Brooks Instrument 5850E - Manual (Page 28)

Brooks ® Model 5850E
3-8
Installation and Operation Manual
X-TMF-5850E-MFC-eng
Part Number: 541B102AAG
September, 2009
Section 3 Operation
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 (+100 times
for Current I/O Version) of the sensor. This voltage can range from -1.2
to -12 Volts, however, it is recommended that this voltage stay between
-2.0 and -9.0 Volts for proper operation. If the recommended voltage
range exceeds the desired range, accuracy and/or signal stability may
not be achieved. If one of the limits is reached, check the restrictor and
orifice sizing procedures. Refer to Sections 4-6 and 4-7 respectively.
g. Set the command potentiometer for zero percent of flow. Connect the
DVM positive lead to flow signal output (Terminal 3 Card Edge, Pin 2 D-
Connector) and the negative lead to TP4. Readjust the zero potentiom-
eter for an output of zero mV ±2 mV as necessary.
h. Set the command potentiometer for 50% of 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
Example:
Error = -1.5%
TP2 correction voltage = -1.5 x 0.450 = -0.675 Volts
New TP2 voltage = zero volts + (-0.675) = -0.675 Volts
j. Set the command potentiometer for 100% flow (5.000V). Connect the
DVM positive lead to TP2 and the negative lead to TP4.
k. Adjust the linearity potentiometer for an output equal to the new calcu-
lated TP2 voltage.
l. Repeat Steps “f, g and h.”
1. If the error recorded in Step “h” is less than 0.5%, then the calibra-
tion procedure is complete.
2. If the error is greater than 0.5%, set the command potentiometer for
100% (5.000V). Connect the DVM positive lead to TP2 (linearity
voltage) and the negative lead to TP4 (circuit common). Calculate a
new TP2 voltage as follows: