Emerson Rosemount 3300 Series Uživatelský manuál stáhnout pdf (Strana 11)

Product Data Sheet

00813-0100-4811, Rev DA

Catalog 2008 - 2009

Level-11

Rosemount 3300 Series

Interface

Rosemount 3302 is the ideal choice for measuring

the interface of oil and water, or other liquids with

significant dielectric differences. It is also possible to

measure interfaces with a Rosemount 3301 in

applications where the probe is fully submerged in

the liquid.

Coaxial, Rigid twin, Flexible twin and Rigid Single

lead probes can be used for measuring interfaces.

The coaxial probe is the preferred choice when not

fully submerged. In applications with a fully

submerged probe, the twin lead probes are

recommended for nozzle installations, and the rigid

single lead probe is best for bridle mounting.

For measuring the interface level, the transmitter

uses the residual wave of the first reflection. Part of

the wave, which was not reflected at the upper

product surface, continues until it is reflected at the

lower product surface. The speed of this wave

depends fully on the dielectric constant of the upper

product.

If interface is to be measured, follow these criteria:

• The dielectric constant of the upper product

must be known and should not vary. The

Radar Configuration Tools software has a

built-in dielectric constant calculator to assist

the user in determining the dielectric constant

of the upper product.

• The dielectric constant of the upper product

must have a lower dielectric constant than the

lower product in order to have a distinct

reflection.

• The difference between the dielectric

constants for the two products must be larger

than 10.

• Maximum dielectric constant for the upper

product is 10 for the coaxial probe and 5 for

twin lead probes.

• The upper product thickness must be larger

than 8 in. (0.2 m) for the flexible twin lead and

the HTHP coaxial probes; 4 in. (0.1 m) for the

rigid twin lead, the Standard and HP coaxial

probes in order to distinguish the echoes of

the two liquids.

The maximum allowable upper product thickness /

measuring range is primarily determined by the

dielectric constants of the two liquids.

Target applications include interfaces between oil /

oil-like and water / water-like liquids with low (<3)

upper product dielectric constant and high (>20)

lower product dielectric constant.

For such applications, the maximum measuring

range is only limited by the length of the coaxial, rigid

twin and rigid single

(1)

lead probes.

For the flexible twin lead probe, the maximum

measuring range will be reduced depending on the

maximum upper product thickness according to the

diagram below. However, characteristics vary widely

between different applications. For other product

combinations, consult factory.

Example:

If maximum measuring range is 75.5 ft (23 m) and

the upper product dielectric is 2 then the maximum

upper product thickness is 5 ft (1.5 m).

Emulsion Layer

Sometimes there is an emulsion layer (mix of the

products) between the two products which can affect

interface measurements. For guidelines on emulsion

situations, consult factory.

(1)

Be aware of the minimum upper product dielectric constant for

the rigid single lead probe, see page 10.

3302 3301

Interface

Level

Level =

Interface Level

Interface Measurement with a Rosemount 3302 and a

Rosemount 3301 (fully submerged probe).

82.0 (25)

78.7 (24)

75.5 (23)

72.2 (22)

68.9 (21)

65.6 (20)

0 (0) 3.3 (1)

6.6 (2)

9.8 (3)

13.1 (4) 16.4 (5)

Maximum Measuring Range, Flexible Twin Lead Probe, ft (m)

Upper Product

Dielectric Constant

Max Upper

Product

Thickness,

ft (m)

1 2 ... 6 7 8 9 10 11 12 13 14 15 16 ... 37 38

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