Chapter 3
46 Mini-Convectron Module Instruction Manual - 275513
3.7 Modules Operating at Low Pressure
During a fast pumpdown from atmospheric pressure, thermal effects temporarily prevent the module
from measuring pressure accurately below 1 x 10
–3
Torr (1.3 x 10
–4
kPa, 1.3 x 10
–3
mbar). After
approximately 15 minutes, pressure indications the 1 x 10
–4
Torr (1.3 x 10
–5
kPa, 1.3 x 10
–4
mbar)
range will be accurate.
When pressure indication in the 1 x 10
–4
Torr (1.3 x 10
–5
kPa, 1.3 x 10
–4
mbar) range has stabilized,
a Convectron gauge calibration at vacuum chamber pressure may be performed.
The calibration may be performed at a higher pressure if readings in the 1 x 10
–4
Torr (1.3 x 10
–5
kPa,
1.3 x 10
–4
mbar) range are not required. In the 1 x 10
–4
Torr (1.3 x 10
–5
kPa, 1.3 x 10
–4
mbar) range,
resolution is ±0.1 millitorr, if the Convectron gauge has been properly calibrated at vacuum chamber
pressure. If the module frequently operates in the 1 x 10
–4
Torr (1.3 x 10
–5
kPa, 1.3 x 10
–4
mbar)
range, Convectron gauge calibration at vacuum chamber pressure should be performed frequently.
3.8 Factory Settings
Table 3-9 lists factory relay setpoint values.
Table 3-9 Factory Settings for Relays
Parameter Factory Setting
Setpoint Below 0.0 vacuum chamber pressure
State Deactivated
Returning pressure hysteresis
• 2% of reading for module without display
• 10% of reading + 1 significant digit for module with optional display
Activation direction Activates below vacuum chamber pressure setpoint, not programmable
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