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Level Measurement · Glossary

What is Specific Gravity?

Symbol: SGdimensionlessLevel Measurement

Specific gravity is the density of a liquid divided by the density of water at a reference temperature.

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Specific Gravity Explained

Level transmitter data sheets often use SG instead of density. An SG of 0.85 means the liquid is 85 % as dense as water, so the same level gives 85 % of the pressure.

State the reference temperature of the water density; 4 °C (1000 kg/m³) and 15 °C or 60 °F are common.

Specific Gravity Formula

SG = ρliquid ÷ ρwater
ρliquidliquid density
ρwaterwater density at the reference temperature
Example: Oil at 850 kg/m³ has SG ≈ 0.85; 3 m of it gives about 25.0 kPa.
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Calculators for Specific Gravity

CalculatorDensity from DP CalculatorFree online calculator with formula and worked example.CalculatorPressure to Level CalculatorFree online calculator with formula and worked example.

Frequently Asked Questions

What is Specific Gravity?

Specific gravity is the density of a liquid divided by the density of water at a reference temperature.

Is SG the same as density?

Numerically close to density in g/cm³, but SG has no units and depends on the water reference.

Can I measure SG with two pressure transmitters?

Yes. DP between two submerged taps a known distance apart gives density directly.

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