Measuring Range; Interface - Emerson Rosemount 3300 Series Reference Manual

Reference Manual
00809-0100-4811, Rev AB
July 2003

Measuring Range

Table 2-3. Measuring Range
Coaxial
19 ft 8 in. (6 m)
1.6

Interface

Figure 2-6. Fully immersed
probe
The measuring range differs depending on probe type and characteristics of
the application. The values given in Table 2-3 can be used as a guideline for
clean liquids.
Rigid Twin Lead Flexible Twin Lead
Maximum Measuring Range
9 ft 10 in. (3 m) 65 ft 7 in. (20 m)
Minimum Dielectric Constant at Maximum Measuring Range
1.9 2.0
(1.6 up to 32.8 ft/10 m)
The maximum measuring range differs depending on application according
to:
• Disturbing objects close to the probe.
• Media with higher dielectric constant (ε
allows a longer measuring range.
• A calm surface gives better reflection than a turbulent surface. For a
turbulent surface the measuring range might be reduced.
• Surface foam and particles in the tank atmosphere are also
circumstances that might affect measuring performance.
• Coating/contamination can reduce the measuring range.
• Disturbing EMC environment in tank.
Model 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 interface with the Model 3301 in bridle/tank applications when the
probe is fully immersed in the liquid.
Rigid twin lead, flexible twin lead and coaxial probes can be used to measure
interfaces. However, the coaxial probe is the preferred choice. 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.
Rosemount 3300 Series
Rigid Single Lead
9 ft 10 in. (3 m)
2.5 (1.9 if installed in a
metallic bypass or
stilling well)
) gives better reflection and
r
Upper product
Lower product
Flexible Single Lead
65 ft 7 in. (20 m)
5.0
(2.5 up to 36.1 ft/11 m)
2-9