Jeff Hulett

Jeff Hulett is the Founder and CTO of Vektrex Electronic Systems, Inc. Because of his vision and leadership, the company grew from a start-up to the market leader. Currently, Hulett is the Chief Architect for Vektrex products placing the highest emphasis on technology and quality. Hulett holds a BSEE from the Illinois Institute of Electronics, and has been awarded four U.S.patents. He is a member of the Illumination Engineering Society of North America (IESNA), and chairs the IESNA LM-80 working group that is focused on LED flux maintenance testing. He has been active in the LED testing and reliability field since 2004. Some important research is found on this page. You may also visit the info page for additional research activity

Use Fast Precise Pulsed SMU to Characterize LED Droop: LED products are typically characterized using methods that increase device heating. These outdated methods, using DC current, long pulses or staircase sweeps result in temperature droop.

✎ Amber LED Light Research: Vektrex amber LED light research project identified and confirmed a light measurement anomaly.  The Instrument Systems CAS-140D, in conjunction with Vektrex pulsed SMU, has allowed us to confirm an amber LED measurement anomaly that was discovered during this research in 2019. 

✎ I-V Curve Tracing for Transistors: IV curve tracing for transistors can best be accomplished using Vektrex precision source measure units. The application is a semiconductor device test and the device is a transistor.

✎ Use Fast Precise Pulsed SMU to Improve High-Power IV Characterization: Devices such as lasers and LEDs are characterized by plotting the forward current vs voltage for the device’s typical operating range – for example from 10% of maximum current to maximum current. The output data is used as input to marketing for development of datasheets.

✎ Application Note: Laser Diode Power Supply Transient Response Under Typical Laser Diode Fault Conditions: Semiconductor laser diodes are often tested under stress conditions. When a laser fails, it can suffer catastrophic damage if the power supply does not have a failsafe to shut down power to devices in the event of a failure.

📰 The Industry Needs Better LED Measurements: Three hundred years ago global navigation was a dangerous undertaking. Ships sailing east and west had to determine their longitude by a tedious method known as dead reckoning. Errors were commonplace and calculations were typically off by a few percent at the end of a long voyage – often enough to make landing in port or on a rocky reef equally likely.

📰 Is Your Light Measurement Method Undervaluing Your LEDs?: The LED industry is facing a roadblock that threatens its continued rapid evolution. Heating effects are making it nearly impossible to accurately measure the performance of new LEDs. 

▶️ Video: Three Steps to Improved LED Light Measurements: Repeatability: This segment of our webinar series discusses which factors must be controlled for optimal repeatability and gives examples of what to look for and what to avoid in your measurement equipment.

▶️ Video: Three Steps to Improved LED Light Measurements: Accuracy: Once you have the capability to use all three measurement methods, the question becomes: which method will yield the most accurate measurements? Vektrex engineers conducted an L-I sweep with the Osram LY W5SM-GZJX-46-0-400-R18-Z Yellow LED using each of the three methods. 

▶️ Video: Three Steps to Improved LED Light Measurements: Power: The three steps to improved LED light measurements begin with power. Jeff Hulett, Vektrex CTO, teaches how to identify current source power limitations that may negatively impact your LED light measurements.

✎ Measuring LED Junction Temperature (Tj): In this technical article, Jeff Hulett dives into the details of measuring junction temperature (Tj). He covers relevant standards, equipment, equations and more.

📰 Improved Photometric Testing for High-Power LEDs: Photometric testing standards first appeared in the late 1800’s; they were needed by the emerging gas lighting industry. 

✎ LM-85 Light Measurements for High Power LEDs: LM-85 is an Illuminating Engineering Society (IES) approved method for the Electrical and Photometric Measurements of High Power LEDs.