Level measurement

80

Continuous level measurement in liquids

4. Instrument selection within the measuring principle

Capacitance

Required application data • Pressure and temperature • Conductivity/dielectric constant of the medium (DC)/media group • Required material compatibility

Starting from a conductivity of 100µS/cm the measured value is not affected by the dielectric constant and the conductivity of the medium. The following table describes different media.

For reliable measurement: Provide proper ground connection between process connection and tank. If required, establish ground connection by potential compensation line. In plastic tanks, use probe with a ground tube or double rod probe Liquicap T, if possible.

• Measuring range • Required accuracy • Mounting position

Application limits for capacitance level measurement • • Temperature up to +200°C/+392°F

• •

C

Operating range of Liquicap

Conductivity (µS/cm)

The accuracy is unaffected by the conductivity and the DC value (dielectric constant)

10 4

aqueous solutions of salts, acids, lyes,

10 3

aqueous dispersions and emulsions, waste water, electrolytes, beverages

Factory calibration for 0% and 100%

10 2

The accuracy is dependent on the DC value and the conductivity of the medium. Measurement not recommended, select another measuring principle.

10

a higher water content, demineralized water

1

Factory calibration for 0%

10 –1

The accuracy is dependent on the DC value.

10 –2

water content below 0.1%, petrols, oils, solvents

10 –3