Trace Mechanism or Snap-Action - What's in Your Pressure Switch?

Complex systems and processes can use either a trace or a snap-action switch to provide an electrical response to the rise or fall in pressure or temperature. System pressures and temperatures rarely follow a smooth pattern of rising and falling. The switches used to track and control the system are subject to those fluctuations, as illustrated in the following graph.

Deciding whether to use a snap-action design is critical to your switch's efficiency, accuracy, and longevity. This video will cover key differences between each device and how they apply to the switch operation. 

What is the difference between a trace switch and a snap-action switch? 

In their simplest form, pressure switches have two components: a mechanism that reacts to a change in pressure and an electrical switch (sometimes called a micro-switch). When the pressure or temperature reaches a certain level (the set-point), the mechanism moves to actuate the switch. This process can either allow or stop currents in the control circuit.

What is a Trace Mechanism?

Common alternative mechanisms to snap-action devices are trace designs, also known as spring-based mechanisms. Switches with a trace mechanism follow or trace the exact pattern of pressure or temperature changes. These trace devices can include a helical spring or spiral spring, a Bourdon tube, or bellows in their mechanism. 

A spring-based trace switch mimics the pattern of changes even after reaching set-point. The mechanism and micro-switch are in constant motion when there are changes in pressure in the system. This continual movement wears on the components of the instrument and electrical switch. And over time, it causes the set-point to drift from the original setting to fatigue and the mechanism's failure. 

What is a Snap-action Mechanism?

Unlike trace switches, a snap-action mechanism remains inactive during system pressure and temperature changes. Upon reaching the set-point, the snap-acting disc immediately reacts to activate the switch. Eliminating this continuous motion until the point of activation and deactivation can reduce the mechanism and switch element wear, extending its duration. 

Snap-action designs are the premium type of switch on the market. They can perform 10 million cycles or more due to the components' low fatigue, including the micro-switch. 

While trace and snap-action pressure and temperature switches may perform the same function, understanding the difference in their movement and precision explains why quality-minded people prefer snap-action controls over other designs. Trace designs fatigue the mechanism and the internal micro-switch through constant motion. Snap-action switches use an innovative snap-action disc spring that remains still despite fluctuations until action is needed. 

CCS pioneered the Dual-Snap, snap-action disc used to provide accurate and reliable pressure and temperature measurement under every operation. For more information on CCS pressure and temperature switches in Virginia, contact Automatic Controls of Virginia.

Automatic Controls of Virginia
(804) 752-1000