Neodyn 123P Series Pressure Switch / Internal Adjustment

A switch that compares the pressure being sensed to that of a perfect vacuum. Construction requires the reference chamber to be evacuated.

Compact, adjustable pressure switch for low to mid-range process applications. Efficient Nega-Rate ® Belleville disc spring for set point stability and vibration resistance. 316 stainless steel exterior and interior plus hermetically sealed, explosion-proof electrical for atmospheric protection. The flush mount (welded diaphragm) process connection makes this switch ideal for viscous process applications.


Stable Set Points – “Eliminates Constant Recalibration”

  • No moving parts except during actuation—no spring fatigue or wear.
  • Set point is mostly a function of the negative rate Belleville spring—variables in snap action electrical have little effect on the set point.
  • Total movement of the Belleville spring compensates for any relocation of the electrical due to case growth—consistent set point over temperature change.
  • No linkage utilized—no wear which can affect accuracy.

Vibration Resistant – “Eliminates Contact Chatter”

  • Belleville spring does not preload the electrical prior to actuation—snap action electrical maintains its vibration resistant characteristic.
  • Small mass and inherent stability of the Belleville spring resists chatter caused by vibration.
  • Snap action electrical is ruggedly mounted with minimal bracketry—no spring mounted electricals or linkages.

High Over-Pressure Capability – “No Affect on Set Point Accuracy”

  • Belleville spring does not contain the pressure—no affect on system or proof pressure capability.
  • The pressure sensing portion bottoms out after actuation and is fully supported—pressure sensing parts are designed for high pressure conditions.
  • Limited movement of spring mechanism—no overtravel of the snap action electrical due to high pressure.

High Cycle Lifer – “Millions of Cycle”

  • Short stroke minimizes wear—Belleville spring mechanism is exercised less than .020″.
  • Snap action of Belleville spring reduces electrical arc—prolongs contact life.


  • aerospace
  • general industrial
  • energy and chemical markets


Model Series

Adjustable Range Number Adjustable Set Point Range Deadband (approximate) Maximum Recommended System Pressure Proof Pressure
Increasing Decreasing
2 3 to 30 1 to 28 2 1350 2000
4 20 to 80 15 to 75 5 1350 2000
5 50 to 250 30 to 230 20 3000 5000
6 200 to 400 175 to 375 25 3000 5000
7 375 to 725 330 to 680 45 3000 5000
8 700 to 1500 620 to 1420 80 3000 5000
9 1500 to 2300 1400 to 2200 100 3000 5000

*All values given in psig.

Standard Specification

Model Explosion Proof Hermetically Sealed (NEMA 4X, 7, 9 and 13)
Electrical Snap action electrical switch assemblies, Part Numbers 057-0770 & 057-0772 (Form C) and 057-0771 & 057-0773 (Form CC), are listed by Underwriters’ Laboratories, Inc., FM Approvals, CSA International and NCC (INMETRO). See the miscellaneous option N for additional listings
Electrical Connection 1/2 NPT male conduit connection with PVC insulated 18 AWG, 18” long leads
Pressure Connection 1/2 NPT Female
Ambient Temperature Range – 40°C to + 82°C
Media Temperature Range – 40°C to + 121°C
Adjustment Internal, slotted adjustment nut with range scale
Shipping Weight Approximately 2.5 pounds


Neodyn 123P Series Pressure Switch Internal Adjustment

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