971B UniMag™
21
Operation manual
Calibration and Adjustment
The 971B is factory calibrated when delivered and in many applications further calibration is not required. If
the sensor element has been contaminated or damaged by process gases, adjustment of zero and full
scale can be executed to compensate for small measurement errors.
Pressure unit setting
The transducer can provide digital and analog output in torr, mbar and Pascal pressure units.
When changing pressure unit all parameters such as setpoint settings are automatically converted to the
new unit, so it will represent the same pressure level. All pressure parameters such as setpoint settings and
calibration values must be entered in the actual transducer unit setting.
Change of pressure unit calibration setup:
Command:
@253U!PASCAL;FF
Command values:
TORR, MBAR, PASCAL
Command reply:
@253ACKPASCAL;FF
Query:
@253U?;FF
Query reply:
@253ACKTORR;FF
Factory default:
TORR
The torr unit is most common in the US and mbar is most common in Europe. Pascal is the official pressure
unit as specified by SI (from the French
Le
S
ystème
I
nternational d'Unités
) and is widely used in Asia.
Cold cathode zero adjustment
The Cold Cathode zero adjustment allows the user to adjust the cold cathode zero reading.
Executing zero adjustment
To obtain measuring performance the transducer should be evacuated to pressure below 5×10
-8
Torr.
If the Cold Cathode zero adjustment is executed at high pressure, the measurement below the
zero value can become unreliable. Always zero at the system base pressure.
Command:
@253VAC3!2.00E-8;FF
Command values:
1.00E-6 to 1.00E-8 Torr
Command reply:
@253ACK;FF Query:
@253VAC3?;FF
Query reply:
@253ACK0.00+00;FF
Reset to default:
@253FD!VAC3;FF
Factory default:
Factory adjustment value
Value out off range: @253NAK172;FF
Cold cathode full scale adjustment
The Cold Cathode full scale adjustment allows the user to adjust the cold cathode reading at high pressure.
Command:
@253CFS!4.00E-3;FF
Command values:
1.00E-4 to 5.00E-3 Torr
Command reply:
@253ACK;FF
Query:
@253CFS?;FF
Query reply:
@253ACK0.00E+0;FF
Reset to default:
@253FD!CFS;FF
Factory default:
Factory adjustment value
Value out off range: @253NAK172;FF
