Intek RheoVac 950A User Manual
TABLE OF CONTENTS
SECTION 1 — GENERAL INFORMATION .................................................................... 1
1.1 INTEK’S POWER INDUSTRY SERVICES................................................................. 1
1.2 INTRODUCTION .......................................................................................................... 2
1.3 PRINCIPLE OF OPERATION....................................................................................... 3
1.4 TECHNICAL SPECIFICATIONS ................................................................................. 3
1.5 PRECAUTIONS AND RECOMMENDATIONS.......................................................... 4
SECTION 2 — INSTALLATION........................................................................................ 5
2.1 RHEOVAC SYSTEM INSTALLATION/SITE SELECTION .......................................... 5
2.2 PROBE INSTALLATION.............................................................................................. 7
2.3 ELECTRICAL CONNECTIONS................................................................................... 8
SECTION 3 — OPERATION ............................................................................................ 15
3.1 SYSTEM START-UP................................................................................................... 15
3.2 PORTABLE USB DATA STORAGE/WARRANTY REGISTRATION INSTRUCTIONS ..... 15
3.3 DISPLAY......................................................................................................................15
3.4 COMMUNICATIONS ................................................................................................. 16
3.5 DATA PROCESSING .................................................................................................. 16
3.6 CUSTOM SOFTWARE ............................................................................................... 18
SECTION 4 — MAINTENANCE...................................................................................... 19
4.1 CALIBRATION ........................................................................................................... 19
4.2 SPARE PARTS............................................................................................................. 19
4.3 TROUBLESHOOTING................................................................................................ 20
4.4 HARDWARE/SOFTWARE MODIFICATIONS AND UPDATES............................ 22
SECTION 5 — CUSTOMER SERVICE FROM THE CONDENSER EXPERTS ...... 23
5.1 QUESTIONS ON EXISTING HARDWARE .............................................................. 23
5.2 TROUBLESHOOTING................................................................................................ 23
5.3 FACTORY AND FIELD SERVICE ............................................................................ 23
5.4 NEW EQUIPMENT AND SERVICES ........................................................................ 23
5.5 CONDENSER MANAGEMENT AND RHEOVAC TRAINING .................................. 24
SECTION 6 — CUSTOM INFORMATION .................................................................... 25
6.1 UNIT IDENTIFICATION............................................................................................ 25
6.2 CONFIGURATION...................................................................................................... 25
6.3 SPECIAL INSTRUCTIONS ........................................................................................ 25
Appendix A - RheoVac Model 950 User Interface Software
Appendix B - RheoVac Model 950 Networking
Appendix C – New Features and Options for the RheoVac Model 950
I:\OFFICE\WPMANUAL\RV950A Rev New.doc
Manual no. RV950A Rev. –
©Intek, Inc. 2010
WARRANTY
Intek, Inc. warrants each RheoVac product to be free from defects
in material and workmanship under normal use and service, Intek's
obligation under this warranty being limited to making good any
part or parts thereof which shall, within one (1) year after delivery
of such product to the original purchaser, be returned to Intek with
transportation charges prepaid and which Intek's examination shall
disclose to its satisfaction to have been thus defective; this
warranty being expressly in lieu of all other warranties, express or
implied and all other obligation or liabilities on Intek's part. The
purchaser will assume all responsibility and expense for removal,
decontamination and reinstallation of equipment.
RheoVac instruments are manufactured under United States patent
numbers 4,255,968, 5,485,754, 5,752,411 and 6,526,755. Intek,
Rheotherm and RheoVac are registered trademarks of Intek, Inc.
Windows is a registered trademark of Microsoft Corporation in the United States and other countries.
Intek, Inc.
751 Intek Way
Westerville, Ohio 43082-9057
Phone (614) 895-0301 – Fax (614) 895-0319
web site – www.intekflow.com
e-mail – techsupport@intekflow.com
SECTION 1 — GENERAL INFORMATION
1.1 INTEK’S POWER INDUSTRY SERVICES
Intek manufactures RheoVac condenser and air in-leak monitor Rheotherm circulating water
flow and fouling meters, flow meters, flow switches, as well as, temperature sensors and pressure
probes. These specialty instruments for the power industry provide continuous monitoring of
critical parameters that have historically been unavailable or inadequately measured since steam
surface condensers were introduced.
The data from these instruments have been used to gain a unique comprehensive understanding
of steam surface condensers and the condensation process. This understanding has enabled us to
help customers troubleshoot condensers with greater speed and accuracy than ever before. We
have expanded our service offerings by developing an online diagnostic toolkit for steam surface
condensers, available at www.MyCondenser.com.
We have also taken advantage of our aerospace design tools and design expertise for the purpose
of designing condenser retrofits for performance and condensate chemistry improvement. Intek
has lead condenser retrofitting projects that have transformed underperforming condensers into
some of the best performing condensers in the world.
The condenser services team under Dr. Joseph Harpster’s leadership has also sought to educate
the industry by contributing volumes of material to ASME and EPRI regarding proper condenser
measurement and steam flow dynamics. Intek also teaches a semiannual Condenser Operations
and Management Workshop accredited by The Ohio State University for Continuing Education
Credit. Tutorials and case studies are also available at www.MyCondenser.com.
Intek is The Gateway to Improved Condenser Performance, Fast Response Maintenance
and Optimized Operations. Thank you for your interest in Intek's Power Industry
Instruments and Services.
- 1 -
1.2 INTRODUCTION
RheoVac technology provides direct measurement of all necessary properties of the gases, in the
condenser exhauster line, to give an accurate determination of air in-leakage and condenser
performance related parameters. The RheoVac instrument is a part of Intek's services that
provide the power industry with the most advantageous and complete measurement and
diagnostic tools for condenser systems. Other measurement instruments offered by Intek include
circulating water flow and fouling meters, flow meters, flow switches, condenser shell pressure
and temperature sensors.
the RheoVac®System*
*USPNs 4,255,648; 5,485,754; 5,752,411; 6,526,755
A model 950 RheoVac system consists of single or multiple probes reporting to a central signal
conditioner and processor unit. The sensing probes, consisting of multiple sensors, are installed
in the vacuum line between the condenser and the exhauster. The sensor assembly employs the
patented Rheotherm
temperature, pressure and water vapor relative saturation measurements are made using high
accuracy platinum resistance temperature detectors (RTD), strain gauge pressure sensor and
specially configured and calibrated water vapor saturation sensor.
®
technology to provide an accurate mass flow measurement. Additionally,
Figure 1 RheoVac Model 950
- 2 -
1.3 PRINCIPLE OF OPERATION
The Rheotherm flow sensor is calibrated to measure the total mass flow of the gaseous water
vapor/air mixture. From the other three measurements, the RheoVac electronics converts the
total gas mass flow signal from the probe into two components, air mass flow rate and water
vapor mass flow rate.
The RheoVac system is fully calibrated at the factory under dynamic fluid conditions identical to
those within the power plant vacuum line. Field adjustments are not required, with the exception
of line size.
1.4 TECHNICAL SPECIFICATIONS
1.4.1 Sensor (Probe) Specifications
Primary Calibration Accuracy:
±5% of total mass flow
Repeatability:
±0.5% of reading
Operating Temperature:
Electronics: 40 to 120ºF (5 to 49ºC)
Probe: 40 to 160ºF (5 to 71ºC)
Never subject probe to temperatures above 210ºF (99ºC)
Operating Pressure:
0.5 to 10 inches Hg absolute
15 psi maximum
Storage Temperature:
-20 to 210ºF (-29 to 99ºC)
Storage Pressure:
15 psig (maximum)
Process Connection:
Hot tap assembly
(1½” thread-o-let must be welded to pipe for hot tap installation)
Wetted Surface:
300 Series SS and engineered plastic
1.4.2 Main Electronics (Remote or PC) Signal & Data Access
Local Display:
Back-lit LCD
Selectable display of air in-leakage and 6 additional instrument output parameters
Parameter scrolling
Metric/English units
Input Power:
100-250 Vac, 50/60 Hz
Signal Output or Data Access:
RS-232/RS-422/Serial Modbus, Ethernet, TCP/IP
Eight 4-20mA signals (optional)
Wireless (Optional)
OPC (Optional)
Temperature Environment:
Operating: 40 to 120°F (5 to 49°C)
Storage: -20 to 210°F (-29 to 99°C)
- 3 -
1.5 PRECAUTIONS AND RECOMMENDATIONS
x Read the entire manual before installing and operating the RheoVac system.
x WARNING — Be sure to power up your RheoVac instrument system and probe(s)
for at least 30 minutes before inserting probes into the vent line hot taps. DO NOT
leave probe in vent line without power or when flooding the condenser.
x Carefully select the best locations for installation of the probes. Access, orientation,
installation clearances, freedom from standing water, absence of water traps, minimum
required straight-run should all be considered when selecting a probe location.
x Use reasonable care in handling the probe — the sensing components are delicate. Do
not bend the probes, damage the tips, or obstruct the sensing ports. If shipping the unit,
make sure the probe is adequately protected from foreign objects and damage; save and
reuse factory provided custom probe protector and shipping boxes.
x Use proper input power — it must be between 100 and 250 Vac (nominal 120/240 Vac)
at 50/60 Hz (60 Hz nominal).
x Confirm the line and environmental temperature is always within the probe and
electronics ratings — never operate a probe at or subject it to temperatures or pressures
beyond its specified limits. (See SECTION 1.4)
x WARNING — Never allow live high temperature steam to flow either direction in
the exhauster line where a probe is located. This can happen if steam jet ejectors
are operated incorrectly.
x WARNING — Do not allow the instrument sensors (or separate RS probe) to come
into contact with liquid water, including water from condenser flooding (hydro
testing) and entrained liquid water — entrained liquid water is an indicator of poor
condenser venting and may be present in your condenser vent line due to design
configuration. See EPRI’s “Air In-Leakage and Intrusion Prevention Guideline,”
TR 1014125. Intek provides analysis and design services to improve condenser
venting and reduce or eliminate entrained liquid water and excess condenser back
pressure.
x Keep moisture out of the enclosures — once all service connections are made, make sure
all gaskets are in place and the enclosure lids are tightly closed. Seal all conduit lines.
x Intek recommends using the RJ-45 network connection for all data traffic (as opposed to
serial and 4-20 mA communication).
x Intek recommends a service contract to ensure probes are within calibration
specifications and electronics are maintained with appropriate software/hardware
updates. Instrument probes should be returned to the factory for inspection and
calibration service every two years.
x Intek recommends the use of condenser diagnostic tools and tutorials provided on
www.MyCondenser.com
.
- 4 -
SECTION 2 — INSTALLATION
These instructions are general guidelines for the installation of RheoVac instruments in their
standard configuration. Additional information pertaining to your unit is covered in SECTION 6
— CUSTOM INFORMATION. Carefully read these instructions prior to installing the equipment. Also, see preceding SECTION 1.5; PRECAUTIONS AND RECOMMENDATIONS.
2.1 RheoVac SYSTEM INSTALLATION/SITE SELECTION
The standard RheoVac 950 can be configured with one, two or three probes. A three probe
system is intended to be installed so that one probe is in each of the two exhaust lines coming out
of the condenser (A side and B side). The third probe should go in the header pipe that runs to
the exhauster(s). Other installation arrangements of multiple probes should be discussed with the
factory. High temperature dual probe systems (where each “probe” is comprised of a matched
main FTP probe and an RS probe pair) have different configuration limitations for a given
RheoVac 950 system.
2.1.1 Probe Site Selection
x The location for each probe should be selected so as to provide the probe sensing area
with well-established mean flow velocity, uniform system temperature and pressure, and
consistent non-liquid phase flow medium. Pipe sections ahead of a probe, in which water
can accumulate, must be avoided. Refer to Figure 2 and select the most preferred
location for each probe. Do not install the probes beyond any “trap” sections as shown in
Figure 2, Configurations B and D. Special installation instructions unique to your unit,
where applicable, will be noted in SECTION 6.3 SPECIAL INSTRUCTIONS. Refer to
this section now to review special instructions.
RheoVac
INSERTION RECOMMENDATION
PROBE
Figure 2 RheoVac Probe Insertion Recommendation
- 5 -
x Check installation clearance. Each transducer probe is approximately 3 feet (0.9m) long
and the hot tap assembly is approximately 13 inches (0.33m) long, therefore, allow
minimum clearance of 4 feet (1.3m) for probe installation. Be sure there are no
obstructions around the vacuum line that will interfere with probe insertion. Figure 3
shows the proper insertion angle. THIS ORIENTATION IS IMPORTANT FOR
PROPER OPERATION.
VACUUM PIPE WALL
VACUUM PIPE WALL
PROBE SHOULD BE
PARALLEL TO FLOOR
REQUIRED INSTALLATION ANGLE
FOR HORIZONTAL PIPE RUN
PROBE SHOULD BE
PARALLEL TO FLOOR
+0°
90°
UP
REQUIRED INSTALLATION ANGLE
FOR VERTICAL PIPE RUN
+0°
90°
-5°
-5°
UP
4'
CLEAR SPACE
1 1/2" THRU HOLE
REV DESCRIPTION DATE APV D
A EDITING CHANGES 11/18/97
Changed installation angleB 11/15/99
Edited Hot Tap Installation
C
Changed Probe Box
D
RHEOVAC HOT TAP INSTALLATION
VACUUM PIPE WALL
WELD
COMPRESSION FITTING
STOP CLAMP (ON PROBE)
10/03/95
JVR
REVISIONS
1 1/2" FNPT THREAD-O-LET
1 1/2" BALL VALVE
Intek, Inc.
751 Intek Way
Westerville, Ohio 43082
A
59936
NTS
RheoVac
94078-3
1 1
12/04/00
12/04/07
MH
BC
BC
BH
Figure 3 Transducer Installation Detail
x It is recommended that only Intek supplied hot taps be used. The hot tap length affects
the insertion depth of the probe and must be accounted for; likewise, the proper port
clearance for the probe’s maximum diameter.
x Observe the selected sites; check for ease of access. They should be convenient for the
removal and replacement of probes at any time for service without ladders, building
scaffolding or waiting for plant shutdown.
x Check operating conditions. The temperature and pressure limits (see TECHNICAL
SPECIFICATIONS; SECTION 1.4) of the unit should be checked to ensure compatibility
with your application.
x Gases in the air removal line should be free of liquid water, mist or fog. Wetness in the
line will result in erroneous readings from the instrument and can damage sensors. If wet
conditions exist in the air removal line, there is either air removal section damage or
design flaws which adversely affect condenser performance. Consult Intek for assistance
in evaluating the severity of the problem and possible remedies.
- 6 -
2.1.2 Electronics Unit Site Selection
The Model 950 typically has two or three electronics enclosures (see Figure 1). The processor
enclosure and other electronics boxes should be installed in a convenient location and should be
kept away from direct sources of heat, such as non-insulated steam lines, or moisture. The
maximum temperature rating of electronics is 120(F; ensure that this temperature will not be
exceeded inside the enclosure. Once the wiring connections are made, close and latch down the
box lid to protect the contents from damage and debris. All these enclosures should be located in
a dry area and should be kept clamped shut during normal operation. Do not allow water to get
into the enclosures. If installed outdoors, build a roof over all enclosures to prevent potential
water infiltration.
x Processor Enclosure: This 12x10 NEMA 4 enclosure houses the display and central
processing unit. Input power (100-250 Vac, 50/60 Hz) is connected inside this enclosure.
x Distribution Box: This 8x6 NEMA 4 enclosure is typically located near the probe that is
closest to the processor enclosure unit. It is connected to the main processor with an RS485 bus DeviceNet™ cable, which can be hundreds of feet long. The probe and
transmitter RS-485 cable connections are also made within this box. The probe and
transmitter cable lengths should be 15 ft or less.
x Transmitter Box (optional): This 10x8 NEMA 4 enclosure contains terminals for
accessing the eight 4-20mA signals. It can be located in or near the control room so that
the 4-20 wires do not have to be run from the plant floor. An RS-485 DeviceNet™ cable
runs from the distribution box to the transmitter box. (There are restrictions on how this
can be done, so check manual SECTION 6, or contact the factory.)
2.2 PROBE INSTALLATION
A. Hot Tap Installation
1. Check hardware. Verify that the probe slides easily through the hot tap assembly and
pipe penetration hole.
2. Verify there is a minimum probe insertion clearance of 4 feet (1.3m) between pipe
surface and any obstruction.
3. Install the mounting hardware. Drill a 1½” through-hole, center the thread-o-let over
the hole and weld it onto the condenser vacuum pipe (see Figure 3). Thread the hot
tap assembly into the thread-o-let. Use thread tape or pipe dope to seal the
connection. (Alternate: weld thread-o-let to pipe wall, then drill a 1¼" hole in pipe
wall using a hot tap drill.)
4. Make sure the probe is parallel to the floor (see Figure 3). Be sure location is
accessible for probe removal and maintenance.
B. Installing/Removing the Probe
1. It may be necessary to apply a force of about 23 lb (102 Newtons) to remove or
replace the probe under plant operating conditions.
2. Check proper installation direction. Each probe has a directional arrow on the
junction box. Before installing the unit, note proper flow direction. This is important
to instrument operation.
- 7 -
3. Check serial number (S/N). If more than one RheoVac system has been purchased,
make sure the first five digits of the serial numbers of the probe(s) match the first five
digits of the serial number of the main processor unit. The electronics and up to three
probes are a matched set. Mismatched components will not work correctly. The
dash number on the probe S/N is the probe number shown on the display. Record the
probe number and installation location for future reference.
4. Verify stop clamp location (see Figure 4). A stop clamp is
attached to each probe as an indication of its insertion depth. It
is important that the stop clamp is securely in place to position
the sensors in the correct location and to ensure that the probes
do not contact the opposite pipe wall. Contact with the pipe wall
could damage the probe. The clamp’s location is determined
based on your submitted pipe diameter, as shown in SECTION
6.2, and is marked with a groove on each probe shaft. Refer to
this mark if a stop clamp is inadvertently moved. When
installed in the line, the two metal probe tips should be in the
middle of the pipe.
5. Prior to inserting probe, loosen the compression nut on the
thermocouple connector of the hot tap and clean the inner surface
STOP
CLAMP
of the thermocouple connector to ensure it is free of particles that
may cause probe damage.
6. Be sure to power up your RheoVac instrument system and
probe(s) for at least 30 minutes before inserting probes into the
vent line hot taps. DO NOT leave probe in vent line without
power or when flooding the condenser.
7. Install each probe. The probe should be mounted through the
pipe wall using the hot tap assembly. The probe installs so that
EXTRACTION
LINE
(ETCHED)
Figure 4 Probe
Stop Clamp
6''
the two sensor tips are side-by-side across the gas stream. Each
probe has a flow directional arrow on the junction box. Make sure the probe
orientation is correct. When installing under vacuum, do not allow the clamp to
“slam” against the seal nut upon opening the valve. Grasp the probe firmly, with
hand against the seal nut, before opening the ball valve. Allow the probe shaft to
slide slowly through the valve by controlling the amount of grip on the probe shaft.
Special installation instructions, if any, will be noted in SECTION 6.
8. When removing the probe from the vent line, loosen the compression on the
thermocouple connector of the hot tap and slowly pull the probe out of the line until
the extraction line is visible (see Figure 4). Close the ball valve and remove the
probe from the hot tap.
2.3 ELECTRICAL CONNECTIONS
IMPORTANT — Inspect and VERIFY these electrical connections carefully. Improper
connection could damage electronic components and sensor function. If additional holes need to
be drilled in the processor enclosure, remove the electronics subassembly (mounted on a mounting
plate) and temporarily store inside an ESD bag in a safe, clean place. Do not drill with electronics
boards inside the enclosure.
- 8 -
A. Main Processor Unit (see Figure 5)
1. Sensor Power and Communication Line
: Connect the distribution box to this main
processor box using the RS-485 communications/power cable. Follow indicated
connector color code. [communications
: white (A), blue (B) and shield (SH); power:
24Vdc, red (+), and black ()]
2. Main Power
: Connect main power terminals to a dedicated 100-250Vac, single phase,
15-amp circuit. An external disconnect switch should be used for disconnecting power to
the system during outages. Power connection wires should be at least 18 gauge and
comply with accepted wiring codes. SW1 on the power input PWA (printed wiring
board #01011-5) is used for cycling power to reset.
3. Network Connection (Recommended): The Ethernet connection at CN3 on the CPU
interface PWA (printed wiring board #08017-1) is an RJ-45 style jack. A 10-foot
Ethernet Cat5 crossover cable is supplied with the unit for laptop connections. Intek
recommends using this connection for all data transmissions and RheoVac
communications because:
a. More measured data is accessible through the network connection.
b. Software and calibration file updates can be done remotely.
c. Archived data files can be easily retrieved and analyzed by Intek through online
software available at www.MyCondenser.com
4. Serial Communication
: Connector JP3 on the CPU interface PWA (printed wiring
.
board #08017-1) is the RS-232 serial communication interface. This interface should
only be used for distances of 20 feet or less, such as to a laptop computer. A 20-foot
serial cable with a DB-9 connector is available from Intek upon request (see Figure 6
and Table 1). An RS-422 serial communication interface is present for long data
communications when configured without 4-20 mA outputs. Note: Intek recommends
using the network connection for all data transmissions and RheoVac communications.
Table 1 RJ-11 to DB-9 Module Adapter
RS-232 CONFIGURATION RS-422 CONFIGURATION
RJ-11 Pin Out DB-9 Pin Out RJ-11 Pin Out DB-9 Pin Out
1 Tx (transmit) 1 N/C 1 Tx+ (transmit+) 1 RxS (receiveS)
2 N/C 2 Tx (transmit) 2 TxS (transmitS) 2 Rx+ (receive+)
3 Rx (receive) 3 Rx (receive) 3 Rx+ (receive+) 3 Tx+ (transmit+)
4 N/C 4 N/C 4 RxS (receiveS)4 N/C
5 Power (+5V) 5 Ground 5 Power (+5V) 5 Ground
6 Ground 6 Pulled high 6 Ground 6 TxS (transmitS)
7 N/C 7 7 TBD
8 Pulled high 8 8 TBD
9 N/C 9 9 TBD
- 9 -
Figure 5 Output Connections and Set-up
Figure 6 Serial Communication Interface
- 10 -
B. Distribution Box (see Figure 7)
1. Connect the RS-485 wires (blue, white and shield) and 24Vdc power (red and black)
from the main processor unit to screw terminal, JP1.
2. Install ½” liquid-tight conduit between the distribution enclosure and the probes unless
½” rigid conduit is used for long distance runs. Use a minimum of 6 feet of liquid-tight
conduit at the probes.
3. The probe connector comes with an adapter which allows the attachment of the ½”
flexible conduit connector.
4. Connect the probes to the distribution enclosure using the manufacturer supplied four
conductor shielded cable to any screw terminals labeled JP3 to JP6. Probe cable
connections are shown in Figure 7.
5. For multiple distribution box configurations, screw terminal JP2 will be used to wire
the manufacturer supplied four conductor shielded cable to screw terminal JP1 on the
next distribution box in series.
6. Optional — Connect the transmitter box to the distribution box using a RS-485 cable.
7. If no additional distribution boxes are used, ensure the outgoing termination resistor
(JP7 or JP8) is enabled.
Figure 7 Distribution Box
- 11 -
C. Transmitter Box (optional, see Figure 8) — For driving eight (8) remote 4-20 mA analog
signals from one RS-485 input port. Note: Intek recommends using the network
connection for all data transmissions and RheoVac communications.
1. Connect the RS-485 communications/power cable from the distribution box (RS-485:
white and blue wires; 24Vdc power: red and black wires).
2. Connect up to eight (8) signal wire pairs to the indicated terminals for isolated 4-20mA
outputs.
Figure 8 Optional Transmitter Box
3. Figure 8 provides the RheoVac wiring detail for the 8 channel 4-20 mA outputs. Table
2 provides the appropriate connection identification. Model 950 transmitters are
configured as active (transmitter sources the current) when shipped. To change to the
passive mode (receiver to source the current), extract each small 4-20 board, find the
JP1 pins, and move the two jumpers from the “Act” pins to the “Pass” pins (two
positions to the right of factory settings). Figure 9 shows the current output circuit.
The figure also illustrates the active mode and the passive mode configurations.
Table 2 Optional 4-20 mA Configuration
Channel
1 Actual Volume Flow
2 Total Mass Flow
3 Water Vapor Flow
4Pressure
5 Water Vapor/Air Mass Ratio
6 Relative Saturation
7 Air In-Leak
8 Temperature
Output Parameter
- 12 -
Active Configuration Passive Configuration
Vdd
from RheoVac Supply
R2
10 Ohm
Terminal
CAUTION: Do not move config.
jumpers if instrument is powered.
Terminal
05026-1
Q1
RFL2N05
or Equiv.
Q1
RFL2N05
R1
75 Ohm
Isolated Circuit Isolated Circuit
or Equiv.
R1
75 Ohm
Figure 9 4-20 mA Output Circuit
- 13 -
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