Brooks Instrument 5860i - Manual (Page 23)

3-7
Brooks ® Model 5860 i
Section 3 Operation
Installation and Operation Manual
X-TMF-5860i-MFM-eng
Part Number: 541B110AAG
November, 2008
3-5 Response (Flow Output Signal)
To achieve the proper response characteristics the response
compensation circuit must be adjusted. This adjustment is performed by
observing the output signal of the meter when the flow is suddenly
stopped. Place a metering valve upstream of the Model 5860
i to control
the flow rate.
A Brooks NRS TM precision metering valve is well suited for this application.
Also place a fast acting shut-off valve immediately downstream of the
flowmeter. A solenoid valve is ideal for this, but a manual toggle valve will
do. Keep the length of interconnecting tubing as short as possible
between the valves and the Model 5860
i since the tubing can have a
dampening effect on the flow and the gas may not stop flowing the instant
the downstream valve is closed as desired. Adjustment of the fast
response circuit will not alter the steady state accuracy of the flowmeter as
adjusted in Section 3-4.
Note: This procedure requires an oscilloscope, chart recorder, or a DVM
with a sample speed three samples per second or greater to monitor the
rate of change of the output signal during the test. Monitor the output signal
at pin 2 of D-Connector. TP4 may be used for ground.
a. With the shut-off valve open adjust the metering valve so that the
output voltage of the Model 5860 i is 5.000 Vdc. Allow the output to
become stable at this setting.
b. Close the shut off valve to stop the flow. Observe the output signal as
it decays.
c. The behavior of the output signal during the transition between 100%
and 0% flow indicates the adjustment required of the anticipate
potentiometer. Refer to Figure 3-4.
1. If the flow signal decays to -0.05 to -0.5V then rises to 0.0V, the
anticipate potentiometer is properly adjusted.
2. If the flow signal decays rapidly and goes below -0.5V before rising to
0.0V, the anticipate potentiometer must be adjusted clockwise and
steps a and b repeated.
3. If the flow signal decays slowly and does not go below -0.05V, the
anticipate potentiometer must be adjusted counterclockwise and
steps a and b repeated.