Macro Sensors (Pennsauken, NJ) offers the HSIR Series LVDT linear position transmitters that can serve as level sensors to measure liquid level changes from a few inches to several feet in gauging tank level volumes when configured with a float. In this configuration, a stainless steel float coupled to a nonmagnetic stainless-steel rod is attached to the armature core of the LVDT. The 4- to 20-mA loop-powered position transmitter senses the position of the core and, therefore, the level of the float. Sensitivity to the change in level depends on the length of LVDT.
As water level changes, the float moves up or down, raising the LVDT core along with it. A threaded stainless steel rod that protrudes from the other end of the core carries two jam nuts that are used to adjust the position sensor output at the desired low water level.
Core position is sensed using magnetic induction. Electronics of the LVDT are hermetically sealed inside a stainless steel housing for protection against water and other environmental elements. A Teflon liner inside the bore minimizes any friction to core motion. As there are no springs to fatigue or parts to wear out, the LVDT sensors are nearly friction-free.
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