Preiffer PKR 251, Руководство по эксплуатации

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Calibration factors
In the pressure range < 10 -5 hPa, the display is linear.
Gas and vapor mixtures
Process gases are mostly mixtures of gas and vapor. Precise measuring of gas and vapor
mixtures is only possible using partial pressure measurement instruments, for example a
quadrupole mass spectrometer.
Gas type Calibration factor (C)
Air, oxygen (O
2
), carbon monoxide (CO), nitrogen (N
2
) 1.0
Hydrogen (H
2
) 2.4
Helium (He) 5.9
Neon (Ne) 4.1
Argon (Ar) 0.8
Krypton (Kr) 0.5
Xenon (Xe) 0.4
The calibration factors provided are mean values.
Tbl. 8:
Calibration factors for the pressure range < 10 -5 hPa
Entering the calibration factor in a total pressure measuring and control unit
► Enter the calibration factor to correct the displayed measured value.
Calculating pressure for gases other than air
► Calculate the effective pressure using the following formula:
P
eff
= C × p
●
P
eff
= Effective pressure
●
C = Calibration factor
●
p = Displayed pressure (gauge calibrated for air)
6.4 Observing ignition delay
Cold cathode measurement systems have an ignition delay when they are switched on. This ignition de-
lay is longer for lower pressures and is typically in clean, degassed units:
● 10
-5 hPa approx. 1 second
● 10
-7 hPa approx. 20 seconds
● 5 × 10
-9 hPa approx. 2 minutes
Switching on at pressure p < 3 × 10 -9 hPa
If you switch on the gauge at a pressure p < 3 × 10 -9 hPa, the gauge will not be able to
detect whether the cold cathode measurement system has ignited. The gauge displays “Pi-
rani-Underrange”.
Maintaining operation of the gauge
If continuous operation of the flange-mounted gauge is maintained regardless of the pres-
sure range, the ignition delay time of the cold cathode measurement system is always neg-
ligible (< 1 s), with minimal thermal stabilization effects.
The ignition is a static process, for which even minimal depositions can have a major influence on the
inner surfaces. As long as the cold cathode measurement system has not ignited, the signal output is-
sues the Pirani measured value only ("Pirani-Underrange" indication at pressures p < 5 × 10
-4 hPa). The
identification output signals Pirani operation only.
Operation
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