|
|
| Accuracy |
The
limit of deviation from the set point of the switch. It is normally
defined in either points per square inch, or percentage of full scale. |
| Actuation
Point |
See Set
Point
|
| Actuation
Value |
The
difference between the set point and the reset point.
|
| Adjustable
Range |
The
range between the lowest or highest point, within which the switch can
be set. It is normally expressed in PSI, inches of mercury or inches
of water column. |
| Deadband |
The
difference between the increasing and decreasing readings when the
switch is operated between set point and reset point. |
| Differential |
The
mechanical motion lost within the electrical switch element while it
reverses itself. This is usually greater in high amperage switches
than in low amperage switches. |
| Electrical
Switching Element |
Opens or
closes an electrical circuit in response to movement from the pressure
or vacuum sensing element. Single pole, double throw (SPDT) snap
action switches are standard, may be used as single pole, single throw
(SPST). NO/NC circuitry is selectable, but it must be specified at
order time. |
| Hysteresis |
The
difference in pressure or vacuum switch response to increasing and
decreasing pressure or vacuum.
|
| Normally
Closed Switching Element |
Current
flows through the switch until it is broken by a pressure or vacuum
change.
|
| Normally
Open Switching Element |
No
current flows through the switch until contact is made by a pressure
or vacuum change.
|
| 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 inches or mercury or
408 inches or water, above absolute "0" ("0" PSIA). |
| Pressure,
Barometric |
Actual
atmospheric pressure in a specific location and altitude. The standard
is 29.22 inches of mercury at sea level at 70°F. |
| Pressure,
Differential |
The
difference between a reference pressure and a variable pressure
|
| Pressure,
Gauge |
Uses
atmospheric pressure as a zero reference point so there is no
compensation for changes in barometric pressure. |
| Pressure,
Maximum System |
System
pressure including surges or spikes.
|
| Pressure,
Proof |
The
maximum pressure which can be applied to a pressure switch without
causing irreparable damage. It is usually 150% of the pressure sensing
element's rated maximum system pressure. |
| Pressure,
System |
Normal
system pressure level not including surges or spi
|
| Pressure
Sensing Element |
The
portion or the pressure switch that moves with a change in system
fluid pressure.
|
| Pressure
Switch |
An
instrument that converts a pressure change to an electrical function
|
| Repeatability |
The
ability of the switch to actuate repeatedly at the desired set point
within sensor tolerance.
|
| Reset
Point |
After
the pressure has reached set point and operated the electrical switch,
it must return to the reset point before the electrical switch returns
to its original position |
| Reset
Point Range |
The
difference between the set point and the reset point. It is caused by
the hysteresis of the pressure or vacuum sensing element and the
differential of the electrical switch. This is a fixed function of the
switch and is not adjustable. |
| Response
Time |
The
amount of time taken between a change in the pressure of the system
and the change in the electrical signal. |
| Set
Point |
The
exact point at which the electrical switching element functions. This
is generally expressed in PSI, inches of mercury or inches of water
column. |
| Set
Point Range |
The
range within which the switch can be set from the lowest to the
highest point, usually expressed in PSI, inches of mercury or inches
of water column |
| Switching
Current, Maximum |
The
maximum amperage load that the electrical switch will carry.
|
| Temperature,
Ambient |
21° C
or 70° F. Also know as "room temperature".
|
| Temperature,
Shift |
A change
in switch set point due to changes in surrounding temperature.
|
| Vacuum |
Gauge
pressure less than ambient pressure using ambient pressure as a
reference.
|
| |
