pg. 19
Resolution
The digital pressure output can provide 3 digit or 4 digit values; however, the resolution is limited in certain
parts of the measuring range.
1.00E-5 to 1.00E-4 Torr
1 digit resolution
1.000E-5
1.00E-4 to 1.00E-3 Torr
2 digit resolution
1.200E-4
1.00E-3 to 900 Torr
3 or 4 digit resolution
1.234E-3
Measuring noise
External sources can interfere with the sensor signal and cause noise in the signal. The low measuring range
is most sensitive to measuring noise due to low signal levels.
Calibration and adjustment
The 910 is factory calibrated when delivered and in most 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 measurement errors.
The 910 is per factory default calibrated for reading in Nitrogen gas. When exposed to
atmospheric air the MicroPirani sensor (PR1) will read higher values, typical 900 Torr
at ambient pressure.
Accuracy and repeatability
The 910 measuring accuracy is specified as transducer reading ± a percentage of the actual pressure. The
basic measuring accuracy is factory calibrated and cannot be user adjusted. The repeatability specification is
the transducers ability to repeat the same measurement value after multiple pressure cycles. Refer to the
transducer specification page 53 for actual values.
Gas calibration
The MicroPirani, used for pressure readings below 5 Torr, is based on measurement of thermal conductivity
of the gas and consequently its reading depends on the gas and gas concentration. The 910 is per default
set to Nitrogen calibration; however, the transducer has calibration curves for several common gases.
Change of gas calibration setup:
Command:
@253GT!ARGON;FF
Command values:
NITROGEN, ARGON, HELIUM, HYDROGEN, H2O, NEON, CO2, XENON
Command reply:
@253ACKARGON;FF
Query:
@253GT?;FF
Query reply:
@253ACKARGON;FF
Factory default:
Nitrogen
Pressure unit calibration
The transducer can provide digital and analog output in Torr, mbar and Pascal pressure units.
When changing unit, all parameters, like setpoint settings, are automatically converted to the new unit, so it
will represent the same pressure level. All pressure parameters must be entered in the actual transducer unit
setting.
Change of pressure unit calibration setup:
Command:
@253U!TORR;FF
Command values:
TORR, MBAR, PASCAL
Command reply:
@253ACKTORR;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.
