Omega LV5000 Series Level Transmitters Owner Manual

MADE IN
WARRANTY
Shop online at
omega.com”
LEOMEGA®
Www.omega.com
mail: [email protected]
ISO9001 [509002
STAMFORD, CT MANCHESTER, UK
= 1V5000 SERIES
LV5900 Level Transmitters
LV5000, 5100, 5200, 5300, 5500
5603 Level Sensing Elements
omega.com®
LEOMEGA”
OMEGAnet“ Online Service Internet e-mail
www.omega.com [email protected]
USA:
ISO 9001 Certified
Canada:
Servicing North America:
One Omega Drive, P.O. Box 4047
stamford CT 06907-0047
TEL: (203) 359-1660 FAX: (203) 359-7700
e-mail: [email protected]
976 Bergar
Laval (Quebec) H7L 5A1, Canada
TEL: (514) 856-6928 FAX: (514) 856-6886
e-mail: [email protected]
For immediate technical or application assistance:
USA and Canada:
Mexico:
Benelux:
Czech Republic:
France:
Germany/Austria:
United Kingdom:
ISO 9002 Certified
Sales Service: 1-800-826-6342 / 1-800-TC-OMEGA®
Customer Service: 1-800-622-2378 / 1-800-622-BEST*
Engineering Service: 1-800-872-9436 / 1-800-USA-WHEN
TELEX: 996404 EASYLINK: 62968934 CABLE: OMEGA
En Espanol: (001) 203-359-7803 e-mail: [email protected]
FAX: (001) 203-359-7807 infoComega.com.mx
Servicing Europe:
Postbus 8034, 1180 LA Amstelveen, The Netherlands
TEL: +31 (0)20 3472121 FAX: +31 (0)20 6434643
Toll Free in Benelux: 0800 0993344
e-mail: [email protected]
Frystatska 184/46, 733 01 Karvina, Czech Republic
TEL: +420 (0)59 6311899 FAX: +420 (0)59 6311114
Toll Free: 0800-1-66342 e-mail: [email protected]
11, rue Jacques Cartier, 78280 Guyancourt, France
TEL: +33 (0)1 61 37 29 00 FAX: +33 (0)1 30 57 54 27
Toll Free in France: 0800 466 342
e-mail: [email protected]
Daimlerstrasse 26, D-75392 Deckenpfronn, Germany
TEL: +49 (0)7056 9398-0 FAX: +49 (0)7056 9398-29
Toll Free in Germany: 0800 639 7678
e-mail: [email protected]
One Omega Drive, River Bend Technology Centre
Northbank, Irlam, Manchester
M44 5BD United Kingdom
TEL: +44 (0)161 777 6611 FAX: +44 (0)161 777 6622
Toll Free in United Kingdom: 0800-488-488
e-mail: [email protected]
It is the policy of OMEGA to comply with all worldwide safety and EMC/EMI regulations that
apply. OMEGA is constantly pursuing certification of its products to the European New Approach
Directives. OMEGA will add the CE mark to every appropriate device upon certification.
The information contained in this document is believed to be correct, but OMEGA Engineering, Inc. accepts
no liability for any errors it contains, and reserves the right to alter specifications without notice.
WARNING: These products are not designed for use in, and should not be used for, human applications.
TABLE OF CONTENTS
1.1
1.2
ee TE TA
GENERAL INFORMATION
1.1.1 Description ............200000000 000000000006 3
Transmitter Versions
Anti-Coat Capability
Output Flexibility
1.1.2 Product identification ........................ 3
1.1.3 Available Models...................0400000000 3
SPECIFICATIONS ............2002 00000000 000000 3-4
2.2
2.3
MECHANICAL REQUIREMENTS
2.2.1 Location ..........4200000 00000 a 00 a 000000 5-6
2.2.2 Integral Mounting ........... ——e-—eeesvecreos 6-7
CE 7-8
ELECTRICAL CONNECTIONS
2.3.1 AC Line-Powered TransmitterS. .............. 9-10
Level Probe
4-20 mA Output
Line Power
Hazardous Area Wiring
2.3.2 DC-Powered Transmitters ................. 10-11
Level Probe
DC Power and Output
Hazardous Area Wiring
3.1
3.2
OPERATING CONTROLS
3.1.1 Calibration. . ..........cc iii. 12
3.1.2 QutputMode. ......... coi 13
3.1.3 Output Damping ..........._eeeeeeeoreoreno. 13
CALIBRATION
3.2.1 With Output In Direct Acting Mode ........... 13-15
Setting The Zero Level Output
Setting The Full Level Output
Adjusting Output Signal Damping
3.2.2 With Output In Reverse Acting Mode ........... 15
-1- Manual M1685
TABLE OF CONTENTS (Continued)
pe ратей
5.1 | GENERAL .........eo..eeconaorocnarecooren. 18
52 | TROUBLESHOOTING .............Ñ.oeeeecoe.. 18-19
ILLUSTRATIONS: | Figure 2-1 Typical Level Probe/Transmitte
Installation Locations ....... ......... 5
Figure 2-2 Integral Mounting ......... ......... 7
Figure 2-3 Remote Mounting......... — andere 8
Figure 2-4 Triaxial Cable Hook-Up Betw: 1
Level Probe J-Box And Remc
Mounted Transmitter. ..... .......... 9
Figure 2-5 AC Line Power Hookup .... ......... 10
Figure 2-6 DC Power and Output Hookt: ......... 11
Figure 3-1 Control Panel Layout ..... ......... 12
Figure 4-1 Instrument Operations Sche ‘ic
Diagram .............. Пень, 16
Manual M1685 -2-
1.1 - GENERAL INFORMATION
1.1.1 Description
Transmitter
Versions
Anti-Coat
Capability
Output
Flexibility
1.1.2 Product
Identification
1.1.3 Available Models
The OMEGA® LV5900 Series RF electronic level transmitters
are designed for continuous level measurement of conductive
and non-conductive liquids, granular materials, slurries and
interface applications. They can be used with any OMEGA
LV5000 through LV5600 Series insulated level sensing
probes.
The LV5900 Series are non-indicating (blind) transmitters.
These transmitters may be mounted directly onto the level
sensing probe or remotely mounted within 150 feet using
special triaxial interconnect cable. The transmitter may be
supplied in a DC-powered version that requires 18-35 VDC
power. An AC line-powered (four-wire) version for operation
with 115 or 230 VAC is optional.
The instrument contains special “anti-coat” circuitry to compen-
sate for the effect of conductive coating which may build up on
the level sensing probe surface.
The transmitter provides a 4-20 mA isolated output with adjust-
able damping. The unit may be field-selected for direct or
reverse acting output modes.
The serial # of your instrument is located on the electronic
chassis next to the power input terminals. Write the serial # in
the space provided below for convenient identification should
technical assistance be required.
Serial #
Model Description
L V5900 Blind transmitter, aluminum enclosure
LV5900P Blind transmitter, PVC enclosure
For AC-powered option, add either "115 Vac" or "230 Vac" to
model number.
1.2 - SPECIFICATIONS
1.2.1 Operational
Ambient Conditions:
In Aluminum Encl. .............. -40 to 160°F (-40 to 71°C), 0 to 95%
relative humidity, non-condensing
In PVC Enclosure ............... -40 to 122” (-40 to 50%), 0 to 95%
relative humidity, non-condensing
Power Requirements:
AC Line-Powered ............... 115 or 230 VAC, 50/60 Hz.
DC-Powered....................... 18 to 35 VDC
-3- Manual M1685
1.2.2 Performance
1.2.3 Mechanical
Manual M1685
Level Probe-to-
Transmitter Distance ..............
Output Load:
Output Damping .....................
Anti-coat Circuitry ...................
Protection ..............e................
Zero Adjustment Range .........
Span Adjustment Range ........
Zero/Span Ratio .....................
Linearity..................c..ee.eomecano
Temperature Stability .............
Enclosure:
Standard .......................e....
Net Weight:
150 feet maximum (when transmitter is
remote mounted)
isolated 4-20 mA, field-selectable
direct or reverse acting
600 ohms max. load
Max. Loop Load (in series with transmitter
and power supply):
550 ohms with 24 VDC power supply
1100 ohms with 35 VDC power supply
NOTE: For long cable runs, the resis-
tance of the wire must be con-
sidered and may decrease
max. load capacity
Adjustable, 0.1 to 10 seconds
Phase-shift type; compensates
automatically for conductive coatings
RFI, EMI and static charge
0 to 500 pF
10 to 10,000 pF
10:1 maximum
0.5% of full scale
Greater of 0.01 pF per °F or
0.01% of span per +
Cast aluminum w/ureihane
finish - NEMA 4, 7 and 9
(weatherproof, hosedown, dust
and vapor explosion-resistant)
PVC - NEMA 4X for corrosive
areas
Model LV5900 (in explosion-
resistant enclosure) ........
Model LVS900P (in PVC
enclosure) .......................
3.6 Ibs. (1.63 kg) approx.
3.4 Ibs. (1.54 kg) approx.
2.1 - UNPACKING
Remove the packing list and verify that you have received all
equipment. If you have any questions about the shipment,
please call the OMEGA Customer Service Department.
After unpacking, open the transmitter enclosure and inspect
the electronic chassis for shipping damage. If there is evidence
of damage, notify the carrier immediately. Save the small
plastic screwdriver and banana plug for later use.
2.2 - MECHANICAL REQUIREMENTS
2.2.1 Location
Mounting positions for the level probe should be carefully
considered. The probe must be installed vertically and its
length must be sufficiently long to handle the entire measuring
range. Do not locate the level probe in a position where the
inflow of measured material could contact it. Also, locations
should be well clear of obstructions and agitators. Figure 2-1
illustrates typical mounting locations.
Level probes used in granular material should be located
halfway between the vessel wall and the apex of the material
pile created by the incoming material. The output will then be
representative of the average level.
For applications involving a vessel =
with non-conductive walls, a AA
ground reference plate or fl
grounded reference level element f N
is required. However, if the meas- J)
ured material is conductive
a
\
Na Recommended
, ) “< —-.. Recomme a
E
(
/;
> £ ( |
vi ( ) eld
Ll 4
FIGURE 2-1 Typical Level Probe/Transmitter Installation Locations
-5- Manual M1685
2.2.2 Integral Mounting
Manual M1685
and grounded, this is not necessary.
WARNING: ALL BARE ELEMENT PROBES MUST NOT
BE USED WITH CONDUCTIVE (LE. WATER-BASED)
LIQUIDS OR CONDUCTIVE SOLIDS (LIKE METAL OR
CARBON OR GRAPHITE POWDERS). THIS WILL
CAUSE THE ELECTRONICS TO SHORT CIRCUIT AND
FAIL.
TYPICAL APPLICATIONS FOR THE BARE ELEMENT
PROBES ARE FOR OILS AND NON-CONDUCTIVE HY-
DROCARBONS OR SOLIDS. HOWEVER, IT MUST BE
NOTED THAT WATER CAN CONDENSE IN TANKS
CARRYING NON-CONDUCTIVE MATERIALS. IN OIL
OR HYDROCARBON APPLICATIONS, THE CON-
DENSED WATER SINKS TO THE BOTTOM OF THE
TANK, WHERE THE WATER THEN CAN TOUCH THE
PROBE AND CAUSE DESTRUCTION OF THE ELEC-
TRONICS.
NOTE: When measuring a non-conductive material in a non-
linear vessel, a concentric shield level probe must be
used or the probe must be mounted in a grounded
metal standpipe. This is necessary because of the
varying distance between the level probe and the
vessel wall, which would otherwise cause the probe to
generate a non-linear capacitance over its length. If the
measured material is conductive and grounded, disre-
gard this note.
The transmitter may be installed directly onto the level probe
(integral mounting) or in a remote location up to 150 feet from
the level probe.
NOTE: Remote mounting is necessary when the temperature
at the transmitter exceeds its rated specification (-40
to 160°F) or if severe vibration exists. Triaxial intercon-
nect cable must be used for remote mounting.
The transmitter has a 1/2-inch NPT hole on the bottom center
of the enclosure for direct mounting onto the installed level
probe. Follow these steps to install the level probe and trans-
mitter:
1. Install level probe into vessel opening without the transmit-
ter mounted on it. Use a wrench on the larger, lower hex
nut portion only of the two-piece fitting to tighten level probe
into vessel.
-6-
2.2.3 Remote Mounting
CAUTION: Do not tighten or loosen the smaller, upper
hex nut portion of the two-piece fitting. This is a com-
pression seal that could be destroyed if the upper
portion is turned.
If the level probe is welded into a mounting flange, simply
bolt flange to the mating flange on the vessel.
2. Install banana plug onto back end of level probe extension
by screwing it into the threaded hole.
CAUTION: Do not tighten plug with excessive force as
it can be easily twisted off.
3. Carefully screw the transmitter enclosure onto threaded
upper portion of fitting on back end of level probe. The
banana plug makes the necessary electrical connection to
the electronic chassis. Screw until tight, but without exces-
sive force to avoid stripping the threads.
NOTE: It may be necessary to rotate enclosure to orient
wiring entrances to a desired position. Use a
wrench to hold the upper, smaller hex nut station-
ary while turning the enclosure.
2.8 —
6.9 pe
(175) | (71) |
1/2” NPT
CONQUIT
HOLE,
2 PLACES
2.5
(64)
IN
DIMS (mm)
FIGURE 2-2
Integral Mounting
An explosion-resistant junction box, which mounts onto the
level probe, an optional remote-mount threaded adapter, and
triaxial interconnect cable are required to remote mount the
-7- Manual M1685
Manual M1685
transmitter:
1.
Install level probe into vessel opening or flange mounting
as previously described in Section 2.2.2, step 1.
Install banana plug onto back end of level probe extension
by screwing it into the threaded hole.
CAUTION: Do not tighten plug with excessive force as
it can be easily twisted off.
Carefully screw junction box (LV5972) onto threaded up-
per portion of fitting on back end of level probe. The same
“CAUTION” regarding the compression seal that's de-
scribed in Section 2.2.2 — step 1 applies here when tight-
ening and orienting junction box onto top of level probe.
Remote mount the transmitter in as clean and dry a loca-
tion as possible where minimal mechanical vibration ex-
ists. Avoid locations where corrosive fluids may fall on the
instrument or where ambient temperature limits (-40 to
160°F, -40 to 71°C) may be exceeded.
Install remote-mount threaded adapter (LV5971) into 1/2-
inch NPT hole in bottom of enclosure.
NOTE: The adapter
must be a solid fitting
if transmitter is
housed in aluminum (169) DIA
enclosure to pre- 6's Ma
serve the explosion- (175) |
proof rating. (Should ) 1
adapter become lost, i |
do not use a pipe nip- 1/7 NAT
ple in explosionproof 17 YZ NRT ole,
installations. Also, т —
use only app roved with ECU оо > OMS (mem)
explosionproof wir-
ing seal fittings — not
provided — in con-
duit entrance holes.)
FIGURE 2-3
Remote Mounting
Surface mount the transmitter with the remote-mount
threaded adapter within 150 feet of the installed level probe.
2.3 - ELECTRICAL CONNECTIONS
2.3.1 AC Line-Powered
Transmitters
Level Probe | MM Integrally Mounted
Connect level probe to the transmitter via the banana plug
installed onto back end of probe. The plug must be securely
fastened and not damaged.
E Remotely Mounted
Use only triaxial interconnect cable (LV5974) to connect
junction box terminals to the transmitter. Any other type
cable causes incorrect instrument operation. Refer to Fig-
ure 2-4 and connect triaxial cable, matching wires to termi-
nals as follows:
Triaxial Cable Wires Terminal Designations
Center wire PROBE
Blue wire (inner braided shield) SHIELD
Green wire (outer braided shield) Ground symbol
hag PROVIDED ON
~— 115 & 230 VAC
MODELS ONLY Ñ
| | | | 1/2" NPT
FIGURE 2-4 Triaxial Cable Hook-Up Between Level Probe J-Box
And Remote-Mounted Transmitter
4-20 mA | Refer to Figure 2-4 and connect the load device to terminals
Output | designated “4-20 mA OUTPUT”, matching polarity as indi-
cated. This isolated output can drive a load of up to 600 ohms.
Line Power | Line power requirements may be 115 VAC or 230 VAC de-
-9- Manual M1685
Hazardous Area Wiring
(transmitter with explosion-
resistant enclosure only)
2.3.2 DC-Powered
Transmitters
Level Probe
DC Power
and Output
Manual M1685
pending on the version provided. Check which voltage is
correct for the unit being installed. Refer to Figure 2-5 and
connect line power to terminals designated “L1/HOT" and “N".
The “L1/HOT” terminal is fused to protect instrument circuits.
Use wiring practices which conform to local codes (National
Electrical Code Handbook in the U.S.A.). This includes:
M Using wire sizes as recommended by the local code for
primary power wiring.
M Using only the standard three-wire connection for AC wiring.
The ground symbol terminal grounds the instrument which
is mandatory for safe operation.
peer
1/H0T
à
В U 1/2" NPT
FIGURE 2-5 AC Line Power Hookup
When installing an AC-powered transmitter in a hazardous
area, it must be used with an insulated type Model LV5000,
LV5100 or LV5500 series level probe. Also, explosionproof-
rated conduit, hubs and fittings must be used for all wiring in
Div. 1 or Div. 2 areas. This includes the line power and 4-20
mA signal wires.
Depending on the way in which the level probe is to be
mounted, refer to the “Integrally Mounted” or “Remotely
Mounted” subsection in Section 2.3.1.
mM When Using A Non-indicating Power Supply
1. Refer to Figure 2-6 and connect non-indicating DC
voltage power supply to terminals designated “18-35
VDC”, matching polarity as shown.
2. Connect an indicating device to terminals designated
-10-
“4-20 mA OUTPUT", matching polarity as shown. This
isolated output can drive a load of up to 550 ohms at 24
VDC. |
E When Using An OMEGA DPF64
1. Connect transmitter “18-35 VDC (+)" terminal to DPF64
#7 terminal.
2. Connect transmitter “4-20 mA (+)” terminal to DPF64 #4
terminal.
3. Connect transmitter “4-20 mA (-)” terminal to DPF64 #3
terminal. This isolated output can drive a load of up to 550
ohms at 24 VDC
> 1/2" МРТ
FIGURE 2-6 DC Power and Output Hookup
Hazardous Area | A DC-powered transmitter housed in the standard aluminum
Wiring | explosion-resistant enclosure is suitable for use in Div. 1 and
Div. 2 hazardous areas. In the optional PVC enclosure, the
transmitter is restricted to use in Div. 2 areas only.
When installing a DC-powered transmitter in a hazardous area,
the transmitter must be used with an insulated type Model
LV5000, LV5100, or LV5500-series leve! probe and explosion-
proof-rated conduit, hubs and fittings must be used for all wiring
in Div. 1 or Div. 2 areas.
-11- Manual M1685
3.1 - OPERATING CONTROLS
3.1.1 Calibration
Manual M1685
All controls used for setup and operation are described in this
section. Familiarize yourself with each item before operating
the instrument. Use the small plastic screwdriver provided to
make control adjustments. Do not force any adjustment past
its stops to avoid breakage.
1.
ZERO COARSE switch
Positions 0 through 9 progressively add 50 pF to the ZERO
FINE control (item 2) adjustment. This switch is used in
combination with the ZERO FINE control to establish the
zero output signal.
ZERO FINE control
Sets the exact zero level to 4 mA output. The range of
adjustment is 60 pF in 40 turns.
CAUTION: Do not force this 40-turn control past its
adjustment stops to avoid breakage.
SPAN COARSE switch
Positions 1 through 6 progressively chan:jes the total span
from a minimum of 0-10 pF to a maximum of 0-10,000 pF.
This switch is used in combination with the SPAN FINE
control (item 4) to establish the total span.
SPAN FINE control
Sets the exact 100% level to 20 mA output. The range of
adjustment is 30 turns.
= “4———— TEST — > +
O О
ZERO SPAN OUTPUT RESP
COARSE FINE COARSE FINE REV DIR
[RIOR = ©
FIGURE 3-1 Control Panel Layout
-12-
3.1.2 Output Mode
3.1.3 Output Damping
5. REV/DIR switch
Selects output to be direct (DIR) or inverted (REV):
DIR - Output increases from 4 mA to 20 mA as measured
level rises.
REV - Output decreases from 20 mA to 4 mA as measured
level rises.
RESP control
Dampens output signal via an RC time constant circuit from
0.1 to 10 seconds by turning clockwise (270° rotation).
3.2 - CALIBRATION
3.2.1 With Output In
Direct Acting Mode
Setting The
Zero Level Output
With material at the desired low leve! (0% full) on the level
probe:
1.
Connect a milliammeter to the transmitter to monitor the
4-20 mA loop current:
A.
Connect milliammeter with test leads to “TEST” jacks
located on control panel, matching polarity as indi-
cated.
Connect a load across — or short together — the “4-20
mA OUTPUT” terminals. See Section 1.2 specifica-
tions for maximum allowable load resistance.
NOTE: If milliammeter resistance is more than 25
ohms, disregard steps 1 and 2. Instead, con-
nect milliammeter in series with a load across
the “4-20 mA OUTPUT” terminals. Do not
exceed maximum allowable load resistance.
Place the following controls and switches to these settings:
Control Setting
ZERO COARSE switch ....... 0
ZERO FINE control .......... Fully counterciockwise
SPAN COARSE switch ....... 1
SPAN FINE control .......... Fully counterclockwise
REV/DIR switch ............. DIR
RESP control ............... Fully counterclockwise
CAUTION: The ZERO FINE control is a glass compo-
-13- Manual M1685
Manual M1685
Setting The
Full Level Output
nent. To avoid breakage, do not force it past its 40-turn
minimum and maximum adjustment stops.
NOTE: The SPAN FINE control does not have adjustment
stops. To set it to the end of its travel, slowly turn
counterclockwise (left) until a “soft clicking” sound
is heard while turning.
Apply power to the instrument. The milliammeter reading
should be 20 mA or higher.
Increase ZERO COARSE switch setting in clockwise steps
until the milliammeter reads 4 mA or lower. Then turn
switch back (counterclockwise) one position step. The
output should increase to 20 mA or higher again. Leave
ZERO COARSE switch at this setting. If switch is at position
9 and output is not yet at 4 mA or lower, leave at setting 9.
Turn ZERO FINE control slowly clockwise (right) until the
milliammeter reads exactly 4 mA. This is the output at 0%
full level. Leave ZERO FINE control at this setting. If output
cannot be adjusted to 4 mA, the zero adjustment range has
been exceeded. Consult OMEGA for assistance.
# # #
Change SPAN COARSE switch setting from 1 to 6 and
SPAN FINE control setting from fully counterclockwise to
fully clockwise (approximately 30 turns).
Manually raise the measured material level up to the
desired “full level” position on the level probe. The milliam-
meter reading should be less than 20 mA. If the reading is
higher than 20 mA, the level probe has produced a capaci-
tance change greater than the maximum span of the
instrument. This is unlikely, except in cases where the level
probe is very long and submerged in a conductive material.
NOTE: If the material level cannot be raised up to the
desired full level position, refer to the ‘special
case” box on the next page for instructions.
Decrease SPAN COARSE switch setting in counterclock-
wise steps until the milllammeter reads higher than 20 mA.
Then turn switch forward (clockwise) one position step.
The output should decrease below 20 mA again. Leave
SPAN COARSE switch at this setting. If switch is at
position 1 and output is still below 20 mA, leave at setting
1 and proceed with step 4.
Turn SPAN FINE control slowly counterclockwise (left)
until the milliammeter reads exactly 20 mA. This is the
output at 100% full level. Leave SPAN FINE control at this
setting. If output cannot be adjusted to 20 mA, the capaci-
tance change produced by the level probe is less than the
minimum measurement span. Consult OMEGA for assis-
tance. |
The instrument is now calibrated.
SPECIAL CASE FOR SETTING FULL LEVEL OUTPUT
It may not be possible to raise the material level up to the
desired “full level” position due to lack of sufficient material.
In this case:
A. Bring as much material into the vessel as possible. Then
calculate the actual level as a percentage of the total
level span and, using the following formula, convert this
value to mA on a 4-20 mA scale.
mA = (% actual level x 16) + 4
Example: Actual level is 50% of full level. Therefore,
mA = (50% x 16) + 4 = 12 MA
Output at this 50% level is 12 mA.
B. Perform steps 3 and 4 exactly as previously described
except using the appropriate calculated mA value in-
stead of 20 mA (12 mA for this example).
NOTE: Calibration using less than a 25% full span level
change is not recommended. It may be necessary
to recalibrate the full level at a later time when the
vessel is full.
Adjusting | Output damping is provided to damp a constantly changing
Output Signal | output signal caused by turbulent material level. Turning the
~ Damping | RESP control clockwise (right) increases the damping from 0.1
to 10 seconds. Turn this control slowly clockwise until any
output ripple is no longer evident.
3.2.2 With Output in The switch and control settings described in Section 3.2.1 are
Reverse Acting exactly the same except set the REV/DIR switch to the REV
Mode position.
The calibration procedure is exactly the same as in the direct
acting mode except that 20 mA is substituted for 4 mA, and
4 mA is substituted for 20 mA wherever referenced.
-15- Manual M1685
See Figure 4-1 for a simplified schematic diagram pertaining
to these descriptions:
1. The power supply section (not shown) converts line power
to appropriate voltages for circuit operation.
2. The OSCILLATOR section produces the triangle wave
signal used to measure the probe impedance and several
square wave signals used to synchronize other parts of the
circuit.
A voltage-controlled square wave oscillator operates at a
frequency four times that of the measuring signal. Two
“flip-flops” divide the oscillator frequency and produce four
square waves with a 90° phase difference between each
successive signal. One of these square waves is applied
through a resistor to a capacitor. The result, a low-voltage
triangle wave with low distortion, becomes the SHIELD
signal.
The SHIELD signal is gated with analog switches control-
led by two of the square wave signals to a differential
OSCILLATOR
Manual M1685
A [EA
70
un Lege
— — ОНИ т J
_— — ECON
TT A
|
| QUTPUT
ZERO | [7 — ———— 7
| = He:
ZL coarse va E
7 PAN o -
|
HELLO S LEE _
FIGURE 4-1 Instrument Operations Schematic Diagram
-16-
amplifier which produces an output voltage proportional to
the peak-to-peak voltage of the SHIELD signal. This volt-
age is compared to a reference voltage by another differ-
ential amplifier which produces an output voltage that is
used to adjust the frequency of the voltage controlled
oscillator. If the SHIÉLD voltage is too low, the amplifier
output increases. This increases the period of the signal
which allows the capacitor to charge to a higher voltage.
The reverse occurs if the voltage is too high. This feedback
circuit maintains a constant SHIELD signal voltage and
compensates for any circuit drift and for any capacitance
at the SHIELD terminal from any cable connected there.
In the DETECTOR section, the SHIELD signal voltage is
amplified and applied to an adjustable ZERO capacitor
which is connected to the PROBE terminal. The probe
forms a variable capacitor to ground. A large adjustable
SPAN capacitor is connected between the PROBE and
SHIELD terminals. Since the impedance of the SPAN
capacitor is much lower than that of the ZERO or PROBE
capacitors, the voltage on the PROBE terminal is approxi-
mately equal to the voltage on the SHIELD terminal. When
the ZERO and PROBE capacitors are equal, no current
flows through the SPAN capacitor. As the PROBE capaci-
tance increases due to increasing level in the vessel,
current through the SPAN capacitor increases. This cur-
rent produces a very small voltage across the capacitor
which is transformer coupled to the input of a high-gain
amplifier.
The output of the amplifier is gated by analog switches to
a differential amplifier which produces a voltage propor-
tional to the capacitance difference. The harmonic content
of the triangle wave signal and the operation of the analog
switches allow the circuit to ignore the effect of probe
buildup. The differential amplifier includes a FINE SPAN
adjustment which controls its gain.
The OUTPUT section includes an adjustment to vary the
unit's response time to allow it to produce a steady output
signal even when there is turbulence in the vessel. A switch
controls whether or not the resulting signal is inverted
before being converted to an output current. If the signal
is not inverted, the output is direct acting and will increase
with rising level. If inverted, the output is reverse acting
(decreases with rising level).
-17- Manual M1685
5.1 - GENERAL
The electronic chassis assembly is held into the enclosure with
two screws in the bottom of the chassis. These are accessible
from the sides of the chassis.
Replacement of circuit board components should be performed
by a qualified technician. Otherwise, return the entire chassis
assembly to the factory after obtaining a return authorization.
If possible, include a brief description of the trouble symptoms.
In some applications it may be necessary to clean the level
probe periodically.
5.2 - TROUBLESHOOTING
Manual M1685
The following simple checks can be used to determine if the
transmitter is operating properly:
1.
Calibrate the transmitter using the procedure in Section
3.2. If calibration is accomplished, the system is operating
properly. If not, perform step 2.
Remove the transmitter from the level probe. With the unit
powered, the REV/DIR switch in the DIR position and any
load(s) disconnected from the output circuit, the transmit-
ter's output should be less than 4 mA. Now short the probe
and ground symbol terminals together and the output
should increase to more than 20 mA. If these checks are
accomplished, the transmitter is probably okay but the
level probe may be defective (see step 3).
Perform the following checks to find common probiems
with a level probe:
m Check that the banana plug on the back of the level
probe is installed and not damaged.
m Check that the probe's mounting gland is sealed to-
gether properly and that there is no moisture in the gland
which could cause a short circuit.
m Check that the level probe is not shorted to the mounting
gland (resistance should be greater than 1 megohm).
m If the probe is an insulated type, check for nicks in the
insulation and that the weld at the probe tip is intact.
NOTE: Do not use Teflon tape or any other pipe sealant on
the 1/2-inch NPT threaded upper portion of the mount-
ing gland. This connection must provide a good ground.
-18-
4. If the previous steps have determined that the transmitter
and level probe are operating properly, the system may be
incorrectly applied. For example, a non-insulated level
probe will not work in conductive material, or an insulated
level probe will not work with conductive material in lined
metal or plastic vessels that are not properly grounded.
Contact OMEGA for application assistance.
Should service, parts or assistance in troubleshooting or repair
be required, please contact the OMEGA Customer Service
Department at 1-800-622-2378 or (203)359-1660.
-19- Manual M1685
Accessories For
Remote Mounting
Electronic Chassis
Assemblies
Fuse
Manual M1685
Description | Part Number
Threaded Adapter ..........................e.osecvcccennos LV5971
Explosion-resistant Junction Box
(with jack and terminal strip) ......................... LV5972
Triaxial Interconnect Cable*......................—.. LV5974
*Cable has stripped and tinned wires at each end. It connects
transmitter to level probe j-box. Specify length up to 150 feet.
DC-Powered
Transmitter (18-35 VDC) ...................c......c... 7005-101
115 VAC Line-Powered
Transmitter (four-wire) .................e-..e.esmrricices 7005-201
230 VAC Line-Powered
Transmitter (four-wire) ...................eeoonnesncccce. 7005-401
1/4 Amp Slo-blow Fuse....................e.....ccccce. 99X1F1036
-20-
LV5000 General Purpose
Level Sensing Elements
* Bare and Insulated Probes for Radio Frequency Capacitive Level Measurement
* Custom Extruded Insulation Minimizes Air Encapsulation and Capacitance Variation
* Captive Sensing Element for Safe Operation in Pressurized Vessels
* Low Cost Probes for Liquid and Granular Materials
The OMEGA LV5000 general purpose sensing elements are used with the LV5900 RF capacitive transmitters
for continuous monitoring of levels in tanks. They are used in common applications for many chemically com-
patible liquids or granular solids which do not leave a conductive coating on the probe surface. General pur-
pose level sensing probes are available with 316SS or Hastelloy C wetted metal parts. The electrode must be
coated with TFE Teflon, PVDF (Kynar), or polyethylene for use with conductive (10 microMhos/cm or greater)
fluids. (Typical process water, excluding purified, distilled, or deionized water, will be much more conductive
than this.) The electrode portion of the standard insulated probe is 316SS, which would not be wetted. The
LV5000 General Purpose probes are not recommended for use in materials which tend to form a conductive
film on the electrode surface. (Use the LV5200 enhanced performance elements in such cases.) Water-
based latex paint, fine carbon powder, or fine metallic powders are examples of materials that leave conduc-
tive coatings on the probes. An optional sheath can be specified to render a portion of the electrode inactive
where the probe will be mounted through a nozzle and fluid contact is possible.
EE
NGTH)-Z* General purpose, 316SS
LV501X-Y-(LENGTH)-Z*| General Purpose, Hastelloy
C electrode for insulated
element is 316SS unless
otherwise specified
“Insert appropriate ordering suffixes Tor °X,” °Y,” and 2” from the
chart below, to complete model number. Specify all lengths in inches.
Maximum length is 234 inches.
Options
0 Bare element- no insulation
1 TFE Teflon
2 PVDF(Kynar)
3 Polyethylene
YO a No ground wire
Y1 316SS ground wire
Y2 Hastelloy C ground wire
pipe
ei
Zo So No sheath required
Z(#) Sheath length in inches
LV5000 Dimensions
DIMENSIONS IN INCHES (mm)
6-32 TAPPED HOLE
0.58 FOR BANANA PLUG
(15) N (INCLUDED)
a
1/2" NPT
2.91
(74)
+ — 3/4" NPT
"s"
SHEATH
LENGTH
+ 0.25
(+3) "x OPTIONAL
SHEATH
"и '
ELECTRODE E
LENGTH ON OPTIONAL
+ 0.25 i | INSULATION
(+ 6) ‘ | 0.38 (10) O.D.
> 4 OVER 0.25 (6)
DIA. ROD
0 | INSULATED
(25.4) | 1 /PLUG (ONLY
ON INSULATED
ELECTRODES)
SPECIFICATIONS
Wetted Materials: 316SS or Hastelloy C; optionally TFE Teflon, PVDF (Kynar)
or Polyethylene
Maximum Temperature: TFE Teflon, 450°F (232°C); PVDF (Kynar), 250°F (121 °C);
Polyethylene, 160°F (71°C)
Maximum Pressure: TFE Teflon, 1000 PSIG @ 150°F, derated to 0 PSIG @350°F;
PVDF (Kynar), 1000 PSIG @ 100°F, derated to 0 PSIG @ 250°F
Polyethylene, 1000 PSIG @ 80°F, derated to 0 PSIG @140°F
Gland Capacitance: 25pF (for TFE Teflon)
Recommended Maximum
Probe Length: 19.5 feet (use LV5300 cable element for longer lengths)
Connection: 3/4" NPT 316SS or Hastelloy C
Electrode Diameter: Bare, 1/4"; Insulated, 3/8"
Teflon is a trademark of DuPont Co.
Kynar is a trademark of Pennwalt Corp.
LV5100 Heavy Duty
Level Sensing Elements
Bare and Insulated Probes for Radio Frequency Capacitive Level Measurement
Custom Extruded Insulation Minimizes Air Encapsulation and Capacitance Variation
Captive Sensing Element for Safe Operation in Pressurized Vessels
Stronger Version of the General Purpose Probe for Most Liquid and Granular Materials
The OMEGA LV5100 heavy duty sensing elements are used with the LV5900 RF capacitive transmitters for
continuous monitoring of levels in tanks. They are used in common applications for many chemically compati-
ble liquids or granular solids which do not leave a conductive coating on the probe surface. Heavy duty level
sensing probes are available with 316SS or Hastelloy C wetted metal parts. The electrode can be coated with
TFE Teflon or PVDF (Kynar) for use with conductive (10 microMhos/cm or greater) fluids. (Typical process
water, excluding purified, distilled, or deionized water, will be much more conductive than this.) The electrode
portion of the standard insulated probe is 316SS, which would not be wetted. The LV5100 heavy duty probes
are not recommended for use in materials which tend to form a conductive film on the electrode surface. (The
LV5200 enhanced performance elements can be used in such applications.) Water-based latex paint, fine
carbon powder, or fine metallic powders are examples of materials that leave conductive coatings on the
probes. An optional sheath can be specified to render a portion of the electrode inactive where the probe will
be mounted through a nozzle and fluid contact is possible.
LV510X-Y-(LENGTH)-Z* | General purpose, 316SS
LV511X-Y-(LENGTH)-Z* | General purpose, Hastelloy C electrode for insulated element
is 316SS unless otherwise specified.
"Insert appropriate ordering suffixes for “X,” “Y,” and “7” from the chart below, to
complete model number. Specify all lengths in inches. Maximum length is 234 inches.
0 Bare elemen
t- no insulation
1 TFE Tefion
PVDF(Kynar)
| YO | No ground wire
Y1 316SS ground wire
| Y2 Hastelloy C ground wire
Zo No sheath required
Z(#) Sheath length in inches
LV5100 Dimensions
SPECIFICATIONS
Wetted Materials:
Maximum Temperature:
Maximum Pressure:
Gland Capacitance:
Recommended Maximum
Probe Length:
Connection:
Electrode Diameter:
DIMENSIONS IN INCHES (mm)
6-32 TAPPED HOLE
0.58 FOR BANANA PLUG
(15) N (INCLUDED)
Ÿ
1/2" NPT
| и /2" №
3.1
(79)
Y =
+ 4 —— 1" NPT
“QC
SHEATH OPTIONAL
LENGTH SHEATH
+0.1
(+3) OPTIONAL
y INSULATION
L Oven) 0s0 (13)
0.50 (1
ELECTRODE GN DIA. ROD
+.25
(+6) в
(25%) o INSULATED
A PLUG (ONL
Y y || | ON INSULATED
-—— ELECTRODES)
316SS or Hastelloy C; optionally TFE Teflon or
PVDF (Kynar)
TFE Teflon, 450°F (232°C); PVDF (Kynar), 250°F (121°C)
TFE Teflon, 1000 PSIG @ 150°F, derated to 0 PSIG @350°F;
PVDF (Kynar), 1000 PSIG @ 100°F, derated to 0 PSIG @ 250°F
42pF (for ТРЕ Teflon)
19.5 feet (use LV5300 cable element for longer lengths)
1" NPT 316SS or Hastelloy C
Bare, 1/2"; Insulated, 3/4"
Teflon is a trademark of DuPont Co.
Kynar is a trademark of Pennwalt Corp.
LV5200 Enhanced Performance
Level Sensing Elements
* Bare and Insulated Probes for Radio Frequency Capacitive Level Measurement
* Custom Extruded Insulation Minimizes Air Encapsulation and Capacitance Variation
* Captive Sensing Element for Safe Operation in Pressurized Vessels
Thin Wall Insulation for Reduced Conductive Coating Error
The OMEGA LV5200 enhanced performance sensing elements are used with the LV5900 RF capacitive
transmitters for continuous monitoring of levels in tanks. They are used in applications for many chemically
compatible liquids or granular solids. Enhanced performance level sensing probes are available with 316SS
or Hastelloy C connections which should be considered as wetted metal parts. The electrode is coated with a
thin coat of PFA Teflon or PVDF (Kynar). The sensing portion inside the standard insulated probe is 316SS,
which would not be wetted. The LV5200 probes are most advantageous in materials which tend to form a
conductive film on the element surface. Water-based latex paint, fine carbon powder, or fine metallic powders
are examples of materials that leave conductive coatings on the probes. An optional sheath can be specified
to render a portion of the element inactive where the probe will be mounted through a nozzle or pipe
extension.
LV520X-Y-(LENGTH)-Z* Enhanced Performance, 316SS
LV521X-Y-(LENGTH)-Z*| Enhanced Performance, Hastelloy C electrode
for insulated element is 316SS unless otherwise
specified
“Insert appropriate ordering suffixes for “X,” “Y ” and “2” from the chart below, to complete
model number. Specify all lengths in inches. Maximum length is 138 inches.
Options
0 o Bare element- no insulation
2 PVDF (Kynar)
4 _ PFA Teflon
Yo } No ground wire
Y1 3165S ground wire
Y2 Hastelloy C ground wire
Zo - No sheath required
Z(#) Sheath length in inches
LV5200 Dimensions
DIMENSIONS IN INCHES (mm)
6-32 TAPPED HOLE
0.58 FOR BANANA PLUG
(15) N (INCLUDED)
$
1/2" NPT
2.91
(74)
| ==—
1 | — 3/4" NPT
"St
SHEATH
LENGTH
+
PAY: "X OPTIONAL
“р SHEATH
E
We =
ELECTRODE E OO oN
LENGTH a 0.50 (13) O.D.
+ 0.25 ‘| ОМЕН 0.44 (11)
(+ 6) 1.11. DIA. ROD
: : 0.75 (19) O.D.
0.20 | | SEALED END CAP
(5) | 1 7(ONLY ON
+ (= INSULATED
7 —-1 ELECTRODES)
SPECIFICATIONS
Wetted Materials: 316SS or Hastelloy C and PFA Teflon or PVDF (Kynar)
Maximum Temperature: PFA Teflon, 450°F (232°C); PVDF (Kynar), 250°F (121°C)
Maximum Pressure: PFA Teflon, 1000 PSIG @ 150°F, derated to 0 PSIG @350°F;
PVDF (Kynar), 1000 PSIG @ 100°F, derated to 0 PSIG @ 250°F
Gland Capacitance: 38pF (for PFA Teflon)
Recommended Maximum
Probe Length: 11.5 feet (use LV5300 cable element for longer lengths)
Connection: 3/4" NPT 316SS or Hastelloy C
Electrode Diameter: Bare, N/A; Insulated, 7/16" electrode and 1/2" O.D.
Teflon is a trademark of DuPont Co.
Kynar is a trademark of Pennwalt Corp.
LV5300 Flexible Cable
Level Sensing Elements
* Insulated and Bare Cables for Radio Frequency Capacitive Level Measurement
* Measures Levels up to 500 Feet Maximum for Most Liquid and Granular Material
(2000 feet for LV5603)
* Aircraft Quality Stainless Wire Rope Construction
The OMEGA LV5300 and LV5603 flexible cable sensing elements are used with the LV5900 RF capacitive
transmitters for continuous monitoring of levels in tanks. They are used in non-coating fluid applications which
require measurements greater than 10 feet in depth. The LV5300 sensing elements are available as bare
316SS wire rope and may be insulated with PFA Teflon, PVDF (Kynar), or polyethylene. The LV5603 is only
available with polyethylene insulation. The LV5603 is designed for use in deep well applications, but can also
be used as a lower cost alternative in non-coating liquid, granular, and interface applications. The flexible
cable elements are not recommended for use in materials which tend to form a conductive film on the
electrode surface. Water-based latex paint, fine carbon powder, or fine metallic powders are examples of
materials that leave conductive coatings on the probes. Termination fittings are machine swaged to exceed
the breaking strength of the flexible cable section. Optional spiral-wrapped ground wires are available for use
In irregularly shaped vessels. A metal tie-down fitting can be specified (LV5300 only) for granular applications
or plastic tie-down for liquids.
: ae Accessory Weights (for LV5300)
Model No — | Description Model No. [Diameter | Weight
LV530X-Y-(LENGTH)-Z*| Flexible Cable, 316SS Lv53W10225 | 1” 2.25 Ibs (1 kg)
LV5603-(LENGTH)* Flexible Cable, 316SS & LVS3W10550 1 5.50 Ibs (2.5 kg)
Polyethylene LV53W15225 1.5” 2.25 Ibs (1 kg)
"Insert appropriate ordering suffixes for “X,” “Y,” and 2" from the 5”
chart below to complete model number. Specify cable lengths in feet. LV53W15550 - 1-5 5.50 !bs (2.5 kg)
Maximum length is 5000 feet for LV5300, 5000 feet for LV5603. Note- use 5.50 Ibs weight for cables 20 feet or shorter.
Ordering Suffix| Description
X - Insulation Options (LV5300 oniy, except
polyethylene)
0 Bare element- no insulation
2 PVDF(Kynar )
3 Polyethylene
4 PFA Teflon
Y - Ground Wire (model LV5300 only)
YO No ground wire
Y1 316SS ground wire
Y2 Hastelloy C ground wire
Z - Tie-Down Fitting (plastic must match
insulation)
— LV5603 has plastic cylinder
temination
TSS 316SS (for granular
materials)
TPV PVDF
THD HDPE-high density
polyethylene
TPF PFA Teflon
LV5300
LV5603
DIMENSIONS IN INCHES (mm)
DIMENSIONS IN INCHES (mm)
6-32 TAPPED HOLE 6-32 TAPPED HOLE
0.58 FOR BANANA PLUG FOR BANANA PLUG
(15) (INCLUDED) (INCLUDED)
Ÿ I
„М? МРТ 1/2" NPT 0.58 (15)
ЕЕ | t
3.1 2.9
(79) (74)
= —— 3/4" NPT
—_— —
! T~—1"NPT
INSULATION
+ 0.13 (3.2)
O.D. OVER
0.06 (1.5)
"LL" ui
OPTIONAL
(ENGTH | | INSULATION LENGTH
0.2 O.D. OVER 51) + 5 WEIGHTS
(+6) 0.22 (6) + STANDARD
WIRE ROPE
ro
0.875" Ta
—* (22.2) DIA. ' ; 0" (25.4)
Je 0.250 3.4 TERMINATION
(97) (6.35) DIA. (86) 0.75" (19.1)
| BOLT HOLE |
SPECIFICATIONS
Wetted Materials:
Maximum Temperature:
Accessory Weights:
Normal Pressure:
Gland Capacitance:
Cable Length:
Diameter of Cable:
Lower Termination:
Mounting Connection:
Break Strength:
316SS, optionally: PVDF (Kynar), Polyethylene (low density), or
PFA Teflon; (316SS and Polyethylene only for LV5603)
Bare 316SS, PFA Teflon, 350°F (176°C); PVDF (Kynar), 250°F (121°C);
Polyethylene, 140°F (60°C)
316SS for LV5300 (to hold down cable)
PFA Teflon, 1000 PSIG @ 150°F, derated to 0 PSIG @ 300°F;
PVDF (Kynar), 1000 PSIG @ 100°F, derated to 0 PSIG @ 250°F;
Polyethylene, 1000 PSIG @ 80°F, derated to O PSIG @ 140°F
25 pF for PFA Teflon; (35pF for LV5603)
Maximum 5000 feet for LV5300; 5000 feet for LV5603
7/32" bare, 3/8" insulated; (1/8" insulated for LV5603)
316SS for granular applications, PFA Teflon or PVDF (Kynar) for
liquid applications; (HDPE only for LV5603)
1" NPT 316 SS; (3/4" NPT for LV5603)
Metal tie-down, 5000 Ibs, plastic tie-down, 200 Ibs;
plastic termination, 200 Ibs for LV5603
Teflon is a trademark of DuPont Co.
Kynar is a trademark of Pennwalt Corp.
LV5500 Concentric Shield
Level Sensing Elements
* Concentric Shield for Plastic Tanks or Vessels with Irregular Shape
* Shields Enable Calibration Outside of Tank
* Custom Extruded Insulation Minimizes Air Encapsulation and Variation in Capacitance
The OMEGA LV5500 concentric shield sensing elements are used with the LV5900 RF capacitive transmitters
for continuous monitoring of levels in tanks. The LV5500 probes are used in clean, low viscosity liquid appli-
cations which do not leave a conductive coating on the probe. The concentric shield level sensing probes are
constructed with 316SS connections and shields. The metal shield provides a linear ground reference for
applications in which non-conductive liquids are contained in irregularly shaped and/or plastic vessels. The
electrode inside the shield is insulated with TFE Teflon, PVDF (Kynar), or polyethylene.
Due to the close proximity of the shield to the measuring electrode, these level sensing elements produce a
high capacitance change with level variation. The concentric shield also makes it possible to pre-calibrate the
electronics outside the main vessel using the same material to be measured.
LVS50X-(LENGTH*) | Concentric Shield element
“Insert appropriate ordering sutfix for “X” from the chart below
to complete model number. Specify all lengths in inches.
Maximum length is 138 inches.
rem Optiol TFE Teflon
2 PVDF (Kynar)
3 Polyethylene
LV5500 Dimensions
SPECIFICATIONS
Wetted Materials:
Maximum Temperature:
Maximum Pressure:
Gland Capacitance:
Recommended Maximum
Probe Length:
Connection:
Electrode Diameter:
DIMENSIONS IN INCHES (mm)
6-32 TAPPED HOLE
0.58 FOR BANANA PLUG
(15) \ (INCLUDED)
_v
1/2" NPT
2.91
(74)
| 3/4" NPT
TN 0.25 DIA.
! Dr VENT HOLES
| CONCENTRIC SHIELD
‚и ¡le (0.75 0.D. X
| Pa 0.035 WALL)
| 1 INTERNAL INSULATING
(D+ SPACER (EVERY 36"
«+ | AND BOTTOM)
+.25 hu:
(+6) hu
, MEASURING ELECTRODE
| 0.38 O.D. INSULATION
| OVER 0.25 DIA.
ROD
- -
=
- -— -
e
4
1.4 (36)
316SS and TFE Teflon, PVDF (Kynar), or Polyethylene
TFE Teflon, 450°F (232°C); PVDF (Kynar), 250°F (121°C)
Polyethylene 140°F (60°C)
TFE Teflon, 1000 PSIG @ 150°F, derated to 0 PSIG @350°F;
PVDF (Kynar), 1000 PSIG @ 100°F, derated to 0 PSIG @ 250°F
Polyethylene, 1000 PSIG @ 80°F, derated to 0 PSIG @ 140°F
25pF (for TFE Teflon)
11.5 feet (use LV5300 cable element for longer lengths)
3/4" МРТ 31655
Concentric shield 3/4" O.D.: 3/8" O.D. insulation on 1/4" 316SS rod
Teflon is a trademark of DuPont Co.
Kynar is a trademark of Pennwalt Corp.
re OMEG A APPLICATION NOTE
DOCUMENT
49001
Interface Level Measurement and Control
introduction
One of the unique capabilities of RF level measuring
instrumentation is to indicate and/or control an interface
between two immiscible liquids, each having a different
dielectric constant.
Oil/water interface measurement is a common
application of this type. The LV5900 series of
continuous level transmitters provides an analog output
proportional to the position of the interface on a
vertically-mounted electrode.
It is important to note that a vertically-mounted
electrode must be fully submerged at all times to
provide correct interface detection. if it isn't, the
electrode will be exposed to two interfaces; the first
being between air or a gas and the upper phase
material, and the second being between the low and
high dielectric constant liquids.
The zero is calibrated when the probe is completely
submerged in the low dielectric constant liquid. The
100% point is established using the span adjustment
when the entire electrode is submerged in the high
dielectric constant liquid. In the oil/water example, as
the interface rises on the electrode, a greater
percentage of it is submerged in the higher dielectric
constant liquid. This causes an increase in the
capacitance generated and a corresponding increase in
the output signal.
To ensure that the measuring section of the electrode is
always fully submerged, a metal sheath of sufficient
length may be included on the probe. The sheath
renders that portion of the electrode insensitive to
capacitance change and variation and the top level is
ignored. Another common approach is to arrange a
control system and a tank overflow so that the upper
level remains constant.
Important Considerations
1. Quality of the Interface—Some materials do not
form a distinct interface, but instead form an
emulsion layer between the two materials.
Calibration of the 0% and 100% points can be made
by establishing a desired position in the emulsion
layer.
2. Agitation—No interface will occur if the material in
the vessel is agitated. The use of a stilling well may
be required. Allow the material to settle before
performing calibrations.
3. Dielectric Constants—Usually the two immiscible
materials forming an interface will have widely
differing dielectric constants. Check Capacitance vs.
Dielectric Constant charts for each material to ensure
a total capacitance change of at least 10 pF, but not
greater than 10,000 pF for transmitter applications.
4. Grounding—In plastic vessels, it is necessary to
electrically ground the conductive phase.
Supply Valve
+ Insulated Electrode
Figure 1
A Sheathed (Inactive) Section Continuous Level Interface
_ Detection
Oil
Emulsion
Water
ét”
<+—— Overflow
SI «— Discharge
Valve
ME OMEG A APPLICATION NOTE
DOCUMENT
49002
RF Level Measurement In Lined Vessels With
Grounded Shell
Introduction
Storage and process vessels for containing highly
corrosive liquids are fabricated of metal, fiberglass or
other plastic materials depending on the pressure rating
required. The application of RF level measuring
instrumentation in these vessels requires some special
considerations and techniques for successful results.
While there are some similarities between level
applications in lined vessels and plastic vessels, the
implementation techniques are different.
For corrosion resistance, metal vessels are generally
lined with rubber, glass or plastic rather than fabricating
the vessel of an expensive, and perhaps exotic metal.
Various techniques are employed to line vessels. These
include spray or brush-on coatings, heat fusion and
sheet or film linings cemented in place with welded
plastic seams.
Most, but not all, of the materials stored or processed in
these vessels are electrically conductive. Hydrochloric,
sulfuric and hydrofluoric acids and caustic in various
concentrations are common applications.
Non-Conductive Materials
In a lined metal vessel (Figure 1), the capacitive
measurement path is from the metal electrode through
the electrode insulation (Cl), then through the measured
material (CM) and finally through the liner (CL) to the
electrically grounded metal shell of the vessel.
The total capacitance measured between the metal
electrode and the grounded metal vessel depends on
the individual capacitances of the electrode insulation
(CI), the measured material (CM) and the vessel liner
(CL). This formula is:
Ci x Cy x Ci
Cr-
CiCu + С/С, + Сиб,
This formula becomes more complex if one substitutes
the dielectric constants of each material into the
formula, but the net result will show that the changing
capacitance measured will be directly proportional to
the changing level of the material in the vessel.
If the vessel is a horizontal cylinder or irregularly
shaped, the measured capacitance with respect to level
LINER (Cy)
MEASURED MATERIAL (Cp)
SENSOR INSULATION (С)
METAL ELECTRODE
-
и а.о. ь
« = … x
. яв.
аа...
кат
+ «тэ.
.» wm.
в. ван
a raw
ааа за
. .. ое
#42 0 5 3
"= a aw
а чье
каки
я... >
ка вв е
.4 0 5 0
в я тие
«rs new
re raw
En eos
=. + + rr A = = » =» SEEN
es EEE Ie
.... re
“ 4
вета
narra
= в «ее ©“ are
т. к аа а Pa aan
я а ет
+2 a = 48
"ea
EARTH GROUND
к
Figure 1 Capacitive Measurement Path in Lined
Metal Vessel
on the sensor will not be linear because of the variable
distance between the electrode and the vessel wall.
One way to solve this problem is to place a grounded,
concentric tube around the measuring sensor. If
corrosion problems or the high cost of the tube makes
this choice undesirable, an alternate solution is to use
another insulated electrode parallel to the measuring
sensor. This reference electrode must be grounded
(perhaps to the grounded metal vessel) and kept at a
constant distance from the measuring sensor using
insulated spacers.
Conductive Materials
The total capacitance output of the sensor in a
conductive media is still a function of two capacitors in
series: sensor insulation (Cl) and vessel liner (CL). The
measured material (CM) is effectively eliminated from
the capacitance equation because the conductive
material has virtually no ability to store a charge. The
total capacitance of a conductive fluid or solid is
approximated by the following equation:
Cr = С, х Ci
С, + Ci
The capacitance of an electrode varies with the choice
of insulation. Table A shows the saturation capacitance
for a variety of OMEGA level sensors. Note that
saturation capacitance is the highest capacitance
generated by an electrode which occurs in an infinitely
conductive material. An enhanced performance
electrode with PVDF insulation has 950 pF per
immersed foot, while a general purpose electrode with
TFE insulation has 76 pF per immersed tool.
Table A
Type of Level Sensor Saturation Capacitance
General Purpose:
TFE Teflon Insulated 76 pF per foot
Polyethylene Insulated 189 pF per foot
PVDF (Kynar) Insulated 350 pF per foot
Heavy Duty:
TFE Teflon Insulated 79 pF per foot
Polyethylene Insulated 198 pF per foot
PVDF (Kynar) Insulated 365 pF per foot
Flexible Cable:
PFA Teflon Insulated 58 pF per foot
Polyethylene Insulated 146 pF per toot
PVDF (Kynar) Insulated 254 pF per foot
Enhanced Performance:
PFA Teflon Insulated 207 pF per foot
Polyethylene Insulated 518 pF per foot
PVDF (Kynar) insulated 950 pF per foot
Let's assume that the capacitance of a particular lining
(CL) in a vessel is about 15,000 pF per foot of height.
The total capacitance measured will then depend on
whether or not the material in the vessel is grounded.
Examples 1 and 2 below illustrate the measured
capacitance using two different sensors with and
without a grounded measured material.
Example 1: Capacitance of Enhanced Performance
Sensor w/PVDF Insulation In
Conductive Material
Measured Material Measured Material
Not Grounded Grounded
Cr = 950x 15,000
= 893.4 pF/t.
Example 2: Capacitance of General Purpose
Sensor w/PVDF Insulation In
Conductive Material
Measured Material Measured Material
Not Grounded Grounded
Cr = 76x 15,000
15,076 Cr = С, = 76.0 Ft.
= 75.6 pFrt t.
When the conductive material is grounded, the second
plate of the capacitor is no longer the vessel wall but
the conductive material. Since the material is in contact
with the sensor insulation, only the capacitance of the
sensor determines the measured value. C, is eliminated
from the equation and Cr now equals С.
The significance of this is important when one does not
intentionally ground the material and calibrates the
system using the metal vessel as ground. As Example 1
shows, the difference between the two measurements
is about 6%. Thus, if the material becomes grounded
due to the opening of a valve or the generation of a
small leak in the lining, the measured reading would
shift by at least 6% of full scale. Each sensor and
insulation will have its own characteristic shift, but when
the best possible accuracy is desired, and the
conductive material tends to coat the electrode, the
“enhanced performance” sensor should be chosen.
If one is not certain that the material will never get
grounded accidentally, ALWAYS INTENTIONALLY
GROUND THE MEASURED MATERIAL. This
eliminates CL from the measurement and prevents
changes in capacitance caused by inadvertent
grounding. The following methods of ground are
recommended.
Grounding Methods
METAL
TANK
PLASTIC
LINER
GROUND WIRE ON
INSULATED SENSOR
it.
1. Ground Wire Wrapped Electrode*—This is a popular
method especially when an exotic metal must be
used for compatibility. The exotic metal wire is less
expensive than rod stock or concentric pipe or tube.
The measuring electrode is normally mounted in a
plastic-faced flange. The small diameter grounded
wire (typically 0.032<) is placed between the flange
face and nozzle flange face and wrapped around the
measuring electrode in a long open spiral. The wire
is held against the electrode insulation with a few
sections of heat shrink plastic tubing and is attached
to the lower end of the electrode. When a measuring
electrode with a threaded rather than flange fitting is
used, the wetted portion of the entrance gland must
be constructed of a compatible metal and the ground
wire must be attached to the grounded face of the
lining.
* This method is not recommended in applications involving
conductive materials that will coat on the level sensor.
PLASTIC METAL
LINER - TANK
INSULATED SENSOR
W/ CONCENTRIC
METAL TUBE
2. Metal Concentric Tube—In some applications, a
metal concentric tube serves as a grounding element
and also as a stilling well. The advantage of the
concentric tube is that it requires only one vessel
entrance which may be threaded or flanged.
However, if the concentric tube must be made of an
exotic material, the cost may be prohibitive.
METAL METAL
ROD TANK
INSULATED
SENSOR PLASTIC
—_— LINER
3. Ground Rod—A metal rod, sufficiently long so as to
always contact the measured liquid, may be
installed. It should be mounted no closer than two
inches from the measuring electrode, with plastic
spacers to maintain this distance. If the ground rod is
mounted at a distance greater than two inches, the
spacers may not be necessary. It is good practice to
mount the ground rod as far from the measuring
electrode as is practical. Please note that after about
10" a ground rod becomes ineffective in non-
conductive materials. It is important to know that the
level reading could change if the ground rod moves
closer to the measuring electrode due to agitation.
Note: Insulated ground rods are not recommended
in conductive materials because the result
would be two capacitors in series, which
could produce erroneous readings if
intermittent grounds exist.
PLASTIC METAL
LINER TANK
ern sens 4—————
INSULATED
SENSOR
|
METAL FLANGE =
4. Metal Drain Fitting—Usually an above ground vessel
will have a drain located in the bottom of the vessel.
In a lined vessel, the drain is likely to be a nozzle
with a cover flange. The nozzle and flange will
contain the same protective coating. In some cases it
is acceptable to replace the flange with a metal
flange of compatible material, and then ground the
flange. However, if an exotic material such as
Hastelloy is required, the cost may be prohibitive.
Other Important Considerations
M A vessel mounted on a concrete pad (with plastic or
lined pipe inlet and outlet) is not necessarily
grounded. If the vessel shell is not grounded, a
person merely walking up to the vessel can influence
the measurement. The best method of grounding a
tank is by running a wire from the LV5900 electronics
to the material in the tank.
EB Excessive use of Teflon thread sealing tape or pipe
joint compound may actually insulate an electrode
fitting from the vessel. Check for good grounding with
an ohmmeter. Run a wire from the gland to the
vessel wall to insure a good ground.
About Conductivity
Non-conductive materials are defined to have a
conductivity less than 0.1 microSiemens/cm.
Conductive materials have a conductivity greater than
10 microSiemens/cm. For materials with a conductivity
between these limits, more analysis is required to
predict the various effects on calibration and accuracy.
Fortunately, most common conductive materials such
as aqueous solutions will be found to be above the high
conductivity limit and non-conductive liquids such as
petroleum-based products will be below the low limit.
Conclusion the material is conductive, ground it and use the
1. The vessel must be grounded in all cases. “enhanced performance” sensor. |
2. Best accuracy carries a price tag. Consider the cost 4. In general, aqueous solutions are conductive—
to obtain high accuracy. petroleum-based materials are non-conductive.
3. If in doubt about buildup and conductivity, assume 5. When in doubt, ground conductive materials.
Sensor Selection Guide For Use in A Lined Metal Vessel With Grounded Shell
Yes Is Measured No
Material Conductive?
No
Is Vessel Linear? Is Vessel Linear?
Use Concentric Probe,
if Fluid Makes This
Yes | Possible (Liquid Must Not Yes No
Clog the Probe).
If Not, Use Enhanced
No Is Material Yes Performance Probe.
Buildup
Expected?
Use Any Sensor.
Grounding
Per Above Notes
Use General Purpose,
Heavy Duty or
Flexible Cable Sensor.
Use Enhanced
Performance Sensor
Use Any Sensor.
Use Any Use A Parallel
Grounding Method. Ground Rod Or
Concentric Metal Tube.
(3: OMEG A APPLICATION NOTE
DOCUMENT
49003
CAPACITANCE LEVEL MEASUREMENT
Basic Measuring Principle
A capacitor is formed when a level sensing electrode is
installed in a vessel. The metal rod of the electrode acts
as one plate of the capacitor and the tank wall (or
reference electrode in a non-metallic vessel) acts as the
other plate. As level rises, the air or gas normally
surrounding the electrode is displaced by material
having a different dielectric constant. A change in the
value of the capacitor takes place because the dielectric
between the plates has changed. RF (radio frequency)
capacitance instruments detect this change and convert
it into a relay actuation or a proportional output signal.
The capacitance relationship is illustrated with the
following equation:
C = 0.225 K (5)
р
where:
C = Capacitance in picoFarads
K = Dielectric constant of material
A = Area of plates in square inches
D = Distance between the plates in inches
ELECTRODE
VESSEL WALL
The dielectric constant is a numerical value on a scale
of 1 to 100 which relates to the ability of the dielectric
(material between the plates) to store an electrostatic
charge. The dielectric constant of a material is
determined in an actual test cell. Values for many
materials are published by the National Institute of
Standards and Technology.
In actual practice, capacitance change is produced in
different ways depending on the material being
measured and the level electrode selection. However,
the basic principle always applies. If a higher dielectric
material replaces a lower one, the total capacitance
output of the system will increase. If the electrode is
made larger (effectively increasing the surface area) the
capacitance output increases; if the distance between
measuring electrode and reference decreases, then the
capacitance output decreases.
Level measurement can be organized into three basic
categories: the measurement of non-conductive
materials, conductive materials and proximity or non-
contacting measurement. While the following
explanations oversimplify the measurement, they
provide the basics that must be used to properly specify
a capacitance measurement system.
mu Non-Conductive Materials—As previously stated,
capacitance changes as material comes between the
plates of the capacitor. For example, suppose the
sensor and the metal wall are measuring the
increasing level of a non-conductive hydrocarbon
such as gasoline. Figure 1 depicts a typical system.
METAL SHELL
MEASURED MATERIAL
SENSOR INSULATION
METAL ELECTRODE
= DE — EARTH GROUND
Figure 1 Capacitive Measurement In
Non-Conductive Media
While the actual capacitive equation is very complex, it
can be approximated for the above example as follows:
0.225 (Kair X Aair)
Dair
+ 0.225 (ÆKmateriai X Amaterial)
Dmaterial
—
—
Since the electrode and tank wall are fixed in place, the
distance between them will not vary. Similarly, the
dielectric of air and of the measured material remain
constant (air is 1 and the hydrocarbon is 10).
Consequently, the capacitance output of the system
example can be reduced to this very basic equation:
С = (1 x Aair) + (10 X Amaterial)
As this equation demonstrates, the more material in the
tank, the higher the capacitance output will be. The
capacitance is directly proportional to the level of the
measured material.
mM Conductive Materials—The same logic for non-
conductive materials applies for conductive
materials, except that conductive material acts as the
ground plate of the capacitor, rather than the tank
wall. This changes the distance aspect of the
equation, whereby the output would be
comparatively higher than for a non-conductive
material. However, it still remains fixed; therefore, as
level rises on the vertically mounted sensor, the
output increases proportionally.
NOTE: A material is considered conductive when it
has a conductivity value of greater than
10 microSiemens/cm.
WARNING: The level sensing electrode must be
insulated. A non-insulated sensor would
be tip sensitive and act like a conductive
switch.
mM Proximity (non-contacting) Measurements—The level
sensing electrode is normally a flat plate mounted
parallel to the surface of the material. The material, if
conductive, acts as the ground plate of the capacitor.
As level rises to the sensor plate, the effective
distance between plates is decreased, thus causing
an increase in capacitance. In non-conductive
materials, the vessel acts as the ground plate and
the mass of material between the plates is the
variable. In the measurement of non-conductive and
conductive materials, the area changes and the
distance is fixed. Proximity level measurement is
exactly the opposite in that the area is fixed, but
distance varies.
Proximity level measurement does not produce a
linear output and can only be used when the level
varies by several inches.
Some typical level sensor installations for measuring
conductive and non-conductive materials and for
proximity level measurement are shown in Figures 2
and 3.
Applications
Applications for RF point level controls and analog
transmitters/controllers are widespread. Granular
applications range from light powders to heavy
aggregates. Applications in liquids, slurries and pastes
are commonplace. Capacitance level can also be used
to detect the interface between two immiscible
materials.
Selecting the proper level sensing electrode and
installing it in the proper location are important factors
|
Figure 3
that contribute to the success of any application. A
thorough understanding of these factors is required.
e Electrode Selection—The electrode is the primary
measuring element and must be capable of
producing sufficient capacitance change as it
becomes submerged in the measured material.
Several electrode types are offered, each having .
specific design characteristics. Capacitance (per foot
of submersion) vs. dielectric constant curves are
published for each type as installed in various size
vessels. For non-conductive materials, these curves
are non-linear. Figure 4 shows a typical set of
curves. As the size of the tank gets smaller, the
capacitance per foot of submersion increases. A
conductive material essentially makes the tank be
the size of the electrode insulation.
Note: Continuous level transmitter applications
require a minimum span of 10.0 pF and a
maximum span of 10,000 pF.
In this case, the saturation capacitance is used.
Table A lists basic capacitance values for different
electrodes and tank sizes.
Capacitance Level Probe Selection Guide
The simplest applications are clean, non-coating
conductive liquids (such as many water-based liquids)
in metallic tanks. An insulated probe must be used, and
the fluid is grounded to the probe through the tank. The
capacitance change per foot = the saturation
capacitance.
Clean, non-coating conductive liquids (such as many
water-based liquids) in non-metallic tanks require the
use of a concentric probe. The capacitance change per
foot = the saturation capacitance. See application note
“RF Level Measurement in Lined Vessels with
Grounded Shell” for details on lined or coated metallic
tank applications. Clean, non-coating non-conductive
liquids (such as many hydrocarbons ) in non-metallic
tanks require the use of a concentric probe. The
capacitance change per foot depends upon the
dielectric constant of the material.
Clean, non-coating non-conductive liquids (such as
many hydrocarbons ) in metallic tanks require special
consideration. A bare (un-insulated) probe can be used,
but one must insure that the probe does not come in
contact with any conductive liquid that may contaminate
the non-conductive liquid (such as water in oil). If this
occurs, the output will be driven to full scale, regardless
of the actual level in the tank. Note that an insulated
probe can also be used. The probe's metal fitting must
be grounded to the metal tank wall, and the distance
from the tank wall to the probe must be constant along
the entire length of the probe, to provide a linear
change in analog output per change in fluid height. If
this is not the case (i.e. the tank is “irregular” in shape),
or if the tank is greater than 15 ft in diameter, a
concentric probe should be used. The capacitance
change per foot depends upon the dielectric constant of
the material, as well as the tank diameter (tank
diameter does NOT effect the concentric probe).
After making a preliminary probe selection based upon
the above considerations, it is important to insure that the
capacitance of the probe selected meets the following
limitations: the capacitance at zero level in the tank is less
than 500 pFd, and the maximum capacitance at full span
level is more than 10 pFd but less than 10,000 pFd. Also,
the zero to span ratio must not exceed 10 to 1. That is, if
the zero pf value is 200, the span must be at least 20 pf.
THIS IS CALCULATED AS FOLLOWS:
For the LV5100 probe, TFE insulated, in a 24" tank,
with a dielectric = 2 (air has a much lower dielectric, so
this calculation is very conservative), the pFd per foot is
6 pFd. The maximum length of this probe is 12 ft, so
that the maximum probe capacitance in the open air is
= (6 x 12) + (42 pFd - gland capacitance) = 114 pFd,
which is less than 500 pFd. Note that no probe has
greater than 50 pFd gland capacitance.
*** Helpful Hint: 500 pFd can only be exceeded with an
LV5300 probe of greater than 25 ft length, or greater
than 9 ft length in the LV5102 PVDF insulated heavy
duty probe, or greater than 9 % ft length in the
polyethylene insulated heavy duty probe.
For the LV5100 probe, TFE insulated, in a 24" tank,
with a dielectric = 2 (this is a typical value for
hydrocarbons) the pFd per foot is 6 pFd. The maximum
length of this probe is 12 ft, so that the maximum span
capacitance is = (6 x 12) + (0 pFd - gland capacitance
is not added to the span) = 72 pFd, which is greater
than 10 pFd and less than 10,000 pFd. Note that if the
probe were only 1 ft long, that the maximum span
capacitance would be only 6 pFd, which is less than the
required 10 pFd.
*** Helpful Hint: 10,000 pFd can only be exceeded with
an LV5300 probe of greater than 39 ft length, or greater
than 10 ft length in the LV5202 or LV5212 PVDF
insulated enhanced performance probe with a
conductive liquid.
*** Helpful Hint: To have less than 10 pFd span, one
must have a span of less than 1 ft for non-conductive
liquid with dielectric less than 20 and in a tank greater
than 1" diameter.
*** Note that the “Saturation Capacitance” values
should be used when the liquid is conductive (i.e.
above 20 microsiemens/cm ), such as water-based
fluids that are not ultra-pure or distilled or deionized.
Field Calibration Required:
Capacitive level transmitters must always be calibrated
for zero and span in the field. The concentric probe can
be tested in a bucket or small tank of the liquid to be
measured; all other probes must be calibrated after final
installation by changing the material level and adjusting
the zero and span pots.
Unlined Plastic Tanks:
Due to the low gains in large tanks, concentric probes
are recommended for unlined plastic tanks to minimize
this effect and to provide a ground reference.
Large Diameter Metal Tanks for Low Dielectric
Fluids (such as Hydrocarbons)
Due to the low gains in large tanks, concentric probes are
recommended for metal tanks greater than 20 foot
diameter used to measure low dielectric fluids (such as
hyrdrocarbons). Also, if concentric probe is impractical,
mount closer to tank wall if possible.
. Electrode Location—Mounting positions should
be carefully considered. They must be clear of the
inflow of material as impingement during a filling cycle
can cause serious fluctuations in the capacitance
generated. Side mounted electrodes with point level
controls are typically mounted at a downward angle to
allow the measured material to drain or fall from the
electrode surface.
GENERAL PURPOSE PROBE - TFE INSULATED
70
60
50
40
30
20
CAPACITANCE PER FOOT (pF)
10
10 20 30 40 50 60
DIELECTRIC CONSTANT
Figure 4
70 80
Electrodes mounted in nozzles should contain a metal
“sheath” extending a few inches past the nozzle
length. The sheath renders that part of the electrode
insensitive to capacitance change, and therefore,
ignores the material which may buiid up
in the nozzle.
WARNING: Vertically mounted electrodes must be
clear of agitators and other obstructions and
far enough from the vessel wall to prevent
“bridging” of material between the electrode
and the vessel wall.
NOTE: In addition to the electrode selection and
location factors, there are other considerations
which can have a significant impact on the
measurement.
Continuous Level Measurement
Various methods are used to minimize the coating
error. These include proper electrode selection, higher EQUIVALENT
frequency measurements, phase shifting and CIRCUITS
conductive component subtraction circuits. 1
Coating error is illustrated by the diagram shown in
Figure 5. The submerged portion of the electrode
generates nearly a pure capacitive susceptance. Since
the electrode is insulated, a conductive component is
virtually non-existent. However, the upper section of the
electrode, coated with conductive material, generates
an error signal consisting of a capacitive susceptance | H 7
ELECTRODE
al
+
Ad LL LL
and a conductive component. The result is an
admittance component which is 45° out of phase with
the main level signal. À study of transmission line I
theory is required to prove this phenomenon. An
equivalent circuit for the coated section is shown as a
ladder network producing the phase shifted error signal.
Figure 5
Special Considerations
One means of canceling the error signal is to measure
the conductive component (c) shown in Figure 6, SUSCEPTANCE
Method A. Since the 45° relationship exists, the
capacitive error component (e) is the same magnitude
and can be subtracted from the total output signal,
thereby effectively canceling the error signal. METHOD A /
Another cancellation method is to introduce a 45° phase ERROR /
shift to the entire measurement as shown in Figure 7, SIGNAL e /
Method B. This automatically cancels the coating error „| 20e
portion because the conductance component (c) still c
has the same magnitude as the error component (e), N. e
resulting in the appropriate level signal. Instruments
which incorporate these techniques are known as 45° METHOD B
“admittance” types. US,
The coatin Iso be reduced by increasing th LEVEL
g error can also be y increasing the SIGNAL
capacitive susceptance. This is accomplished by
increasing the frequency of measurement and/or
decreasing the electrode insulation wall thickness. CONDUCTANCE
It should be noted that any of these techniques cannot
perfectly cancel the coating effect, but each tends to
reduce the error. | |
. Admittance Vector Diagram
WARNING: For all of the preceding reasons, RF Figure 6
continuous level instrumentation is not used
in inventory control applications.
These are process control devices which require careful
evaluation of the listed considerations to provide
satisfactory results.
Table A—Capacitance Values (pF per foot)
Conductive
Non-Conductive Materials/Tank Diameter Material
Dielectric = 2 Dielectric =20 Dielectric = 80 (Saturation
Type of Sensor 17 24” | 96” 1” 24” | 96” 1” 24” | 96” | Capacitance
General Purpose
(LV5000 Series):
TFE Teflon Insulated 15 pF | 4 pF |2 pF | 63 pF {39 pF|34 pF | 73 pF | 62 pF | 58 pF 76 pF
Polyethylene Insulated 16 pF | 6 pF |3 pF {123 pF {57 pF | 46 pF |167 pF| 120 pF 117 pF 189 pF
PVDF Insulated 18 pF | 7 pF |4 pF |178 pF |68 pF| 50 pF |280 pF| 169 pF 142 pF 350 pF
Heavy Duty (LV5100 Series):
TFE Insulated 35 pF | 6 pF |4 pF | 74 pF {44 pF|36 pF | 78 pF | 66 pF | 62 pF 79 pF
Polyethylene Insulated 48 pF | 5 pF |3 pF |172 pF {66 pF|52 pF {190 pF| 131 pF[116 pF 198 pF
PVDF Insulated 52 pF | 8 pF |5 pF |282 pF | 78 pF| 58 pF [340 pF| 190 pF 158 pF 365 pF
Enhanced Performance
(LV5200 Series):
PFA Teflon Insulated 23 pF | 5 pF |3 pF [147 pF 160 pF| 48 pF |187 pF| 128 pF 114 pF 207 pF
Polyethylene Insulated 22 pF | 8 pF |5 pF {260 pF | 78 pF | 58 pF |410 pF| 210 pF 165 pF 518 pF
PVDF Insulated 25 pF [10 pF |8 pF 1330 pF |80 pF | 60 pF [640 pF| 260 pF ROS pF 950 pF
Flexible Cable (LV5300 Series):
PFA Teflon Insulated 14 pF | 5 pF |3 pF | 50 pF (34 pF | 30 pF | 57 pF | 49 pF | 30 pF 58 pF
Polyethylene Insulated 17 pF | 5 pF |3 pF {103 pF {52 pF | 43 pF |132 pF | 101 pF | 91 pF 146 pF
PVDF Insulated 18 pF | 5 pF {3 pF [154 pF |62 pF | 48 pF |222 pF| 145 pF{128 pF 254 pF
Concentric (LV 5500 Series)
Teflon 25 67 75 76
Polyethylene 25 142 175 189
Kynar 35 220 305 350
WARRANTY/DISCLAIMER
OMEGA ENGINEERING, INC. warrants this unit to be free of defects in materials and workmanship for a
period of 13 months from date of purchase. OMEGA's WARRANTY adds an additional one (1) month
grace period to the normal one (1) year product warranty to cover handling and shipping time. This
ensures that OMEGA's customers receive maximum coverage on each product.
If the unit malfunctions, it must be returned to the factory for evaluation. OMEGA's Customer Service
Department will issue an Authorized Return (AR) number immediately upon phone or written request.
Upon examination by OMEGA, if the unit is found to be defective, it will be repaired or replaced at no
charge. OMEGA's WARRANTY does not apply to defects resulting from any action of the purchaser, includ-
ing but not limited to mishandling, improper interfacing, operation outside of design limits,
improper repair, or unauthorized modification. This WARRANTY is VOID if the unit shows evidence of
having been tampered with or shows evidence of having been damaged as a result of excessive corrosion;
or current, heat, moisture or vibration; improper specification; misapplication; misuse or other operating
conditions outside of OMEGA’s control. Components which wear are not warranted, including but not
limited to contact points, fuses, and triacs.
OMEGA is pleased to offer suggestions on the use of its various products. However,
OMEGA neither assumes responsibility for any omissions or errors nor assumes liability for any
damages that result from the use of its products in accordance with information provided by
OMEGA, either verbal or written. OMEGA warrants only that the parts manufactured by it will be
as specified and free of defects. OMEGA MAKES NO OTHER WARRANTIES OR
REPRESENTATIONS OF ANY KIND WHATSOEVER, EXPRESS OR IMPLIED, EXCEPT THAT OF TITLE,
AND ALL IMPLIED WARRANTIES INCLUDING ANY WARRANTY OF MERCHANTABILITY AND
FITNESS FOR A PARTICULAR PURPOSE ARE HEREBY DISCLAIMED. LIMITATION OF
LIABILITY: The remedies of purchaser set forth herein are exclusive, and the total liability of
OMEGA with respect to this order, whether based on contract, warranty, negligence,
indemnification, strict liability or otherwise, shall not exceed the purchase price of the
component upon which liability is based. In no event shall OMEGA be liable for
consequential, incidental or special damages.
CONDITIONS: Equipment sold by OMEGA is not intended to be used, nor shall it be used: (1) as a “Basic
Component” under 10 CFR 21 (NRC), used in or with any nuclear installation or activity; or (2) in medical
applications or used on humans. Should any Product(s) be used in or with any nuclear installation or
activity, medical application, used on humans, or misused in any way, OMEGA assumes no responsibility
as set forth in our basic WARRANTY/DISCLAIMER language, and, additionally, purchaser will indemnify
OMEGA and hold OMEGA harmless from any liability or damage whatsoever arising out of the use of the
Product(s) ir in such a manner.
| a - RETURN REQUESTS/INQUIRIES
Direct all warranty and repair requests/inquiries to the OMEGA Customer Service Department. BEFORE
RETURNING ANY PRODUCT(S) TO OMEGA, PURCHASER MUST OBTAIN AN AUTHORIZED RETURN
(AR) NUMBER FROM OMEGA'S CUSTOMER SERVICE DEPARTMENT (IN ORDER TO AVOID
PROCESSING DELAYS). The assigned AR number should then be marked on the outside of the return
package and on any correspondence.
The purchaser is responsible for shipping charges, freight, insurance and proper packaging to prevent
breakage in transit.
FOR WARRANTY RETURNS, please have the FOR NON-WARRANTY REPAIRS, consult OMEGA
following information available BEFORE for current repair charges. Have the following
contacting OMEGA: information available BEFORE contacting OMEGA:
1. Purchase Order number under which the product | 1. Purchase Order number to cover the COST
was PURCHASED, of the repair,
2. Model and serial number of the product under 2. Model and serial number of the product, and
warranty, and 3. Repair instructions and/or specific problems
3. Repair instructions and/or specific problems relative to the product.
relative to the product.
OMEGA'’s policy is to make running changes, not model changes, whenever an improvement is possible. This affords
our customers the latest in technology and engineering.
OMEGA is a registered trademark of OMEGA ENGINEERING, INC.
© Copyright 2003 OMEGA ENGINEERING, INC. All rights reserved. This document may not be copied, photocopied,
reproduced, translated, or reduced to any electronic medium or machine-readable form, in whole or in part, without the
prior written consent of OMEGA ENGINEERING, INC.
Where Do | Find Everything | Need for
Process Measurement and Control?
OMEGA...Of Course!
Shop online at www.omega.com
TEMPERATURE
# Thermocouple, RTD & Thermistor Probes, Connectors, Panels & Assemblies
L¥ Wire: Thermocouple, RTD & Thermistor
# Calibrators & Ice Point References
¥ Recorders, Controllers & Process Monitors
W Infrared Pyrometers
PRESSURE, STRAIN AND FORCE
[¥ Transducers & Strain Gages
MY Load Cells 8 Pressure Gages
M4 Displacement Transducers
LA Instrumentation & Accessories
FLOW/LEVEL
WM Rotameters, Gas Mass Flowmeters & Flow Computers
MY Air Velocity Indicators
M Turbine/Paddlewheel Systems
(4 Totalizers & Batch Controllers
pH/CONDUCTIVITY
LY pH Electrodes, Testers & Accessories
MA Benchtop/ Laboratory Meters
M Controllers, Calibrators, Simulators & Pumps
WA Industrial pH & Conductivity Equipment
DATA ACQUISITION
Y Data Acquisition & Engineering Software
WM Communications-Based Acquisition Systems
[# Plug-in Cards for Apple, IBM & Compatibles
iF Datalogging Systems
[# Recorders, Printers & Plotters
HEATERS
MY Heating Cable
L# Cartridge & Strip Heaters
4 Immersion & Band Heaters
L# Flexible Heaters
MM Laboratory Heaters
ENVIRONMENTAL
MONITORING AND CONTROL
MY Metering & Control Instrumentation
M Refractometers
[4 Pumps & Tubing
LF Air, Soil & Water Monitors
Y Industrial Water & Wastewater Treatment
Y pH, Conductivity & Dissolved Oxygen Instruments
M1685/0203