PS61 switch: Piston vs. Diaphragm - Benefits in high pressure high cyclical applications.

The PS61 Pressure Switches are available in two versions: Diaphragm and Piston.  The major differences between the two are the different methods that Gems uses to seal off the fluids or gases on the customer’s side of the pressure switch. 

  • The Diaphragm style is much like a flat disk and is perfect for general use as well as heavy duty applications.  It is designed to hold both oils as well as gases.   
  • The Piston style is more like a donut shape that seals the oils inside the switch and is geared towards high cycle/high pressure applications like Off-Highway Vehicles, Transportation and Alternative Energy.  The Piston style works excellent with oils but does not seal well against gases.



What are the differences? 

Most specifications (current capability, temperature ranges, shock & vibration, environmental sealing, etc.) for both versions are the same.  The exceptions are:   


Diaphragm Style 

Piston Style 

Recommended Media (fluids) 

Liquids & Gases 

Liquids Only 

Wetted parts options, elastomers 

Nitrile, FVMQ, FKM, EPDM 

Nitrile, FKM, EPDM 

Wetted parts options, housing 

12L14 Zinc-Plated Steel or 316 Stainless Steel 

12L14 Zinc-Plated Steel 

Set point range 

10 to 1,350 psi 

0.7 to 93 bar 

510 to 4,350 psi 

35 to 300 bar 

Proof pressure 

6,000 psi 

414 bar 

7,000 psi 

483 bar 

Burst Pressure 

9,000 psi 

620 bar 

22,000 psi 

1,517 bar 


Small to medium range 

Wide range 


Small range 

Medium range 

When would I use each one? 

When you have many options on which version of the PS61 Pressure Switch to choose from, it can be challenging.  The chart below can assist you in the decision-making process: 

Pressure Set Point 


Deadband Requirement 

Proof Pressure 

Gems Pressure Switch  

Web Link 

< 510 psi < 35 bar 

Liquid or Gas 


< 6000 psi 

< 414 bar 

PS61 w/ Diaphragm 

<1350 psi 

<93 bar 

Liquid or Gas 


< 6000 psi 

< 414 bar 

PS61 w/ Diaphragm 

> 510 psi 

> 35 bar 



< 7000 psi 

< 483 bar 

PS61 w/  


> 510 psi 

> 35 bar 



< 6000 psi 

< 414 bar 

PS71 (PS61’s are not rated for use with gases with set points over 510 psi / 35 bar) 



Other notable BLOG's: