Frequently Asked Questions
General Inquiries
A pressure switch is an electromechanical device that measures the pressure in a system, and when the pressure reaches too high or too low of a given setpoint, the device will “switch.” This terminology means that it will open or close a circuit that powers a certain device (such as an alarm system or a shutdown valve).
A pressure transmitter is primarily an electronic device that measures pressure, but instead of signaling a switch, it merely sends a read-out signal of what the specific pressure value is to a remote location.
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Media temperature is the temperature range of the monitored media. However, ambient temperature is the temperature range the whole unit will be exposed to. Lastly, operating temperature is the standard temperature the unit will see during operation.
Pressure & Temperature Transducers
A temperature transducer measures temperature providing constant output.
A pressure transducer measures pressure by providing a constant output (please see question 33 for standard applications).
Pressure transducers can be used anywhere that the pressure of a media needs to be measured within aerospace applications. Types of applications include the following systems.
- Fuel
- Engines
- Bleed air
- Lubrication
- Landing gear
- Hydraulic systems
- Fluid management
- Nitrogen generation
- Environmental control
CCS transducers have a 10 second temperature response time.
Pressure Switches
Pressure switches are instruments used to turn on/off a device in a process control system.
Once it’s set at the factory, typical switch accuracy and repeatability is within 1%-2% of the nominal setting.
The functionality of a CCS pressure switch is to monitor and control fluid systems while maintaining efficiency and safe operations.
The difference between single pole and double pole switch is that SPDT connections are used to control one device at a given setpoint, but DPDT connections are used to control two devices at a given set point.
Maximum Proof pressure is what the pressure switch can see and withstand without permanent damage.
Pressure settings are externally adjustable (this is not applicable if units are factory set). The steps are as follows:
- If the electrical circuit cannot be used for testing, disconnect electrical power and use a suitable circuit tester or lightbox. Loosen access cover and turn the adjustment screw using screwdriver slot as illustrated; turn clockwise to increase settings and/or turn counterclockwise to decrease the setting.
- Re-tighten access cover.
- Reconnect electrical circuit, 12 ft. lb. max.
- Return power to the unit.
Our switches react in less than 1 millisecond, or a time equal to one-thousandth (0.001) of a second. In fact, it’s much faster than the blink of an eye, which takes 300 to 400 milliseconds.
Unfortunately, our Dual Snap switch designs do not meet one million operation cycles. However, you can use our electronic switches.
Gauge or gage pressure switches are used in sensing media pressure referencing atmospheric pressure. Conversely, differential pressure switches sense the difference between two line pressures.
A vacuum pressure switch will sense pressure below atmospheric or sometimes referred to as ‘barometric pressures’ (typically 14.7 psi).
First, you should test the pressure switch by applying either force of pressure through a line or manually. Be sure to check the setpoint pressure and see if it is changing from closed to open and from open to closed. If it fails that test, dewire the wire connection and screw the switch off the pressure line and replace it with a new switch.
The CCS Piston O-ring is a design that adds a piston and O-rings to our standardized Dual Snap switch, located between the diaphragm and microswitch. This device was crafted to protect the microswitch in high-pressure applications.
Design & Development
Dual-Snap is a registered trade name of CCS’ switch designs. We use a Belleville disc spring that snaps from convex to concave at a designated pressure, activating the micro-switch to an electrically-closed state (also known as Snap #1).
By contrast, when the pressure decreases to a specific point below the activating pressure, the disc spring snaps back to its original convex state. This causes the microswitch to transition to an electrically open state (or Snap #2).
The key benefits of our Dual-Snap design include the following:
- No recalibration
- No drift in set point
- No effects of vibrations
- No additional maintenance
The Dual-Snap system is also significantly improved for reliability and eliminates “contact chatter,” caused by vibration.
The “disc-spring” snaps only at the design pressure. However, a “trace” or bellow-type pressure switch design has a working principle that continues to move as the pressure changes–resulting in exhaustion, overstress, and material fatigue.
Our wetted materials can be aluminum, stainless steel, Brass, or polyimide (H-Film). These mediums were selected to be compatible with the given media.
CCS pressure and temperature switches are typically made out of aluminum and stainless steel for the process connection, diaphragm, and housing/body. The aluminum material is most commonly 6061 grade. Additionally, we offer several grades of stainless steel, such as 316 for higher corrosion applications, 302 and 304 for less sensitive applications. For extremely high corrosive chemicals, such as hydrosulfuric acid and ammonia, Hastelloy and Monel material is available for the wetted area.
CCS offers the following switch components on each design.
- Viton-Dacron
- 316 stainless steel
- Diaphragms made of Polyimide
- Piston made of 316 stainless steel
In selecting a switch model suitable to your specific application requirements, initial questions related to:
- Media
- Proof pressure
- Pressure settings
- Ambient temperature
Larger configurations on the pressure sensing area (above pressure port) will more likely be suitable for low-pressure settings. The other configuration requirements (i.e. electrical switching and connection, the material of construction, weight, etc.) are determined by the application.
Gold contacts allow the switch to be installed in applications, with a current rating of 1 amps or lower.
Technology & Technical Support
CCS has a vast range of MIL-DTL-38999/25YA35PN electrical connectors. Our transducers or switches also have free leads (wires) in its durable, reliable build.
The advantages of the Belleville disc spring are similar to the Dual-Snap, there’s no need for re-calibration, plus, it’s reliable and maintenance-free.
At CCS, our innovation-led switches are significantly more reliable, accurate, highly-resistant to contact chatter or vibration, and have long-term stability during each operation.
For industrial purposes, the standard port connections are 1/4-18 NPTF or 1/2-14 NPTF. However, MS33656-4 (MOD) .4375-20 UNJF-3A THD (REF) is standard on airborne pressure switches.
The standard tolerance on a CCS switch is within 5% of the settings. Less than 5% is achievable but may require additional design and testing.
Pressure Sensors
There is no such thing as an ambient sensor. Ambient means the surrounding pressure or temperature.
Calculations
You can use one of our quick and simple unit conversion tools to convert both pressure and temperature units.
Through basic algebra and by employing the P=VA equation, one can determine the maximum current rating by referencing the electrical ratings of a microswitch. Ratings from the datasheet can be accessed on our product pages.
For example:
The 6900GZE series can support 11 A at 250 VAC, producing the following wattage.
- Power (W) = Volage (V) x Current (A)
- W = 250 VAC x 11 A
- W = 2750 W
If the desired power is 225 VAC, the maximum current output?
- 2750 W = 225 VAC x A
- A = 2750 W / 225 VAC
- A = 12.2 A
A technician must consider the load type (inductive, resistive, and LRC) and heat dissipation at the point of the contacts when determining applicability.
Dead Bands
A dead band period is between the actuation and deactuation points of a pressure switch. It is based on the snap-action mechanism of the Belleville disc spring. When a pressure setpoint is reached, the disc spring snaps forward and then back to its original state once it resets. Dead band is caused by the inherent hysteresis that is mechanically-embedded in the disc spring. It is the effect of friction on the operation of the spring between the inner and outer peripheries of the spring and load surfaces coming in contact with those faces.
Dead bands are typically narrower the lower the pressure and wider, the higher the pressure.
CCS switches do not have adjustable dead bands, only fixed. This is due to the mechanics of the Belleville disc spring. Adjustable dead band switches are more susceptible to inaccuracy and drift since they do not use Belleville disc spring technology. They also trace devices that use helical springs, for instance, and lose accuracy from the wear and tear of the helical spring over time.
Safety
Explosion-proof and intrinsic safety are two separate certifications that use different concepts to prevent an explosion in a hazardous area.
Explosion-proof products are engineered to contain an explosion within the heavy protective housing enclosure of electrical components. The ignition of a vapor or gas may occur, but the housing enclosure is designed robustly with adequate sealing to prevent it from escaping into the external environment.
Intrinsic safe products are not designed to enclose or contain an explosion within a housing. Instead, the product is made to stop electronics or electrical wiring from accumulating too much energy to ignite the gas or vapor in the surrounding area. This approach limits energy in the circuits to a level below that’s required to ignite combustible atmospheric mixtures. A product must have both certifications to be considered explosion-proof and intrinsically safe.
CCS switches are certified explosion-proof by UL, CSA, ATEX, and IECEx. For applications in America, the UL standard is most commonly applied. For Canada, CSA applies. In both scenarios, switches are rated to Division I and II; Class 1, Groups A, B, C, and D; Class 2, Groups E, F, and G. And in European markets, ATEX is the standard, but the international market has recently adopted IECEx. Switches for both ATEX and IECEx are rated to Ex d IIC T6.
The FAA (or Federal Aviation Administration) is a branch under the U.S. Department of Transportation that regulates civil aviation over land and sea on U.S Territory and neighboring international waters.
FAA controls the replacement of aircraft parts on certified aircraft during maintenance by requiring these parts to be marked “FAA/PMA.”