FLOW SENSOR USER MANUAL
Contents
1. If your flow microsensor is of the flow through type connect a tracer source to one of the steel capillaries The tracer source is a tank of suitable tracer gas with an outlet valve which leads the tracer through a soft tube By inserting a T piece with a side tube opening at the bottom of a beaker of water a suitable pressure can be obtained Adjust the outlet flow from the tracer tank to a level just under the point when bubbles appear from the side tube It is generally best to minimize the length of the tubes used in the set up If the sensor is of the closed reservoir type with a refill system start by refilling the reservoir if necessary The refill system consists of two glass tube inlets with a silicone septum and sealed with wax which closes the two steel capillaries of the tracer reservoir To refill the reservoir proceed as follows Insert a 0 5 mm syringe needle through both wax plugs proceeding slightly into the silicone membrane After piercing the wax plugs a fresh 0 5 mm syringe needle is carefully inserted through the hole of each wax plug and pushed through the silicone membrane A dry 20 ml syringe is filled with the desired tracer e g 10096 hydrogen from a tracer source The tracer must be dry The syringe is attached to the needle in one of the inlets Atmospheric contamination of the tracer in the syringe during transfer can be avoided by keeping the nozzle blocked when possible or by releasing a small tracer f2. days from shipment Standard Oxygen sensors 180 days from shipment All other sensors excluding special sensors 90 days from shipment If within the above specified period the sensor s fail to perform according to the specifications Unisense will replace the sensor s free of charge Unisense will only replace dysfunctional sensors if they have been tested according with the instructions in the manual upon receipt of the sensor s The warranty does not include repair or replacement necessitated by accident neglect misuse unauthorized repair or modification of the product Physical damage to the tip of the sensor is not covered by the warranty Liability In no event will Unisense be liable for any direct indirect consequential 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 REPAIR OR ADJUSTMENT Sensors and electrodes cannot be repaired Other equipment that is not covered by the warranty will if possible be repaired by Unisense with appropriate charges paid by the customer In case of return of equipment please contact us for a return authorization For further information please see the documents Conditions for Sale and Delivery for Unisense and Warranty and Shipping Information 13 TROUBLE SHOOTING Problem Possible cause Solution Problem Possible cause Solution Problem Possib
3. flow microsensor is placed in a calibration set up Such a set up consists of a device that allows the sensor tip to be immersed in a liquid medium which can be moved at controlled linear velocities Alternatively the sensor tip is moved at controlled velocities through a stationary medium The set up is activated through a range of known velocities and when it has stabilized the signal is logged at each velocity The readings are used to produce a calibration curve through which a measured signal can be converted into a velocity IMPORTANT small dust particles may adhere to the flow microsensor tip and strongly influence the signal If this happens IMPORTANT It is necessary to perform calibration and subsequent measurements in solutions with the same temperature and salinity IMPORTANT Flow microsensors are not completely symmetrical which means that there is some directional sensitivity Always calibrate with the sensor oriented in the same way relative to the direction of flow as in the system to be studied remove the particles by carefully brushing the tip with a very fine paintbrush the finest type that can be bought for art painting The brush is preferably mounted under water with its hairs pointing up the sensor tip is cleaned by moving it back and forth with the micromanipulator controls through the tips of the brush hairs If you touch the tip with coarser parts of the brush the sensor may break Che
4. tip transporting tracer molecules away from the sensor tip the lower the resulting hydrogen concentration at the tip The hydrogen tracer concentration level is detected by the micro transducer and the signal size from the micro transducer can thus be correlated with the velocity of the medium The flow microsensor must be connected to a picoammeter e g the Unisense Microsensor Multimeter or Microsensor Monometer p1en6 sapn u1 o21gen 110419591 19381 THIS MANUAL COVERS THE UNISENSE SENSORS FS20 outer tip diameter 20 30um FS spec Flow sensors with customer specified specifications dn sosuas Gnid OW31 PRECAUTIONS PARTICLES AT THE SENSOR TIP The signal is very sensitive to particles adhering to the tip Even small dust grains attached to the tip will create a significant signal increase due to the associated stagnant water For this reason it is recommended that a fine brush is implemented into the measuring setup so the sensor tip can be cleaned at regular intervals DIRECTION OF FLOW The flow sensors are always somewhat directionally sensitive This is because it is impossible to build the sensor completely symmetrically Thus you either need to know the direction of flow in your system and calibrate in the same direction or you operate with substantial uncertainties especially at high velocities CALIBRATION OF FLOW SENSOR You need a dedicated calibration setup preferable consisting of a system
5. we will answer you within one workday 17 A UNISENSE UNISENSE DENMARK www unisense com info unisense com
6. FLOW SENSOR USER MANUAL A UNISENSE i FLOW SENSOR MANUAL UNISENSE A S FLOW SENSOR MANUAL Copyright 2012 Unisense A S Version April 2012 TABLE OF CONTENTS SUPPORT ORDERING AND CONTACT INFORMATION OVERVIEW nasse PRECAUTIONS menant sea Rae ERA PUR OUR RII RAE GETTING STARTED hassan UNPACKING A NEW SENSOR POLARIZATION CONNECTING THE MICROSENSOR PRE POLARIZATION SUPPLY TRACER CALIBRATION GENERAL USE OF THE FLOW SENSOR MOUNTING OF THE SENSORS ELECTRICAL NOISE INTERFERENCE ADVANCED USE OF THE FLOW SENSORS STORAGE AND MAINTENANCE 4 42 REFERENCES aus remain a TR a tace teens WARRANTY AND LIABILITY 00 000 eem emn REPAIR OR ADJUSTMENT TROUBLESHOOTING au ER a des JO UT UI UI u UI o ovo wo CONGRATULATIONS WITH YOUR NEW PRODUCTI SUPPORT ORDERING AND CONTACT INFORMATION If you wish to order additional products or if you encounter any problems and need scientific technical assistance please do not hesitate to contact our sales and support team We will respond to your inquiry within one working day E mail sales unisense com Unisense A S Tueager 1 DK 8200 Aarhus N Denmark Tel 45 8944 9500 Fax 4 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 provid
7. bed at our web page under flow sensors specifications The options include e g customer specified dimensions response time stirring sensitivity pressure tolerance flow range and detection limit If your specifications for a special flow sensor are not described at our web page please contact sales unisense com for further options and prices EXAMPLES OF ADVANCED APPLICATIONS Measurements of blood flow Monitoring bioturbation by measurements of flow in worm tubes contact sales unisense com for further details STORAGE AND MAINTENANCE Store the sensor in the protective plastic tube used for shipping The hydrogen microsensor can be stored with the tip exposed to water or air The room in which the hydrogen microsensor is stored should be dry and not too hot 10 30 C If the sensor is used regularly it can be stored polarized and connected to the amplifier 11 R EFERENCES Revsbech N P and B B Jorgens 1986 Micorelectrodes Their Use in Microbial Ecology p 293 352 In K C Marshall ed Advances in Microbial Ecology vol 9 Plenum New York K hl M Revsbech NP 2001 Biogeochemical microsensors for boundary layer studies In Boudreau BP Jorgensen BB editors The Benethic boundary layer New York Oxford University press p180 210 WARRANTY AND LIABILITY Microsensors are consumable items The sensors are tested thoroughly before packaging and shipment Warranty for sensors N O sensors 60
8. ck and repeat calibration at appropriate intervals to ensure that all measurements can be calibrated to correct velocities To minimize the need for calibrations keep the sensor polarized between measurements unless the time between measurements exceeds several days The gas permeability of flow microsensor membranes changes with time so a change in signal of up to 5096 may occur over months If the sensor functions according to the above procedure the seal and protective plastic tube can be carefully removed before making measurements GENERAL USE OF THE FLOW SENSOR Flow sensors can be used for a wide variety of measurements see www unisense com for further information but they are most commonly used for monitoring flow in boundary layers between water and the sea floor leaves stones etc Often they are used in systems where a high spatial resolution is required or for flow measurements in water samples MOUNTING OF THE SENSORS During measurements the sensor should be properly mounted in a stable set up Due to the small size of the microsensor tip and the steepness of flow gradients in many environments even a few microns displacement of the sensor tip may change its immediate flow environment Furthermore lateral movements of the sensor while it is in contact with solid substrate may harm the sensor Therefore measurements should be performed only in a stabilized set up fixed on a sturdy table free of moving or vibrating de
9. ed 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 Microsensor Monometer Multi channel amplifier Microsensor Multimeter OVERVIEW The Unisense flow microsensor is based on a unique principle WARNING which allows fluid velocity measurements to be performed at Unisense sensors the very tip of a sensor with a tip diameter of 10 50 microns are neither The sensor is applicable within several areas of research e g intended nor physiology hydrology biotechnology and environmental sciences approved for use on humans With its minute tip size the Unisense flow microsensor makes it possible to make reliable and fast fluid velocity measurements with a high spatial resolution The Unisense flow microsensor is a based on a miniaturized amperometric hydrogen micro transducer surrounded by a tracer gas reservoir which is closed by a tip membrane The hydrogen tracer gas will diffuse out of the tracer reservoir and result in a build up of hydrogen around the sensor tip If the medium is stagnant the hydrogen tracer will build up to a relatively high steady state concentration The faster the medium moves relative to the sensor
10. le cause Solution Problem Possible cause Solution Problem Possible cause The calibration response has changed A disturbing object is adhered to the sensor tip Carefully brush the sensor tip with a very fine brush preferably under water see section on Calibration If the deposits consist of grease rinse with ethanol before brushing A high and drifting signa Gas bubbles are present inside the micro transducer tip due to short circuit or electrical shock Produce degassed water by boiling and subsequent 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 flow microsensor tip is broken Replace the flow microsensor The signal is very low Contamination of the cathode surface e g by sulfide or loss of anode material due to excessive vibrations Replace the flow microsensor Signal is unstable or fluctuates when the set up is touched or equipment is introduced in the measurement medium Electrical disturbance of the sensor through the membrane Solution Ground the set up by connecting the provided blue grounding cable supplied with the measurement medium If you are measuring in e g a sediment just put the open wire end in the water column Problem Possible cause Solution If you encounter other problems and need scientific technical assistance please contact sales unisense com for online support
11. low through the nozzle when it is not blocked When the syringe is attached to the needle the tracer is slowly injected Make sure that the reservoir is actually flushed This is achieved when a tracer stream flows from the needle in the other inlet This can be detected by feeling the gas stream against the eye or by observing bubbles when a soap covered finger is held lightly against the top of the needle Be careful not to introduce moisture into the reservoir When the reservoir has been flushed with at least 10 ml of the tracer remove the syringe and the attached needle Wait 3 seconds then remove the needle in the other inlet The silicone membrane will now keep the tracer inside the reservoir but to make the final gas tight seal the wax plugs must be re melted This is done by heating a metal object e g the tips of a pair of tweezers and holding it against the outside of the glass inlet just long enough for the wax to become clear and liquid When the wax hardens the refill is completed When the tracer is present in the reservoir the signal should decrease when the water in which the sensor tip is immersed is moved by gently moving the beaker up and down If the sensor responds consistently in this fashion it is functioning correctly CALIBRATION Calibration must be performed after the signal has stabilized during pre polarization Please consult the software manual for instruction on how to calibrate in the software The
12. tails on how to set and check the polarization consult the user manual of the picoammeter to be used If you are using a PA2000 amplifier please check the polarization voltage before connecting the sensor since incorrect polarization may destroy the sensor CONNECTING THE MICROSENSOR Connect the LEMO connector to the input terminal The LEMO connector contains connections for both reference guard and sensing cathode PRE POLARIZATION When the sensor is not in use H will build up inside the electrolyte of the hydrogen transducer This must be removed in order to obtain a stable zero current as background for calibrations and measurements Therefore a period of polarization is necessary before you can use the sensor This is called the pre polarization period Just after connecting the sensor the signal will be very high and then drop rapidly over the first few minutes After that the signal will drop slowly for up to 1 hour If the sensor is new or has not been operated for several days it must be polarized for at least 1 hour before it can be calibrated and used After shorter periods without polarization the sensor should be polarized until it has exhibited a stable signal for 10 minutes The signal depends on the specific sensor see the value in the specifications that came with the sensor If the signal does not stabilize or is too high or too low refer to the Trouble shooting section of this manual SUPPLY TRACER
13. vices We recommend the Unisense Laboratory Stand LS18 and the Unisense micromanipulators for this purpose ELECTRICAL NOISE The signal of the microsensor is very small 103 to 10 amp Although both the amplifiers and the 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 and the sensor or wires are not touched during measurements and signal recording INTERFERENCE The presence of sulphide gas can seriously affect measurements The sensitivity to sulfide gas can be as much as 10 of the hydrogen sensitivity In addition exposure to high sulfide gas concentration can affect the calibration of the hydrogen sensor Therefore measurements done in environments with high sulfide concentrations are not recommended IMPORTANT When the sensor tip is in contact with a solid substrate do not make lateral movements of the microsensor and avoid disturbing the microsensor equipment or table IMPORTANT Closely monitor the temperature as 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 FLOW SENSORS Unisense can construct flow sensors for customer requested applications at additional costs The most frequently requested construction options are descri
14. with stagnant water which can be moved at well defined speeds Contact Unisense about details and support on this issue HYDROGEN SUPPLY A source of hydrogen gas must be available for a continuous flushing of the tracer reservoir gas consumption approx 5 ml minute Alternatively the sensors can be made with a refillable but closed reservoir for measurements where a source of hydrogen gas is not available However the signal will decrease at arate of typically 1096 day due to inevitable leakage necessitating re calibration at regular intervals TEMPERATURE Like al other sensors the flow sensor is temperature sensitive GETTING STARTED The signal from the flow sensor is generated in pA Therefore the WARNING sensor must be connected to a picoampere amplifier like the Do not remove Unisense Microsensor Multimeter seal and protective plastic tube before UNPACKING A NEW SENSOR the following steps are successfully 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 completed POLARIZATION The signal from the flow sensor is generated in picoampere Therefore the sensor must be connected to a polarizing picoammeter e g a Microsensor Monometer a Microsensor Multimeter or the Unisense PA2000 Flow sensors should be polarized at 1000 mV The polarization voltage is set in the amplifier For de
Download Pdf Manuals
Related Search