Siemens 7ME3510, Руководство по эксплуатации, Страница: 17 / 214

Description
3.3 Theory of Operation
FUP1010 IP67 Portable
Operating Instructions, 03/2012, A5E02951522-02
15
Typical Industries Serviced
● HVAC (Hotels, Airports, Government)
● Power Generation (Nuclear, Fossil, and Hydro)
● Chemical Processing
● Food and Pharmaceutical
● Aircraft Avionics and Ground Support
● Water and Wastewater
● Aerospace
● Automobile Manufacturing
● Hydrocarbon Industries
3.3 Theory of Operation
The liquid flow meter relies on the MultiPulse transit. Two WideBeam ultrasonic sensors per
measuring path, alternating as transmitter and receiver, are used to interrogate the liquid
flowing within the metering section. The resulting time of arrival for each direction of transmit
(upstream and downstream) is then measured using a highly accurate and stable digital
signal processing method.
Using this detection scheme, the flow meter is capable of resolving the relative transit-time
difference (dT) to within ±100 psec. Considering typical liquid flow transit-time differences
ranging from 1x10
4
to 1x10
6
psec, the flow meter is capable of providing an exceptional turn-
down ratio. The flow meter also incorporates a correlation technique which enables the
system to detect very high flow velocities with the same high degree of resolution. The
ultrasonic sensors are designed with sufficient beam divergence characteristics to insure that
the receive sensor will always have sufficient signal to maintain operation under conditions of
high beam blowing associated with high flow velocities.
With accurate signal arrival time available, the flow meter can compute the raw flow velocity
from the measured upstream and downstream transit times.