Percent Oxygen Sensor

Percent Oxygen Sensor
Instruction Sheet
PN 51A-4000/rev.C
January 2009
Model 4000
Percent Oxygen Sensor
• STABLE, RELIABLE amperometric Oxygen Sensor
• LONG LIFE, LOW MAINTENANCE rechargeable sensor
• ROBUST DESIGN for harsh applications*
• RAPID CALIBRATION using ambient air
• COMPATIBLE WITH 5081-A, 1056 AND 1055 INSTRUMENTS
APPLICATIONS
The Model 4000 sensor is used to monitor percent
oxygen concentrations in gaseous streams. The most
common use is to monitor oxygen headspace concentration for nitrogen blanketing applications. The sensors are also used in other applications where oxygen
levels are controlled and monitored.
FEATURES
The Model 4000 Series Percent Oxygen sensor is a
membrane-covered amperometric sensor. The membrane consists of a gas permeable Teflon ®1 membrane stretched tightly over a gold cathode. A silver
anode and an electrolyte solution complete the internal circuit. The sensor body is constructed of
Ryton®2, which can withstand exposure to hydrocarbons and other corrosive chemicals.
Gas permeates through the membrane, and the oxygen in the sample is reduced at the cathode. A voltage is applied across the cathode and anode,
generating an electrical current that is directly proportional to the oxygen concentration in the sample.
Since the rate of oxygen diffusion through the membrane is temperature dependent, the sensor response
must be corrected for permeability caused by temperature. A Pt 100 RTD in the sensor accurately measures temperature, and the analyzer automatically
performs the correction.
The sensor is easy to maintain. For calibration simply
expose the sensor to ambient air and press the air
calibration button. The analyzer measures the barometric pressure using an on-board pressure sensor
and calculates the equilibrium solubility of atmospheric oxygen at the prevailing temperature and pressure.
Replacing the membrane requires no special tools or
fixtures. To replenish the electrolyte solution, unscrew
the fill plug, add the reagent, and replace the plug.
TYPES OF SENSORS:
Rechargeable with a fast response flow assembly —
allows minimum volume gas flow that permits mounting sensor in a flowing gas stream. Sample is supplied
at slightly above atmospheric pressure, flows through
the assembly, and discharges to atmospheric pressure. Internal volume is low to minimize sensor
response time. Refer to Figure 1 for mounting instructions.
Rechargeable In-line flow — In line pressure compensated flow assembly permits mounting the sensor
in a variable pressure gas stream at pressures up to
50 psig. This may or may not include a gland on the
sensor body. Refer to Figures 2, 3, and 4 for mounting
instructions.
*
RYTON is resistant to 30% sulfuric acid, 85% phosphoric acid,
30% sodium hydroxide, gasoline, aliphatic alcohols, esters, ethers,
and ketones, as well as to aromatic amines. It is not particularly
suited for service in strong oxidizing agents, aliphatic amines, chlorinated hydrocarbons, or aromatic nitrites, aldehydes, and nitro compounds.
1
Teflon is a registered trademark of E.I. du Pont de Nemours & Co.
2
Ryton is a registered trademark of Chevron Phillips Chemical Company LP.
MODEL 4000
SPECIFICATIONS
SPECIFICATIONS
Range: 0-25% Oxygen
Linearity: For constant sample temperature after correction for sensor zero offset: ±1% of full scale
Repeatability: ± 0.1% of range
Stability:
Zero drift ± 0.25% O2 per week @ 25°C;
Span drift ± 0.25% O2 per week @ 25°C
Response Time: 90% in 20 seconds for a step change, using an equilibrated sensor at 25°C
Sample Pressure: 0 to 50 PSIG
Sample Temperature: 32 to 110°F
Humidity: up to 95% non-condensing
Wetted materials: Ryton®1, Teflon®2
1
Ryton is a registered trademark of Chevron Phillips Chemical Company LP.
2
Teflon is a registered trademark of E.I. du Pont de Nemours & Co.
FIGURE 1. Rechargeable Sensor with Fast Response Flow Assembly (6A00184G01)
2
MODEL 4000
INSTALLATION
FIGURE 2. Vertical Installation (Preferred)
FIGURE 3. Horizontal Installation
INSTRUMENT SET UP FOR % OXYGEN MEASUREMENT
For the 1055, access menu by selecting program, then measurement, configure Sensor 1. For manufacturer
select Rosemount, for application select Other, for S1 Units select % sat.
For the 5081A, access the menu by using Program Key on the infrared remote. Select Display, Type=O2,
Unit=%, Sensor=AdO.
For the 1056, access the menu by selecting program, then measurement, choose sensor 1 or 2 measurement =
oxygen. In the “SN configure” screen, under “type” select “% 02 in gas” for “units” select “% oxygen in gas”.
3
MODEL 4000
WIRING
FIGURE 4. Wiring to Model 1055-01-10-25
FIGURE 5. Wiring to Model 1055-01-11-25
FIGURE 6. Wiring to Model 5081
4
FIGURE 7. Wiring to Model 1056
MODEL 4000
MAINTENANCE
CALIBRATION
Air calibration is recommended. Using a certified span gas is an option, but since the concentration of oxygen in
ambient air is close to 21% at sea level, this is the best solution. Refer to the instrument instruction manual for
details on how to access the calibration menu.
Note: An “inprocess” calibration is required. Input 21% O2 as the process concentration. For model 1056, air
calibration can be performed.
TROUBLESHOOTING
The most frequent fault is a progressive development of insensitivity of the sensor. If sensor calibration is sluggish, then the sensor should be recharged with new electrolyte and the membrane may need to be replaced.
Listed below are some common troubleshooting techniques
SYMPTOM
PROBABLE CAUSE
CORRECTIVE ACTION
Abnormally high oxygen readings
(unable to calibrate)
1. Hole in sensor membrane
2. Gold cathode loose
3. Open RTD
1. Replace membrane
2. Replace sensor
3. Replace sensor
Abnormally low oxygen readings
(unable to calibrate)
1.
2.
3.
4.
1.
2.
3.
4.
Sensor noisy (motion sensitive)
1. Membrane loose
2. Low electrolyte level
3. Cathode contaminated
1. Replace membrane
2. Fill properly
3. Replace sensor
Upscale reading with known
oxygen-free sample
Gold cathode loose
Replace sensor
High internal cell resistance
Membrane loose
Contaminated electrolyte
RTD shorted
Replace sensor
Tighten cap / replace membrane
Clean / recharge sensor
Replace sensor
5
MODEL 4000
MAINTENANCE
PROCEDURE TO RECHARGE THE SENSOR:
Refer to Figure 8 for an exploded view of the sensor.
1. Unscrew the knurled cap from the sensor body. Remove the membrane assembly. Empty all electrolyte from
the sensor. Flush the sensor with distilled or deionized water to remove all particulate.
2. Place a piece of adhesive tape over the breather hole in the pressure compensation diaphragm port (not the
slotted fill plug).
3. Examine the cathode for staining or uneven coloration, which indicates the cathode should be rejuvenated.
Also inspect the grooves that surround the cathode for any deposited material, which will typically be white
to gray in color. Most of these deposits are water soluble and can be removed via a water jet from a
squeeze bottle. Any insoluble deposits may be removed with a toothpick, but care must be used to avoid
deforming the grooves.
4. Disassemble the membrane assembly. Remove the retainer from the holder by placing your finger into the
center hold of the holder and pressing your fingernail against the inner edge of the retainer. Remove and
discard the old membrane.
5. Verify that the o-ring is properly positioned in the associated groove holder.
6. Holding a single membrane by the edges only, place it across the membrane holder and snap the retainer in
place.
7. Using a sharp razor blade, carefully trim away excess membrane around the edges. Take care that the razor
blade does not cut into the edges of the membrane assembly.
8. Set the sensor body on a flat surface with the cathode facing upward. Verify that the o-ring is properly positioned around the cathode. Pour the electrolyte over the cathode / central post assembly so it runs down
into the sensor electrolyte well. Fill the well to a level flush with the top of the sidewall. Put the membrane
assembly directly onto the cathode so that the face of the holder fits against the o-ring in the end of sensor
body. The membrane is now in place.
9. Carefully place the cap on the sensor body. Screw the cap on, finger-tight only. Then lay the sensor on its
side with the side port up. Remove the side port screw, rubber pressure-compensating diagram, and washer.
Add electrolyte, if necessary, to bring the level even with the shoulder. With the side port still facing up, tighten the cap further until it is snug and the membrane is stretched taut across the cathode. Any excess electrolyte displaced from the well may now be removed by blotting with a tissue.
10. Insert the new rubber diaphragm into the side port, place the new washer over the diaphragm, and secure
the side port screw. Do not overtighten the screw.
11. Inspect the sensor for possible leaks or damage to the membrane.
12. Remove the adhesive tape in step 2. The sensor is now ready for operation.
FIGURE 8. Rechargeable Sensor — Exploded View (6A00181G01)
6
ORDERING INFORMATION
The Model 4000 sensor is housed in a molded Ryton®1 body for insertion or in line flow installations. A Pt 100
allows for accurate temperature compensation. The Model 4000 amperometric sensor provides real time
measurement, excellent performance,a nd reliability in various detection and analysis applications.
MODEL 4000 PERCENT OXYGEN SENSOR
PART #
1
DESCRIPTION
6A00181G01
Percent Oxygen Sensor, Rechargeable, Ryton®
6A00182G01
Percent Oxygen Sensor with Gland, Rechargeable, Ryton®
6A00184G01
Percent Oxygen Sensor with Fast Response Flow Assembly, Rechargeable, Ryton®
1
1
1
Ryton is a registered trademark of Chevron Phillips Chemical Company LP.
ACCESSORIES
PART #
6A00195G01
DESCRIPTION
Cable, 10 ft
SPARE PARTS
PART #
6A00194G01
DESCRIPTION
Rebuild Kit
7
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Specifications subject to change without notice.
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Liquid Division
2400 Barranca Parkway
Irvine, CA 92606 USA
Tel: (949) 757-8500
Fax: (949) 474-7250
http://www.raihome.com
© Rosemount Analytical Inc. 2009
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