Capacitance and Point Level Measurements
Capacitance switches are also contact instruments, but they measure the capacitance, or the medium’s ability to hold an electrical charge. These types of switches can be used with both conductive or non-conductive liquids and solids and are looking for step changes in standing capacitance, measured in picofarads.
To create a capacitor, two plates are needed. The capacitance changes when the distance between those two plates changes, the size of the plates changes, or the product’s dielectric changes. Once the liquid or bulk solid being measured reaches the area between the two plates, the capacitance changes, and the switch output changes state.
These types of switches require more of a set-up than their vibrating counterparts. These instruments must be installed and set up in process to see the different states expected for changes. These switches need to know the different capacitance values for a vessel that’s full and a vessel that’s empty.
Point level detection without a probe
The two technologies discussed so far both involve a probe touching the material being measured. That’s not the case for microwave barrier and radiometric switches. Both of these technologies use a beam of sorts, and once that beam is broken or interrupted, the switch is activated. This also means both of these technologies use two different parts – a transmitter or source from where the beam originates and a receiver. Both technologies can be used for liquids and solids, and each are non-contact.