Ultrasonic Distance Sensor

Requirements

• 1mm accuracy optimal, 3 mm is absolute max
• Open source version of http://www.cnccontrols.com/thcontrol.asp - 20-250 mm range for pointing to metal, with no obstructions

Tech Support

• Sparkfun has them - [1]. Online chat at https://www.sparkfun.com/technical_assistance

YouTube

• Ultrasonic sensor on plasma table - [2]

R&D

• Making a better HC-SR04 distance sensor - Emil - [3]

Selection

• Maxbotics - 1 mm resolution options, not water protected - 12" minimum distance - $40 - [4]. Adafruit has it.
• Microptik - 3 mm resolution - http://www.micropik.com/PDF/HCSR04.pdf - 2-400 cm range - services@elecfreaks.com. Sample Arduino sketch - [5]
• HC-SR04 - appears to get 3 mm accuracy - [6]. Sparkfun has the sensor + code - [7]

• Video shows 15 cm measurement, with oscillation +- 1mm - and text says well within 2% accuracy. 2% of 15 cm is 3 mm - so this would do for measurements of torch height for 1/2" steel easily (12 mm thickness).

Comparisons

• http://www.robotshop.com/en/compare-infrared-ultrasonic-distance-sensors.html

Explanation

• Nice video - [8]

Sourcing

• 4-30 cm - $99 - [9]
• 1-100 inch - $25 - [10]
• $4 Sparkfun - 6"-10' - [11]
• $6 - .5 cm accuracy - [12]