Measurement and Instrumentation in PE Power
Wasim Asghar 
May 16, 2023Welcome to the PE Power measurement and instrumentation study routine to learn, implement, and shine. Measurement and instrumentation is where accuracy and precision are crucial to ensure the safety and efficiency of power generation and distribution systems.
The demand for advanced measurement and instrumentation technologies has never been higher in this dynamic and rapidly evolving field. From substation monitoring to high-voltage transmission lines, every aspect of the power system requires reliable and accurate measurements to maintain the balance between supply and demand.
This is where sophisticated instrumentation and measurement tools come into play, allowing us to monitor and control the power system in real time.
The ability to measure various parameters, such as voltage, current, frequency, power quality, and temperature, has become increasingly important as the demand for renewable energy sources and smart grid technologies continues to grow.
With the advent of digital and wireless communication systems, we can now monitor and analyze data from multiple points in the power system, enabling us to detect faults and abnormalities before they escalate into significant disruptions.
This blog will explore the latest trends and technologies in PE Power measurement and instrumentation, highlighting the challenges and opportunities ahead. So, fasten your seatbelts and get ready to delve into the exciting world of measurement and instrumentation in PE Power!
Basic Concepts of Measurement in PE Power
Let’s start by discussing some fundamental aspects of measurements.
Units of measurement and systems of units
Units of measurement are standardized quantities used to express the magnitude of a physical quantity. A system of units is a collection of such units that are interrelated by a set of rules and conventions.
This section will explain the three most commonly used unit systems – the SI, CGS, and FPS systems. But wait, let’s start by learning what fundamental and derived quantities are.
Fundamental and Derived Quantities
In the SI system, the seven fundamental quantities are defined as base units, from which all other units are derived. Fundamental quantities are those physical quantities that cannot be defined in terms of other quantities. Derived quantities are those that can be expressed in terms of fundamental quantities.
For example, length, mass, and time are fundamental quantities, while area, volume, velocity, acceleration, force, and energy are derived quantities. The units of these derived quantities are obtained by multiplying or dividing the units of fundamental quantities.
The SI system of units
The International System of Units, abbreviated as SI, is the world’s most widely used system of units. It is based on the metric system and is used to measure physical quantities such as length, mass, time, temperature, electric current, luminous intensity, and amount of substance.
The SI system is built on seven fundamental quantities, which are defined by international agreements and are considered as base units. All other units are derived from these base units.
Fundamental Quantities and Base Units of the SI System
| Fundamental Quantity | Base Unit | Symbol |
| Length | Meter | m |
| Mass | Kilogram | kg |
| Time | Second | s |
| Electric current | Ampere | A |
| Temperature | Kelvin | K |
| Luminous intensity | Candela | cd |
| Amount of substance | Mole | mol |
Examples of Derived Quantities and Units of the SI System
| Physical Quantity | Derived Unit |
| Area | m^2 |
| Volume | m^3 |
| Velocity | m/s |
| Acceleration | m/s^2 |
| Force | N (kg*m/s^2) |
| Energy | J (N*m) |
Measurement accuracy and precision
Measurement accuracy and precision are two essential concepts in measurement and instrumentation. Accuracy refers to how close a measured value is to the actual value of a measured quantity.
On the other hand, precision refers to the degree of reproducibility or consistency of a measured value.
In other words, precision measures how well a set of measurements agree with each other.
The Hubble Space Telescope is a prime example of the importance of measurement accuracy and precision. The telescope was launched into space in 1990, and it was discovered shortly afterward that there was a minor error in the thickness of the primary mirror. This caused the images sent back by the telescope to be blurry and unusable.
The error was corrected during a servicing mission in 1993, and the Hubble has since provided stunning images and groundbreaking scientific discoveries. The Hubble example shows how a small measurement error can significantly impact a system’s performance and accuracy.
Measurement accuracy and precision are essential in various engineering fields, including manufacturing, construction, electrical, and transportation. For example, in manufacturing, precise measurements are critical for ensuring the quality and functionality of products. In construction, accurate measurements are necessary for ensuring structural integrity and safety.
In transportation, precise speed, distance, and time measurements are essential for navigation and safety. For instance, modern aircraft are equipped with advanced instruments that provide accurate and precise measurements of various parameters, including airspeed, altitude, and heading. These measurements are critical for safe and efficient flight operations.
Types of measurement errors
1. Random Error
Definition – Random error is an unpredictable and inconsistent error caused by measurement process variations.
Example – Instrument noise or operator error can cause random errors. For example, measuring a temperature with a thermometer whose needle oscillates due to environmental vibrations can cause random errors.
Method of Correction – Random errors can be reduced by increasing the number of measurements taken and using statistical methods to calculate the average value.
2. Systematic Error
Definition – Systematic error is a consistent error caused by a flaw or bias in the measurement process.
Example – A clock that consistently runs 5 minutes fast is an example of a systematic error.
Method of Correction – Systematic errors can be corrected by calibrating the measuring instrument, ensuring proper alignment, and correcting any environmental factors affecting the measurement process.
3. Gross Error
Definition – Gross error is caused by a substantial deviation from the actual value, often due to human error or equipment malfunction.
Example – An example of a gross error is measuring a distance of 10 km instead of 100 km due to a misreading or a typo in the measurement process.
Method of Correction – Gross errors can be corrected by repeating the measurement, checking for errors, or replacing faulty equipment.
4. Environmental Error
Definition – Environmental error is caused by environmental changes, such as temperature or humidity, that affect the measurement process.
Example – Measuring the length of a metal rod at a high temperature, which causes the rod to expand, is an example of environmental error.
Method of Correction – Environmental errors can be corrected by controlling the environmental conditions during the measurement process or compensating for the environmental factors in the data analysis.
5. Sampling Error
Definition – Sampling error is a type of error that occurs when a sample is used instead of an entire population, leading to variations in the results.
Example – Surveying a small group of people to predict the political preferences of the entire population is an example of sampling error.
Method of Correction – Sampling errors can be reduced by increasing the sample size and using statistical methods to analyze the data.
6. Instrument Error
Definition – Instrument error is a systematic error caused by faults or defects in the measuring instrument, such as calibration errors or drift.
Example – A thermometer that is not calibrated correctly is an example of instrument error.
Method of Correction – Instrument errors can be corrected by calibrating the measuring instrument, ensuring proper alignment, and correcting any environmental factors affecting the measurement process.
7. Approximation Error
Definition – Approximation error is a type of error that arises due to rounding off numbers or using an approximation method instead of an exact method.
Example – Calculating the area of a circle using the approximation of pi as 3.14 instead of the exact value of 3.14159 is an example of an approximation error.
Method of Correction – Approximation errors can be reduced by using more precise calculation methods and avoiding rounding off numbers until the final result.
8. Mean Absolute Error
Definition – Mean absolute error (MAE) measures the average deviation between measured and actual values.
Example – Calculating the difference between the actual and measured temperatures and taking the average of the absolute values is an example of calculating MAE.
Method of Correction – MAE can be reduced by improving the precision and accuracy of the measurement process and by using statistical methods to analyze the data.
9. Parallax Error
Definition – Parallax error is a type of error that is caused by the observer’s position or angle not being perpendicular to the measurement scale.
Example – An example of parallax error is reading a measurement from an angle instead of directly perpendicular to the scale, such as reading the liquid level in a beaker from the side instead of the top.
Method of Correction – Parallax errors can be corrected by ensuring that the observer’s position is directly perpendicular to the scale during measurement.
10. Scale Factor Error
Definition – Scale factor error is a type of systematic error caused by a difference between the actual scale of the measuring instrument and the nominal scale or value.
Example – A ruler that is not calibrated correctly, leading to measurements that are consistently off by a particular factor, is an example of scale factor error.
Method of Correction – Scale factor errors can be corrected by calibrating the measuring instrument and ensuring it is aligned correctly or using a conversion factor to adjust for the difference between the nominal and actual scales.
Electrical Measurements in PE Power
Regarding electrical measurement in the PE power exam, your main concern will be the parameters and instruments used to measure voltage, current, resistance, and other relevant quantities.
Let’s discuss the instruments used to measure these crucial quantities in detail.
Voltmeter
A voltmeter is an instrument used to measure the potential difference or voltage between two points in an electrical circuit. It is connected in parallel with the circuit element whose voltage will be measured.
The voltmeter has a high input impedance, which ensures that it draws negligible current from the circuit and, thus, does not affect the measured voltage.
Ammeter
An ammeter is an instrument used to measure the electric current flowing through a circuit. It is connected in series with the circuit element whose current will be measured. The ammeter has a meager resistance so that it does not alter the current being measured.
Ohmmeter
An ohmmeter is an instrument used to measure the resistance of an electrical component or circuit. It applies a known current to the component and measures its resulting voltage.
The ohmmeter is connected in parallel with the component whose resistance is to be measured, and the circuit being tested should be disconnected from any source of power.
Multimeter
A multimeter is a versatile instrument that can measure voltage, current, and resistance, as well as other electrical quantities such as capacitance and frequency.
It consists of a voltmeter, an ammeter, and an ohmmeter combined into a single device. The multimeter is connected similarly to the individual meters, depending on the measured quantity.
Wattmeter
A wattmeter is an instrument used to measure the electrical power consumed by a load or generated by a source. It is connected in series with the load or source and measures the voltage across and the current through the load or source. The wattmeter can measure both AC and DC power.
Energy Meter
An energy meter is an instrument used to measure the amount of electrical energy consumed by a load or produced by a source over time. It is typically used to measure energy consumption in homes, commercial buildings, and industrial facilities.
The energy meter is connected in series with the load or source and measures the cumulative amount of energy consumed or produced over time.
Oscilloscope
An oscilloscope is an instrument that displays and analyzes electrical signals in the time domain. It can measure frequency and phase by observing the signal’s waveform and measuring the time difference between two or more points on the waveform. The oscilloscope can also measure the signal’s amplitude, period, and other characteristics.
Phase Meter
A phase meter is an instrument used to measure the phase difference between two electrical signals. It can measure the phase angle between two voltages or currents or the phase shift introduced by a circuit element or component. Phase meters typically use a reference signal to compare the phase of the measured signal.
Instrumentation in PE Power
Analog and digital instruments
The table below outlines the key differences between analog and digital instruments.
| Category | Analog Instruments | Digital Instruments |
| Definition | Instruments that measure and display signals in a continuous, proportional manner using a physical pointer or dial. | Instruments that measure and display signals discretely, binary manner using numeric displays or computer screens. |
| Examples | Some common examples are analog voltmeters, ammeters, thermometers, barometers, oscilloscopes, etc. | Some common examples are digital multimeters, oscilloscopes, thermometers, barometer, etc. |
| Use Cases | Analog instruments are used in applications where continuous, real-time monitoring is required, such as in audio and video recording, industrial process control, and medical monitoring. | Digital instruments are used in applications where precise, accurate measurements are required, such as in electronics, telecommunications, and scientific research. |
| Advantages | Analog instruments provide a visual indication of the magnitude and direction of a signal and are often easier to read and interpret than digital instruments. They are also less prone to quantization noise and distortion. | Digital instruments offer higher precision and accuracy than analog instruments and can be easily programmed to perform complex calculations and analyses. They also have the ability to store and recall data and can be interfaced with computers for data processing and analysis. |
| Disadvantages | Analog instruments are subject to drift, hysteresis, and other non-linearities, which can cause measurement errors. They also have limited resolution and accuracy. They are more difficult to calibrate than digital instruments. | Digital instruments are subject to quantization errors, noise, and distortion, affecting measurement accuracy. They also have limited dynamic range and can be affected by electromagnetic interference. |
| Error Correction | Analog instruments can be calibrated and adjusted to minimize measurement errors, but the process is often time-consuming and requires specialized equipment and expertise. | Digital instruments can be calibrated and adjusted using software, which is often easier and faster than analog calibration. Digital instruments can also be programmed to compensate for errors and can provide on-screen error messages and alerts. |
Control loops and feedback systems
Control loops and feedback systems are essential components in measurement instruments that help to maintain accurate and stable measurements over time. A control loop is a closed-loop system that continuously measures a process variable, compares it to a setpoint, and adjusts the process to maintain the desired setpoint.
The feedback system is a process of continuously monitoring a system output and using that information to adjust the system input, ensuring that the output remains within acceptable bounds.
In measurement instruments, a control loop typically consists of a sensor that measures the process variable, a controller that compares the measured variable to the setpoint, and an actuator that adjusts the process to maintain the desired setpoint.
The feedback system works in a similar way, with the system output serving as the process variable and the system input adjusted to keep the output within acceptable bounds.
The control loop and feedback system work together to provide stability and accuracy in measurement instruments. The control loop continuously measures the process variable.
It makes adjustments to keep it within the desired range, while the feedback system monitors the system output and adjusts the system input to keep the output within acceptable bounds.
Using both systems, measurement instruments can maintain accurate and stable measurements over time, even in changing conditions or external factors.
A temperature controller is an example of a measurement instrument that uses control loops and feedback systems. In this system, a temperature sensor measures the process variable (temperature), which is then compared to a setpoint by the controller.
The controller then adjusts the system input (heating or cooling) to maintain the desired temperature. The feedback system continuously monitors the temperature output and adjusts the heating or cooling input to keep the temperature within the desired range.
Data acquisition and processing
Data acquisition and processing are critical components in the measurement process, enabling the collection and analysis of data from sensors and other measurement instruments.
Data acquisition involves the conversion of analog signals from sensors into digital signals that computers and other digital devices can process. Data processing involves manipulating and analyzing this data to extract meaningful insights and information.
The data acquisition process begins with measuring a physical quantity using a sensor or other measurement instrument. The sensor generates an analog signal representing the measured quantity, such as voltage, temperature, or pressure.
This analog signal is then passed through an analog-to-digital converter (ADC), which converts the analog signal into a digital signal that computers and other digital devices can process.
Once the data has been acquired and converted into a digital format, it can be processed using various techniques. Data processing may involve filtering, averaging, or other mathematical operations to reduce noise and extract meaningful information from the data.
Statistical analysis may be used to identify trends or patterns in the data and machine learning algorithms may be applied to predict future outcomes based on past data.
In the context of measurements, data acquisition and processing are essential for generating accurate and reliable measurements. By converting analog signals into digital signals and processing the resulting data, measurement instruments can produce precise and consistent measurements over time.
Data processing techniques can also help identify trends or patterns in the data, enabling insights into the system’s behavior being measured.
There are several types of data acquisition and processing systems, ranging from simple standalone systems to complex networked systems that can simultaneously collect and analyze data from multiple sensors and measurement instruments.
Some systems are designed for specific applications, such as industrial automation or scientific research, while others are more general-purpose and can be used in various contexts.
Resources for Preparing for Measurement and Instrumentation on the PE Exam
Preparing for the Professional Engineering (PE) exam can be daunting, especially regarding the measurement and instrumentation section. But fear not! Many resources are available to help you prepare for this critical exam section.
One excellent resource for PE exam preparation is “Study for FE.” This online platform provides comprehensive study materials and practice exams designed explicitly for the PE exam.
The “Study for FE” allows you to access detailed video lectures, practice problems, and other resources to help you master the material and ace the exam.
But simply having access to study materials isn’t enough. To effectively prepare for the measurement and instrumentation section of the PE exam, you’ll need to develop effective study habits and test-taking strategies.
Here are some tips to help you make the most of your study time –
- Create a study schedule – Set aside dedicated study time each day or week and stick to it. This will help you stay on track and ensure that you cover all the necessary material before the exam.
- Practice, practice, practice – The best way to prepare for the measurement and instrumentation section of the PE exam is to practice solving problems. Work through as many practice problems as possible, and use the solutions to identify areas where you need more practice.
- Focus on understanding concepts – Don’t just memorize equations and formulas. Ensure you understand the underlying concepts behind the equations to apply them to new and unfamiliar problems.
- Take breaks – Studying without breaks can lead to burnout and decreased productivity. Take breaks and give your brain a chance to rest and recharge.
- Stay organized – Keep track of your progress and keep study materials organized. This will help you stay focused and avoid wasting time searching for information.
By following these tips and utilizing resources like Study for FE, you can effectively prepare for the measurement and instrumentation section of the PE exam and increase your chances of passing.
So start studying today and get one step closer to becoming a licensed professional engineer!
Interested in learning more about what we offer and how it can help you prepare for the PE exam? Click here to check it out and start your journey toward exam success.
Conclusion
Measurement and Instrumentation play a crucial role in the field of PE Power. It ensures that engineers can accurately measure and analyze various parameters such as voltage, current, power, and energy.
A strong understanding of different measurement techniques and tools is essential for success in the PE Power exam. Remember to study and practice effectively with the available resources, such as Study for FE, to increase your chances of success.
Licensed Professional Engineer in Texas (PE), Florida (PE) and Ontario (P. Eng) with consulting experience in design, commissioning and plant engineering for clients in Energy, Mining and Infrastructure.