GE Sensing XMT868i Specifications
GE
Measurement & Control
™
DigitalFlow
Panametrics Liquid Flow Ultrasonic
Transmitter
The DigitalFlow XMT868i liquid fl ow transmitter is
a complete ultrasonic fl ow metering system for
measurement of:
Applications
• Hydrocarbon liquids
XMT868i
• Liquefi ed natural gas (LNG)
• Crude oil
• Lubricating oils
• Diesel fuel oils
• Solvents
• Water and wastewater
• Hot/chilled water
• Chemicals
• Beverages
• Other liquids
Features
• Economical non-intrusive fl ow measurement
• Hazardous (classifi ed) location certifi cations
• Simple set-up and installation
• Suitable for wide range of pipe sizes and materials
• Two-channel/two-path version available
Panametrics Liquid Flow Ultrasonic
Transmitter
The DigitalFlow XMT868i ultrasonic fl ow transmitter
combines state-of-the-art fl ow measurement capability
with a low-cost transmitter package that can be installed
right at the process measurement point. The XMT868i
carries appropriate certifi cation for for installation in
hazardous (classifi ed) locations commonly found in
petrochemical and chemical processing environments.
The all-digital XMT868i has no moving parts, requires
minimal maintenance and provides long-term, drift-free
operation. An onboard microprocessor provides exclusive
digital signal coding and correlation detection routines,
automatic adjustment to changing fl uid properties, and
dynamically-confi gured operating software to simplify
programming.
Improved Programming Capability
The DigitalFlow XMT868i introduces an infrared
six-button keypad to allow safe programming and
diagnostics verifi cation in your hazardous (classifi ed)
location. There is no need to open the case to use a PC
to program and no need for an additional handheld
programmer. Just touch the glass of the XMT868i and
the IR buttons will sense your touch. If you prefer your
PC interface, the DigitalFlow XMT868i maintains its RS232
capability, providing full access to the meter’s diagnostics
and programming using PanaView™ software. PanaView
also provides continuous logging capability.
Wetted or Clamp-On Transducers
Ultrasonic fl ow transducers are classifi ed as either wetted
or non-wetted (clamp-on). Clamp-on transducers are
clamped onto the outside of the pipe and never come
into contact with the process fl uid. Wetted transducers
are mounted into the pipe or fl owcell in direct contact
with the process fl uid.
Clamp-on transducers offer maximum convenience,
fl exibility and a low installation cost compared to
traditional fl ow metering technologies. With proper
installation, wetted transducers provide maximum
accuracy (better than 0.5 percent of reading) in most
applications.
The DigitalFlow XMT868i can be used with a variety of
wetted solutions including the PanaFlow™ system. The
PanaFlow meter system relies on the XMT868i as an
integral component to simplify installation. A DigitalFlow
XMT868i is easily mounted to the top of a PanaFlow
system and is shipped ready to install.
Dual-Channel Version Reduces Costs
and Improves Performance
The optional dual-channel/dual-path model can be userconfi gured for a variety of applications. It can be set up
to measure fl ow in two separate pipes with one meter to
reduce the cost-per-measurement point.
To minimize the effects of fl ow profi le distortions, fl ow
swirl and cross fl ow, and for maximum accuracy, you
can install the two sets of transducers on the same pipe.
DigitalFlow XMT868i shown with clamp-on transducers
DigitalFlow XMT868i Flow Transmitter
Uses Transit-Time Flow Measurement
Technique
Flowmeter transducers
Fluid
fl ow
Automatically Adjusts to Changing
Fluid Properties
Standard in all DigitalFlow XMT868i transmit ters, our
unique Automatic Tracking Window™ (ATW™) feature
ensures accurate fl ow measurements even when fl uid
properties are unknown or changing. Like the seek mode
on your car stereo, ATW dynamically sweeps the receiver
window whenever the sound speed of the fl uid changes.
This powerful feature lets you measure fl ow when the
fl uid sound speed is unknown, is changing due to large
temperature shifts, or when a new liquid starts to fl ow in
a multiproduct pipeline.
Ultrasonic signal path
Transit-time fl ow measurement technique
In this method, two transducers serve as both ultrasonic
signal generators and receivers. When mounted on a
pipe, they are in acoustic communication with each other,
meaning the second transducer can receive ultrasonic
signals transmitted by the fi rst transducer and vice versa.
In operation, each transducer functions as a transmitter,
generating a certain number of acoustic pulses, and
then as a receiver for an identical number of pulses.
The time interval between transmission and reception
of the ultrasonic signals is measured in both directions.
When the liquid in the pipe is not fl owing, the transit-time
downstream equals the transit-time upstream. When the
liquid is fl owing, the transit-time downstream is less than
the transit-time upstream.
The difference between the downstream and upstream
transit times is proportional to the velocity of the fl owing
liquid, and its sign indicates the direction of fl ow.
ATW works for both clamp-on and wetted transducer
applications by searching for a reliable ultrasonic
receive signal. It does this by varying the time between
the transmit signal and the receive signal window until
the receive signal is found. The tracking window automatically sweeps through a range of time intervals based
on the minimum and maximum expected sound speeds
programmed by the user.
The window moves (tracks) in response to changes in the
fl uid sound speed. Once the optimal signal is found, ATW
locks onto it until another large change in sound speed
occurs. When this happens, ATW returns to the seek
mode until the optimal signal is found again.
Variable time interval
Receive signalTransmit signal
Tracking window
locked onto
receive signal
Range of tracking window
ATW ensures accuracy when fl uid conditions change
Time
Loading...