Guided wave radar interface measurement medium identification

1. A guided wave radar transmitter for interface measurement comprising:

a probe defining a transmission line for sensing level of two immiscible liquids to define an interface therebetween;

a pulse circuit connected to the probe for generating pulses on the transmission line and receiving a reflected signal from the transmission line, the reflected signal selectively including a level pulse representing material level and an interface pulse representing interface level; and

a controller operatively connected to the pulse circuit, the controller operating in an interface mode to determine the material level and the interface level responsive to receiving the level pulse and the interface pulse, and operating in a medium identification mode responsive to not receiving the interface pulse, comprising calculating an estimated amplitude of the level pulse for the two immiscible liquids and comparing actual amplitude of the level pulse to the estimated amplitude of the level pulse to identify the medium in the vessel.

2. The guided wave radar transmitter of claim 1 wherein the estimated amplitude of the level pulse comprises average of expected amplitude for each of the two immiscible liquids.

3. The guided wave radar transmitter of claim 1 wherein the estimated amplitude of the level pulse comprises average of expected amplitude for each of the two immiscible liquids plus an offset amount.

4. The guided wave radar transmitter of claim 1 wherein the estimated amplitude of the level pulse is periodically calculated based on measured material level.

5. The guided wave radar transmitter of claim 1 wherein the estimated amplitude of the level pulse is calculated based on reflection coefficient of the two immiscible liquids.

6. The guided wave radar transmitter of claim 5 wherein the estimated amplitude of the level pulse is calculated based on gain applied to the reflected signal and cable attenuation.

7. A time domain reflectometry measurement instrument for interface measurement comprising:

a probe defining a transmission line for sensing level of two immiscible liquids to define an interface therebetween;

a pulse circuit connected to the probe for generating pulses on the transmission line and receiving a reflected signal from the transmission line, the reflected signal selectively including a level pulse representing material level and an interface pulse representing interface level;

a signal processing circuit connected to the pulse circuit for developing a time representation of the reflected signal; and

a controller operatively connected to the pulse circuit, the controller operating in an interface mode to determine the material level and the interface level responsive to receiving the level pulse and the interface pulse, and operating in a medium identification mode responsive to not receiving the interface pulse, comprising calculating an estimated amplitude of the level pulse for the two immiscible liquids and comparing actual amplitude of the level pulse to the estimated amplitude of the level pulse to identify the medium in the vessel.

8. The time domain reflectometry measurement instrument of claim 7 wherein the estimated amplitude of the level pulse comprises average of expected amplitude for each of the two immiscible liquids.

9. The time domain reflectometry measurement instrument of claim 7 wherein the estimated amplitude of the level pulse comprises average of expected amplitude for each of the two immiscible liquids plus an offset amount.

10. The time domain reflectometry measurement instrument of claim 7 wherein the estimated amplitude of the level pulse is periodically calculated based on measured material level.

11. The time domain reflectometry measurement instrument of claim 7 wherein the estimated amplitude of the level pulse is calculated based on reflection coefficient of the two immiscible liquids.

12. The time domain reflectometry measurement instrument of claim 11 wherein the estimated amplitude of the level pulse is calculated based on gain applied to the reflected signal and cable attenuation.

13. A method of measurement medium identification comprising:

providing a probe defining a transmission line for sensing level of two immiscible liquids to define an interface therebetween;

generating pulses on the transmission line and receiving a reflected signal from the transmission line, the reflected signal selectively including a level pulse representing material level and an interface pulse representing interface level; and

operating a programmed controller operatively connected to the pulse circuit for controlling the pulse circuit, the programmed controller operating in an interface mode to determine the material level and the interface level responsive to receiving the level pulse and the interface pulse, and operating in a medium identification mode responsive to not receiving the interface pulse, comprising calculating an estimated amplitude of the level pulse for the two immiscible liquids and comparing actual amplitude of the level pulse to the estimated amplitude of the level pulse to identify the medium in the vessel.

14. The method of claim 13 wherein the estimated amplitude of the level pulse comprises average of expected amplitude for each of the two immiscible liquids.

15. The method of claim 13 wherein the estimated amplitude of the level pulse comprises average of expected amplitude for each of the two immiscible liquids plus an offset amount.

16. The method of claim 13 wherein the estimated amplitude of the level pulse is periodically calculated based on measured material level.

17. The method of claim 13 wherein the estimated amplitude of the level pulse is calculated based on reflection coefficient of the two immiscible liquids.

18. The method of claim 17 wherein the estimated amplitude of the level pulse is calculated based on gain applied to the reflected signal and cable attenuation.