Control Systems: Open vs Closed Loop

Laboratory Experiment 1: Control Systems

• The semester is Spring 2024/2025
• The course is Measurement and Instrumentation with course code MET222
• The notes are for engineering students
• The lab experiment was performed at the Sharjah Maritime Academy
• Performed on 22/01/2025, from 12:30 to 14:20 in room 11-03
• The experiment is worth 4 marks and there are 8 papers
• Understand the concept of open and close loop systems and compare their performance
• The PCT 100 is used in this experiment
• Control can be manual or automatic.

Manual Control System

• A human operator manually controls the input to acheive the desired output

Automatic Control System

• A system that regulates itself to maintain a desired output and does not require continuous human intervention.

Open Loop Control System

• The output relies on the input, lacking feedback mechanism.

Closed Loop Control System

• A system where, the controlling action relies on the generated system output, using feedback to control system states.

Overshoot

• The maximum amount by which the response exceeds the final steady state value of the process variable and can be a percentage.

Steady State Error

• The final difference between the process variable and the set point

Rise Time

• The time it takes for the response to rise from 10% to 90% of its final steady state value.

Settling Time

• The time required for the response to reach and remain within a specified tolerance band around its final steady state value eg 5% tolerance.

Open Loop Procedure

• Switch on the computer and PCT 100 unit.
• Open the training program on the computer and select an open loop.
• Set the input to step function with SP = 40% and start the measurement.
• Save the output after it reaches a steady state.
• From the result find the parameters below: (0.75 Mark)
• Overshooting: maximum point higher than setpoint – setpoint =0
• Settle time: when it becomes stable, settling time = 6 s
• Steady State Error: setpoint – final value = 2 -1.8 = 0.2 L/min
• Draw the response time for open loop controller.
• Draw a block diagram showing components and describe the open loop process

Open Loop Process Parameters

• Input (Setpoint): Required flow rate
• Controller: Generates a signal to control valve opening and DC motor speed according to the required rate without measuring the output.
• Actuator: Opens/closes the valve based on the controller signal, adjusts motor speed to control pump speed.
• Output: Actual flow rate.
• Process: Controls the flow rate and filling of the tank.

Close Loop Procedure

• Close the open loop and set the system to close loop which is flow control in PCT unit.
• Set the value of PG to 4 and SP to 1.5.
• Disable I & D parameters.
• Start measurement and save the graph.
• From the graph get the below values: (0.75 Mark)
• Overshooting: maximum point higher than setpoint – setpoint 1.63 – 1.5=0.13 L/min
• Settle time: when it becomes stable, settling time = 4.4 s
• Steady State Error: setpoint – final value = 1.5 – 1.4= 0.1 L/min
• Draw the time response for close loop controller.
• Draw the block diagram and briefly describe each parameter for the close loop.

Close Loop Process Parameters

• Input (Setpoint): Required flow rate.
• PID Controller: Compares the setpoint to the actual output measured by sensor and generates the control signal based on the error between setpoint and actual output to minimize the error.
• Actuator: Opens/closes the valve according to the controller signal and adjusts the motor speed to operate the pump.
• Output: Actual flow rate.
• Process: Controls flow rate and tank filling.
• Sensor: Flow rate sensor

Comparison of Open loop and Closed loop System

• Open loop system is independent of the output vs Close loop which depends on the output for control action
• Open loop is simple with Controller+valve+dc motor component vs Close loop is complex with Controller+valve+dc motor+sensor components
• Open loop is affected by disturbance vs Close loop is not

Laboratory Experiment 3: Specifications of Measuring Instruments

• The semester is Spring 2024/2025
• The course is Measurement and Instrumentation with course code MET222
• Performed at the Sharjah Maritime Academy
• Performed on 12.02.2025, from 12:30 – 14:20 in room 11-11
• Worth two marks, there are 5 papers

Objective

• To measure resistance using current and voltage circuits

Instruments & Equipment

• Electronic Circuits Board
• Resistors
• Multimeter

Theory

• Electrical quantities (Voltage and Current) require measuring devices.
• Voltage measurement needs parallel connection while current measurement occurs in series
• Current measurement needs circuit disconnection to connect in series, ensuring same current flow for consumers and measuring devices.
• The ammeter shows the current flowing on the internal resistance of the voltmeter and in the resistor R

Current and Voltage Measurement

• Voltage measurement connects Voltmeter in parallel
• Current measurement connects Ammeter in series

Voltage Measurement Formula

• VR = U * (R / (Ri + R))

Error Formula

• Error (%) = (True value – Measured value) / True value

Measuring device characteristic

• Accuracy:measurement, calculation, represents true value or reality directly
• Tolerance: variation or deviation allowable
• Precision: difference between a measured value and the arithmetic mean value

Procedure

• Connect the circuit and set U = 5 V
• Connect the circuit and set U = 5 V
• Use a multimeter to measure the value of R, and enter readings in the table.
• Measure the current and voltage for both consumers and enter the readings in the table.
• Calculate error between measurements

Measuring resistor

• Current circuits results in smaller errors when compared to voltage circuit in order to calculate the value of the low resistor (33 Ω)

Error analysis (2% tolerance)

• If the first current circuit's error is less than 2%, the value complies with tolerance.
• The second measurement value is a higher error than acceptable tolerance.
• Current and voltage circuits provide the same error value to calculate the value of the high resistor (22 KΩ)

Maximum voltage measure

• with multimeter is 1000V

Voltage error Measurement

• Assuming minimum value is 40mV with a voltage reading at 22K Ω
• Calculate
• ± 0.5% of reading (4.99V)
• ± 0.1% of FS, then +0.15% of span

Current Voltage Measurements

• Input different voltage (V) given in tables
• Mesaure current and voltage readings
• Find precision value

Calculations

• Use current circuit and 22Ω to find Ohm's Law, (R = V/I) and Precision.
• Calculate Mean and Standard Deviation

Experiment 5: Resistors Sensors PTC, NTC and LDR

• The semester is Spring 2024/2025
• The course is Measurement and Instrumentation with course code MET222
• Conducted at the Sharjah Maritime Academy
• Performed on 05.03.2025, from 10:25 – 11:45 in room 11-11
• 3 marks and has 4 papers

Objective:

• To study the characteristics of NTC and PTC thermistor resistors.
• To study and analyze the characteristics of LDR resistor.

Instruments & Equipment:

• Electronic Circuits Board
• NTC & PTC resistors
• LDR resistor
• Multimeter

NTC Resistors

• Negative Temperature Coefficient
• Resistance decreases as the temperature rises & conductivity improves when “hot”

PTC resistor

• Positive Temperature Coefficient Commonly
• commonly, resistance increases as temperature rises, improving conductivity when "cold"

Photoresistors

• Light Dependent Resistor (LDR) reduces resistance as lights increases are wherever clear differences in luminance intensity need to be electronically

LDR Properties

• An LDR comprises of a special semiconductor material.
• In total darkness, it has a "dark resistance" of over 10MW.
• Absorbing light increases conductivity by releasing charge carriers

Procedure

• Connect the circuit and confirmation
• For NTC, record voltage readings in a table as you adjust the DC source
• For PTC, repeat voltage measurements by increasing DC valures and stable current readings in the second reading
• For LDR, record voltage measurements with the multimeter and calculate R for value

Results

• In NTC, as the current increases, temperature increases, but increasing current and temperature, the NTC decreases.
• In PTC, as the current increases, temperature increases and the PTC increases
• In LDR, as the voltage increases, the current and light intensity from the source increase. When Light Increase the LDR resistance decrease.

Laboratory Experiment 2: Sensors

• The semester is Spring 2024/2025
• The course is Measurement and Instrumentation with course code MET222
• Conducted at the Sharjah Maritime Academy
• Conducted on 05.02.2025, from 12:30 – 14:20 in room 11-11
• 3 marks, has 9 papers

Objective

• To study the characteristics of level, flow, and temperature transducers

Instruments & Equipment

• Multimeter
• PCT-100

Temperature Measurement (PCT-100)

• The temperatures range from 10°C to 60°C
• Platinum resistance thermometers (PRT) are used which operates on resistance of platinum which changes with temperature.
• Electrical resistance of platinum increases approximately linearly with absolute temperature & reading converted to temperature using a calibration equation.
• Measure voltage through the voltmeter by measuring current through the wire

Flow Measurement (PCT)

• Turbine flow rate sensor measures water flow rate and rotational speed of the mechanical rotor, with magnets fitted to rotor blades
• Frequency of passing rotor blades (pickup point) generates pulse
• The higher rate of water flow increases the turn of rotors and gives high pulse numbers.

Level Measurement (PCT-100)

• magnetostrictive transducer makes measurements, using magnetostrictive level transmitter
• a float in transmitter stem detects the level by magnetic elements inside the float
• Electronic circuit with specific frequency, which sends short current through the entire length
• Torsional force that travels and it measures with time-of-flight (TOF) is precise value present in level signals.

PCT 100 main components:

• Process tank, Digital LCD displays, Indicator lights, Heater, Pressure relief valve, One way check valve, Needle valve, 2/2 Proportional drain valve, Sump tank, Float switch, Pressure transducer, Level sensor, Overflow/Vent valve, Flow rate sensor, Cooler Unit, 2/2 Proportional control valve, 3/2 Diverter valve, Variable speed pump with filter and pressure switch & Sump tank temperature sensor (PRT)

Level Sensor Procedure

• Switch on both the computer and PCT 100 unit.
• On the computer, train program and select manual control
• Tank liquid level increases by by setting pump control and flow control to 100%. Then close pump with “F2”
• Measure the output

Flow Sensor Procedure:

• Open the training program on the computer and select manual control
• Then the flow rate value recorded in the table after set the flow control to 100

Temperature Sensor Procedure:

• Liquid level increasing with pump control on 100%
• Close it when 40% is reached with pump control on "F2.

Graph Observations:

• Level Sensor exhibits between level and voltage relation, rising level, the voltage shows an increase.

Level measurement Graph

• Considers two points to linear graph relation
• Voltage at 85% determined

Flow Rate -Voltage:

• linear relation to flow rate and voltage. If flow shows increase, the voltage shows increase.

Flow rate-voltage graphs

• 1.25 L/m has voltage to find out graph relation

###Temperature Graph

• Relations between temperature and voltage, if temperature increases graph relation shows increases.

Comparing Manual control to automatic

• Required human intervention to perform actions Manual

###Manual control properties

• High precision Accuracy and Precision
• Fast response time Slow
• Over than one cost
• Highly scalable scalability

Experiment 4: Voltage Divider Circuit

• Spring 2024/2025 Semester
• Marine Engineering Technology Department
• Instrumentation and Measurements/MET222 Course Code
• By Eng. Ibtihal Ahmed
• Performed on 19.02.2025 from 12:30 – 14:20
• Located in 11-11 Room Number
• The grade was 3 with 6 papers

Lab Objective

• Connect and explore the potentiometer and voltage divider circuit

Equipment

• Electronic Circuits Board
• Resistors
• Multimeter
• Potentiometer

Voltage Divider and Potentiometer theory

A voltage divider divides voltage into two or more parts, and the voltage crosses the resistance is proportional to resistance depending in relation to resistance

The Potentiometer

Three-terminal and adjustable is called the potentiometer, it can be adjustment with manual for adjusting two fixed electrical terminals.

The Output

• The output can be shown as function depend of the ratio between it and voltages with resistors

Calculate Value

Connect the given circuit, then supply is turned on with multimeter

Comparing Values

Find 470 and 1000 in value parallel to compare then use V=IR to divide values

Calculating Gain

Find gain using this circuit VBG and VCG in a specific table

###Laboratory Experiment 6: Operational Amplifier as Non-Inverting Amplifier

###Objective Learn how to use an operational amplifier to assemble a non-inverting amplifier. Examine amplifier gain and how it can be changed.

###Instruments & Equipment: Electronic Circuits Board Resistors Multimeter Potentiometers Op-Amps

###Theory An op-amp non-inverting amplifier is an electronic circuit that uses an operational amplifier (op-amp) to amplify an input signal while maintaining the same polarity as the input. This configuration is typically used to provide signal amplification and impedance matching. The output is then measured

Procedure

1 . Connect the circuits, as the value is changed for Voltage Divided 2 . Set the Volts 3 . Then calculate the values using gain from

Lab Values and Equations

Formulas:

1. Voltage and Resistor formulas can be compared, tested, and determined

Equations:

• U1=…

Lab Results

1. Regarding circuits using gain it can be amplified through Voltage and Gain

###Exercising Theory

1. Given some values in an equation, can be determine through gain the different formulas

###Laboratory Experiment 7: Operational Amplifier as Inverting Amplifier

Objective:

Understand to connect Op amp circuit so it can act as an inverting amplifier

Equipment:

• Electronic Circuits Board
• Resistors
• Multimeter
• Potentiometer
• Op-amp

Theory:

inverting it can measure phase shift with output signals, If that measure voltage change it will have cause to voltage decreases vice versa, The Descriptive formulas use a minus symbol the inversion to know what value.

To create amp inverting

Connect the input

Procedure:

Connect figure show below from Circuits Board, Input voltages and using those measure the voltage As increase the R2 the voltage out increase

Formulas

Calculation

Voltage Resistors

Experiment 8: Operational Amplifier as Voltage Follower and Summing Circuit Objectives

• Understand and test the loading effect of one circuit by another, which is one of the most important concerns in analogy signal conditioning.
• Learn how to use an operational amplifier to assemble a voltage follower (buffer circuit).
• Understand and implement the Op amp circuit connection to act as a summing amplifier. Instruments & Equipment:
• Electronic Circuits Board
• Resistors
• Multimeter
• Potentiometer
• Op-Amp

Theory:

Voltage Follower: The loading effect in sensors refers to the impact that the act of measuring or sensing a quantity has on the system or process being measured. This effect is a fundamental consideration when using sensors or instruments to monitor or control various physical parameters. The loading effect can introduce changes or disturbances in the system, which may affect the accuracy and reliability of the measurement. The most common loading effect in sensors is electrical loading. When a sensor is connected, it often draws some current or voltage from the system being measured. This can affect the accuracy of the measurement, especially if the system's characteristics change as a result. As a solution, a voltage follower can be used as a buffer because it draws little current due to the high input impedance of the amplifier, thus eliminating loading effects while still maintaining the same voltage at the output.

Procedure:

Voltage Follower: Using the voltage divider circuit in Figure below, change the value of potentiometer and then calculate the bi-polarity range of the output voltage V_BG which is voltage 𝑉𝑑.
Range of 𝑽𝒅 = 4.85 V– 64 mV Max value of 𝑉𝑑 = 2.935 𝑉
Min value of 𝑉𝑑 = 51.5 mV Comment on these results compared to step 1 results after connecting load: When the load connected the voltage drops due to loading effect.

Graph Values

A range from 4.56 to 46mV can be recorded the measure Input and output can be relate with a relation A summing amplifier can be used to sum up any input voltages with a 180° phase shift on the output. You can expand the input side of the circuit to any number of inputs. U2: = - Uin1 + (-0.45 (4.6 V)) = - Uin1 – 2.07 V = -8.17V