A tridelta pressure switch is a mechanical device that activates once a certain threshold or setpoint is reached. They consist of a Bourdon tube, piston, or diaphragm that moves or deforms to actuate the switch when fluid pressure exceeds or drops below a preset pressure level.
Several factors influence pressure switch accuracy. These include:
Accuracy
The accuracy of a tridelta pressure switch refers to its ability to correctly detect an increase or decrease in process pressure and actuate at the correct point. This is often called the switch’s adjustable range or working pressure range. The switch should be operated in the upper half of its operating range for optimal accuracy. This will allow for greater accuracy and a longer switch life.
Depending on the type of pressure switch, there are many different ways that it can achieve this level of accuracy. Diaphragm switches use a weld-sealed diaphragm to activate the switch, while Bourdon tube switches have a weld-sealed Bourdon tube that actuates the switch.
Electronic pressure switches utilize an internal sensor to actuate the switch when they detect an increase or decrease in process pressure. The internal sensor can be either electronic or mechanical. Electronic sensors can provide greater accuracy and are more reliable than mechanical devices, but they may be susceptible to electromagnetic interference.
Repeatability
Pressure switches are a vital safety device in gas furnaces to ensure the inducer motor is running at the correct RPM and creating the proper vacuum to flue safely. These simple devices detect a change in pressure through the compression of a diaphragm and are available in various sizes to suit various applications. They are also available in Ex versions for potentially explosive areas and SIL-tested versions for safety-critical systems.
When choosing a pressure switch, it is essential to look at repeatability. This describes how accurately the switch can be switched with a repeated approach to a pressure value, for example, 1%.
Traditionally, this was tested by increasing and decreasing the set, resetting pressure with a pump, and using a DMM to verify continuity. However, new tools are now available, making this task much more accessible. These allow you to quickly and automatically capture the left-hand data and upload it directly to your calibration management system.
Temperature Range
A pressure switch monitors liquid and gaseous media’s overpressure, vacuum, or differential pressure. The Pressure Equipment Directive (PED) also uses it for safety functions.
A mechanical pressure switch is triggered when the pressure forces on a diaphragm compress the calibrated spring. This activates the contacts in a NO switch or opens them in an NC switch and signals a signal to open or close the processing circuit.
Electronic pressure switches replace mechanical switches and provide more information than the analog signal they generate. They offer local LED displays, allowing users to see trends quickly. They are also more reliable than mechanical switches and will not suffer the same fatigue or mechanical wear associated with many switching cycles. They can be programmed to reset their tridelta pressure switch points on demand and can better prevent oscillations in the system. This is because they do not have the same physical moving parts.
ATEX/IECEX Rating
Our most popular pressure switch, the Series AT-1900, is now available in an ATEX/IECEX flameproof package. This compact, low-difference switch is an excellent solution for alarm, shutdown, or process control in hazardous areas with limited space and compatibility.
It uses a diaphragm to detect pressure that compresses a calibrated spring. When the pressure reaches or exceeds the set point, it closes the contacts in an NO or NC switch. The electrical contacts then allow current to flow, providing an output signal.
Solid-state pressure switches do not experience fatigue or mechanical wear, unlike electromechanical switches. This makes them able to deliver a much higher number of life cycles than their counterparts. Moreover, electronic pressure switches can be connected to a display that helps provide local indication and system trending, thus eliminating the need for costly analog pressure gauges.
