Walla Walla University: Chaos, Robots, & DC Machines
The labs and research environments at Walla Walla University (WWU) received a boost in 2011 from a donation of seven 2530B digital storage oscilloscopes to the Physics department, and a Model 8500 DC electronic load to the Engineering department, to help further their academic studies and research.
During the winter quarter of each academic year, the Physics Department at WWU offers a number of labs ranging in complexity from general science to nanotechnology. To help more than 120 students learn in these labs, the WWU Physics Department replaced their former oscilloscopes with B&K Precision’s 2530B digital storage oscilloscopes and have since discovered great features they now can’t do without.
Shortly after delivery and setup of the 2530Bs, students taking a lab in Experimental Physics studied chaos in an electrical circuit. Normally, they would plot voltage as a function of time and observe the peaks in the voltage change as a function of the chaotic nature of the circuit. The students were slowly collecting data using this method until one of the students asked Dr. Tom Ekkens, Chair of the Physics Department, if he could explain why the output on his 2530B display looked the way it did. The student had accidentally switched to X-Y mode, which changed the measurement of the level of chaos to counting the number of loops on the screen. Dr. Ekkens changed the requirements of the lab right away and directed all the other students to set their oscilloscopes up the same way. “Our older oscilloscopes can do X versus Y, but the image quality changes, so it is hard to use,” said Dr. Ekkens. The use of the B&K Precision 2530B in this mode allowed the lab to be completed in record time and gave students a better understanding of chaos.
Demonstrating the Chaos Butterfly Effect using X-Y mode on one of the 2530B digital storage oscilloscopes.
WWU’s Robotics Club also utilized the new 2530B DSOs for their quad-copter project, which consisted of four motors controlled by a microprocessor. The problem that the members of the club encountered early on was the uncertainty of what signal the microprocessor should be sending the motors. Using a 2530B DSO, they were able to easily capture the voltage profile from a standard RC controller and determine what the correct output signals were for their microprocessor to control the four motors. In particular, the team found the feature to save their waveform data directly to a flash drive extremely useful. “It is something that our old oscilloscopes do not have and something we use all the time now,” stated Darryl Masson, senior physics major and president of the robotics club at WWU.
Students testing with a pair of 2530B digital storage oscilloscopes.
School of Engineering
The WWU School of Engineering’s Electromechanical Energy Conversion class covers practical applications of electromagnetics with emphasis on the fundamental types of electric machines. The class includes laboratory exercises covering magnetic circuits and materials, synchronous and induction AC machines, and DC machines. In one laboratory session on DC machines, the students performed a load test on a small 175 W DC machine operated as a cumulatively compound generator, taking it well into the overload region. Because of the overload, it was necessary to obtain measurements efficiently to avoid overheating. Using pre‐calculated values of load resistance, the B&K Precision 8500 DC electronic load made this task easy.
Students were instructed to obtain voltage, current, resistance, and speed data for a load test by increasing the load (dropping the electronic resistance). Starting from about 1000 Ω, resistance was dropped by a factor of one‐half in multiple steps down to 125 Ω. From there, students used log spacing for about 10 values down to about 40 Ω. For the lower resistance loads, both the driver and the generator will be in significant overload, so it was necessary for students to pre‐calculate the resistance values to minimize the length of time to get the data. “After one demonstration of setting a resistance value on the Model 8500, all students proceeded without further hesitation or questions,” stated Dr. Carlton Cross, Professor Emeritus of Engineering at WWU. “As compared to passive resistive loads, the lack of thermal variation in the resistance value contributed to the efficiency of the data collection since there was never a need to wait for thermal equilibrium.”
The protective features of the 8500 DC load also prevented damage in a few cases of reversed polarity and potential overload, which are common hazards when testing DC machines. Dr. Cross expects other functions of the DC electronic load to be useful such as constant voltage and constant current modes, and will be exploring other laboratory activities in this class to take advantage of the 8500’s capabilities.
One of three stations in the Electromechanical Energy Conversion Lab.
The B&K Precision 8500 DC Electronic Load is connected to a LabVolt 8211‐00 DC Motor / Generator,
driven by LabVolt 8221‐00 Four‐Pole Squirrel‐Cage Induction Motor.
Walla Walla University
Founded in 1892, Walla Walla University is a fully accredited private university affiliated with the Seventh-day Adventist Church. Walla Walla University offers more than 100 areas of study in liberal arts, professional, and technical programs and has an enrollment of 1,800 students.