Atec DF868 User Manual

GE

Sensing

DigitalFlow

™

DF868

Panametrics Liquid
Ultrasonic Flowmeter

DigitalFlow DF868 is a Panametrics
product. Panametrics has joined
other GE high-technology sensing
businesses under a new name

_

GE Industrial, Sensing.

Applications

The DF868 liquid flowmeter is a complete ultrasonic flow
metering system for measurement of:

• Refined hydrocarbons

• Petroleum products

• Crude oil

• Lubricating oils

• Diesel and fuel oils

• Solvents

• Water and wastewater

• Hot/chilled water

• Water/glycol solutions

• Chemicals

• Other liquids

Features

• Economical, nonintrusive flow measurement

• Hazardous (classified) location certification

• Simple setup and installation

• Suitable for a wide range of pipe sizes and
materials

• Two-channel/two-path version available

• Energy measurement option

• Large backlit LCD display

• Velocity, volumetric and energy flow rates

• Totalized flow and trend data

g

GE

Sensing

Panametrics Ultrasonic
Liquid Flowmeter

The DigitalFlow DF868 is a full-featured, fixed-installation
liquid flowmeter designed to meet all your flow metering
and energy measurement needs. Its patented
Correlation Transit-Time™ digital signal processing
provides drift-free measurements in ultraclean and most
"dirty" liquids. This includes fluids with gas bubbles and
entrained solids that have previously required
Doppler-type meters.

Dual-LCD Display, Datalogger and a
Wide Variety of I/O Options

Whether single-channel or dual-channel, all DF868
meters feature two independent, user-programmable,
graphic LCDs, giving you simultaneous access to more
data. There is complete flexibility to display any
parameter on either LCD in a variety of numerical and
graphic formats. Examples include numerical display of
real time flow measurements, real time flow graphs and
diagnostic waveforms, and numerical/graphic display of
data from the meter's built-in 43,000 point datalogger.
Up to 12 isolated 4 to 20 mA outputs, up to six
hermetically sealed or standard alarm relays, and up to
12 frequency/totalizer outputs can be added.

Built-In Energy
Measurement Capability

Another feature that makes the DigitalFlow DF868 meter
such a powerful and versatile flowmeter, is the energy
measurement software included in every meter. The
DigitalFlow DF868, with optional RTDs and input boards,
extends the benefits of ultrasonic flow measurement to
energy measurement. Benefits include measurement of
flow and temperature without pipe penetration, and
compatibility with pipes from 1 to 200 in
(25.4 mm to 5 m) in diameter. The DigitalFlow DF868
meter measures energy flow in water and water/glycol
heating and cooling systems with temperatures from

-4°F to 410°F (-20°C to 210°C). Consult GE for use with

other liquid systems.

To ensure compatibility with existing or preferred
temperature instrumentation, the DigitalFlow DF868
meter is available with three analog input boards. The
transmitter input board provides 24 VDC loop power and
two isolated 4 to 20 mA inputs for transmitters. For
applications requiring raw RTDs, the RTD input board
provides two isolated, three-wire RTD inputs for
temperatures from -148°F to 662°F (-100°C to 350°C).

Measure Flow from Outside the Pipe

Using clamp-on flow transducers, the DigitalFlow DF868
measures flow rate through metal, plastic or even
concrete-lined pipes without penetrating the pipe wall.
To hold clamp-on transducers in place, a variety of
clamping fixtures are available to accommodate
different pipe sizes, transducer types and attachment
methods (e.g., chain, wire rope, Velcro®strap or a
magnetic, bolt-on, or weldable steel yoke with metal
band). Our universal clamping fixture includes ruled slide
tracks to simplify transducer spacing for accurate flow
measurements. There's even a special small-pipe
clamping fixture with miniaturized transducers to
simplify flow measurement on 0.5 to 2 inch
(15 to 50 mm) lines.

Dual-Channel Version Reduces Costs
and Improves Performance

The optional dual-channel/dual-path model can be
user-configured for a variety of applications. It can be
set up to measure flow in two separate pipes with one
meter to reduce the cost-per-measurement point.
To minimize the effects of flow profile distortions, flow
swirl and cross flow, and to provide maximum accuracy,
two sets of transducers can be installed on the same
pipe.

Wetted Transducers for
Maximum Accuracy

Obstructionless wetted transducers are readily available
for maximum performance. After proper installation,
transit-time accuracies of better than 1 percent are
achievable in most applications, matching the

performance of expensive factory-calibrated meters.
Measurement range is 0.1 to 40 ft/s (0.03 to 12.2 m/s) for
a turndown ratio of 400 to 1 in pipes from 1 to over 200
inches in diameter. Measurement is noncontaminating,
obstructionless and causes no pressure drop. The
DigitalFlow DF868 is all digital so measurements don't
drift, and it doesn't need regular maintenance since
there are no moving parts to wear out or orifices to clog.

GE

Sensing

Transmit

signal

Tracking

window

locked onto

receive signal

Time

Variable time

interval

Range of tracking window

Receive

signal

ATW ensures accuracy when fluid conditions change.

Flowmeter Transducers

Fluid
Flow

Ultrasonic Signal Path

Transit-time flow measurement technique

The difference between the downstream and upstream
transit times is proportional to the velocity of the flowing
liquid, and its sign indicates the direction of flow.

The DF868 Flowmeter
Uses the Transit-Time Flow
Measurement Technique

The transit-time technique uses a pair of transducers,
with each transducer sending and receiving coded
ultrasonic signals through the fluid. When the fluid is
flowing, signal transit time in the downstream direction is
shorter than in the upstream direction. The difference
between these transit times is proportional to the
velocity of the flow. The DigitalFlow DF868 measures this
time difference and uses programmed pipe parameters
to determine flow rate and direction.

Automatically Adjusts to Changing
Fluid Properties

Our unique Automatic Tracking Window™ (ATW™)
feature, standard in all DigitalFlow DF868 meters,
ensures accurate flow measurements even when fluid
properties are unknown or changing. Like the seek mode
on a car stereo, ATW dynamically sweeps the receiver
window whenever the sound speed of the fluid changes.
This powerful feature enables flow measurement when
the fluid sound speed is unknown, when it is changing
due to large temperature shifts, or when a new liquid
starts to flow in a multiproduct pipeline.

Is Built to Be Economical and
Stay Economical

To be of real value, a flowmeter must be as economical
to own and operate as it is capable in the field. Using the
latest microcircuit and manufacturing technologies, the
DigitalFlow DF868 flowmeter is built to stay in service for
many years. Completely solid state, the
DigitalFlow DF868 rarely wears out or needs servicing,
resulting in little downtime and low maintenance costs.

The DigitalFlow DF868 will continue to save money by
streamlining the measurement process and trimming
labor costs.

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
fluid 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.