OXYGEN SENSOR USER MANUAL
Contents
1. 10 to 10 ampere Although both the Unisense amplifiers and oxygen microsensors are very resistant to electrical noise from the environment electrical fields may interfere with the sensor signal Therefore we recommend that unnecessary electrical mechanical equipment is switched off Also be careful not to touch the sensor or wires unnecessarily during measurements INTERFERENCE Sulfide can affect the sensitivity of the oxygen microsensor and the calibration of the oxygen sensor can thus change when exposed to sulfide Exposure to high concentrations of sulfide should be avoided measuring in sulfide rich environments the oxygen sensors can be pre contaminated with sulfide to avoid large changes in calibration values for the sensor Contact Unisense for more information TEMPERATURE Closely monitor the temperature because the sensor signal is very dependent on temperature The temperature coefficient varies from sensor to sensor but is approximately 2 3 96 per C ADVANCED USE OF THE OXYGEN SENSORS Unisense can construct oxygen sensors for customer reguested applications providing several options for customizations e g tip size response time pressure tolerance and stirring sensitivity and adaptations e g mounting in needle or flow through cell making accurate measurements possible for even more applications EXAMPLES OF ADVANCED APPLICATIONS Gross photosynthesis measurements by the light dark s2. a high sensitivity picoampere amplifier e g OXY Meter Microsensor Multimeter or Microsensor Monometer The cathode is polarized against the internal reference Driven by the external partial pressure oxygen from the environment penetrates through the sensor tip membrane and is reduced at the gold cathode surface The picoammeter converts the resulting reduction current to a signal The internal guard cathode is also polarized and scavenges oxygen in the electrolyte thus minimizing zero current and pre polarization time The LEMO connector contains connections for both reference guard and sensing cathode di 1osuas WARNING Unisense sensors are neither intended nor approved for use on humans sepnpul elqeD Bnid O31 GETTING STARTED UNPACKING A NEW SENSOR When receiving a new microsensor remove the shock absorbing grey plastic net Please do not remove the seal and protective tube before the following steps are successfully completed POLARIZATION The signal from the oxygen sensor is generated in picoampere Therefore the oxygen sensor must be connected to a Unisense picoampere amplifier during measurements Oxygen sensors should be polarized with 0 80 V On the OXY Meter this polarization is pre set On the Microsensor Multimeter and Microsensor Monometer lemo oxygen sensors are automatically recognized and polarization should be pre set If you are using another amplifier or sensor connection t
3. used sensor may reguire calibration only every 24 hours or less To minimize the need for calibration it isrecommended to keep the sensor polarized between measurements The membrane permeability of oxygen microsensors changes with time so a change in signal of up to 50 may occur over months This does not affect the guality of the measurements as long as the sensor is regularly calibrated If the sensor functions according to the above procedure the seal and protective plastic tube can be carefully removed and measurements can be started 11 MEASUREMENTS MOUNTING THE SENSORS Although the Unisense microsensors are made of glass the tip is flexible and can bend slightly The sensor is thus surprisingly sturdy even in coarse sediments or tough tissues However larger obstacles or lateral movements of the sensor while the tip is in contact with a solid substrate may cause the tip to break Also due to the small size of the microsensor tip and to the steepness of gradients in many environments a displacement of the sensor tip of even a few microns may change its environment We therefore recommend that measurements are performed only in a stabilized set up free of moving or vibrating devices We recommend the Unisense lab stand LS18 and micromanipulator MM 33 MM33 2 for laboratory use For in situ use we recommend our in situ stand 1519 and a micromanipulator ELECTRICAL NOISE The signal of the microsensor is very small
4. 3 7 223 3 205 7 190 3 12 0 420 3 368 4 326 7 292 6 264 5 240 9 220 9 203 6 188 4 14 0 414 5 363 5 322 5 289 1 261 4 238 2 218 5 201 4 186 5 16 0 408 8 358 7 318 4 285 5 258 3 235 5 216 1 199 3 184 6 18 0 403 2 354 0 314 4 282 1 255 3 232 8 213 7 197 2 182 7 20 0 397 7 349 3 310 4 278 6 252 3 230 2 2114 195 1 180 8 22 0 392 2 344 7 306 5 275 2 249 3 227 6 209 1 193 0 179 0 24 0 386 8 340 2 302 6 271 9 246 4 225 0 206 8 191 0 177 1 26 0 381 5 3357 298 7 268 5 243 5 222 5 204 5 189 0 175 28 0 376 2 331 2 294 9 265 3 240 6 219 9 202 3 187 0 1735 30 0 371 0 326 9 291 2 262 0 237 8 217 4 200 1 185 0 WAL 32 0 365 9 322 5 287 5 258 8 235 0 215 0 197 9 183 0 170 0 34 0 3609 3183 2839 2557 2322 2125 1957 1811 1682 36 0 8559 314 1 280 3 252 5 229 5 210 1 193 6 179 2 166 5 38 0 351 0 309 9 276 7 249 5 226 8 207 7 191 4 177 3 164 8 40 0 346 2 305 8 2782 246 4 224 1 205 4 189 3 175 4 163 1 42 0 3414 301 8 269 4 243 4 22175 203 1 187 3 173 6 161 5 Sources Garcia H E and Gordon L I 1992 Limnol Oceanogr 37 1307 1312 Millero F J and Poisson 1981 Deep Sea Res 28 625 629 19 dy UNISENSE UNISENSE DENMARK www unisense com infogunisense com
5. Vh UNISENSE OXYGEN SENSOR USER MANUAL OXYGEN SENSOR USER MANUAL Copyright O 2014 Unisense A S Version January 2014 OXYGEN SENSOR USER MANUAL UNISENSE A S TABLE OF CONTENTS SUPPORT ORDERING AND CONTACT INFORMATION OVERVIEW ee Re a a UR EORR REDE acts GETTINGSTARTED ii ient DURER RU ERA DR mets UNPACKING A NEW SENSOR POLARIZATION CONNECTING THE MICROSENSOR CALIBRATION MEASUREMENT en handen MOUNTING THE SENSORS INTERFERENCE ADVANCED USE OF THE OXYGEN SENSORS STORAGE AND STORAGE CLEANING THE SENSOR REFERENCES EI TROUBLESHOOTING regnet i pto laman alas a APPENDIX EQUILIBRIUM O CONCENTRATIONS WARRANTY AND LIABILITY NOTICE To PURCHASER This product is for research use only Not for use in human diagnostic or therapeutic procedures WARNING Microsensors have very pointed tips and must be handled with care to avoid personal injury and only by trained personnel Unisense A S recommends users to attend instruction courses to ensure proper use of the products VVARRANTY AND LIABILITY The oxygen sensor is covered by a 180 days limited warranty Microsensors are a consumable Unisense will only replace dysfunctional sensors if they have been tested according with the instructions in the manual within 14 days of receipt of the sensor s The warranty does not include repair or replacement necessitated
6. by accident neglect misuse unauthorized repair or modification of the product In no event will Unisense A S be liable for any direct indirect conseguential or incidental damages including lost profits or for any claim by any third party arising out of the use the results of use or the inability to use this product Unisense mechanical and electronic laboratory instruments must only be used under normal laboratory conditions and a dry and clean environment Unisense assumes no liability for damages on laboratory instruments due to unintended field use or exposure to dust humidity or corrosive environments REPAIR OR ADJUSTMENT Sensors and electrodes cannot be repaired Eguipment that is not covered by the warranty will if possible be repaired by Unisense A S with appropriate charges paid by the customer In case of return of eguipment please contact us for return authorization For further information please see the document General Terms of Sale and Delivery of Unisense A S as well as the manuals for the respective products CONGRATULATIONS WITH YOUR NEW PRODUCT SUPPORT ORDERING AND CONTACT INFORMATION The Unisense oxygen microsensor is a miniaturized Clark type oxygen sensor that facilitates reliable and fast measurements with a high spatial resolution designed for research applications If you wish to order additional products or if you encounter any problems and need scientific technical assistance please do not h
7. esitate to contact our sales and support team We will respond to your inguiry within one working day E mail salesaunisense com Unisense A S Tueager 1 DK 8200 Aarhus N Denmark Tel 45 8944 9500 Fax 45 8944 9549 Further documentation and support is available at our website www unisense com REPLACEMENT OF SENSORS Unisense will replace sensors that have been damaged during shipment provided that The sensors were tested immediately upon receipt in accordance with the delivery note and the manual The seal is still intact The sensors are returned to Unisense for inspection within two weeks The sensors are correctly packed for return to Unisense in accordance with the note included in the sensor box RECOMMENDED AMPLIFIERS One channel amplifier OXY Meter or Microsensor Monometer Multi channel amplifiers for oxygen Microsensor Multimeter or Microsensor Multimeter 4 channel Oxymeter OVERVIEW This manual covers all the Unisense oxygen sensors The Unisense oxygen microsensor is a miniaturized Clark type oxygen sensor with a guard cathode designed for research applications within physiology biotechnology environmental sciences and related areas With the minute tip size excellent response time and insignificant stirring sensitivity the Unisense oxygen sensor facilitates reliable and fast measurements with a high spatial resolution MEASURING PRINCIPLE The sensor should be connected to
8. gensen 1986 Microelectrodes Their Use in Microbial Ecology p 293 352 In K C Marshall ed Advances in Microbial Ecology vol 9 Plenum New York Please see our website for more references TROUBLE SHOOTING Problem Possible cause 1 Solution Possible cause 2 Solution Problem Possible cause Solution Problem Possible cause Solution Problem High and drifting signal Gas bubbles present inside the sensor tip due to short circuit or electrical shock Degas water by boiling and subseguent cooling or by 10 minutes of vacuum treatment Immerse the sensor tip for 20 min in the degassed water Repeated or prolonged treatment may be necessary The sensor tip is broken Replace the oxygen microsensor Signal very low Contamination of the cathode surface e g by sulfide or loss of gold tip due to excessive vibrations Replace the oxygen microsensor Signal constantly very low and no response to oxygen Gas bubbles present inside the tip of the sensor causes a disruption in the electrolyte Degas water by boiling and subseguent cooling or by 10 minutes of vacuum treatment Immerse the sensor tip for 20 min in the degassed water Repeated or prolonged treatment may be necessary Slow response TROUBLE SHOOTING Possible cause Solution Problem Possible cause Solution Problem Possible cause Solution Insoluble compounds deposited at the sensor tip Rinse with 96 e
9. hift method Respiration production rates in small samples in Unisense micro respiration chambers Measurements of oxygen under high external pressure e g in closed pressurized systems underwater and deep sea applications Long term oxygen monitoring Oxygen in flow through cells Please visit our website for more information 13 STORAGE AND MAINTENANCE STORAGE Store the sensor in the protective plastic tube used for shipping The oxygen microsensor can be stored with the tip exposed to water or air The room in which the oxygen microsensor is stored should be dry and not too hot 10 30 If the sensor is used regularly it can be stored polarized connected to a Unisense amplifier CLEANING THE SENSOR Depending on which substance is present on the sensor tip or membrane the sensor can be cleaned with different solutes The standard method is to rinse with 9696 ethanol then rinse with 0 01 M HCl and rinse with water This will remove most substances Alternatively it is possible to rinse with 0 1M NaOH isopropanol or different detergent REFERENCES Revsbech N P 1989 An oxygen microsensor with a guard cathode Limnology and Oceanography 34 2 474 478 Gundersen J K Ramsing N B and Glud R N 1998 Predicting the signal of O microsensors from physical dimensions temperature salinity and O concentration Limnology and Oceanography 43 8 1932 1937 Revsbech N P and B B Jor
10. libration must be performed after pre polarization when the sensor signalhas stabilized Always use a calibration solution with the same temperature and salinity as the sample solution IMPORTANT The O sensor signal is sensitive to temperature and the O solubility depends on both salinity and temperature Calibration chamber CAL300 insert it in to your sample Vigorous bubbling with oxygen free inert gas e g N It is important to ensure vigorous bubbling over a time period sufficient to flush all oxygen out Furthermore it is important to prevent any contact of oxygen with the water during bubbling as oxygen will otherwise be continuously reintroduced to the water In practice this means that the headspace above the water must be closed except for a hole slightly larger than the microsensor shaft This effectively prevents ambient air from entering the vessel Please see warning below right We recommend the Unisense calibration chamber CAL300 in which 5 minutes of bubbling at a rate of 0 5 L gas per minute is sufficient to drive 9996 of the oxygen out A zero reading can be obtained with many other methods A solution of yeast will use all oxygen within hour or a small container with active sediment sludge will also become anaerobic When measuring in sediment you can also use the oxygen free sediment to obtain CALIBRATION As oxygen microsensors respond linearly to changes in oxygen conce
11. lowly for up to two hours for needle and some custom made sensors slightly longer The sensor signal depends on the specific sensor see the delivery note which came with the sensor If the signal does not stabilize or is too high or too low refer to the Troubleshooting section CALIBRATION Please consult the software manual for instruction on how to calibrate in the software ATMOSPHERIC READING Place keep the sensor tip in a well aerated calibration solution e g by bubbling with air in the Unisense calibration chamber After complete aeration of the water 5 minutes of vigorous bubbling turn off any bubbling After the water movement has stopped note the signal reading on the display and or your data acguisition device or add the point to the calibration in the software This signal is your calibration value for atmospheric partial pressure Sat conditions ZERO READING An anoxic solution can be prepared in ONE OF several ways 1 Preparea solution of sodium ascorbate and NaOH both to final concentrations of 0 1M 2 g sodium ascorbate in 100 ml of 0 1M NaOH Stir briefly and allow the water to stagnate This zero calibration solution can be stored in a closed container for 1 2 weeks Place the sensor in its protective tube in the solution and wait for the signal to stabilize Rinse the sensor by flushing it in tap water Make sure that all the anoxic solution is rinsed off the sensor before you IMPORTANT Ca
12. ntrations a two point calibration is sufficient 2 examples of calibration curves WARNING Bubbling of water with gas may cause the water to change temperature due to the gas temperature or evaporative cooling Monitor the temperature to find a suitable bubbling rate which does not change the water temperature significantly your zero reading Place the sensor in the anoxic solution The signal reading is the calibration value for zero oxygen partial pressure 50 The value should be less than 10 of the signal for atmospheric saturation otherwise see Troubleshooting Read the value on the display or add it to the software calibration Oxygen sensors respond linearly in the range of 0 to 10096 oxygen and signals can be linearly converted to partial pressure To convert a signal S from partial pressure to the equivalent concentrations of oxygen C perform a linear conversion and multiply with the atmospheric level solubility a of oxygen in the relevant liquid at the relevant temperature see Table 1 in this manual S 50 Sat 50 If you use any of our programs in the SensorTrace series this is done by the software Consult your software manual for details Check and repeat calibration freguently to ensure that all measurements are calibrated to correct concentrations When the sensor is new you may need to calibrate more often while an older and extensively
13. thanol rinse with 0 01 M HCI and rinse with water Slow response OX N sensors A gas bubble trapped in the needle tip Remove the air bubble gently by repositioning the sensor Unstable signal or the signal fluctuates if the setup is touched or eguipment is introduced in the medium you are measuring in Electrical disturbance of the sensor through the tip membrane Ground the set up using the blue grounding cable supplied with the picoammeter Connect the reference plug on the picoammeter blue plug with the medium you are measuring in If you encounter other problems and need scientific technical assistance please contact sales unisense com for online support we will answer you within one workday 17 APPENDIX EOUILIBRIUM O CONCENTRATIONS Detailed tables are available at our web page http www unisense com technical information At 20 C and 1 atm 1 umol O I 0 032 mg O I 0 024 ml O Table 1 Equilibrium concentrations of oxygen umol O litre at ambient partial pressure of 0 21 atm in water as a function of temperature and salinity o 0 0 5 0 10 0 15 0 20 0 25 0 30 0 35 0 40 0 0 0 456 6 398 9 352 6 314 9 283 9 257 9 235 9 217 0 200 4 2 0 450 4 393 6 348 1 311 1 280 6 255 0 233 3 214 7 198 3 4 0 444 2 388 5 343 7 307 3 277 3 252 1 230 8 2124 196 3 6 0 438 1 383 3 339 4 303 6 274 0 249 3 228 3 210 2 194 3 8 0 432 1 378 3 3855 299 9 270 8 246 5 225 8 207 9 192 3 10 0 426 1 373 3 330 8 296 2 267 6 24
14. ype please check the polarization voltage before connecting a sensor since incorrect polarization may destroy the oxygen sensor For details on how to set the polarization consult the user manual of the amplifier that you are using CONNECTING THE MICROSENSOR Connect the LEMO connector to the input terminal The LEMO connector contains connections for both reference guard and sensing cathode For fast responding sensors it is strongly recommended to ground the system as the ultra thin silicone membrane could be damaged by static electricity PRE POLARIZATION When the sensor is not in use oxygen will build up inside the electrolyte This oxygen must be removed by the sensing cathode and the guard cathode before stable operation of the sensor is possible Therefore a period of polarization is necessary before you can use the sensor This is called the pre polarization period If the sensor is new or has not been operated for several days WARNING Do not remove the seal and protective plastic tube before these steps and calibration are successfully completed it must be pre polarized for at least 2 hours before it can be calibrated and used After shorter periods without polarization the sensor should be pre polarized until it has shown a stable signal for at least ten minutes When pre polarization is initiated the signal will be very high and then drop rapidly over the first few minutes After that the signal will drop s
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