Flow Conditions; Low Flow Rates; Flow Data Scatter And Damping; Fuh1010 Damping And Slewing Controls - Siemens SITRANS FUH1010PVDX Operating Instructions Manual

CQO:1010PVXFM-3
Section 4
4.4

FLOW CONDITIONS

Very rarely are real-world flow conditions uniform and predictable. Therefore, the FUH1010 operating
system provides a considerable degree of control over the stability/agility of the flow rate output. The
FUH1010 is significantly more agile in tracking pressure wave induced Vs transients, and will recover
from mistracking more quickly and smoothly than any other competing transit-time flowmeter.

4.4.1 LOW FLOW RATES

The FUH1010 provides a flow resolution and measurement range that surpasses any other type of
flowmeter. Therefore, it operates superbly for low or high flow rate applications. However, with our clamp-
on systems, using the highest resolution when measuring a low flow rate may cause natural data scatter
to become a high percentage of the reading. Since it is data scatter, it will not contribute any error to a
totalizer reading accumulating for at least several minutes. However, if the flow rate is extremely low
(e.g., under 0.25 ft/sec) the minute zero drift retained by the system may cause an observable perfor-
mance decline. Therefore, if your application involves extremely low flow velocities, and your line size is
2" or under, our 992DFT or 1011FT Flow Tubes might serve you best.

4.4.2 FLOW DATA SCATTER AND DAMPING

The transit-time flowmeter's ability to respond to the extremely fast flow fluctuations that characterize
"real" flow may surprise you. Most conventional flowmeters cannot detect these rapid flow fluctuations
since they are subject to unavoidable mechanical inertia. The FUH1010 response speed is ideal for
tracking fast flow transients. However, if this performance is unnecessary, you can smooth the FUH1010'
response time to suit any application.

FUH1010 Damping and Slewing Controls

The FUH1010 can detect and display minute flow fluctuations that are always present, though not usu-
ally detectable by typical flowmeters. This rapid response accommodates applications that require the
tracking of fast flow transients.
Time Average is our recommended filter that controls the output damping (the number of samples
averaged together to produce the instrument's primary rate output). It integrates the instantaneous flow
rate over a selectable time period. Time Average function is very useful when stability in flow readings
are essential.
It allows the user to enter a value in seconds that the flow computer uses to integrate its response to flow
changes. Do not confuse this with the update speed of analog outputs. This occurs every 0.2 seconds,
regardless of the time average that you select. One practical application is to set the time average
damping so that the meter maintains a smooth output when it is installed downstream from devices
(e.g., a positive displacement pump) that may cause regular surges in the liquid flow.
SmartSlew is a digital signal processing method that generates a variable time constant based on the
real-time assessment of collected data. When the flow data exhibits a steady trend, SmartSlew extends
the time constant and the resulting output is smooth data.
4-4