Jefferson Pham, Alexa Woppman, Dr. Joseph Morgan, Professor Matthew Leonard
Texas A&M University
Electronic Systems Engineering Technology (ESET)
Multidisciplinary Engineering Technology (MET)
During the height of COVID-19, Moku:Lab was shipped to two Texas A&M students for them to work with and evaluate. Working with the Oscilloscope, Waveform Generator, Frequency Response Analyzer, and Spectrum Analyzer, students self-directed the evaluation from the time of unboxing to the finalization of the paper. Read more on their findings in the full report.
A team of students and faculty from the Engineering Technology and Industrial Distribution (ETID) department at Texas A&M University in College Station collaborated with Liquid Instruments to test the capabilities of the company’s flexible hardware product Moku:Lab in an undergraduate engineering environment. Moku:Lab is a software-configurable hardware platform built as one compact device capable of simulating 12 different professional-grade electronic test and measurement instruments. The team evaluated Moku:Lab by completing a black-box analysis and experiments often performed in an undergraduate laboratory. This product was tested based on the following criteria: flexibility of use, functionality, and Engineering Technology and Industrial Distribution class relevance. These testing criteria were used to determine the viability of using a product like Moku:Lab at the undergraduate level.
Background & Introduction
At Texas A&M University, one of the major characteristics that differentiate engineering technology programs from the large number of engineering programs is the emphasis on hands-on, experiential learning. This is very true in both the Electronic Systems and Mechatronics program where all technical courses, from the sophomore level through the final capstone design experience, include an integrated laboratory. Students advance their learning and understanding by translating classroom theory into working laboratory experiments and projects.
In such an environment, the use of test and measurement equipment is fundamental to the overall learning process. To support a wide range of technical subjects requires a number of dedicated physical laboratories and each lab requires a suite of test equipment. Procuring and maintaining industry-quality test and measurement equipment is a daunting task. In addition, the lack of a common user interface between one piece of equipment and another on the same lab bench presents a roadblock for students in learning and using each of the tools efficiently and effectively.
The Electronic Systems and Mechatronics programs have tried to standardize the test and measurement equipment across their various labs, but this still requires up to five or six different pieces of specialized test equipment; all requiring space, power and interconnect to the students’ experiments.
Recently, Dr. Joseph Morgan, Professor Emeritus, and Professor Matthew Leonard, Adjunct Faculty and President of Texas Space Technology Applications and Research (T STAR) were contacted by Liquid Instruments. The purpose of this interaction was to determine the level of interest engineering technology programs at a major engineering school would have in its new test and measurement device, Moku:Lab which is a reconfigurable hardware platform with a common graphical user interface. Leonard and Morgan have focused a significant amount of their efforts on sponsoring and conducting capstone design projects related to space/NASA interests. Leonard (T STAR) generally participates as the project sponsor/customer and Morgan is the technical advisor for the teams. Both individuals are aware of and concerned with issues associated with test and measurement equipment. In discussions with Liquid Instruments Vice President of Marketing, Mr. Douglas Phillips, it was agreed that his company would loan a Moku:Lab to a small team of engineering technology students, who would then evaluate the multi-instrument system’s impact on typical laboratory assignments and the overall learning experience as compared to the typical suite of lab equipment. This paper describes the steps taken in evaluating Moku:Lab and the findings and conclusions of the students involved.
Liquid Instruments has designed Moku:Lab, a hardware platform that provides a collection of virtual testing and measurement instrumentation on a single device. The tool utilizes a field-programmable gate array (FPGA) that supports analog inputs and outputs. Consolidating multiple testing and measurement tools into a single device enables the product to be software configurable, and it also has the benefit of a mobile controller for added portability and ease of use. These features can improve the educational experience in undergraduate studies by streamlining the process by which electronic signals are tested and logged. Moku:Lab provides an interface that allows for the transition from overly expensive and complicated test equipment to a single unit that combines all the features of industry-grade equipment into a single compact platform that is easy-to-use. The virtual instruments currently supported at the time of writing this evaluation are:
- Lock-In Amplifier
- Arbitrary Waveform Generator
- PID Controller
- Frequency Response Analyzer
- Laser Lock Box
- Spectrum Analyzer
- Digital Filter Box
- Waveform Generator
- Data Logger
- FIR Filter Builder
Moku:Lab provides the user with two high-speed analog inputs, two high-bandwidth DC-coupled analog outputs, an external trigger connection, input clock reference, output clock reference, SD-card slot, Ethernet Port, MicroUSB connection, and a USB-A port . The specification sheet from Liquid Instruments states the frequency range of the inputs at a maximum of 200MHz . The output ports have a maximum frequency bandwidth of 300MHz. The inputs can also be configured for either AC or DC coupling while maintaining an input resolution of up to 500MSa/s . The outputs feature anti-aliasing filters that allow for interfacing between the equipment and measuring inputs simultaneously. The device can utilize industry-standard impedance values of either 50Ω or 1MΩ . The device includes an internal clock that is stable to over 500ppb accuracy . These features allow the tool to be competitive in an industrial environment where a set of high precision testing and measurement tools are required. There are also two push-button switches on the bottom of the device that can be pressed using a small pin. One button can trigger a factory reset, and the other button will toggle airplane mode. LED lights by the inputs and outputs of the device function as status indicators. A single push-button switch is located under Moku:Lab’s logo and has a status indicator LED that becomes solid blue when the device is ready to use, blinks orange when shutting down or setting up, and turns off when the device is off. The light bars under the inputs and outputs flicker when modifications are being made on Moku:Lab’s application. These nuanced features increase the ease-of-use and aids in device recognition when multiple units are deployed in a single laboratory. Moku:Lab can also utilize a WiFi protocol and broadcasts an SSID to allow mobile devices to interface directly through a wireless connection. From the standpoint of an undergraduate student, the enhanced usability of Moku:Lab and its small form factor provide a solution that can improve the learning experience in the laboratory. An external overview of Moku:Lab was created by performing a black-box analysis of the device. A diagram was generated from the black-box analysis and is shown in Figure 1.
Figure 1: Black Box Diagram of Inputs and Outputs of Moku:Lab
The black box analysis performed on Moku:Lab provided insight towards the exact inputs and outputs integrated within the device. To allow for connectivity between the controller application and the device, a wireless connection can be used. There is also an option to physically wire the device into the local area network and mount the device directly to a lab station. Liquid Instruments has also engineered a safety and security component into the chassis of the product by adding a Kensington Security Slot  to the side of the device to lock it to a workstation. This feature adds value to the product as it can more easily be deployed in a public laboratory environment with more traffic. The two analog inputs, two analog outputs, external clock inputs and outputs, and trigger connections are all BNC style connectors. This style of connector is currently the industry standard for test and measurement instrumentation and can integrate well with existing solutions and equipment currently in use commercially. A MicroUSB input can also connect the device directly to a computer to support control and data logging on either MAC or Windows computers. There is also an SD card port offered to store logged data internally until it can be retrieved for analysis at a later time. Moku:Lab provides a way to factory reset the device by using a pin under the device. There is also a button to toggle airplane mode which can be useful for mobile applications or in laboratories that do not want a large amount of wireless interference from multiple devices all broadcasting an individual SSID. There is a barrel connector that supplies D/C input power to the device. The power from an A/C power source is converted using a power converter to 12 V D/C and provided to Moku:Lab. The device can then be powered on using the button under the logo sticker. The output analog ports can supply a maximum voltage of 1V. LED indicator lights are embedded within the chassis for easy recognition of the state the device is in. A single USB-A port is also incorporated into the device and can charge an external mobile device that connects to it. The physical device and its external connections are shown in Figure 2.
Figure 2: Inputs and Outputs of Moku:Lab from Specification Sheets 
The device is a small-form-factor product with a physical maximum diameter of 225 mm and a height of 50 mm. Moku:Lab’s small size allows it to easily fit into a laboratory environment without much hassle and adds to the flexibility of the product.
Moku:Lab can be controlled using an iPad application, LabVIEW, Python, MATLAB, or a windows application that is still in beta. An iPad is included with Moku:Lab and can be placed in a slot on top of the device while in use or held while walking around a lab because WIFI is the only connection required. The option to use an ethernet connection is also available.. This report will focus on the iPad software platform.
The iPad application uses twelve bubbles with graphics inside each one that indicates the instrumentation options as shown in Figure 3.
Figure 3: User Interface of the Moku:Lab iPad Application
An instrument is selected for use by pressing on a bubble and is changed by pressing a different bubble. The software is designed to correspond to 2 hardware inputs and 2 outputs though some of the instruments are able to use a simulated input signal if desired. Axis values for graphs in each of the instruments are able to be customized or automatically set based on the range of input data values received. There is an instrument reset button within the iPad application that returns all settings on both the software and hardware back to the defaults. Moku:Lab has the ability to individually calibrate each instrument based on the current selection in the software application. Calibration occurs quickly by pressing a button.
Dropbox, iCloud, MyFiles, an SD Card, and email are options that have been integrated into the software to export data collected using Moku:Lab. The software allows for various formats of data to be created and exported depending on the instrument used for the data collection on the device. There are options for PNG screenshots using the iPad, JPEG versions of graphs, and CSV files to list a few.
Liquid Instruments provides software updates regularly for the device. These updates include improvement to existing instrument options, patches for bugs, and the addition of new instruments for measurements that don’t require changes to Moku:Lab hardware.
Evaluation Process and Assessment
Liquid Instruments supplied a Moku:Lab device to Texas A&M University’s Engineering Technology and Industrial Distribution Department for use and evaluation. The device shipped with an iPad, an iPad charger cable, a AC to DC power converter, and Moku:Lab in a hard case. The online documentation indicated the product would ship with an SD card, however, no card was found. The storage capabilities of the Data Logger could not be tested due to this. The setup process was fairly straightforward, however, the power button was difficult to locate as it was hidden under the company logo. There was also no user guide in the box, and information about the device was found from Liquid Instrument’s website . When the device was plugged in and powered on, it completed its initialization cycle. The iPad could be connected to it using an ad-Hoc link initiated by using the SSID broadcast by Moku:Lab. The application on the iPad came preloaded with the full software suite which includes all twelve instruments currently developed for the device. The pricing changes based on the combination of software and hardware package that is purchased.
The three main evaluation areas of Moku:Lab are the flexibility of use, functionality, and ETID class relevance. The flexibility of use was evaluated by the device’s ability to be used for different purposes and its ease of use in an undergraduate laboratory. The functionality of the device was determined by the device’s ability to work properly and the quality of the results. Lastly, the device was evaluated to determine the relevance and ability to be utilized in ETID classes. These criteria are important to assess the effectiveness and quality of using the device in an undergraduate setting. All evaluations were conducted with the same Moku:Lab device and iPad application.
The evaluation process began by taking baseline measurements of some of the more commonly used instruments in an undergraduate laboratory to compare the results with Moku:Lab’s results.
The oscilloscope is used in Electronics Systems and Engineering Technology (ESET) courses for measurements in embedded systems, various analog and digital circuits, and many other labs. A sample of various lab processes that require an oscilloscope was taken from the ESET lab manuals and were used to evaluate Moku:Lab. The Analog Electronics Laboratory uses the oscilloscope to test the response of analog components as waveforms are applied to them. The Radio Frequencies and Electromagnetism Laboratories utilize oscilloscopes to examine the reaction of signals at high frequency in regards to losses and reflection for different materials. Embedded Systems courses often use an oscilloscope to verify an output created by a microcontroller. Therefore, it is important to evaluate Moku:Lab with a broad variety of experiments. With that in mind, Moku:Lab was compared against an oscilloscope often used in ESET laboratories. Both instruments measured the same output signal from an external source. The source was a square wave generated using a TI MSP432P401R microcontroller. The usage and programming of the microcontroller are often studied in the scope of three computer programming courses in the department. Embedded Systems Software, Microcontroller Architecture, and Embedded Systems Development in C all utilize the MSP432 to analyze the uses of embedded systems and methods of programming. To verify the correct output magnitude and frequency, an oscilloscope can be used. Modifications to the frequency and duty cycle can be adjusted through code and measured externally. This can create pulse width modulated (PWM) signals based on the duty cycle. Measurement devices must have the capability to measure using both AC and DC coupling to receive the actual waveform and the offset voltage of the signal. When utilizing the math function to calculate DC offset between DC and AC coupling inputs, Moku:Lab performed this task with no issues. The analog inputs of the waveform read from the microcontroller matched with the waveform presented on the oscilloscope. However, Moku:Lab had the added benefit of pinch scaling for the voltage and time divisions, so the results could be fit to the iPad easier than on a regular oscilloscope. The results could then be recorded on the iPad and wirelessly transmitted to a computer for data processing. This added flexibility makes result transfer seamless for large data acquisitions. There is also the added flexibility of using Moku:Lab’s inputs and outputs at the same time. Integrated into the Oscilloscope tool is an option to enable the waveform generator for each of the analog outputs on the device. The refresh rate of data acquisition on the oscilloscope is quick and responsive, and the run and stop function is clearly indicated by the pause-play button at the bottom of the iPad application. There is an option to open the measurements pane, and the software will automatically retrieve the frequency, period, duty cycle, pulse width, and negative width with options for many more measurements. Cursors are easy to create and the adjustability of the cursors can be accomplished by simply sliding the cursor. In comparison to a high-end Rigol oscilloscope with a touch screen display, the iPad application is more streamlined and easy to use. However, there is the issue of having only two channels. On Rigol and Tektronix oscilloscopes more channels are employed each with their own display space. There is only a single display on Moku:Lab, and all waveforms have to share the same plot. Different waveforms can be separated using a voltage offset. There is no embedded capability for real-time waveform video recording. The use of multiple iPads, or multiple applications with the current version of Moku:Lab is currently unsupported. The oscilloscope user interface of Moku:Lab is shown in Figure 4.
Figure 4: Oscilloscope User Interface for Moku:Lab’s Measuring Square Wave Output at 1 kHz
Moku:Lab has the capability of generating a waveform output while simultaneously recording information through the analog inputs. The integrated waveform generator for the oscilloscope outputs a wave that matches the expected characteristics of a square wave. The type of waveform and its parameters can be adjusted using the control panel on the same screen. To test the proper functionality of Moku:Lab’s Oscilloscope, an analog input was connected to the analog output using a 50 Ohm RG58 coaxial cable with BNC connectors on either end. By connecting Moku:Lab’s input directly to the output, the oscilloscope’s accuracy can be verified by comparing the signal shown on the iPad to the expected output. The oscilloscope enables the usage of cursors that can be customized to automatically track voltage and time spans. The cursors can be used in conjunction with the easy read-out to quickly obtain key measurements from an input waveform. The easy read-out includes options to add five concurrent data indicators that can each be individually adjusted to the exact measurement a user needs for each input channel. The output waveform generator allows for a voltage from peak to peak of -1V to 1V centered at the ground. There is also an option to offset the output waveform by adjusting the DC offset to change the reference to the ground. However, there is still the maximum output voltage limitation of 1V that must still be maintained. Figure 4 displays an oscilloscope which recorded a maximum voltage of 508.1 mV and a minimum of -509 mV. The span of the two voltages totals 1.0171V which yields a percentage difference of about 1.7% from the 1Vpp parameter defined by the user. The difference represents an amount of uncertainty between the input and the output that is relatively low. The frequency of the generator was set to 1kHz, and the oscilloscope measured a frequency of 999.1 Hz which is about 0.09% different from the user set value of 1 kHz. This low percentage difference shows that the frequency and period match the user-defined values. The duty cycle selected was 50%, and the oscilloscope measured a duty cycle of 49.9% which results in a percentage difference of about 0.02%. The difference in duty cycle is negligible in the lower-level applications of undergraduate studies and the signal is stable enough to be used for analog signals testing and data acquisition using an oscilloscope. However, an issue presents itself when the frequency is increased. The waveform shows some distortion at higher frequencies as shown in Figure 5.
Figure 5: Square Wave Recorded from Moku:Lab’s High-Frequency Output
The frequency of Moku:Lab’s analog output was increased until distortion began to appear, and the frequency in which distortion became evident was at 10 MHz. The distortion occurs at the peak voltage values as shown by the overshoot in both the negative and positive voltages. The overshoot was measured by using the oscilloscope’s cursors and the positive overshoot voltage 567.8 mV while the stable voltage was about 508.8 mV. The difference between the two values yields a delta of 59mV. The overshoot was also measured on the negative peaks of the square wave. The negative overshoot voltage -564.2 mV while the stable voltage was about -505.2 mV. The absolute difference between the two values also yields a delta of 59 mV. The overshoot is the same for both the negative and positive peaks and indicates a good level of consistency. This amount of overshoot is also relatively low, but the distortion increases as a function of increased frequency which should be noted for high frequency applications. The square wave output was then measured using a Tektronix Oscilloscope and the same distortion appears which verifies the transmission line is causing a negligible amount of attenuation at high frequency. The distortion of the output’s signal generation indicates a hardware limitation of Moku:Lab’s FPGA solution that causes a square wave output to have some minor distortion at peak values. The higher frequency distortion on the square wave was compared to a sine wave, and the waveform is shown in Figure 6.
Figure 6: Sine Wave Input from Moku:Lab’s High-Frequency Output
The measured frequency was 10.01 MHz and the duty cycle was 49.97%. The sine wave does not show distortion at the peaks. Moreover, there are no voltage fluctuations at peak voltage. The absence of voltage variation indicates the sine wave output for Moku:Lab is very consistent with not much deviation in regards to time. The maximum and minimum voltage levels were 1.016V and -1.016V. This yields a total delta of about 0.032V from the user-specified 2Vpp. This is a very small deviation which shows that Moku:Lab can maintain a precise output for the sine wave. Tracking the voltage changes can be done using the cursors. There are many options that can be selected for the cursors as shown in Figure 7.
Figure 7: Cursor Selections for Tracking Voltages in Real-Time
The cursors can automatically track the voltage or time changes on an input waveform, and there are measurement tools integrated into the oscilloscope. Moku:Lab’s oscilloscope application supports five concurrent time cursors and five concurrent voltage cursors on the same screen. The time cursors can be dragged to measure the time between two data points, and reference time can be added as well. Options for modifying the voltage cursors are shown in Figure 7, and include:
- Manual Cursor Dragging
- Track Mean Voltage
- Track Maximum / Minimum Voltage
- Hold at Maximum / Minimum Voltage
- Indicate a Reference Voltage
- Indicate a User Input Voltage Level
- Switch Cursor Channel
- Remove Cursor
The graphical user interface can be switched between a dark background and a light background for added visibility, and the overall look of the application is clean and not cluttered. The functions are color-coded and simple to use. Learning to use Moku:Lab is simple, and an undergraduate student would have no issue using this all-in-one tool within a laboratory setting.
The Waveform Generator is another virtual instrument on Moku:Lab that generates a wide variety of waveforms based on a set of parameters defined by the user. However, the device does have a limitation on the maximum voltage output of 1V. Although the voltage peak to peak can be greater than 1V, the voltage must make use of the negative one volt from Vref zero to create this waveform. The voltage limitation is detrimental to the laboratory experience because many microcontrollers and integrated circuits utilize a 5V DC or 3.3V DC power source. The waveform generator has a very low voltage range and cannot be used as a power supply above 1V. There are many different waveforms that can be generated.
Moku:Lab’s Waveform Generator can create:
- Sine Waveform
- Square Waveform
- Ramped Waveform
- Pulse Waveform
- DC Waveform
Liquid Instruments has focused on creating analog outputs with a greater resolution and precision that match the standards of the instrumentation currently used by industry. The outputs also have anti-aliasing that allows for loads to be placed on the outputs while still being able to take accurate measurements. The output impedance is 50 ohms. Therefore, any circuit matched to the same impedance will have a response that maximizes power transfer. The shape of each waveform is shown in Figure 8.
Figure 8: Five Wave Options for the Waveform Generator
Each waveform presents a way to modify the analog outputs on the device. All waveforms in Figure 8 are shown while at 1 Vpp with the exception of the DC output voltage which is at 1 V. All of the waveforms are centered at zero volts. The first waveform in Figure 8 is a Sine waveform followed by a square wave. The next row shows the ramp and pulse wave options. The last wave shown is a DC output waveform. These waveforms displayed on the iPad do not change when their amplitudes, voltages, and frequency are modified except for the Pulse wave, and only the output changes. Both of the output channels can be driven at the same time, this is useful when working with filters because the voltage rails can be independently driven from the input voltage. However, when driving both outputs at the same time, the oscilloscope cannot be used. This is a disadvantage of the device. The waveform generator is the tool most often used in analog electronics testing. The voltage outputs must be stable at any frequency value. For some of the high-frequency applications in radio frequency and electromagnetism undergraduate courses, the device cannot be used as a frequency generator. The device has an amount of high-frequency attenuation – as shown in Figure 5 – and this limitation should be noted. Each wave option for the generator was tested at 0.5 and 1 Vpp output and measured using an external digital multimeter (DMM). The results are shown in Table 1 in both DC and AC measurements.
Table 1: Waveform Generator Evaluation Measurements using a Digital Multimeter
The results of Table 1 show the accuracy of the waveform generator for each wave that can be produced with Moku:Lab. The pulse wave was tested at six different duty cycles to show the varying DMM results between AC and DC. The variations in voltage from the output to the DMM are a result of the Vrms averaging that the DMM performs to calculate the effective applied voltage. The results in Table 1 are consistent with the expected voltage values.
Arbitrary Waveform Generator
Circuits often receive an input that is not always cyclic in nature. Therefore, an arbitrary waveform generator can be useful when simulating an input that is more erratic. Circuit responses to stimuli can also verify whether a component is functioning properly and is often employed when building filters to test for cutoff. A circuit can be designed for a set of cut-off frequencies and by controlling the input to be greater at the stop-bands, the circuit can be tested for proper functionality. Simulating worst-case scenarios will allow a circuit to be designed for irregular signal inputs and excessive stresses. Moku:Lab can create various waveforms for enhanced signal testing, and one of the waveforms can be seen in Figure 9.
Figure 9: Arbitrary Waveform Generator: Gaussian Output (left) with External Oscilloscope Response (right)
The setup used to obtain the response waveforms from Moku:Lab’s arbitrary waveform generator involved the use of an external Tektronix oscilloscope to capture the output waveform. Moku:Lab’s analog output was connected to the input of the oscilloscope, and the resulting waveforms were captured. One of the arbitrary waveforms that Moku:Lab can generate is the Gaussian curve. It is often referred to as the bell curve and simulates repetitive voltage spikes in an otherwise grounded device. The fault test can determine whether or not a device has been protected against ground faults. This test is often performed in electronics test classes and can help design against improperly bonded grounds or short circuits. This waveform can be used to test electronics for fault tolerance and improve designs. Another waveform Moku:Lab’s Arbitrary Waveform Generator can create is the Exponential Rise as shown in Figure 10.
Figure 10: Arbitrary Waveform Generator: Exponential Rise Output (left) with External Oscilloscope Response (right)
An exponential Rise may result when a static charge begins to build up in a circuit without an earth ground. As devices become integrated with more sensitive components and MOSFETS, static discharges through the components may destroy them. The static charge in conjunction with an improperly grounded circuit can result in a failed device. Furthermore, an exponential rise is often seen from a capacitor in an AC circuit, so testing using this waveform can simulate the cyclic discharge and recharge of a capacitor. The Exponential Fall Waveform can be produced as shown in Figure 11.
Figure 11: Arbitrary Waveform Generator: Exponential Fall Output (left) with External Oscilloscope Response (right)
The arbitrary waveform generator can apply the voltages for applications that require an instantaneous voltage jump then falls to a reference voltage. This reference voltage can be changed using Moku:Lab parameters. Many MOSFETS which take the signal input from another subsystem can make use of a changing voltage value with stable Vref to generate a clock. Clock generation is another use of the Exponential Fall Waveform within a circuit. Clock frequencies are an important area of study in undergraduate electronics because it serves as a reference for communications within digital systems, analog systems, embedded systems, high-frequency systems, and many other systems studied within the scope of an undergraduate engineering curriculum. Moku:Lab combines intuitive software with a hardware platform that is flexible and mobile. The Cardiac Waveform of Moku:Lab’s Arbitrary Waveform Generator is shown in Figure 12.
Figure 12: Arbitrary Waveform Generator: Cardiac Output (left) with External Oscilloscope Response (right)
The cardiac waveform is often used to simulate parasitic voltage responses from a heart rhythm. This waveform is necessary when evaluating medical equipment to ensure that the life-saving equipment functions as it should every time. Undergraduate studies can branch into many different majors, and by creating a device that has applications in more than just an electronics course, Moku:Lab can be useful in a variety of majors. The variety of interdisciplinary courses offered in undergraduate studies including biomedical, mechatronics, robotics, and many other disciplines can all benefit from the versatility of Moku:Lab’s testing and measurement capabilities. Moku:Lab can also create waveforms based on a user input function. An example of a function generated waveform is shown in Figure 13.
Figure 13: Arbitrary Waveform Generator Equation-Based Output (left) with External Oscilloscope Response (right)
A user can generate an equation that produces a specific waveform, and Moku:Lab’s Arbitrary Waveform Generator will be able to produce it. This allows for precision waveform generation based on a known set of parameters. An example function and how it can be modified is shown in Figure 14.
Figure 14: Arbitrary Waveform Generator: Equation-Based Output Modification Window
The example equation, exp(-10*(t-0.5^2)*sin(5*pi*t)^20, shown in Figure 14 was generated by Moku:Lab’s Arbitrary Waveform Generator and the response waveform was recorded in Figure 13. The equation editor features a scientific calculator layout that allows for easy modification of the waveform. There is also the capability to input multiple equations and have the generator produce different waveforms next to one another in the same period. The ability to simulate any custom waveform adds another set of functions to the device as it can be made to generate any waveform and apply it cyclically to a circuit.
Frequency Response Analyzer
A frequency response analyzer is used in a few ESET courses to measure circuit response, high frequency printed circuit board attenuation, and coaxial cable frequency response. The frequency response analyzer was evaluated using a Nagoya NA-771 15.6” Vertical omnidirectional antenna. The antenna was connected directly to the device where its response to a range of frequencies was measured up to 120 MHz. In terms of functionality, this analyzer was simple to use and to ensure an accurate measurement was taken between the hardware antenna connection and the software. The data collected is represented by two graphs showing the gain and phase relationship as a function of frequency. The response of the antenna to applied power is shown in Figure 15.
Figure 15: Frequency Response of a 15.6” Vertical Omnidirectional Antenna
It was determined that Moku:Lab’s Frequency Response Analyzer is able to operate effectively at high frequencies up to 120 MHz. This capability is needed for a number of ESET classes where high frequencies systems are a focus and quality equipment is needed to see how standard characteristics of antennas and printed circuit boards change based on the operating frequency range. However, higher frequencies are required for further signal testing of electromagnetic systems.
The spectrum analyzer can accept input signals and create a plot that details the magnitude of a signal at a particular frequency. This is particularly useful when examining a system where the power input at different frequencies is unknown . The Spectrum Analyzer was tested on Moku:Lab, and the results helped to verify the effective operation of an antenna. A 15.6” vertical omnidirectional antenna was attached to the Spectrum analyzer, and the power input at each frequency was plotted. The power response at a span of frequencies was recorded and shown in Figure 16.
Figure 16: Free-Air Frequency Input from a 15.6” Vertical Omnidirectional Antenna
The frequencies indicated an increase of power between the frequencies of 80.1MHz and 108.1 MHz. Referencing some internet documentation showed that FM radio broadcasts at this frequency thus resulting signal increase . The ability to plot power inputs as a function frequency helps to check which radio stations in the area have the strongest signal. Moreover, the spectrum analyzer has many other applications including government agencies scanning for broadcasts that are creating radio interference. The FCC employs the use of many spectrum analyzers with special data logging and tracking systems to regulate the public broadcast space. This is helpful in undergraduate studies because it adds to a student’s exposure to instruments used commercially. Spectrum Analyzers often cost hundreds of dollars . Moku:Lab’s platform offers a cost-effective solution to expensive test equipment and tools. The virtualization of different instruments allows for a versatile conglomeration of tools that can easily be switched without having to rewire a circuit to a different tool for each test. This is useful in test laboratories with limited space and funding. Each lab station can have its own Moku:Lab instead of multiple separate instruments. The minimization of instrumentation on a laboratory bench also reduces the total number of wiring harnesses that need to be used which also results in a workspace that is less cluttered.
Moku:Lab is capable of combining 12 testing and measurement instruments that are commonly used in both professional and undergraduate laboratories. The device was evaluated using the black box analysis technique to gain a deeper understanding of the many functions and applications of the device in terms of software and hardware. Using this understanding the device was evaluated based on the flexibility of use, functionality, and ESET class relevance to conclude the usefulness of the device at an undergraduate level.
The instruments chosen for evaluation were the oscilloscope, waveform generator, arbitrary waveform generator, frequency response analyzer, and spectrum analyzer based on relevance to undergraduate studies at Texas A&M. Each one was tested using a lab that is currently conducted in undergraduate courses and results were compared to a standard piece of equipment. Moku:Lab was found to be useful in many courses across the ESET department and effective in its performance. The broad spectrum of interdisciplinary courses offered in undergraduate studies including biomedical, mechatronics, robotics, and many other disciplines can all benefit from the versatility of Moku:Lab’s testing and measurement capabilities. Moku:Lab combines intuitive software with a hardware platform that is flexible and mobile. However, there are some limitations to the operation of the device. One of the limitations includes a slight amount of distortion that occurs at high frequencies for the analog outputs when generating a square-wave. In conclusion, it was determined that Moku:Lab is viable for use at the undergraduate level based on a typical engineering program due to its ease of use, quality results, and applicability to coursework.
Moku:Lab expands the spectrum of tools a student has exposure to and enables a broader span of experiments and laboratories to be learned through experiential processes that create a positive impact on a student’s education. Moku:Lab’s ease-of-use, streamlined interface, and instrument variety all help to improve the overall learning experience.
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