Low-Velocity Flow Calibration Device
Precision calibration system for airflow sensors at velocities below 1m/s using rotational motion
Image represents the actual instrumentation developed for this project. Technical details have been abstracted for confidentiality purposes.
Challenge
Airflow sensors operating below 1m/s are critical for applications like building ventilation monitoring, clean room validation, and respiratory research, but they suffer from frequent drift requiring regular calibration. Creating controlled airflow at such low velocities is technically challenging - wind tunnels and conventional flow sources struggle with stability and uniformity at this range. Commercial calibration services are expensive and time-consuming, creating bottlenecks in research workflows. The challenge was to develop an in-house calibration system achieving high accuracy and precision at very low flow velocities.
Solution
Instead of generating controlled low-velocity airflow, developed a system that moves the sensor through stagnant air at precisely controlled velocities. This inverse approach provides superior accuracy by converting the challenging fluid dynamics problem into a straightforward precision motion control problem. Large-diameter rotational system with absolute encoding achieves the required velocity control while maintaining excellent accuracy.
Key Technical Features
- • Large diameter disk with square-slotted absolute encoder at edges
- • IR photo sensors creating high-resolution absolute position encoding
- • NEMA stepper motor with precision driver for velocity control
- • Microcontroller integration: encoder reading, position determination, motor control
- • Velocity and acceleration profile programming for smooth motion
- • Sensor mounting at controlled radius from rotation centre
- • Variable serial port supporting multiple sensor communication protocols
- • Rotary slip-ring system for cable management during rotation
- • Digital-only signals through slip rings (avoiding analog noise)
- • Enclosed upper section ensuring stagnant air conditions
- • Negligible air friction and turbulence at calibration velocities
- • Direct laptop connection for calibration software interface
- • Eliminates challenges of creating stable low-velocity airflow
Applications
Sensor Calibration
Precision calibration of low-velocity airflow sensors
Research Metrology
In-house calibration capability for research laboratories
Quality Control
Regular sensor validation without external calibration services
Sensor Development
Characterisation of prototype airflow sensing technologies