Both measurement methods can be used to measure the distance between the torch and the work piece. However, there are differences between the two methods and they both have advantages and disadvantages that I would like to briefly explain.
The first question is, am I cutting dry or under water? With a capacitive sensor, I can cut only dry as otherwise it is the distance to the water surface that is measured and not the distance to the workpiece. With an inductive sensor, the water has no effect on the measurement.
A good capacitive sensor (such as one from the IHT range) is both more accurate and more robust than an inductive sensor. Measurement accuracy is higher and the influence of temperature on the measurement is lower. Using an inductive method the cost of additional temperature compensation is very high.
With a capacitive sensor I can automatically prevent a collision of the burner with the workpiece or any slag that has been produced; this is not possible with an inductive sensor.
In summary, both measurement methods have their place but when oxy-fuel cutting, the capacitive method is always preferred. The only exception is when cutting underwater.