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RoadTests & Reviews

12 Posts authored by: neuromodulator
Introduction  The modulation capability of the instrument virtually turns the instrument into a voltage amplifier with gains of 0.5, 1 or 2. As previously shown in the regulation tests, during modulation the instrument samples the input signal at 1 kHz. To show the modulation feature applied to a more realistic application I decided to use it to build a temperature control system     Setup  The system was made of a beaker filled with ~300 ml of water whose temperature was r ...
Introduction  To explore the regulation capabilities of the SMU I performed a few tests to see how it behaved in voltage priority mode (VPM), current priority mode (CPM), and in the (voltage) modulation mode. Let's briefly explain what all this modes are. VPM is the standard operation mode of power supplies, in this mode, the SMU starts in constant voltage (CV) (i.e., the SMU control loop regulates the voltage), so there is very little voltage overshoot. The SMU stays in CV unless the curr ...
Solar Cell Characterization (Workflow Comparison) Solar or photovoltaic cells are devices that convert light energy into electric energy through the photovoltaic effect. Optimizing power conversion from solar cells is not trivial because of the shape of the I/V curve:       Parameters that define the I/V curve of a solar cell for a defined light condition are the short circuit current (Isc), the open circuit voltage (Voc) and the maximum power (Pmax), which is the power at Vma ...
Introduction  A Peltier device is a solid-state heat pump that transfers heat from one side to the other. The heat transfer simultaneously reduces the temperature at one side of the device and increases it at the other side, generating in this way a temperature gradient across the sides of the device.   Peltier cooling is not efficient compared to vapor-compression refrigeration, but Peltier devices have the advantage of being small, having a long life, no moving parts, making no noi ...
Introduction  DC-DC converters are devices that convert a source at one DC voltage into another. They can be classified in many ways, such as between linear and switching, step-up and step-down, based on their topology, and so on. Depending on the application one may prioritize different figures of merit. For instance, for IoT applications the efficiency is one of the most critical figures, as it affects the life of the battery, while for other applications, the quality of the output could ...
Introduction  Properly optimizing energy consumption of battery powered microcontrollers is fundamental to extend the battery life. Questions like when it is better to keep the device idling and when to enter light- or deep-sleep cannot be answered without measuring the power consumption during those sleep modes and the time and energy overhead of entering those modes. Likewise similar measurements are required to evaluate when it is better to stay connected to the WiFi, and when to discon ...
3.6 Remote monitoring  Here I will show how the Keithley 2450 (but also any other TSP-enabled Keithley instrument) can be used to measure and record data to a centralized server. This could be useful in a production setting were instruments measure components to ensure compliance to the manufacturer's specifications, or to continuously measure sensor data. The TSP scripting engine, implemented in Keithley's newest instruments, allows them to operate in a stand-alone way, completely elimina ...
3.5 Capacitor Characterization  An ideal capacitor can be specified by a single value: its capacitance. Here I will show how I measured 2 capacitor non-idealities: the dielectric absorption and the dielectric leakage.  Dielectric absorption is an effect caused by the "alignment" and the "dealignment" of the molecular dipoles of the capacitor dielectric caused by the application of an electric field. While dielectric leakage is the current that crosses the capacitor dielectric and slow ...
3.4 LEDs 3.4.1 Steady state LED I-V curve variability 3.4.2 LED step-stress and I-V characterization     3.4 LEDs  Diodes are two-terminal electronic devices that facilitate current conduction in one direction and block it in the opposite direction. Their electrical characteristics can be described by the Shockley diode equation which defines the relationship between current and voltage across a diode:     Where: I is the diode current. Is is the reverse bia ...
3.3 DC-DC converter efficiency measurement   The use of DC-DC converters has become almost universal in modern electronics. One important factor that needs to be evaluated, especially when the power comes from a battery, is the conversion efficiency.   I decided to evaluate a MAX 17503 step-down DC-DC converter evaluation board efficiency at an 8 Ω load. The SMU was connected to the DC input of the converter, and a Keithley DMM6500 to the output. By dividing the output power (wh ...
3.2 Battery Characterization   Battery selection for a specific application can depend on multiple factors: price, size, weight, safety and its electrical properties. Manufacturers are known for making dubious claims about their batteries lifetime and capacity, so the proper way to evaluate a battery is to characterize it.   Batteries are complex electrochemical devices that do not behave as constant voltage sources (Figure A). Their terminal voltage depends on the amount of charge in ...
3.1 Solar cell characterization (worflow comparison) 3.1.1 Front panel 3.1.2 Web remote control 3.1.3 KickStart 3.1.4 I-V tracer app 3.1.5 Remote control 3.1.6 Standalone script     3.1 Solar cell characterization (worflow comparison)  Solar or photovoltaic cells are devices that convert light energy directly into electricity. The shape of the solar cell I-V curve makes the maximization of the output power an important goal to maximize the efficiency of ...

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