Brooks Instrument 5851i - Manual (Page 23)

3-5
Installation and Operation Manual
X-TMF-5851i-MFC-eng
Part Number: 541B109AAG
September, 2009
Brooks ® Model 5851 i
Section 3 Operation
f. Connect the DVM positive lead to TP1 (100x sensor voltage) and the
negative lead to TP4 (circuit common). The setpoint should still be
set at 100% flow (5.000V). Measure the flow rate using suitable
volumetric calibration equipment. To adjust the controller to the
proper full scale flow, calculate a new TP1 voltage using the following
equation:
Adjust the span potentiometer until the voltage at TP1 is equal to the value
calculated above. Recheck the flow rate after the flow is stable (at least
two minutes). Repeat this check and adjustment procedure until the
measured flow rate is within 1% of the desired flow rate.
NOTE: The voltage at TP1 is 100 times the output voltage of the sensor.
This voltage can range from 1.2 to 12 volts, however, it is recommended
that this voltage stays between 2.0 and 9.0 volts for proper operation. If the
recommended voltage range exceeds that desired, accuracy and/or signal
stability may not be achieved. If one of the limits is reached, check the
orifice and restrictor sizing procedures. Refer to Sections 4-6 and 4-7
respectively.
g. Adjust the command potentiometer for 0% flow. Connect the DVM
positive lead to 0-5V signal output ( Pin 2) and the negative lead to
TP4. Readjust the zero potentiometer for an output of 0 mV ±2 mV
as necessary.
h. Set the command potentiometer for 50% flow (2.500V) and measure
the flow rate. Calculate the error as a percentage of full scale.
Example:
What is the percent of full scale error when full scale is equal to 100
sccm?
Measured flow rate = 48.5 sccm
Desired flow rate = 50.0 sccm
i. Calculate the TP2 correction voltage: (error recorded in step "h") x
0.450 volts.
Error = -1.5%
TP2 correction voltage
= -1.5 x 0.450 = -0.675 volts
New TP2 voltage = 0 volts + (-0.675) = -0.675 volts