MKS Series 275 MiniConvectron, Instruction Manual

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Chapter 2
22
Mini-Convectron Module Instruction Manual - 275513
2.3.5 Configure the setpoint relays for the application
To configure setpoint relays for the module, see Section 3.3.
If the module will measure the pressure of a gas other than N
2
or air, you
must
adjust relay setpoints
for the process gas. The true pressure of a gas other than N
2
or air may be substantially different from
the pressure that the output indicates. For example, outputs might indicate a pressure of 10 Torr
(1.33 kPa, 13.3 mbar) for argon, although the true pressure of the argon is 250 Torr (33.3 kPa, 333.3
mbar). Such a substantial difference between indicated pressure and true pressure can cause
over-pressurization resulting in an explosion.
2.3.6 Calibrate the Convectron gauge
Calibration improves the accuracy and repeatability of the Convectron gauge. To calibrate the
Convectron gauge, see Section 3.5 and Section 3.6.
2.3.6.1 Atmospheric Pressure Calibration
An atmospheric calibration is performed on the Convectron gauge, using N
2
, at the factory before the
module is shipped. The factory calibration sets the atmospheric calibration point to 760 Torr (101.3
kPa, 1013 mbar) of N
2
.
Because performance varies depending on the process gas, you may wish to reset the atmospheric
calibration point if a gas other than N
2
or air is being used. Periodic resets of the atmospheric
calibration point also improve the accuracy and repeatability of the Convectron gauge near
atmospheric pressure, even if the process gas is N
2
or air.
2.3.6.2 Vacuum Chamber Pressure Calibration
Periodic resets of the vacuum chamber pressure calibration point improve the accuracy and
repeatability of the Convectron gauge.
Explosive Environment
Failure to use accurate pressure conversion data for N
2
or air
to other gases can cause an explosion due to
over-pressurization.
If the module will measure any gas other than N
2
or air,
before connecting relays to system control devices, adjust
setpoints for the process gas that will be used.