1. Mark the correct statement(s)

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1. Mark the correct statement(s) Figure to the right shows a mass measurement scale using a spring. 1.1 The span of the scale is a) 16 kg b) 21 kg c) 11 kg d) 5-16 kg 1.

1 1. Mark the correct statement(s) Figure to the right shows a mass measurement scale using a spring. 1.1 The span of the scale is a) 16 kg b) 21 kg c) 11 kg d) 5-16 kg 1.2 The range of the scale is a) 16 kg b) 21 kg c) 11 kg d) 5-16 kg 1.3 The resolution of the measurement device is a) 0,5 kg b) 1 kg c) 11 kg d) 5-16 kg 1.4 Two resistors R 1 =36Ω ± 5% and R 2 =75Ω ±5% are connected in series. Their total resistance is a) 111 ± 0 Ω b) 111 ± Ω c) 111 ± 5.55 Ω d) 111 ± 5% 1.5 Three-wire connection of RTD and temperature transmitter is used a) So that one wire is spare (if one of the two is cut, it can replace it) b) To decrease resistance of wires between RTD and TT c) To ground the temperature element d) To cancel out the influence of wire resistance on the measurement 1.6 Gauge pressure transmitter measures a) Pressure relative to vacuum b) Pressure relative to the surroundings c) Pressure difference between two points in the measured fluid d) Is used to measure flow in a pipe or level in a vessel

2 1.7 The following instruments give digital signals a) Thermometer b) Pressure switch c) Thermistor d) Thermo couple e) Hand switch 1.8 Standard current analog signal ranges from a) 4 ma to 20 ma b) 0 V to 10 V c) 0 5 Amp d) 0 ma to 24 ma 1.9 The smallest incremental value that can be generated, modified, measured, or displayed is known as the measurement a) parameter b) precision c) Repeatability d) resolution 1.10 Figure to the right shows measurement results with a certain error. The type of error is e) Random error f) Bias (zero) error g) Sensitivity error h) Hysteresis error 1.11 One amp applied for one second will result in one a) volt b) watt c) siemens d) coulomb 1.12 A sensor is a device that converts: a) physical quantity into electrical signal only b) physical quantity into some measurable signal c) electrical signal into physical quantity d) physical quantity into mechanical signal only

3 1.13 Which of the following temperature measuring devices typically uses a Wheatstone bridge circuit? a) thermistor b) thermocouple c) RTD d) infrared pyrometer e) None of the above 1.14 Select the statement that best describes the operation principle of a fluid thermometer a) Most fluids contract when they are heated and expand when they are cooled b) Fluids change resistance when temperature changes c) Most fluids expand when they are heated and contract when they are cooled d) Fluids are not affected by changes in temperature 1.15 Select all of the actions that occur when the temperature surrounding an RTD increases a) The resistance of the RTD changes b) The circuit detects a change in the current flow c) The wire in the RTD contracts d) The circuit increases voltage to the RTD 1.16 What happens when heat is applied to the joined ends of the wires of a thermocouple? a) The wires contract b) The wires start to rotate c) The wires generate a small voltage d) The wires separate e) The thermocouple changes resistance 1.17 The output voltage of a typical thermocouple is a) less than 100 mv b) greater than 1 V c) Thermocouples vary resistance, not voltage. d) None of the above 1.18 What is the measurable property that changes with temperature in a RTD? a) Expansion b) Electrical resistance c) Thermal radiation d) Voltage

4 1.19 When pressure in a chamber containing a liquid increases, the following is usually true a) The boiling point of the liquid decreases, b) There is no relation between the boiling point and the pressure to which the liquid is exposed, c) The boiling point of the liquid increases, d) None of the above 1.20 Using differential pressure transmitter, it is possible to measure a) Flow in a pipe, b) Level of liquid in a vessel, c) Pressure in a vessel, d) Temperature of a fluid, e) Content of oxygen in a fluid, 1.21 The device that changes one instrument signal value to another instrument signal value is known as: a) a filter b) a sensor c) a transducer d) a transmitter 1.22 A sensor is a device that converts: e) physical quantity into electrical signal only f) physical quantity into some measurable signal g) electrical signal into physical quantity h) physical quantity into mechanical signal only 1.23 The temperature unit Kelvin a) depends on the pressure of a measured object, b) can be transformed linearly to Fahrenheit scale, c) can only be used on Earth, d) can be expressed in units of length and time.

5 2. Transmitter Calibration An electrical temperature transmitter is calibrated to measure the water temperature in a pressurized tank. If the maximum expected temperature is 180 C, while the minimum is 10 C find: a) The output of the transmitter if the temperature is 75 C and 400K b) The temperature of liquid if the output 15 ma c) Range and span of the transmitter d) Suggest type of the sensing element 3. Sensitivity A differential pressure transmitter has an electrical output which is approximately linear. When the differential pressure is 0 kpa, the output is 4 ma and when the differential pressure is 40 kpa, the output is 20 ma. What is the sensitivity of this device? 4. Temperature measurement A table of resistances of Pt100 temperature element is given in Appendix A. You will find that resistance at 0 C is 100Ohm, and at 43 C, it is 116,7Ohm. a) Assume linear relationship of resistance and temperature. Taking the mentioned points, derive the linear of resistance as a function of temperature R(T). b) What does the table say and what does the equation say what is the resistance at the temperature of -116 C? 5. Wheatstone bridge An RTD Pt50 is used within a Wheatstone bridge for temperature measurement, as shown in figure below. Answer the following questions: a) What is the Wheatstone bridge used for? b) What are the important factors that need to be considered when using RTD within Wheatstone bridge (Name Two)? c) At what temperature the bridge is balanced? d) If the RTD had a temperature coefficient of Ohm/ C find the output at 75 C? e) What is the temperature if the output is 0.5 V?

6 6. Wheatstone bridge A circuit consists of two resistors with resistances R 1 =6 Ohm and R 2 =1.5 Ohm, a variable resistor, the resistance R var which can be adjusted, a resistor of unknown value R u, and 9.0 volt battery connected as shown in the figure. When R var is adjusted to 12 Ohms, there is zero current through the ammeter. What is the unknown resistance R u? 7. Strain gauge A uniaxial strain gauge with an unstrained resistance of 100 Ohm and a gauge factor of 3 is glued onto an aluminum rod 1m long. The rod is placed under tension and it stretches by 2mm. a) What will the new resistance of the strain gauge be? Remember that The rod has a circular cross-section with a diameter of 10mm. The Young s Modulus of aluminum is assumed to be 69 GPa. The bar is then pulled by a force of 5kN. F A b) How much strain will be placed on the bar if we know that and c) What will the resistance of the strain gauge be after the bar is stretched? Use d) The strain gauge is a part of a Wheatstone bridge, together with three resistors with equal and fixed resistance of 100 Ohm each. Sketch the Wheatstone's bridge! e) Derive an expression for output voltage of the bridge as a function of the resistance change R! Substitute R =R S and try to simplify the expression further! 8. Wheatstone bridge and signal conditioning 8.1 Consider the schematic diagram of a simple Wheatstone bridge circuit:

7 This Wheatstone bridge is balanced when R 1 R 3 = R 2 R 4. a) TRUE b) FALSE 8.2 If R1=100 Ohm, R2=330 Ohm, R3 is Pt1000 and R4=470 Ohm. You have a 1 kohm variable resistor. What is the best way to connect this component and make it possible to balance the bridge at a certain temperature above 0 C? a) In parallel with R1, b) In series with R1 c) In parallel with R4 d) In parallel with R2 e) You suggest 8.3 Supply voltage is 15V. What is the current in RTD? How can you limit it and why? 8.4 In principle, the Wheatstone bridge detects change in unknown resistance by comparing it to a standard resistance a) TRUE b) FALSE 9. Amplifier Consider the following schematic diagram: If V in = 1.5 V, what is V out (in volts)?

Consider the following schematic diagram. The output of the bridge is amplified through the amplifier circuit; Vcc for the Op-Amps are +/- 12V. a) What kind of amplifier is shown here?

8 Consider the following schematic diagram. The output of the bridge is amplified through the amplifier circuit; Vcc for the Op-Amps are +/- 12V. a) What kind of amplifier is shown here? b) What is the gain of this amplifier? c) What are the maximum and minimum values for Rx which will give meaningful output V 0? 10. Level meter A technician is calibrating an eletronic pressure transmitter, to act as a level transmitter of an open water tank. The tank is placed in corrosive environment. The water is destilled and at a constant temperature. The tank is cylindrical in shape, 6m high and 2m in diameter. Assume density of water=1000 kg/m3. The transmitter is mounted 1m below the tank bottom. A technician would like to have 4-20mA signal to a control unit and the option to read the current value of level on local indicator. a. What is the span requirement of the electronic pressure transmitter? b. What range will it have when calibrated correctly? c. What current does the transmitter produce if the level in tank is 3.5m? Sketch the dependency level vs. current in a graph, clearly indicating the slope and intersection point. d. Assume the maximum error of 1% of the span. What is the maximum error expressed in mass (kg) of water that can be measured? e. What is the sensitivity of this pressure transmitter?

9 11. Pressure, Level Figure below shows a tank with ultrasonic level sensor located on a sea coast. The time delay between transmitted and reflected ultrasonic pulse is seconds, while the velocity of ultrasonic wave is 330m/s. The fluid in the tank is fresh water, and the height h=15m. Answer the following: a) Find the depth d of the water in the tank. b) Find the gauge pressure and the absolute pressure at the bottom of the tank. c) If the mass of water is kg, find the maximum capacity of the tank 12. Flow 12.1 Differential pressure of a DP flow meter increases 1.5 times as a result of a change in flow. The flow just a) Increased 1.5 times, b) Increased 0.75 times, c) Increased 2.25 times, d) Decreased 1.5 times Electromagnetic flow meter a) Uses Faradays law to determine the flow, b) Can only measure the flow of conductive fluids, c) Creates a large pressure drop in the pipe, d) Measures mass flow rate, e) Actually measures the velocity of fluid in the pipe and calculates the volumetric flow.

10 12.3 A pressure sensing device has an electrical output and is approximately linear. When the input is 100 kpa, the output is 5 m V and when the output is 1000 kpa, the output is 125 m V. What is the sensitivity of this device? 12.4 The vacuum pressure at a certain location in an experiment is measured as 4.50 psi. The local atmospheric pressure is equal to psi. Calculate the gage pressure at the same location in the experiment. 13. Units, General 13.1 Units a. Name a few commonly used units of pressure. b. What is luminous intensity? What is its unit? c. How many nano-joules is 1MW/s? d. Express 0.01mm in km. e. Name a few commonly used units of temperature. f. What is the unit of electrical current? What is its unit? How is it defined? g. Express 0.01MWh in Joule The device that changes one instrument signal value to another instrument signal value is known as: e) a filter f) a sensor g) a transducer h) a transmitter 13.3 A sensor is a device that converts: a) physical quantity into electrical signal only b) physical quantity into some measurable signal c) electrical signal into physical quantity d) physical quantity into mechanical signal only 13.4 The pressure unit Pascal (Pa) is a) defined as N/m, b) equal to 10-5 atm. c) Can be related linearly to psi, d) Is always zero in conditions of zero gravity.

11 13.5 Complete to make equal quantities 100 Kelvin = C 1 Newton = Joules 100 m = m 10 liters = cm 3 1 cm 3 = m Connect units and corresponding physical variables. Energy Length Conductance Temperature Force Time Resistance Power Current Light-year Ohm inch Joule Fahrenheit Watt Ampere Volt Newton Siemens Millennium 13.7 Aluminum has a density of 2,70 g/cm 3. Find the volume (in ml) of a piece of aluminum with a mass of 0,1242 kg? 13.8 Complete to make equal quantities 25 C = K 1 Watt = 10 km = nm 5 liters = cm 3 1 cm 3 = dm 3

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