A solid-state, open-system, differential calorimeter.

This article details the design, modeling, construction, and evaluation of an open system calorimeter that operates in a normal room environment to measure endothermic or exothermic events in a system subjected to a steady heat flux. The calorimeter is unique because it allows the measurement of energy and power from an "open" system, where a heat flux enters and leaves the calorimetric boundary in a well-controlled manner. It is also novel because it utilizes a solid state heating and cooling assembly that acts as an electronic heat reservoir. The system is capable of measuring power levels from a few milliwatts to several watts, and it has been designed and optimized to be nearly immune to variations at ambient temperature and room airflow. The calorimeter was modeled using lumped parameter electrical-thermal equivalent circuits in SPICE software. This modeling in the electrical domain led to the use of a mathematical correction factor that mitigates mismatches in thermal conduction paths between an active and a passive cell as well as correcting differences in the sensitivities of the flux sensors employed for heat flow measurement. After obtaining a viable design, a prototype was constructed and validated with precise input power delivered via electric joule heating of a resistive element.

An open circuit voltage decay system for performing injection dependent lifetime spectroscopy.

Of all of the material parameters associated with a semiconductor, the carrier lifetime is by far the most complex and dynamic, being a function of the dominant recombination mechanism, the equilibrium number of carriers, the perturbations in carriers (e.g., carrier injection), and the temperature, to name the most prominent variables. The carrier lifetime is one of the most important parameters in bipolar devices, greatly affecting conductivity modulation, on-state voltage, and reverse recovery. Carrier lifetime is also a useful metric for device fabrication process control and material quality. As it is such a dynamic quantity, carrier lifetime cannot be quoted in a general range such as mobility; it must be measured. The following describes a stand-alone, wide-injection range open circuit voltage decay system with unique lifetime extraction algorithms. The system is initially used along with various lifetime spectroscopy techniques to extract fundamental recombination parameters from a commercial high-voltage PIN diode.

A 500 A device characterizer utilizing a pulsed-linear amplifier.

With the advent of modern power semiconductor switching elements, the envelope defining "high power" is an ever increasing quantity. Characterization of these semiconductor power devices generally falls into two categories: switching, or transient characteristics, and static, or DC characteristics. With the increasing native voltage and current levels that modern power devices are capable of handling, characterization equipment meant to extract quasi-static IV curves has not kept pace, often leaving researchers with no other option than to construct ad hoc curve tracers from disparate pieces of equipment. In this paper, a dedicated 10 V, 500 A curve tracer was designed and constructed for use with state of the art high power semiconductor switching and control elements. The characterizer is a physically small, pulsed power system at the heart of which is a relatively high power linear amplifier operating in a switched manner in order to deliver well defined square voltage pulses. These actively shaped pulses are used to obtain device's quasi-static DC characteristics accurately without causing any damage to the device tested. Voltage and current waveforms from each pulse are recorded simultaneously by two separate high-speed analog to digital converters and averaged over a specified interval to obtain points in the reconstructed IV graph.

An evaluation system for experimental silicon and silicon carbide super gate turn off thyristors.

This paper describes the design and implementation of a small-scale pulsed power system specifically intended to evaluate the suitability of experimental silicon and silicon carbide high power Super Gate Turn Off thyristors for high action (500 A(2) s and above) pulsed power applications where energy is extracted from a storage element in a rapid and controlled manner. To this end, six of each type of device was placed in a controlled three phase rectifier circuit which was in turn connected to an aircraft ground power motor-generator set and subjected to testing protocols with varying power levels, while parameters such as offset firing angle were varied.

Automated modular high energy evaluation system for experimental thyristor devices.

A high energy, modular, completely automated test bed with integrated data acquisition and characterization systems was successfully designed in order to perform both safe operating area as well as very high volume reliability testing on experimental silicon carbide Super Gate Turn Off (SGTO) thyristors. Although the system follows a modular design philosophy, with each functional block acting as a peripheral to a main control module and can be adapted to arbitrary power and pulse width levels, for the specific SGTO devices initially evaluated it was configured to have the device discharge variable current levels of up to 6 kA into a 0.5 Ω resistive load with a relatively square pulse fixed at 100 µs full width at half maximum delivering energy levels up to 1.8 kJ to the load.

Haptic controlled three-axis MEMS gripper system.

In this work, we describe the development and testing of a three degree of freedom meso/micromanipulation system for handling micro-objects, including biological cells and microbeads. Three-axis control is obtained using stepper motors coupled to micromanipulators. The test specimen is placed on a linear X-stage, which is coupled to one stepper motor. The remaining two stepper motors are coupled to the Y and Z axes of a micromanipulator. The stepper motor-micromanipulator arrangement in the Y and Z axes has a minimum step resolution of ∼0.4 µm with a total travel of 12 mm and the stepper motor-X stage arrangement has a minimum resolution of ∼0.3 µm with a total travel of 10 mm. Mechanical backlash error is ∼0.8 µm for ∼750 µm of travel. A MEMS microgripper from Femtotools™ acts as an end-effector in the shaft end of the micromanipulator. The gripping ranges of the grippers used are 0-100 µm (for FT-G100) and 0-60 µm (for FT-G60). As the gripping action is performed, the force sense circuit of FT-G100 measures the handling force. This force feedback is integrated to a commercially available three degree of freedom haptic device (Novint Falcon) allowing the user to receive tactile feedback during the microscale handling. Both mesoscale and microscale controls are important, as mesoscale control is required for the travel motion of the test object whereas microscale control is required for the gripping action. The haptic device is used to control the position of the microgripper, control the actuation of the microgripper, and provide force feedback. A LABVIEW program was developed to interlink communication and control among hardware used in the system. Micro-objects such as SF-9 cells and polystyrene beads (∼45 µm) are handled and handling forces of ∼50 µN were experienced.