We distribute the Delta range of mechanical switches, supplied by Delta Controls Ltd in England, and the Dewer electronic pressure switch from Canada. These are both designed for process applications.

Pardon us for stating that most pressure switch enquiries are poorly specified. Our policy in such cases is to specify default values where no requirement has been stated, which puts the burden on the purchaser to advise us if our assumptions are incorrect.

Selecting a Pressure Switch

To find your product, start by selecting the measurement mode.

(These comments are written with mechanical switches in mind, but much is applicable to electronic switches.)

What do you want? You want a switch.
What must it interrupt, and what configuration is required? The circuit is probably electric, but may be pneumatic. The following is written with electricity in mind, adapt accordingly for pneumatics.Specify current, voltage and frequency. Our default is SPDT, DPDT can usually be provided by ganging two SPDT switches together. Note any special requirement such as environmental or hermetic sealing. Such sealing increases both price and deadband.

What kind of switch do you want? You want a pressure switch. Tell us the desired setpoint as well as the maximum pressure likely to be applied. If you want us to set the switch, you must tell us if the setpoint is on rising pressure or on falling pressure. What is the working and maximum temperature? What about wetted materials? Brass, where available, is cheapest. Stainless steel and Monel are available for more corrosive applications. We assume a clean low viscosity pressure medium. If not, tell us. A chemical seal or flanged design may be necessary. Process connection is usually ¼” female, but others are available.

What kind of enclosure do you need? The default is weatherproof, in aluminium or zinc alloy. Stainless steel is an option. If you need explosion proof, be sure to specify zones and groups. (Note that mechanical pressure switches as “simple apparatus” generally do not require certification for use in an intrinsically safe circuit.) What about electrical entry?

What kind of mechanism do you need? While pressure switches are traditionally mechanical devices, electronic switches are becoming quite common. Click here for a detailed discussion. The important point here is deadband, or switching differential, since process conditions will usually define the pressure element. Click here for a detailed discussion on deadband. Delta switches are of fixed deadband design by default, and this design will minimise deadband. If you require more control over deadband, let us know, since there are narrow and wide adjustment designs available in mechanical switches. Most electronic switches allow free setting of deadband.

What kind of switch element do you need? (Electro-mechanical switches only)
The first requirement is the capacity to interrupt your load. The default Delta switches are precision AC (00) or general purpose (02). Very light currents eg PLCs may benefit from gold plated switches (04) since the higher current switches tend to rely on “wetting” currents to keep the contacts clean. Environmental protection comes in 2 forms. We define “environmentally sealed” as using elastomeric seals to keep the environment out of the switch internals. “Hermetically sealed” uses fusion joints for this purpose. Other suppliers may have different definitions.

What process connection can you live with? The norm with Delta is ¼” BSPT or NPT, and these will always be least cost options. Connections larger than ½” may be best served with a chemical seal.
The Delta product code requires the following requirements to be defined:
Enclosure, mechanism, electrical entry, wetted parts, setpoint range, switch type, process connection.

Pressure Switch Enquiry Sheet

Gauge Pressure Switches
We distribute the Delta range of mechanical switches, supplied by Delta Controls Ltd in England, and the Dewer electronic pressure switch from Canada. These are both designed for process applications.

For help on selecting a pressure switch, click here.

For an electronic switch, select XS2100

For a mechanical switch, Delta offers three product ranges:
Classic Range Most flexibility, widest range of switches, best repeatability, calibrated scales, low cost if brass selected, poor overpressure.
Sovereign Range Lower cost in stainless steel or explosion-proof, high overpressure capability, restricted scope.
Compact Range Like Sovereign, but compact body, hermetically sealed switch capsule, good for corrosive atmospheres.

There are a couple of shortcuts, click for details

Setpoints less than 300 Pa:
Use a DP switch with LP vented to atmosphere. Type 310 has limited overpressure, restricted materials, and goes to –250 + 250 Pa. Type 306 goes down to –60 + 60 Pa. (Link to Classic DP Page)

Dual Setpoint Mechanism:
(Two switches in one) Only available in Classic type 201 (281: setpoints below 7 500 kPa) or 231 (234: higher pressures than type 201).

Wide Adjustable Deadband:
Only available in Type 201 (203)

Pneumatic Switching:
Only available in Type 201

Absolute Pressure Switches
We have a very limited offering here. In mechanical switches, Delta have the Type 207 available. A wider scope is available from the Dewer XS2100.

Differential Pressure Indicators
We have two product ranges for you. The Orange Research gauges have magnetic movements, and are meant to operate under rising pressure, eg filter applications. Significant hysteresis impairs accuracy on falling pressures, but the design is capable of very high overloads and static pressures, at very reasonable cost.

Piston designs are used on liquids only, on applications where some liquid migration from high to low is acceptable.

1201 35-700 kPad @ 20 MPa liquid with some liquid migration
1301 1 000 – 7 000 kPad @ 35 MPa liquid with some liquid migration

Diaphragm designs are used on other applications
1502 35 – 700 kPad @ 20 MPa
1516 7 to 35 kPad @ 10 MPa
1831 1,5 to 50 kPa @ 1 MPa

More conventional designs are available from Stewart Buchanan.
4503 30 kPad – 10 MPad at static 3-6 times dp
4901 10 to 200 kPad @ 2 500 kPa static
4906 10 to 2 000 kPad @ 22 MPa static (DP Cell)