# Level

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1.  How do ultrasonic transmitters measure level?
By generating high frequency sound waves and evaluate the echo which is received back by the sensor.
2. What is blocking distance when referring to ultrasonic and radar measurement?
Blocking Distance is when ultrasonic and radar sensors take a small amount of time to be transmitted
3. 3. What are some of the factors that make ultrasonic unsuitable for measurement?
Anything that will effect the signal like foam, dust, condensation

• Foam
• Dust
• Condensation
• Anything that will effect the signal
4. 4. Is the speed of sound constant?
• No
•  It varies based on the medium that it is traveling through.
5. 5. How do radar transmitters measure level?
• When the beam detects a change of impedance it will reflect a signal back to the receiver. The amount of signal returned is dependent upon the change of impedance.
Radar signals travel along a wire rope or rod that extends from the transmitter head and are used when there are obsicles in the tank that may effect the signal
7. What could be done to minimize the effect of turbulence in a vessel on the level measurement?
8. 8. How is capacitance used to measure level?
Use 2 probes at top and bottom of ofthe tank, and as the level in the tank increases the capacitance of the probe increases and the level is measured.
9. Explain how differential pressure can be used to measure level in a pressure vessel?
Fit a transmitter to the top of a tank and this transmitter reading is subtracted from the bottom transmitter reading as the bottom transmitter will read the pressure of the liquid plus the head pressure. The head pressure is subtracted from the bottom reading
10. What is a sealing pot used for?
So maintenance can be made to a transmitter without emptying the tanks, this done by transferring the pressure from the tank to the capillary tube that connects to the transmitter
11. What is "Elevated" and "suppressed" zero? How does it affect the level calculation from the transmitter reading?
Suppressed zero is where transmitters are not at tank level and a capillary tubes is added to measure the pressure so that reading can be added to the reading

Elevated zero is where a transmitter is located above the bottom of the tank, and the amount that the transmitter is above the tank needs to be subtracted from the transmitter reading.
12.  Draw a diagram of a bubbler level system and explain how it can be used to measure level?
An air bubbler system uses a tube with an opening below the surface of the liquid level where a fixed flow of air is passed through a tube with an opening below the surface of the liquid level. The Pressure in the tube is proportional to the depth and density of the liquid over the outlet of the tube.
13.  When all else fails what is the level measuring system that will usually work?
• nuke it!!
14. 14.What are gamma rays?
Gamma radiation is electromagnetic radiation of high frequency which means it has a very short wavelength
15.  What are the two types of radiation source in common use for measurement?
Cobalt and caesium
16. 16.What does the term half life refer to in relation to radiation?
The half-life is a measure of radioactive decay and is the time it takes the isotope to decay to half its original size.
17. 17.What is half value layer?
18. a decrease per unit in particles
19. 18. What is the SI unit for biological effect of radiation?
20. The Sievert
21. 19. What is a Scintillator? How does it work?
• A Scintillator is a tube that produces a pulse of light when it detects gamma rays.
• It works by using a photo multiplier to amplify a signal to produce a series of pulses which measures the amount of gamma rays received.
22. 20. What is a Geiger-Muller tube? How does it work?
The Geiger-Muller-tube consists of a glass tube filled with an inert gas like Argon. There is a cathode and anode with a high voltage and when the gamma rays strike the tube it will discharge and produce a series of counts where the frequency is dependent on the amount of radiation received.
23. 21. What is the principle of operation of a tuning fork level switch?
The tuning fork sensor consists of a piezo transmitter, a receiver and circuitry to produce an output when the level is reached.
24.  How does a float switch couple the movement of the float to produce an electrical signal?
The float has a magnetic coupling to a switch inside the transmitter unit. As the float rises the transmitter will produce an alarm output.
 Author: george123 ID: 164674 Card Set: Level Updated: 2012-08-01 10:59:44 Tags: level Folders: Description: level Show Answers: