A digital refractometer reads the refractive index of a drop of liquid and converts it to a concentration, so the right model depends on what is dissolved in the sample: sugar (Brix), table salt (sodium chloride) or seawater salts. ERE lists three Hanna Instruments families, one per job. Pick by the solution, then check the range and the stated accuracy against the tolerance you must hold.
In this guide
- Which digital refractometer do you need?
- What does a refractometer actually measure?
- What happens if you use the wrong model?
- How accurate is ±0.2 in practice?
- How do you calibrate and use one?
- Can a Brix refractometer be used for maple syrup?
- How do you choose, step by step?
- Frequently Asked Questions
Which Digital Refractometer Do You Need?
Match the model to the dissolved substance. The sugar family reads Brix, the sodium chloride model reads salt in food and brine, and the seawater model reads salinity. The table uses the figures on the product records.
| Model | Reads | Range | Resolution / accuracy | Typical samples (from the record) |
|---|---|---|---|---|
| Sugar Refractometers (HA-96801 sucrose, HA-96802 fructose, HA-96803 glucose, HA-96804 invert sugar) | % Brix (sucrose model); % by weight for the others | 0 to 85 % | 0.1 / ±0.2 % | Fruit, juices, jam, honey, soups, condiments, energy drinks |
| Sodium Chloride Refractometer (HA-96821) | g/100 g, g/100 mL, °Baumé, specific gravity | 0 to 28 g/100 g; 0 to 34 g/100 mL; 0 to 26 °Baumé; SG 1.000 to 1.216 | 0.1 / ±0.2 (SG 0.001 / ±0.002) | Salad dressings, cheese, pickles, canned foods, brines, whey |
| Digital Seawater Refractometer (HA-96822) | PSU, ppt, specific gravity (20/20) | 0 to 50 PSU; 0 to 150 ppt; SG 1.000 to 1.114 | 1 / ±2 (SG 0.001 / ±0.002) | Natural or artificial seawater, brackish water |
All three share the housing and the basics: stainless steel ring with flint glass prism, 100 µL minimum sample to cover the prism, about 1.5 seconds per reading, IP65 enclosure, 9 V battery for roughly 5,000 readings, 192 x 102 x 67 mm and 420 g. See the full refractometers collection. For other water measurements, the water quality meters range covers conductivity, pH and more.
What Does a Refractometer Actually Measure?
It measures how much light bends as it passes from the prism into the sample, then converts that refractive index to a concentration using a stored table. The instrument does not detect sugar or salt directly. It reports the concentration of whichever solute its table assumes, which is why the model must match the sample.
Brix is the standard sugar scale: one degree Brix is one gram of sucrose per 100 g of solution. On a mixed sample such as juice, the reading is a sucrose-equivalent figure, not a laboratory sugar assay. The three non-sucrose sugar variants report % by weight of fructose, glucose or invert sugar instead.
What Happens If You Use the Wrong Model?
You get a number that looks precise and is wrong. The record for the sodium chloride model says plainly that it is not intended for seawater salinity measurements, and the seawater record says its conversions use the physical properties of seawater, not sodium chloride. Seawater carries sulfate, magnesium and other ions, so a NaCl table and a seawater table disagree on the same drop.
- Brine or food salt: use the sodium chloride model (HA-96821).
- Seawater, brackish water, aquaculture water: use the seawater model (HA-96822).
- Anything sweet: use a sugar model, sucrose for Brix.
- Mixed solutions with several solutes: a refractometer gives one combined index, so treat the result as a screening figure and confirm with a lab method.
If you need continuous or in-situ salinity from conductivity instead of a drop-by-drop reading, see our salinity meter buyer's guide.
How Accurate Is ±0.2 in Practice?
It depends on the reading. A fixed accuracy figure is a smaller share of a large reading and a larger share of a small one. The table applies the stated accuracy to example readings. These percentages are our own arithmetic, not a manufacturer claim.
| Model | Example reading | Stated accuracy | Error as a share of the reading |
|---|---|---|---|
| Sugar (Brix) | 66 % Brix | ±0.2 | about ±0.3 % |
| Sugar (Brix) | 12 % Brix | ±0.2 | about ±1.7 % |
| Sodium chloride | 25 g/100 g | ±0.2 | about ±0.8 % |
| Sodium chloride | 3 g/100 g | ±0.2 | about ±6.7 % |
| Seawater | 35 ppt | ±2 | about ±5.7 % |
The lesson is to compare the accuracy to your acceptance limit, not only to the range. A sodium chloride model suits a 20 to 26 g/100 g curing brine well, but a 3 % pickle brine sits where the same ±0.2 is a much bigger slice. For a tight low-end tolerance, ask us about the application before you buy.
How Do You Calibrate and Use a Digital Refractometer?
Zero the instrument on distilled or deionized water, then place a small drop of well-mixed sample on the prism, read, and clean the prism fully before the next sample. The product records describe the same simple user calibration with deionized or distilled water. The Canadian Food Inspection Agency gives a practical procedure in its maple syrup grade verification guide, and most of it applies to any refractometer (CFIA, Operational procedure: Maple syrup grade verification).
- Bring the sample to temperature. CFIA says to bring syrup to 20 °C, or correct for temperature, and notes that a sample that is too hot gives no sharp line and can damage the instrument.
- Stir first, then apply a drop or two with a plastic applicator. CFIA warns never to use glass or metal applicators, which can scratch the surface.
- Clean between readings. CFIA says humidity, residual water or poorly dried sugar on the prism causes a false reading; use soft cotton or lens paper.
- Check against a known standard. CFIA's worked example: if a 66 °Brix calibration solution reads 65.8, the instrument is reading 0.2 low, and 0.2 is added to results.
Temperature compensation is automatic on these models. The records give the compensation window as 10 to 40 °C in the specification bullets and 0 to 40 °C in two of the tables, so confirm the window in the manual before you rely on it at the edges.
Can a Brix Refractometer Be Used for Maple Syrup?
Brix is the measurement the rules are written around, but whether a particular instrument is acceptable for regulated grading is for the CFIA and your licence to decide, not for a distributor. The regulation sets Canadian maple syrup at a soluble solids content of at least 66 per cent and at most 68.9 per cent, determined by a refractometer or hydrometer at 20 °C (Canada Gazette, Regulations Amending the Maple Products Regulations). CFIA adds that the minimum to place a grade name on syrup is 66 °Brix and that the equipment maker's precision and accuracy must be taken into account when calibrating.
On the numbers, the sucrose model's ±0.2 % Brix is about ±0.3 % of a 66 % reading. For a producer finishing syrup near the 66 limit, that is a real margin to plan around. Treat it as an in-process check, and confirm any compliance use with the CFIA first.
How Do You Choose a Digital Refractometer, Step by Step?
- Name the solute. Sugar, sodium chloride or seawater salts decide the model.
- Check the range. Brix to 85, brine to 28 g/100 g, seawater to 150 ppt or 50 PSU. A sample outside the range reads nothing useful.
- Set the tolerance. Compare the stated accuracy to your acceptance limit at the typical reading, using the table above.
- Pick the unit you report in. Brix, g/100 g, °Baumé, ppt, PSU or specific gravity.
- Plan the sample handling. Distilled water for zeroing, plastic applicators, lens paper and a way to bring samples to temperature.
- Plan verification. Keep a known standard and log the check, so a drifting reading is caught early.
Need help choosing a refractometer?
ERE Inc. has been Canada's environmental equipment specialist for 30+ years. Tell us the sample and the tolerance, and we will match the model.
→ Request a Quote | 1-888-287-EREC | Browse Refractometers | sales@ereinc.com
Frequently Asked Questions
What is a digital refractometer used for?
A digital refractometer measures the concentration of a dissolved substance in a liquid from a single drop. Common uses are sugar content in food and drink, salt in brines and food, and salinity in seawater.
What is the difference between a Brix refractometer and a salinity refractometer?
They use different conversion tables. A Brix model converts the refractive index to sugar concentration, and a salinity model converts it to salt concentration. Each is only valid for its own kind of solution, so the model must match the sample.
Can a sodium chloride refractometer measure seawater?
No. The manufacturer's record states the sodium chloride model is not intended for seawater salinity measurements. Use the seawater model, which converts using the physical properties of seawater.
How do you calibrate a digital refractometer?
Zero it with distilled or deionized water, then read the sample. To verify, measure a known standard and compare. CFIA's procedure applies a correction when a 66 °Brix standard reads 0.2 off.
How much sample does a digital refractometer need?
The ERE records state a minimum of 100 µL, enough to cover the prism completely. Readings take about 1.5 seconds.
Related articles
- Salinity Meter Buyer's Guide for Canada
- Water Quality Meters for Environmental Work: A Buyer's Guide
- Portable Conductivity Meter Buyer's Guide for Canada
Lire en français : Guide du réfractomètre numérique : modèles Brix, chlorure de sodium et eau de mer au Canada