dry matter measurement with the zeal manual hydrometer

Zeal Manual Hydrometer

Test the average dry matter and specific gravity of a bulk sample

The Zeal Manual Hydrometer is a traditional industry tool for fast intake sampling and measurement of potato dry matter and specific gravity (density). It is used extensively throughout the potato world by producers of crisps, french fries, potato wedges and canned, frozen and powdered potato products.

zeal manual hydrometer basket holds potatoes for testing
dry matter measurement with the zeal manual hydrometer

Key Features

  • Simple and quick to use – static unit, uses a large water container (c.175 litre/45 gallon)
  • Accurate – easy calibration (weight supplied); uses precisely-weighed potato sample
  • 3 models – to suit dry matters from 14 to 27% (1.055 to 1.114 g/ml specific gravity)

3 Dry matter ranges available

zeal manual hydrometer comes with calibration weight and basket


Range 17-25% dry matter

1.065-1.110 g/ml specific gravity


Range 14-23% dry matter

1.055-1.095 g/ml specific gravity


Range 18-27% dry matter

1.070-1.114 g/ml specific gravity

All models include flotation ball and hook, vertical stem with dry matter % and specific gravity scales, numbered sample basket, stainless steel calibration weight.

Which manual hydrometer model should you buy?

The Zeal Manual Hydrometer is made with 3 different scales to allow for different ranges of dry matter being measured for different varieties of potato. Dry matter is not constant for a variety – it can change between years according to growing conditions and irrigation. Hence, it is not always possible to predict in advance the range of dry matter that will need to be measured.

The standard range of 17-25% (Model: POT/HYDROMETER) covers most situations. The other models (POT/HYDROMETERD4501 and 4502) tend to be used with specialist varieties.

Zeal manual hydrometer takes dry matter readings in water
Zeal manual hydrometer takes specific gravity readings in water
Zeal manual hydrometer takes dry matter readings in water

How to use the Zeal Manual Hydrometer

An exact weight of potatoes (3.63Kg/8lbs) is placed in the basket. The hydrometer and basket are suspended in a large container of clean water at approximately 15°C/60°F. The hydrometer with basket attached must float freely. The buoyancy of the unit in water (with potatoes in the basket) determines the water level against the vertical scale in the stem which gives the readings of dry matter and specific gravity.

The point at which the water surface crosses the vertical scale is the dry matter (right) and specific gravity (left) reading.

The Zeal hydrometer is supplied with a calibration weight that lets the user check if it is floating at the Zero point on the scale in the stem before the potatoes are added to the basket. If it is not at Zero, the screw at the top of the tube can be turned slightly to raise or lower the scale inside the tube until the hydrometer floats at exactly Zero.

zeal manual hydrometer basket
Easy calibration with the calibration weight supplied
Full Details and Specifications

Model range

HydrometerProduct codeDry matter rangeSpecific gravity
D4500POT/HYDROMETER17 - 25%1.065 - 1.110g/ml
D4501POT/HYDROMETER450114 - 23%1.055 - 1.095g/ml
D4502POT/HYDROMETER450218 - 27%1.070 - 1.114g/ml

Technical Specifications

Water container
WaterShipping box dimensionsWeight
Min. 356mm dia x 660mm deep
175 litre/45 gallon
Clean metal or plastic
Hydrometer must float freely
Clean water
c.15°C / 60°F
45 x 34 x 28cm2.13Kg

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