| Accuracy (Repeatability) - Accuracy is the maximum allowable set-point deviation of a single pressure switch under one given set of environmental and operational conditions. Actuation and
Deactivation Point - The actuation point (sometimes called set point) is the exact point at which the electrical circuit controlled by the switching element is opened (or closed) on
increasing pressure. The deactivation point is the opposite, or the point at which the electrical circuit is closed (or opened) on decreasing pressure.
Adjustable Range - The total range within which the actuation point (set point) of a pressure or vacuum switch may be adjusted.
Ambient Temperature Range - The maximum and minimum temperature that will surround the sensor during use and/or test.
Critical Set Point - The critical set point is the set point of the unit which is held to the closest tolerance. It can be either the actuation (increasing) or
deactivation (decreasing) point.
Charge - The fluid with which the temperature sensing probe is filled.
Deadband (Differential, Actuation Value) - The difference between the actuation point and the
deactivation point. For instance if a pressure switch reaches its actuation point and closes the snap action switch at 100 psi, it is in an actuated condition. If the pressure then drops and the switch
deactivates (returns to its normal condition) at 90 psi, it is said to have a deadband of 10 psi.
Dual Setting - A dual setting pressure sensor has two independently adjustable electrical switches that are actuated by a shared pressure source. Equivalent to two field adjustable pressure switches in one package.
Electrical Switching Element - Opens or closes an electrical circuit as a result of the movement and force it receives from the pressure sensing element. See description below:
- Single Pole Double Throw (SPDT) Switching Element - A SPDT switching element has one normally open, one
common and one normally closed terminal. Three terminals mean that the switch can be wired with the circuit either normally open (N/O) or normally closed (N/C).
- Double Pole Double Throw (DPDT) Switching Element - A DPDT switching element has six electrical terminals. In simple terms, it is two SPDT switches combined for simultaneous operation. This type of switch can handle two independent circuits without using a relay.
- Double Break Switching Element - A double break switching element has two isolated circuits; one normally open and one normally closed, the four terminals facilitate wiring.
Normally Closed (N/C) Switching Element - Is one in which the terminals are wired so that current can flow through the switching element until the plunger pin is actuated to open the electrical circuit.
Normally Open (N/O) Switching Element - Is one in which the terminals are wired so that no current can flow through the switching element until the plunger pin is actuated to close the circuit.
Flow Switch - Senses differential pressure generated by flow through a venture to actuate an electrical switch at a predetermined flow level.
Polyimide - A polymeric film possessing a unique combination of physical and mechanical properties which include long life, excellent deformation/set resistance, high actuation point that the media will be when the sensor resistance to temperature extremes, good tensile strength, and outstanding resistance to organic compounds. Polyimide is not recommended for water service above 14O°’F (60°C).
Pressure, Absolute - The difference between zero pressure (a perfect vacuum) and some known pressure. It may be arrived at by adding barometric pressure to gauge pressure.
Pressure, Ambient - The pressure (usually but not necessarily atmospheric) surrounding a pressure switch.
Pressure, Atmospheric - The actual weight of the earth’s atmosphere at a given locale and altitude. Atmospheric pressure at sea level is approximately 14.7 psi or 30 inches of mercury or 408 inches of water. |
Pressure, Barometric - Actual weight of the earth’s atmosphere at a given locale and altitude as measured by a barometer; usually expressed in measurement of a column of mercury. Standard barometer reading at sea level is 29.92 inches of mercury at 32 degrees F. Pressure, Differential - The difference between a reference pressure and a variable pressure.
Pressure, Gauge - Gauge pressure uses atmospheric pressure as a reference, and therefore will vary according to the barometer reading.
Pressure, Proof - Proof pressure (normally 11/2 times system pressure) is the maximum pressure which may be applied to any switch without causing permanent degradation.
Pressure, Surge - A transient pressure varying in amplitude, frequency, and duration. It is difficult to measure without complicated electronic instrumentation. If the duration and/or amplitude of the pressure surge are large, a pressure sensing element rated for the maximum surge pressure should be used. There are surge dampening devices and techniques that can reduce the amplitude of pressure surges.
Pressure, System - The nominal pressure level that a system will operate at including work load.
Pressure Sensing Element - That portion of the pressure switch that is in contact with and moves as a result of a change in pressure of the fluid. The most common type of pressure sensing elements are diaphragms, accordion bellows, bourdon tubes, and pistons.
Pressure Switch - An instrument that upon the increase or decrease of a pressure or vacuum, opens or closes one or more electrical switching elements at a predetermined actuation point (setting).
Factory Set - Tamperproof sensor which can be set only r-at the factory to customer I s requirements.
Field Adjustable - A pressure switch design that provides for adjustment of set points in the field.
Limp Diaphragm - An Elastomer or plastic diaphragm which is used in a pressure sensor. This type of diaphragm conforms to the shape of the sensing pressure plate and has no rigid structure itself. CCS uses Polyimide or Viton/Dacron limp diaphragms.
Preset - A factory set pressure switch available from stock, set to a predetermined set point.
Proof Temperature - The maximum temperature of the media which the sensing portion of the switch can be subjected to without causing permanent damage.
Temperature Lag - The number of degrees above the actuation point that the media will be when the sensor operates. The lag is expressed for a designated rise rate (degrees per second), flow (feet per second), and system pressure (PSIG). The la ,q is determined by multiplying the rise rate by the response time. Example: If a system with a constant flow, pressure, and rise rate of 10'F per second incorporated a sensor with a response time of 3 seconds, the lag would be 30
degrees.
Temperature Switch - A temperature switch is a sensor that upon the increase or decrease of a temperature, opens or closes one or more electrical switching elements at a predetermined set point.
Thermowell - A housing that can be provided with temperature switches to isolate the temperature probe from the media.
Response Time or Time Constant - The amount of time (in seconds) in which the sensor operates after being subjected to a step temperature increase where the difference between the initial soak temperature and actuation temperature equals 63% of the step temperature. The response time is expressed for a designated flow (feet per second), media and system pressure (PSIG).
Rise Rate or Ramp Rate - The number of degrees (Fahrenheit or Celsius) that the media will increase in a unit of time (minute or second).
Wetted Parts - Components of a sensor that are directly exposed to the media
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