you MUST use “Steam Distilled Water” ] and then -- load the pan ½ way with “steam distilled water” ( you can’t use RO or DI water for this unit ) and press “zero” by doing this you are sure no residual salt or refraction material is on the lens– Another note: Your solution should always have a pan volume that is 1/3 to ½ full of distilled water for the zero and also that much of the tested sample. In addition, never double test the same sample – if you want to do a retest dump the first sample, flush the pan or blot out leftover first sample liquid and go back to the original source and get another sample. This is to prevent sedimentation of the sample that will give a distorted reading on the second reading.
To validate accuracy you should be using Seawater validation solution that is provided with your unit. @ ( 1.025 SG ) – Never use conductivity calibration solution. The reason is that Conductivity probes, like the Neptune and Pinpoint, are designed for NaCl testing and not Seawater. Most "validation" liquids for refractometers are made from Sodium Chloride [NaCl ] @ 99% - one of the providers of this on the internet is Sybon Scientific and there are others. The problem with their solution is that it is designed for Salinity validation not for Seawater. Their solution is Sodium Chloride [NaCl ] @ 99% and seawater is made up of Sodium Chloride [ NaCl ] @ 97% and Potassium Chloride [ KCl ] @ 2% and Other Trace Minerals Salts @ 1% and that 3% makes a huge difference.
Using this popular salinity liquid sellers, Sybon's, own chart
http://www.premiumaquatics.com/prodimages/tropiceden/Sybon_refracto_cal_solution.jpg you will see that their solution is rated at 35ppt of Sodium Chloride and has a SG of 1.0264 SG and 53 mS/cm @ 77F which is their target for their salinity measurement units but that is for "Salinity Meters, Testers & Refractometers" not Seawater and their primary target is PPT/PSU or mS/cm. However, the optimum target for a seawater aquarium is 1.0250 sg @ between 68° F to 72° F (20/20). -- this brings up a point that all of this should be done at 70 F not 77 F.
The only way to validate your unit is with an independent actual seawater validation solution kit however if you are at +/- 0.001 SG you are within the units’ accuracy specification.
