FAQs and Definitions
Frequently Asked Questions
What is the difference between Absolute and Gauge Pressure?
Absolute pressure is zero-referenced against a perfect vacuum, so it is equal to gauge pressure plus atmospheric pressure. Gauge pressure is zero-referenced against ambient air pressure, so it is equal to absolute pressure minus atmospheric pressure.
There are several units of pressure measurement that are used based on your reference point. Some common examples of Absolute reference are Torr and psia. Some examples of Gauge reference are psig and inches of mercury (vacuum).
Do you have any in stock?
Short answer: No, Wasco builds to order as we have over 6000 user customized applications. We stock thousands of components to minimize lead time.
What is your warranty policy?
Based on the variability of our products our warranty is up to 2 years or 2 million cycles, which ever comes first. Please visit our Terms & Conditions for product-specific warranty.
Who can I speak to about technical issues?
We have a dedicated team of on-site engineers that can help answer your technical questions. Fill out this contact form for customer service to connect you to our engineering team.
Where do you ship?
We currently ship everywhere allowed by U.S. law.
Can I pay with credit card?
Yes!
Are you ISO9001 certified?
Yes!
Are you CE compliant, UL recognized, and RoHS compliant?
Yes, we are CE compliant, UL recognized, and RoHS compliant.
Do you have distributors?
We sell direct, and we also have some distributors. Please contact Wasco so we can better serve you.
Definitions for Pressure and Vacuum Applications
Accuracy
The limit of deviation from the set point of a pressure or vacuum switch. It is usually a percentage of full scale.
Actuation Point
See "Setpoint"
Adjustable Range
The limits between which the setpoint can be adjusted.
Burst Pressure
Pressure which causes failure of the pressure element, resulting in permanent damage.
Cycle
One complete sequence of values usually above and below the setpoint, which occurs during a time period.
Dead-band
The difference between the setpoint and the point where the switch re-actuates.
Differential Pressure
A measured pressure difference between two pressure sources.
Electrical Switching Element
Opens or closes an electrical circuit due to a movement from the pressure or vacuum sensing element.
Hysteresis
The difference in readings of an instrument when it is approached from two different directions.
Maximum System Pressure
The highest pressure that a switch may safely operate at.
Maximum Operating Pressure
The designed safe pressure limit of a sensing element at which regular use will cause no damage
Normally Closed
Current flows through the switch until the contact is broken by a pressure or vacuum change.
Normally Open
No current flows through the switch until contact is made by a pressure or vacuum change.
NEMA 4
Water tight and dust tight enclosure.
NEMA 4X
Water tight, dust tight, and corrosion resistant enclosure.
Pressure, Absolute
A pressure scale based on PSIA “0” or a perfect vacuum.
Pressure, Ambient
The pressure immediately surrounding a pressure switch.
Pressure, Atmospheric
The pressure caused by the actual weight of the earth’s atmosphere. At sea level, atmospheric pressure equals 14.7 PSI, 30” HG, or 760 Torr.
Pressure, Barometric
Actual atmospheric pressure in a specific location.
Pressure, Burst
The maximum pressure the unit can withstand without causing a release of the application media.
Pressure, Differential
The difference between a reference pressure and a variable pressure.
Pressure, Gauge
Uses atmosphere as a zero reference point so there is no compensation for changes in barometric pressure.
Pressure, Maximum System
Normal system pressure level not including surges and spikes.
Pressure Proof
Pressure in excess of the maximum operating pressure to which the sensor may occasionally be subjected to.
Pressure, Sensing Element
The portion of the pressure switch that moves with a change in system fluid pressure. Wasco, Inc. pressure switches use capsule, diaphragm, and piston sensing elements.
Pressure, Switch
An instrument that converts a pressure change to an electrical function.
Radio Noise
Electromagnetic interference (EMI)
Reset Band
The difference in pressure between the setpoint and the reset point.
Reset Point
The point at which the electrical switching element snaps back to the position it was at prior to initial actuation.
Response Time (Reaction Time)
The amount of time taken between a change in pressure and a change in the electrical signal.
Repeatability
The ability of the switch to actuate repeatedly at the desired set point within the sensors tolerance.
Setpoint
The exact point at where the electrical switching occurs. This is generally expressed in PSI or inches of mercury.
Setpoint Range
The range from which the switch can be set from the lowest to the highest point.
Switching Current, Maximum
The maximum load (amperage) the electrical switch will carry.
Temperature, Ambient
The temperature immediately surrounding a pressure switch.
Temperature, Shift
A change in setpoint due to changes in ambient, or fluid temperatures.
Vacuum
The value pressure of below atmospheric pressure.
Wetted Parts
Components that come in direct contact with the process media.
Working Pressure Range
The pressure range where the sensor can safely operate and still maintain the setpoint