MKS 651C - How To Zero a Sensor

How To Zero a Sensor Cha
p
ter Five: Local O
p
eration
54
How To Zero a Sensor
Zeroing a sensor is performed to correct sensor zero offsets.
1. Turn the gas flow off.
2. Fully open the control valve.
3. Wait until the system is pumped down to base pressure.
In order to achieve a proper zero, the pressure of the system must be
lower
than the
resolution of the Baratron used to measure system pressure. If the pressure reading (at
base pressure) is greater than 4% of full range, the sensor will not be zeroed.
4. Press the [Z
ERO
] key for at least three seconds.
The system responds by flashing on a light in the [Z
ERO
] key, and zeroing the sensor.
The front panel window shows a pressure reading of zero.
The front panel display changes to reflect a change in system pressure as soon as a
change occurs.
How To Use Special Zero
The special zero function is used to zero base pressure in systems where the known pressure is
not
at
, but
near
zero (displayed on another readout in the system).
1. Press [
] and the [Z
ERO
] key simultaneously for about three seconds, until the
front panel displays
zero base pressure
and the pressure level.
2. Use the Adjust knob to reconcile the pressure reading on the display with the known base
pressure reading (displayed on another readout in the system).
3. Press the [S
TOP
] key to exit.
How To Remove Zero
The remove zero function removes the zero correction factor stored in memory, and is used to
determine the uncorrected signal from the pressure transducer. Each time a sensor is zeroed, the
offset changes. In some applications it may be important to keep the zero offset within a specific
range.
Press the [S
TOP
] key and the [Zero] key simultaneously for about three seconds until the
front panel display changes from a zero pressure reading to the uncorrected signal level.