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Instruction Manual
4.4.3 Relay setpoint characteristics (atmospheric pressure (ATM) setpoint)
The setpoints <SP1> and <SP2> of gauges with separate atmospheric pressure sensor
atmospheric pressure setpoint (ATM setpoint) via the diagnostic port.
The ATM setpoint is defined as a factor of the current atmospheric pressure and can be set to any pressure
within the measurement range of the gauge. The relay switches when the pressure in the vacuum system has
reached the defined value.
Example:
ATM setpoint: 110% of the atmospheric pressure (= factor 1.1)
Switching characteristic: High Trip Point
Hysteresis: 10 Torr
In this example the relay energizes when pressure inside the vacuum system is 10% higher than the atmospheric
pressure.
If you have acquired the gauge with the ATM setpoint option, <SP1> and <SP2> parameters can only be set via
the use of the diagnostic port. These parameters are Factor of ATM, Low Trip Enable, Low Trip Point
Hysteresis, High Trip Enable, High Trip Point Hysteresis, Setpoint Mode(assigns setpoint to absolute pressure
or ATM setpoint). Note that with the ATM setpoint option, <SP1> and <SP2> buttons cannot be used to set any
of the setpoint parameters. Pushing these buttons will display a meaningless number for the ATM setpoint.
WARNING!
Malfunction
If processes are controlled via the analog output signal, keep in mind that by pushing an <SP> button the measurement
signal is suppressed and the corresponding threshold value is output instead. This can cause malfunctions. Push the <SP>
button only if you are sure that no malfunction will occur.
1
)
The atmospheric pressure sensor measures the atmospheric pressure (pressure outside the vacuum system and can be calibrated against the diaphragm capacitive sensor
in the gauge.
InstruTech
Measurement signal
(Pressure p)
ATM setpoint 110%
(= factor 1.1)
836 Torr
Atmospheric pres-
760 Torr
sure (ambience)
Off
On
Threshold value
Hysteresis (10 Torr)
Off
PCM301 Busy Bee
1)
can be programmed to
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