Siemens SITRANS FUH1010PVDX, Operating Instructions Manual, Page: 36 / 308

1-4
CQO:1010PVXFM-3
Section 1
For transit-time operation, the flow computer converts a series of electronic pulses to high frequency
sonic signals. Transducers inject these sonic signals through the pipe wall into the flowing liquid. Each
transducer alternates as either a transmitter or a receiver of the high frequency signals. This causes the
direction of the sonic signal to alternate between the downstream direction (traveling with the flow) and
the upstream direction (traveling against the flow). The transit-time technique relies on the effect of the
flowing liquid on the amount of time it takes to travel “downstream” versus “upstream.”
FLOW
1.3 DESCRIPTION OF CHANNEL FUNCTIONS (FUH1010PVDX Systems only)
Dual channel FUH1010PVDX systems provide two flow sensing paths that allow its operation as two
completely independent single-path flowmeters. On single channel systems, you do not get a choice of
meter types since this requires two independent measurement channels.
Dual Path Flow
Dual Path Flow uses two measurement channels to achieve a single output via a “virtual” third channel.
The resultant data is the average of the two channels. This meter type only supports clamp-on or in-line
transit-time operation. Benefits include highest available precision and enhanced immunity from dis-
torted flow profile conditions.
Virtual
Channel
3
Channel 1
Flow
Channel 2
Flow
Ch1 + Ch2
2
Output
(average of
Ch 1 & Ch 2)
Pipe
1.4 CLAMP-ON TRANSIT-TIME THEORY OF OPERATION
Note that in the figure on the next page, two transducers are mounted to the outside of a pipe. If we
identify the direction of flow through the pipe, you can see that one transducer location is “upstream” and
the other transducer location is “downstream” with respect to the direction of flow.
Upstream
Transducer
Downstream
Transducer
FLOW