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Menu | Calibrate
The Menu | Calibrate command is used to perform the calibrations on all of the sensors utilized
by the ADTS. The RUSKA 7750i can be completely calibrated using the front panel interface.
It does not require any external computer or software in order to perform a successful calibration.
It also has the capability of being calibrated remotely through either the RS232 or IEEE-488
interface. The RUSKA 7750i will guide the operator through a menu driven calibration procedure
identifying the pressures that should be supplied by a standard. Following the calibration
procedure, the RUSKA 7750i calculates and saves its own coefficients. The calibration
coefficients are date stamped so the user can easily identify the last time the instrument went
through a full calibration, when the coefficients were last edited or when the ADTS was
re-zeroed.
The calibration section in the ADTS can be password protected to prevent any unauthorized entry
into the calibration section of the system. Please refer to Chapter 6, Maintenance, of the manual
for more detailed information regarding the calibration of the ADTS. The calibration menu is
identical in both channels. Press the Sensor function key to select the correct sensor from either
channel.
Calibration Password
The calibration password allows the user to protect access to ADTS calibration constants and the
calibration procedure. If the calibration password is set to any number other than zero, it is
required before the user is allowed to calibrate the ADTS or manually change the calibration
constants.
It is recommended that the access password be recorded and filed in a secure
location.
1. The calibration password is set from the Calibration Menu. From the Main Menu (press
PREVIOUS until the Main Menu appears), press Menu [F6], Menu [F6], then Calibrate [F3].
2. Press the Access [F4] key. If there is a password in the system other than 0, then the current
valid password must be entered into the RUSKA 7750i before password modification will be
allowed.
3. Use the numeric keypad to enter the new calibration password. Setting the calibration
password to zero allows free access to ADTS calibration and constants. Press ENTER.
4. Press Yes [F4] to acknowledge changing the calibration password. Press No [F5] to reject
changing the calibration password.
Zeroing
The ADTS should be zeroed once a day to maintain optimal performance. The zero drift
specification is defined in Appendix A, under General Specifications. Refer to Chapter 6,
Zeroing, for the zeroing procedure. On the differential Qc sensor, the zeroing procedure
automatically ties both test and reference ports of the quartz sensor together and performs the
zeroing routine.
On the permanent absolute Ps sensor, a high capacity vacuum pump is required to zero the
instrument. A vacuum gauge sensor is installed internally to the Ps sensor very near to the quartz
sensor. The zeroing command will cycle the internal valves allowing the external vacuum pump
to pull a hard vacuum on the quartz sensor. The sensor should be pulled down to a vacuum of less
than 100 mtorr in order to obtain a proper zero. Note, for the highest measurement performance,
it is recommended to zero the RUSKA 7750i at a vacuum level of 60 mtorr or less. This is
typically achievable within 30 minutes; however, in high humidity situations the drying time can
extend to 45 minutes. It is also important that the vacuum level be stable to at least 5 mtorr per
minute. Once the vacuum level is stable, the user initiates the zeroing procedure. Please refer to
Note
4
Local Operation
Menu
4-17
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