Specifications

RUSKA 7250, 7250i, 7250xi & 7250LP
Users Manual
2-12
thermally stable by viewing the Menu | Display screen and verifying that the temperature
is at 50
o
C. In addition to the temperature, this screen will show the duty cycle of the
oven.
When operating the system in either a very cold or hot environment, if the oven in unable
to maintain the temperature of the internal oven, the Calibrator will generate an Oven
Control Failure error messages. The operator can review the temperature and duty cycle
of the oven by pressing the Menu | Display keys. The unit must have been warmed up for
a minimum of 3 hours prior to determining the condition of the oven temperature control.
The temperature of the sensor should be controlled to 50
o
C. The Duty Cycle indicates
the amount of time (in units of percentage) that the oven control is turned on in order to
maintain the oven at the proper set-point of 50
o
C. A unit that is operating properly, after
it has fully warmed up, should indicate a sensor temperature of 50
o
C and a duty cycle
between 10 to 90%.
If operating the instrument in a very cold environment and the oven duty cycle is at a
high percentage (>90%) you will need to turn the fan off. If you are operating in a warm
environment or when multiple systems are housed in consoles without adequate
ventilation, the system may become too hot and generate the Oven Control Failure error
message. If operating the instrument in a warm environment and the oven duty cycle is at
a low percentage (>10%) you will need to turn the fan on. See Chapter 6, Fan Operation.
When the operator changes the status of the fan, it will remain in that condition until the
operator changes the setting.
gkn012.bmp
Figure 2-8. Menu | Display - Menu
Pressure Reading and Correction
The sensor’s analog output is processed by an analog-to-digital circuit that results in an
output referred to as counts. This output is corrected for the applied effects listed below.
The counts are linearized and the resulting pressure value is corrected for the variations in
head pressure, vacuum, case effect, and oven temperature effects.
The following equations are used by the control algorithm to adjust and correct the
pressure signal.
Zero Coefficients
CsH Zero correction for High FSR (Full-Scale Resistors) Value is in counts
(7,381,975 = full scale of current sensor).
CsL Zero correction for Low FSR. Value is in counts (7,381,975 = full scale of
low FSR)