Output Filter - Teledyne HFM-301 Instruction Manual

301/303/305/306/307 Flowmeters and Controllers Instruction Manual
SOLUTION:
Use the formulas above:
Scale the output of controller A by 0.5 (half) and route the signal to the setpoint of controller B to flow
5% of controller A.

Output Filter

Occasionally noise from a user's system is superimposed on
the output signal voltage. This noise may be due to high
turbulence in the flow stream (the sensor is fast enough to
measure this) or it could be electrical noise when the flow
instrument has a high internal gain (flow instruments with low
full-scale flows ~ 25 slm). Varying levels of radio frequency
noise or varying airflow over the electronics cover can also
induce noise.
Noise can be most pronounced when measuring the flow
output with a sampling analog/digital (A/D) converter. When
possible, program the system to take multiple samples and
average the readings to determine the flow rate.
If less noise is desired, install a jumper over the pins of JP1 on
the flow measurement card. See Figure above and right.
Covering the two bottom pins (2 & 3), will activate a resistor-
capacitor (RC) filter that has a time constant of 0.1 second.
This will increase the settling time of the indicated flow rate to approximately 0.4 seconds and remove
much of the noise. Covering the top two pins (1 & 2), will increase the filter time constant to 1
second. This will increase the settling time to approx. 4 seconds and remove most of the noise.
This adjustment will not affect the calibration of the flow meter circuit or the actual flow response to
change in command signal (flow controllers). This will only slow down the indicated response (output
voltage/current).
EAR99 Technology Subject to Restrictions Contained on the Cover Page
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( 0.05 )( 100 )( 5 )
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( 10 )( 5 )
= 0.5
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