Brooks Instrument SLA7810/20 - Manual (Page 27)

4-3
Section 4 Maintenance Installation and Operation Manual
X-PR-SLA7800-PC-eng
Part Number: 541B047AAG
December, 2008
Model SLA7810 & SLA7820
Example of calculations (Analog Version)
a. Pressure controller is calibrated to 1000 torr full scale
b. Therefore a 5 volt output represents 1000 torr.
c. When the pressure controller is open to atmosphere, the actual output
signal from the pressure controller is 3.78 Volts DC.
Atmospheric pressure is nominally 14.7 psia (760 torr)
d. The calculated analog output is: (760 torr/1000 torr) x 5 VDC= 3.80
Vdc.
e. The actual output of the pressure controller is within 5% of the
calculated value.
Example of calculations (DeviceNet Version)
a. Pressure controller is calibrated to 1000 torr full scale.
b. 100% output equals 1000 torr.
c. When the pressure controller is open to atmosphere, the actual output
signal from the pressure controller is 78%.
Atmospheric pressure is nominally 14.7 psia (760 torr)
d. The calculated output is: (760 torr/1000 torr) x 100%= 76%
e. The actual output of the pressure controller is within 5% of the
calculated value.
If the pressure controller output is within limits, the problem is in the control
valve or the system itself. Please contact Brooks Instrument for further
recommendations.
C. Disassembly
It is not practical to disassemble the controller in the field. The spacing
between the valve and the orifice is critical and could change when
disassembled and reassembled. New screws and metal seals must be
used for all pressure boundary components.