Sensors used for electronic digital caliper are mainly grating sensors, electromagnetic induction sensor (including inductosyn, (self , mutual ) inductance sensors, eddy-current sensors, etc.), capacitive sensors and gate magnetic sensors.
These various sensors have their own advantage and disadvantage. Grating sensors had been used in digital caliper in the 70’s of last century. It’ not practical because of its strict requirements for the work environment. Capacitive senors have fewer requirements for the work environments and therefore are most widely used for digital calipers at present. The prototypes of digital calipers made of eddy-current sensor or inductosy sensor in the late 90’s of last century failed to be commercialized due to its low accuracy and high power consumption. Digital calipers made of gate magnetic sensor at the beginning of this century failed to become the most ideal digital caliper due to its being easily magnetized by strong magnetic field.
At present, most digital calipers in the markets are made of capacitve sensor with incremental encoding system. Such digital calipers have the shortcomings of poor reliability and non-waterproof.
The latest design of IP67 digital caliper with absolute encoding system is made of special electromagnetic induction sensor. Its absolute encoding system is also specially designed. Japanese absolute encoding system adopts 2 encoding. The pitches in the 2 encoding are unequal. The absolute displacement is calculated by the pitch differential value. High accuracy for the 2 encoding is required. Otherwise there will be calculation errors.Our IP67 digital caliper adopts 2 encoding or more encoding. But the accuracy is decided by only one of its 2 encoding and will not be affected by other encoding. This reduces the difficulty and cost of manufacturing. At present, it’s the world’s cheapest and most reliable waterproof digital caliper made of electromagnetic induction sensor with absolute encoding system.