ADS Environmental Services Model 3600 530002 A2 - Manual (Page 32)

Flow Measurement 3-7
Ultrasonic Depth Data Scrubbing
There are a number of difficulties inherent to accurately measuring data in a sewer
system, particularly at sewer manholes. Some of the common problems interfering
with flow measurement are noise in the sewer, turbulent (non-laminar) flow, and flow
that is not level or has foam on the surface.
To minimize the effects of these disturbances, bad data points can be eliminated (data
scrubbing) at two different times. The first data scrubbing is done routinely as the
monitor collects readings. This routine incorporates the following procedures.
l Multiple readings are taken by each sensor and averaged.
l Readings that are clearly erroneous (they are well outside the spectrum of the
majority of the readings) are discarded.
l The percentage of all acceptable readings used to arrive at the average value is
recorded.
The second opportunity to scrub data occurs when the data is transferred to the
computer. The data analyst has the option to eliminate bad data points using
parameters specified in QuadraScan. These operations are described in detail in the
QuadraScan User’s Guide.