Dynasonics DXN Portable Ultrasonic Measurement System - Manual (Page 59)

Example:
If the average flow rate is 100 gpm and the Hysteresis is set to 10%, a filter window of 90 ... 110 gpm is established. Successive
flow measurements that reside within that window are recorded and averaged in accordance with the Damping setting. Flow
readings outside of the window are rejected or accepted in accordance with the Bad Data Rejection setting.
Filter settings for example:
Filter Method Adaptive
Damping 40 seconds
Sensitivity 60%
Hysteresis 10%
Bad Data Rejection 3
Flow Within
Hysteresis Limit ±10% Hysteresis
Limit
Flow
Flow Within
Hysteresis Limit ±10% Hysteresis
Limit
Flow
150
100
50
0
110
90
Figure 75: Hysteresis Window
Bad Data Rejection (Number of Samples) [Range 0…10 Samples]
Bad Data Rejection is a value related to the number of successive readings that must be measured outside of a the hysteresis
value before the flowmeter will consider the new flow value valid. In the example a hysteresis setting of 10% would produce a
± 10% band centered on the current valid flow rate of 100 gpm.
The Bad Data Rejection setting is the number of successive samples that must be outside of the Hysteresis Window before
the flowmeter will consider the change in flow is real. Larger values are entered into the Bad Data Rejection window when
measuring liquids that contain gas bubbles, as the gas bubbles tend to disturb the ultrasonic signals and cause more
extraneous flow readings to occur. Larger Bad Data Rejection values tend to make the flowmeter less responsive to rapid
changes in actual flow rate.
Installation & Operation Manual
Page 59 February 2013