FREQUENTLY ASKED QUESTIONS

The key factor missing in prior technology was enough sensitivity to effectively make a good measurement. Capacitance measurements are good enough for 0.5% to 15% measurements as long as the medium under measurement does not absorb much of the low frequency energy. Some crudes do absorb energy and therefore the measurement becomes more difficult for standard technology since this further reduces the sensitivity. Capacitance measurement is a single factor measurement, it just measures the amount of energy stored between two metal plates. This limits the capability of this type of measurement

8. Microwave Measurement - The Old Way.

Microwave energy provides for a more complex measurement and provides enough information to improve the measurement to include absorptive crudes. Once the absorption becomes too great (such as in the water continuous phase), the measurement once again degrades to a point where the resolution of the parameters are too small to be effective.

An additional problem with standard microwave equipment is the complexity of the equipment required to make the measurement. A stable oscillator with amplifiers is used to obtain the frequency and microwave energy for the measurement. A sample must be obtained of the energy leaving the system to compare to the energy transmitted or reflected in the measurement section. The energy must then be transmitted across a barrier (a seal plug or the like) into the fluids under measurement. The introduction of this energy must be done in accordance with electrical design constraints in order to actually get it into the fluids instead of reflected back into the source. This is comparable to the lens of a camera. The more expensive camera lens have special coatings which prevent reflections and therefore get more light through the lens and onto the film.

The energy then enters the fluids and propagates along the structure of the measurement section which is again designed to allow proper electrical properties to contain and control the energy. Typically, an additional barrier (microwave window and seal plug) and the associated structure to allow the energy to be received must be introduced into the measurement section. This allows the energy which has now been affected by the fluids under measurement to be sent back to the electronics and measured and compared to the energy originally sent out.

The measurement at this point takes the energy incident upon (introduced into) the measurement section from the oscillator and amplifiers and compares it to the received energy. This is done with additional amplifiers, amplitude detectors, phase detectors, mixers and local oscillators for the down conversion. This is technology which is standard in many military and commercial communication systems. The problem here is twofold; one is the complexity of the system, and the second is that all of this still doesn't give the required sensitivity for obtaining a good measurement in the water phase and in other situations.

The complexity of standard microwave systems lead to:

1. short time between failures
2. difficulty of maintenance
   (most electronic technicians cannot troubleshoot such a system)
3. expense of the parts
4. the requirements for two microwave "windows" into the fluid
5. sensitivity is still reduced from what is required

Typically, these systems obtain increased sensitivities by using a resonant structure (similar to an organ pipe, the length and diameters determine the note or resonance) . The microwave energy is introduced into the fluids and the measurement section is designed as the resonant structure. The problem with a resonant structure is that it goes away when you introduce absorptive materials (such as salt water or some crudes). This is like placing a rubber plug into the organ pipe, the strength of the vibrations is vastly reduced and the clarity of the tone is gone.

9. What benefits does the Oscillator Load Pull have?

What is required to make a good measurement comes down to reduction of the complexity and improvement of the sensitivity. Oscillator load pull is a parameter of an oscillator which is a measure of how much the oscillator changes its frequency when the load that is connected to it changes. This is a parameter which is usually designed out by preventing the oscillator from ever seeing the changing load though the use of isolation means. Typically amplifiers will be used after the oscillator to isolate the oscillator from the load. This is like a guard rail around the pipe organ's pipes to prevent people from touching the pipes and therefore changing their tone. Interestingly, no one ever used load pull for a measurement before, they just always knew that they needed to design it out. Therefore, a patent was issued on this technique.

The advantages of load pull are simplicity, the source of the microwave frequency and energy is both the transmitter and the receiver. In addition, the use of oscillator load pull increases the sensitivity to the measurement parameters by 100 to 1000 times over conventional microwave measurement techniques. This increase in sensitivity also brings the capability to measure highly absorptive fluids such as 28% salt in water. Because of simplicity the entire system is very easy to trouble shoot and is very stable and reliable.