MKS Series 275 MiniConvectron, Instruction Manual

Page: 44 / 64

Chapter 3
44
Mini-Convectron Module Instruction Manual - 275513
3.4 Reading Relay Status
If the module without a display has one setpoint relay, or if the module has the optional display, use
the setpoint LEDs to read activation/deactivation status of relays.
3.4.1 If the module without a display has one setpoint relay:
The RELAY ON LED is solid green when the setpoint relay is activated.
3.4.2 If the module has a digital display:
• The RELAY ON SP1 LED is solid green when relay 1 is activated.
• The RELAY ON SP2 LED is solid green when relay 2 is activated.
You cannot read relay status if the module without a display has two setpoint relays.
3.5 Calibrate the Convectron Gauge at Atmospheric Pressure
An atmospheric pressure 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 for N
2
to
760 Torr (101 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.
Regardless of the process gas that is being used, you should always use N
2
or air to calibrate the
Convectron gauge at atmospheric pressure.
The procedure for calibrating the Convectron gauge at atmospheric pressure depends on whether or
not the module has the optional display.
3.5.1 If the module does not have a digital display:
1. Shut off the pump and, using N
2
or air, allow the vacuum chamber pressure to increase to the
value at which the atmospheric pressure point will be set.
2. Use a high-precision, high-input impedance DVM to measure the voltage across the MONITOR
ANALOG and MONITOR COMMON test points on the module front panel.
3. Use a flat-head instrument screwdriver to adjust the ADJUST ATMOSPHERE potentiometer to a
voltage that corresponds to the atmospheric pressure at your location. Table 3-8 on page 45 lists
typical atmospheric pressure at altitude/Torr/voltage relationships.
3.5.2 If the module has a digital display:
1. Shut off the pump and, using N
2
or air, allow the vacuum chamber pressure to increase to the
value at which the atmospheric pressure point will be set.
2. When the display indicates that pressure has achieved the atmospheric pressure point, use a
flat-head instrument screwdriver to adjust the ADJUST ATM potentiometer to a voltage that
corresponds to the displayed pressure. Table 3-8 lists typical atmospheric pressure at
altitude/pressure/voltage relationships.