Programmable System-on-Chip (PSoC) Embedded Readout Designs for Liquid Helium Level Sensors.

Area of Science:

• Cryogenics
• Sensor Technology
• Embedded Systems

Background:

• Accurate measurement of liquid helium levels is crucial for cryogenic applications, particularly in sensitive equipment like magnetoencephalography (MEG) systems.
• Traditional methods can be complex or expensive, necessitating simpler, more reliable alternatives.

Purpose of the Study:

• To develop a cost-effective and reliable embedded readout system for liquid helium level sensing.
• To utilize programmable system-on-chip (PSoC) technology for integrating multiple functions onto a single chip.
• To implement a resistive liquid vapor discrimination method for accurate level detection.

Main Methods:

• Designed a PSoC-based system incorporating a constant current source, multiplexer, buffer, and analog-to-digital converter (ADC).
• Employed three carbon resistors as cost-effective sensors placed at specific heights within a helmet-shaped cryostat.
• Utilized localized electrical heating of resistors to differentiate between immersion in liquid helium versus its vapor based on heat transfer rates.

Main Results:

• Successfully developed a single-chip PSoC solution for driving sensors, acquiring data, and displaying the liquid helium level.
• Demonstrated the effectiveness of resistive liquid vapor discrimination using temperature-dependent resistance of carbon resistors.
• The system provides a cost-effective and reliable method for inferring liquid helium levels.

Conclusions:

• The PSoC-based embedded readout system offers a significant advancement in cost-effective and reliable liquid helium level measurement.
• This design is well-suited for integration into specialized cryogenic environments, such as those used in magnetoencephalography.
• The use of simple carbon resistors and PSoC technology simplifies the sensor readout design, enhancing its practicality.