971B UniMag™
20
Operation manual
Cold Cathode protect setpoint
The Cold Cathode protect setpoint automatically turns off the Cold Cathode high voltage if the cold cathode
measurement exceeds 5.00E-3 Torr for 120 seconds. The protect setpoint can be turned off (disabled) or
time set between 0 and 999 seconds.
Command:
@253PRO!ON;FF
Command values:
ON (120), OFF, 0 to 999 seconds
Command reply:
@253ACK120;FF
Query:
@253PRO?;FF
Query reply:
@253ACK120;FF
Factory default:
OFF
If FP is set to “ALWAYSON” the protect setpoint is automatically disabled. (See page 15)
Cold cathode pressure dose
The Cold Cathode pressure dose continuously monitors the Cold Cathode time on as function of the
pressure. If the cold cathode is on for 100 hours at 1E-4 Torr the pressure dose is 100×1E-4 = 1E-2 Torr
hours. The pressure dose readout can be used to determine the time interval between Cold Cathode
maintenance and service.
Pressure dose request:
Query:
@253TIM3?;FF
Query reply:
@253ACK1.23E-2;FF
Reset of pressure dose:
Command:
@253TIM3!;FF
Command values:
-
The pressure dose reading can be user reset after the transducer has been cleaned or the anode assembly
has been replaced.
The pressure dose reading is only a rough indication of the cold cathode status. When the cold
cathode is contaminated the sensitivity of the gauge is decreased and it will provide a lower reading
than actual pressure. Therefore the calculated pressure dose can be lower than the actual
pressure dose.
Cold Cathode pressure dose setpoint
The Cold Cathode protect setpoint can be used to determine when a defined pressure dose is exceeded.
The transducer status readout (see page 21) is used to monitor pressure dose setpoint status.
Command:
@253PD!1.00E-2;FF
Command values:
1.00E-3 to 10 Torr
Command reply:
@253ACK;FF
Query:
@253PD?;FF
Query reply:
@253ACK120;FF
Factory default:
1.00E+00