Capacitance is the ratio of the change in an electric charge to the corresponding change in its electrical potential (i.e., voltage). Capacitors, components that that have the “capacity” to store an electric charge, consist of conductive parallel plates that don’t touch or connect with each other. Instead, these metal plates are electrically-separated by air or a layer of insulating material (i.e., the dielectric).
MTI’s technology is based on the principles of parallel plate capacitor measurement and uses a probe as one of the plates and a grounded target as the other. The electrical capacitance that’s formed between the probe and the target varies as a function of the distance (gap) between these two surfaces. An amplifier converts the capacitance of the gap into an output voltage that’s proportional to the gap.
Because capacitance doesn’t require physical contact between the sensor and the target, there’s no mechanical loading, probe or target wear, or target distortion. Capacitive probes also cost significantly less than laser interferometers while matching or exceeding them in terms of stability, precision and resolution.
Importantly, capacitive probes provide reliable performance in extreme environments. For example, they can withstand temperatures as high as 1200°F (650°C) and as low as 4°K (-269.15°C). Capacitive probes also work in very strong magnetic fields (2 Tesla) and operate under vacuum conditions (10-7 Torr). They withstand humidity, too.
Now that you know some basics, it’s time to examine uses and applications. You’ll also benefit by reading MTI’s case studies from different industries. Before using capacitance for your own application, however, you need to account for design considerations. Comparing the capacitance measurement systems that are available from MTI Instruments can also support your efforts.