IM-P505-02-US
Issue 1
52
UTM20 Series Ultrasonic Transit-time Flowmeters
10.8.1 Filter Parameters
Filter Method (Default: Adaptive)
The UTM20 flow meter offers three levels of signal filtering:
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None imposes no filtering on the signal from the transducers
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Simple with Rejection uses Damping and Bad Data Rejection to filter the flow data
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*Adaptive filtering allows the meter’s software routines to alter the filtering, depending on the
variability of the transducer’s signal The Adaptive filter uses a combination of Damping, Bad Data
Rejection, Sensitivity and Hysteresis to modify the flow input data
Damping (Range 0 to 100 Seconds; Default: 40 Seconds)
Damping is the approximate amount of time the filtering routines use to attain a 99% stable rate value
Generally, the higher the damping value, the more stable the rate readings are—but at the expense
of response time
Sensitivity (Range 0 to 100%; Default: 60%)
Sensitivity determines how fast the adaptive filtering responds to a change in rate Increasing the
sensitivity decreases the filtering, which allows the display to respond to rate changes more rapidly
Hysteresis (Range 0 to 25%; Default: 5%)
Hysteresis creates a window around the average flow measurement reading, defining the limits at which
the automatic damping increases occur If the rate varies within the hysteresis window, greater damping
occurs up to the maximum values set by the flow filter Damping entry The filter also establishes a
flow rate window where measurements outside of the window are captured by the Bad Data Rejection
window Enter the value as a percentage of actual flow rate
For instance, a Hysteresis setting of 5% allows the flow to vary ± 5% from the currently established
flow rate without automatically decreasing the value of the Damping