FEMA VCM / VNM negative pressure switches or vacuum pressure switches detect the pressure difference relative to atmospheric pressure. All specifications for switching pressure ranges, as well as the scale markings on the devices, should therefore be understood as the pressure difference between atmospheric pressure and the set switching pressure. The “zero” point on the scale represents the current atmospheric pressure. The switches are housed in robust, seawater-resistant die-cast aluminum enclosures. On VCM models, the switching differential is fixed and cannot be adjusted, whereas VCMV types offer an adjustable switching differential. Both VCM and VNM pressure switches are calibrated for falling pressure, meaning the set value on the scale corresponds to the switching point as the pressure decreases.

Features and Benefits:

• Vacuum pressure switch calibrated for falling pressure
• Wide control range
• SIL2 approved according to IEC 61508-2

Documentation: