Hydrometers

Choose a range around the density you expect. A narrow range gives a finer scale and therefore a more precise reading: the hydrometer for 1.000–1.100 g/ml with 0.001 g/ml division covers 0.100 g/ml on its stem. A wide range, such as the hydrometer for 1.000–2.000 g/ml with 0.010 g/ml division, is useful for a first estimate when you do not yet know the density. Many labs use one wide-range hydrometer to find the right range, then a narrow-range one for the actual measurement. Tell us your liquid: sales@luminixhealth.com.

Density changes with temperature, so a hydrometer is only correct at its reference temperature. A built-in thermometer lets you read the liquid's temperature at the same moment, so you can correct the reading or wait until the sample has reached the right temperature. The density hydrometer 1.000–1.100 with thermometer, built to DIN 12791, is an example. Without a thermometer the hydrometer is simpler and cheaper to replace, but you then need a separate thermometer in the cylinder. For official or calibrated measurements, a version with thermometer is the practical choice.

The scale depends on your application. A density hydrometer reads g/ml directly and suits general laboratory work. An alcoholometer reads alcohol content by volume and is used for spirits and distillates. Baumé scales are common in industry, for acids, lyes and syrups, for example the plastic Baumé hydrometer, 0–12 °Bé, and sugar scales such as the simple saccharimeter are used for musts and juices. For workshops there are dedicated testers, like the battery tester and the antifreeze tester with coloured markings.

The reference temperature is the temperature at which the scale is correct, and it is marked on the hydrometer itself. For laboratory density hydrometers, 20 °C is the usual reference, as with the hydrometer for 1.000–1.100 g/ml at 20 °C. Some industrial and workshop instruments use 15 °C, for example the simple saccharimeter and the battery tester. Measure at that temperature or correct your reading with a table. When you replace a hydrometer, choose the same reference temperature as your method so results stay comparable.

A hydrometer floats in a liquid and the stem reading is the density or a related scale such as Brix. The liquid has to be at the temperature printed on the stem, or a correction is required. A chip on the stem changes the reading. One hydrometer does not cover every density.

Density is mass divided by volume. A hydrometer floats at a depth that depends on the density of the liquid. A pycnometer is a vessel of known volume that is weighed full. Viscosity is the resistance to flow. A capillary viscometer times how long a volume takes to fall through a tube. Both measurements need a stated temperature, because liquids change density and viscosity as they warm. The units trace to the BIPM and to NIST.

This shelf belongs to Density & viscosity measurement, inside Lab instruments. Luminix Health distributes this range for laboratory use.

The neighbouring shelves are Viscometers and Density meters & pycnometers. The category above this shelf is Density & viscosity measurement.

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