Echotel
®
Model 355
Non-Contact Ultrasonic
Two-Wire Transmitter
for Level, Volume, or
Open Channel Flow
DESCRIPTION
Echotel
®
Model 355 is a two-wire, loop-powered, non-
contact ultrasonic transmitter that performs liquid level,
volume, and open channel flow measurement. Model
355 Transmitters feature a powerful 60 kHz ultrasonic
transducer and advanced digital signal processing to
reliably measure out to a 20 feet (6 m) maximum range.
The Model 355 provides unsurpassed ease of
configuration with either the menu-driven
4-push-button, 2-line
×
16-character display, HART
®
digital communications, or PACTware
™
. This enables a
complete configuration to be performed via the local
user interface, or remotely with the extra capability of
capturing echo wave forms, and viewing trend data,
diagnostic conditions, and all transmitter configuration
parameters.
The integral mount electronics are housed in either a
cast aluminum housing or Lexan
®
thermoplastic
housing. The intelligent electronics analyze the
ultrasonic echo profile, apply temperature
compensation, reject echoes from false targets, and then
processes the true echo from the liquid surface. This
results in an extremely reliable measurement even
when applications difficulties like turbulence and false
echoes exist.
The 60 kHz ultrasonic transducer is offered in
polypropylene, or Kynar
®
Flex for superior performance
in harsh environments. These powerful transducers
feature a 10° conical beam and 10
"
(250 mm) blocking
distance to maximize measurement capabilities in a
wide variety of applications.
Cast aluminum housing with
Kynar Flex
®
transducer
Lexan
®
housing with
polypropylene transducer
FEATURES
•
Two-wire, loop-powered transmitter for level,
volume and open channel flow measurement
•
Maximum range of 20 feet (6 meters)
•
PACTware PC program using HART Communications
for remote configuration and troubleshooting
•
Menu-driven 4-push-button, 2-line
×
16-character
LCD user interface
•
Temperature compensated echo rejection profile
identifies true echo from liquid surface
•
Two 7-digit flow totalizers, one resettable, and one
non-resettable
•
Common tank shapes and 20-point custom table for
fast and accurate volume configuration
•
60 kHz transducer with 10° beam angle and 10
"
(250 mm) blocking distance
•
Dynamic baseline noise compensation provides reliable
performance in the presence of electromagnetic noise
•
Generic Discharge Flow Equation and 53 flume/weir
primary elements for open channel flow applications
APPLICATIONS
•
Chemical storage tanks
•
Vessels with highly viscous media
•
Paint, ink and solvent tanks
•
Industrial wastewater processing
•
Volume in batch and day tanks
•
Open channel flow weirs and flumes
TECHNOLOGY
Non-contact ultrasonic measurement is obtained by emit-
ting an ultrasonic pulse from the transducer and measuring
the time required for the echo to reflect from the liquid sur-
face and return to the transducer. The Model 355
measures the time of the round trip pulse, and calculates
the distance using the equation:
transducer to provide compensation for changing air
temperatures. Level is computed by the 355 electronics
using the measured distance and the configuration data
that has been entered for the vessel dimensions.
By inputting the type and geometry of a vessel, the elec-
tronics can calculate the liquid volume in the vessel. In a
similar operation, the Model 355 can perform open chan-
nel flow measurement by converting the level reading into
units of volume per time. Common tank shapes, flumes
and weirs are stored in the 355 software. A 20-point cus-
tom table is also available for unusual tanks or primary
flow elements.
D = Distance to target
V
a
= Velocity of sound through air (1,128 ft/sec.)
T = Time for one round trip sound pulse
Since the speed of sound is temperature dependent, the
transducer also measures the temperature at the
V T
D=
a
2
Model 355
Blocking
Distance
Flow
Distance (measured)
Range
Parshall
Flume
Level (range - distance)
Level/Volume Application
Open Channel Flow Application
PERFORMANCE
Model 355 Transmitters are high performance units that
feature a powerful 60 kHz transducer, and advanced
digital signal processing. These features allow the 355 to
accurately track the liquid level in difficult applications
involving agitation and light foam. The narrow 10° beam
angle, shown on the right, allows the 355 to be used in
applications where other units with wider beam angles
fail due to false reflections from obstructions in the tank.
5 feet
r=5.2 inches
10 feet
r=10.5 inches
15 feet
r
r=15.7 inches
20 feet
r=21.0 inches
Beam Radius (r) vs. Distance
2
MEASUREMENT
RANGE
CALCULATIONS
Ultrasonic non-contact transmitters are typically rated for
a maximum range in ideal conditions. Experience has
shown that the maximum range must be reduced for
certain factors. Although the maximum range rating is
somewhat conservative, each application must be
evaluated for specific conditions in the tank.
Several application parameters that affect ultrasonic
performance are shown in the tank at the right. Each of
these parameters is assigned a Performance Multiplier in
the chart below. Multiply the maximum potential range
(20 feet) of the Model 355 by each of the applicable
Performance Multipliers to calculate the maximum
allowable range for the application.
Vapors
Foam
Surface
agitation
Beam spread
interference
Beam spread
interference
OPERATING PARAMETER
SURFACE AGITATION:
Surface agitation or waves can degrade
the performance. Moderate agitation results in only slight degrada-
tion of performance. The worst case is when the surface is a good
reflector, but in the wrong direction.
CONDITION
PERFORMANCE
MULTIPLIER
Smooth, glass-like surface . . . . . . . . . . . . . . . . . . . . . .1.0
Slight agitation, choppiness . . . . . . . . . . . . . . . . . . . . .0.9
Heavy agitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.8
Slight vortex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.7
VAPORS AND STEAM:
Vapors can cause problems when the
liquid process temperature is well above the temperature of the
airspace. The greater the difference, the more expected vapor
problems. The problems result from condensation or layering in the
sound path, both of which attenuate the sound signal, and degrade
performance. If a vent is used, be sure that it is well away from the
transducer.
BEAM SPREAD INTERFERENCE:
It is recommended that no
obstructions, such as ladder rungs, fill pipes, support struts, etc., be
allowed within the 10° ultrasonic beam. If an obstruction is unavoid-
able, make it as far away as possible from the transducer.
Interference from agitator blades is only an intermittent interference
that usually has little effect on performance. A special software algo-
rithm can also help suppress false echoes from agitator blades that
are within the beam angle.
FOAM:
Foam can attenuate the ultrasound and render the system
inoperative. If possible, moving the transducer to an area in the tank
where there is less foam will improve the performance. Thick, heavy-
density foams can sometimes produce a reflection from the top of
the foam. The multipliers shown at right are general guidelines. For
further assistance consult the factory.
No condensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.0
Little condensation . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.9
Much condensation/ foggy appearance . . . . . . . . . . . .0.8
No interference within 5° half beam angle . . . . . . . . . .1.0
Agitator at speed less than 60 RPM . . . . . . . . . . . . . . .1.0
Agitator at speed greater than 60 RPM . . .Consult factory
Interference outside 2°, far from
transducer (in bottom third of range) . . . . . . . . . . . . . .0.8
Interference outside 2°, near to
transducer (in top third of range) . . . . . . . . . . . . . . . . .0.5
No foam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.0
Light froth, less than 0.25" thick . . . . . . . . . . . . . . . . . .0.8
Light foam, less than 0.5" thick . . . . . . . . . . . . . . . . . .0.5
Light foam, more than 1" thick . . . . . . . . . . . . . . . . . . .0.1
EXAMPLE:
A slightly agitated 12-foot tank with no condensation, no interference, and a light froth on the surface.
Maximum allowable range: 20'
×
0.9
×
1.0
×
1.0
×
0.8 = 14.4 feet
Since the maximum allowable range is 14.4 feet, the 355 is suitable for this 12-foot tank.
NOTE: The multipliers shown above are general guidelines. For further assistance consult the factory.
3
LEVEL
&
VOLUME
APPLICATIONS
The Echotel Model 355 Transmitter utilizes an advanced, patent-pending signal processing technology to provide
excellent performance in difficult process conditions. Dynamic baseline noise compensation, temperature compensated
echo rejection, and extensive self-diagnostics all combine to provide extremely reliable level and volume measurement.
Temperature Compensated Echo Rejection
Ultrasonic transmitters use temperature compensation to
adjust for speed-of-sound changes throughout the operating
temperature range of the transducer; however, most
transmitters do not apply this compensation to their false
target rejection scheme. This can result in unreliable level
measurement when the temperature inside the tank changes, and the echo
rejection profile contracts or expands. The Model 355 has a patent-pending echo
rejection technique that constantly adjusts the rejected echo profile based on the
current sound propagation velocity. This technique keeps the transmitter tracking
the actual liquid level as opposed to false targets even when temperature changes
alter the shape of the echo rejection profile.
Dynamic Baseline Noise Compensation
Electromagnetic and acoustical noise can adversely affect
instrumentation by decreasing the signal-to-noise ratio, and
degrading overall measurement performance. The Model
355 continuously monitors for the presence of excessive
electrical noise. If noise levels are above a set limit, the
electronics will dynamically adjust the baseline to compensate for the electrical
interference. This dynamic baseline adjustment enables the 355 to keep tracking
the proper echo even in the presence of excessive electrical noise.
Stored Tank Shapes for Volume
Volume configuration with the 355 is as easy as selecting
the tank shape and inputting 1–3 dimensions. While a
20-point custom table is also available, selecting the actual
tank shape provides for a fast and accurate configuration
for a variety of common tanks shapes.
OPEN
CHANNEL
n
FLOW
APPLICATIONS
Q=K(L-CH)H
Model 355
Flow
Parshall
Flume
Extensive Selection of Primary Flow Elements
With a total of 53 flume and weir curves stored in the
electronics, it would be hard to find an open channel flow
application that cannot be handled by the 355 transmitter.
Unusual flow applications can readily be accomplished
through the use of either the 20-point Custom Table or the
Generic Discharge Flow Equation which allows a direct entry
of unique flow equations.
Dual Flow Totalizers
Two 7-digit flow totalizers are provided for recording flow
in cubic feet, gallons, million gallons, liters, million liters, or
cubic meters. One totalizer is resettable and the other is
non-resettable. Several multipliers are selectable to allow
for proper scaling. Totalizer time is also recorded to show
how long each totalizer has been recording flow.
4
ELECTRONICS
Supply Voltage
IS Entity Parameters
SPECIFICATIONS
XP & GP 16 to 36 VDC
IS 16 to 28.6 VDC
FM/FMc Vmax = 28.6 V, Imax = 140 mA
Pmax = 1.0 W, Ci = 5.5 nF, Li = 9.4 µH
ATEX Ui = 28.4 V, li = 94 mA, Pi = 0.67 W
Ci = 5.5 nF, Li = 370 µH
Power Consumption
Output
Less than 1 Watt
Type 4–20 mA with optional HART digital signal
Range 3.8 to 20.5 mA useable
Diagnostic Alarm Selectable from 3.6 mA, 22 mA or HOLD
Damping Adjustable from 1–60
Digital Communication
Display
Keypad
Ambient Temperature
Housing Material
Cable Entry
HART version 5.x compatible
2-line x 16-character LCD
4-push-button menu-driven
-40° to +175° F (-40° to +80° C)
Cast aluminum or Lexan
Two ¾" NPT or M20 entries
TRANSDUCER
Maximum Range
Minimum Range
Blocking Distance
Frequency
Process Connection
Process Temperature
Process Pressure
Material
Beam Angle
SPECIFICATIONS
20 feet (6 meters)
13 inches (330 mm)
10 inches (250 mm)
60 kHz
2" NPT
-40º to +175º F (-40º to +80º C)
0 to 43.5 psig (0 to 3 bar)
Kynar
®
Flex (PVDF) or polypropylene
10º conical
PERFORMANCE
SPECIFICATIONS
Accuracy
Repeatability
Resolution
Linearity
Response Time
Warm-up Time
Greater of ± 0.2% of range or 0.24 inch (6 mm)
± 0.125 inch (± 3 mm)
0.1 inch (2.5 mm)
± 0.4 inch (±10 mm)
Less than 1 second (typical)
30 seconds
Performance is based on a reference operating condition of an ambient temperature of +60º to +77º F (+15º to +25º C),
45 to 75% relative humidity, transducer vertically aligned over an ideal reflecting surface, and no false targets within the
ultrasonic beam angle.
5
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