The suction lance is designed to continuously measure and display a value (the solution level) on the pump display, in percent or litres. This device needs to be coupled with the appropriate diaphragm metering pump or peristaltic metering pump. This suction lance works very well with feed chemicals containing a lot of water, such as diluted acids and alkalis, sodium-calcium hypochlorite. The dielectric constant εr must be higher than 30. It does not work with feed chemicals, such as pure oil or fats.