Interface Measuring Range - Emerson Rosemount 3308A Reference Manual

Specifications and Reference Data
August 2017
A.1.3 Interface measuring range
The maximum allowable upper product
thickness/measuring range is primarily determined by the
dielectric constants of the two liquids.
Typical applications include interfaces between oil/oil-like
and water/water-like liquids, with a low (<3) dielectric
constant for the upper product and a high (>20) dielectric
constant for the lower product. For such applications, the
maximum measuring range is limited by the length of the
coaxial and rigid single lead probes.
For flexible probes, the maximum measuring range is
reduced by the maximum upper product thickness,
according to the diagram below. However, characteristics
may vary between the different applications.
Figure A-1. Maximum Upper Product Thickness for
Flexible Probes
39.4 (12)
32.8 (10)
26.2 (8)
19.7 (6)
13.1 (4)
6.6 (2)
10
0
1 2 3 4
Upper product dielectric constant
Example: With an upper product
dielectric constant of 2, and a
lower product dielectric constant
25 ft.
DC 2
of 20, the maximum upper
(7 m)
product thickness is 25 ft. (7 m).
DC 20
112
PRELIMINARY
Lower product
dielectric constant
80
40
20
10
80
5 6 7 8 9 10 11
Reference Manual
00809-0100-4308, Rev CA
Specifications and Reference Data