1. RF Admittance Continuous Basics Theory of Operation
AMETEK Drexelbrook
205 Keith Valley Road
Horsham, PA 19044
(215)
This presentation will discuss the theory of how an RF Admittance Continuous Level.

2. Continuous RF Admittance Theory

3. Capacitance Transmitters -- how they workL1 L2
gnd
Amp
chopper
LLFS
C probe
2 terminal cable
2 terminal probe
100kHz
Osc.
Power
supply + -
4-20 mA
step span
fine span
step & fine zero
HLFS
Second Question:
Who can tell me what they think will happen as the level rises on the sensing element?
What could happen if:
A) Gland C changes?
B) Coax C changes? 5

4. Capacitance Instruments.... the effects of a coating
100% 0%
70%
Highly Conductive Liquid
50% 16

5. The Anatomy of a Coating
Small amounts of RF
current flow (both
Resistive and Capacitive)
due to the Coating
Teflon Insulation
Coating
probe rod Xc
High Resistance
Tank
Wall R
Little to No Resistance 17

6. Problems with Capacitance
No coating rejection
Coax cable can affect output / calibration
Coax Cable must be short

7. Capacitance Disadvantages
Capacitance devices can only measure capacitive current flow.
Conductive coatings generate a resistive current flow from the coating in addition to capacitive current flow from the bulk mass of the level.
Capacitance systems will read the additional resistive current flow and produce level reading that are higher than the actual level due to this additional increase in current flow

8. RF Admittance Transmitters -- how they work
power
Amp
chopper
HLFS
LLFS
C probe
step & fine zero
3 terminal cable
2 terminal probe
100kHz
Osc.
4-20 mA
step span
fine span
drive
100 kHz
1:1
Cote Shield
Amplifier + -
How is an Admittance Transmitter different than a Capacitance Transmitter?
What does the Chopper drive circuit do?
Where do the resistive currents come from? 22

9. RF Admittance Advantages
Advantages over Capacitance:
Ignores Coatings on sensor
Coax cable does not affect output / calibration
Coax Cable can be 100 ft. (30 m)

10. RF Admittance Advantages
System output unaffected by:
Process material coating the sensor
Conductivity changes
Temperature changes
Pressure changes
Specific Gravity changes
Density changes
Highest accuracy in short span measurements
RF Admittance accuracy is +/- 1% of calibrated span
No moving parts to break or wear out

11. Laptop PC Calibration Software makes commissioning and configuration easy

12. Laptop Software Version 6.0

13. RF Admittance Continuous Level Products

14. RF Technology used in Liquid/Liquid Interface

15. Oil / Water Interfaces

16. Free Water Knock-out
Automatic Well Tester is a small vessel that accepts the Gross Production from one well (30% - 90% water). This is nothing more than a holding tank that allows initial emulsion separation, and interface is controlled by RF transmitter controlling a dump valve. AWT oil output goes to FWKO for further separation.
FWKO is typically 12 ft. dia. X 60 ft. long. Emulsion enters with about 60% water and may exit with about 30% water.

17. Heater Treater
Gravity separation that uses Heat and Chemicals to further break down emulsions. Typically mechanical elements which aid in the coalescing of the water droplets.
Dry Oil is skimmed off over a weir.

18. Stock Tank
Where Dry Oil is stored before it goes to the LACT unit and pipeline.

19. Skim Tank
Where wastewater from earlier separation vessels goes to allow recovery of entrained oil.

20. Interface Level Typical Rag / Emulsion Make-up
RF Technology Frequency Advantage:
Repeatable indication of electrical cross over between continuous conducting to continuous insulating emulsion phase
Insulating Phase
Rag Layer:
Optical Interface
VS.
Electrical Interface
Aqueous Phase

21. Desalter Interface System+ -
Electrostatic Grids
Inactive Section
Active Section
Oil
Brine
AC Interference Filter
Smart Desalter
Interface Transmitter
Integral or Remote
4-20mA HART or Honeywell protocol
1 ft.
1 ft.
1 ft. clearance from Grids to Probe has been found to provide the best immunity to signal interference.