MKS 651D Series, User Manual, Page: 73 / 162

Chapter Four: Local Operation Operation
61
How To Use the Sensor Zero
The sensor zero function corrects any sensor zero offsets.
To zero the currently displayed sensor
(indicated on the display by a ‘H” for the H igh pressure sensor or an ‘L’ for the L ow pressure
sensor)
1. Turn the gas flow off.
2. Open the control valve fully by pressing the [O
PEN
] key.
Refer to How To Drive the Valve to Full Open .
3. Pump the system down to base pressure.
In order to achieve a proper zero, the pressure of the system must be lower than the
resolution of the sensor used to measure system pressure.
4. Press the [Z
ERO
] key for at least three seconds.
The LED in the upper left corner of the [Z
ERO
] key remains on as the sensor is
zeroed. The front panel display shows a pressure reading of zero, and changes to reflect
changes in system pressure as soon as a change occurs.
Note
If the pressure reading (at base pressure) is greater than 4% of full range,
the sensor will not be zeroed.
To change the displayed sensor
Enter setup mode (see setup section), press the [ ] key to advance to the Channel Select
screen, and select the desired channel (High or Low). Press the STOP key to return to
the default
Pressure and Position display screen and follow steps 1 through 4 above.
How To Use the Special Zero
The special zero function zeros the base pressure in systems where the known base pressure is
not
at , but near zero (as measured by another transducer in the system).
To use the special zero:
1. Press the [ ] and the [Z
ERO
] keys simultaneously for about three seconds.
The screen displays: