Repeatability; Data Stability; Data Scatter; Data Drift - Siemens SITRANS FUG1010 IP65 NEMA 4X Instruction Manual

Section 6 1010GCNFM-3C

6.2.2 REPEATABILITY

Some applications emphasize repeatability rather than absolute accuracy. FUG1010GCN features ex-
cellent repeatability specifications since its digital "no moving parts" design avoids the adverse effects of
hysteresis and other wear mechanisms typical of mechanical devices.

6.2.3 DATA STABILITY

Two main factors influence the system's data stability: Data Scatter and Drift

Data Scatter

Data scatter is defined as a rapid variation in flow readings (within a span of about 0.1 to 5 seconds).
Minimal data scatter (approximately 0.005 to 0.01 ft/sec) is a natural by-product of the digital computa-
tion that extracts the extremely small difference in the up vs. down sonic transit time. However, minimal
data scatter will not influence the integrated flow total over periods as short as several minutes. Natu-
rally, it will be a greater percentage of reading when the meter measures extremely low flow rates. Poor
fluid sonic conductivity could attenuate the sonic signal to a level that increases data scatter. You should
check the signal level (Valc %) item on the Diagnostic Menu. Usually, this condition is indicated by a low
Valc % value (less than 30).
FUG1010GCN does not exhibit inertia since it has no moving parts. In addition, it takes readings ten
times per second. Therefore, it can detect and track very brief flow fluctuations that are beyond the
response capability of some conventional meters. This performance level is required for detecting very
fast and short flow transients or for a fast-response servo control loop application. However, you can use
the damping and slewing controls to smooth the output response if you want the system to ignore rapid
flow fluctuations or data scatter.

Data Drift

Drift is a defined as a long-term cyclical flow deviation resulting from the variation of fluid temperature or
fluid sonic velocity. Drift may be more noticeable when combined with a poor signal-to-noise ratio.
FUG1010GCN is carefully designed to minimize the effects of drift. There are no drift-prone analog
phase-locked loop devices in the primary detection circuits.
6.3

FLOW CONDITIONS

Very rarely are real-world flow conditions uniform and predictable. Therefore, the FUG1010GCN operat-
ing system provides a considerable degree of control over the stability/agility of the flow rate output.
FUG1010GCN is significantly more agile in tracking pressure wave induced Vs transients, and will re-
cover from mis-tracking more quickly and smoothly than any other competing transit-time flowmeter.

6.3.1 LOW FLOW RATES

The FUG1010GCN 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.
6-2