Liquid Level Sensors

Liquid Level Sensor


For many applications there is a need for a device to detect the presence or level of liquid in a process tank. In the Semiconductor and other high tech manufacturing environments, this device needs to withstand many different types of chemistries, sometimes at very high process temperatures. They must be reliable and must not pose a risk of contamination. The LLS-100 system is ideal for virtually all liquid level sensing requirements commonly used in the semiconductor and related industries.

Theory of operation

With the pressure regulator set between 5-7 PSI, a small volume of N2 flows through the supplied ¼” PFA tube which is terminated at the desired level sense height of the process tank. When liquid is present at the end of the tube the resulting back pressure activates the pressure differential switch and the electrical contacts close. If no liquid is present there is insufficient back pressure to activate the switch.

This pressure differential type sensing system is very flexible in that it can be set to work with all kinds of chemistries at varying temperatures. It has no moving parts or electronics in the process area and nothing comes in contact with the process except the PFA PTFE tubing and the nitrogen you supply. This type of sensor has been used for decades in the Semiconductor industry and has proven to be extremely reliable.


8 x 4 x 4 inches
N2 Supply
10-15 psi static
No electrical supply required.
Normally open
(closed when liquid is present)
dry contact switch.
Contact rating, 125VAC
or 250VAC, 10 amperes.
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