A sensor that measures the concentration of analyte by the current generated by an electrochemical reaction involving the analyte. The current in the measuring circuit thus depends on the concentration of the analyte.
", "", "", false); fb[1] = new Array(10, "Analyte", "The chemical compound that is detected by a sensor. The primary analyte is the chemical of interest that may be detected directly or through conversion to/by a secondary analyte in a conversion sensor.
", "", "", false); fb[2] = new Array(8, "Analyte, primary", "The chemical compound of interest that may be detected directly by a sensor or through quantitative conversion to a measurable secondary analyte in a conversion sensor.
", "", "", false); fb[3] = new Array(9, "Analyte, secondary", "A directly measurable chemical compound that is used in a conversion sensor to measure another compound, the primary analyte. The secondary analyte is either produced by or consumed by the conversion reaction of the primary analyte.
", "", "", false); fb[4] = new Array(11, "Cable, guard", "A guard electrode is frequently mounted behind the sensing electrode to electrochemically prevent interfering compounds within the electrode from affecting the sensor signal. The guard electrode is usually polarized using a separate guard cable that is connected to the meter using a standard mini-jack (yellow cable).
", "", "", false); fb[5] = new Array(12, "Cable, signal", "The electrical cable between the electrochemical sensor and the Ampere meter/Voltmeter. The sensor signal is usually transferred within a shielded coaxial cable as the currents and potentials generated by microsensors are easily disturbed by exterior electromagnetic fields. The coaxial cable is connected to the Ampere meter/Voltmeter through a standard BNC connector", "", "", false); fb[6] = new Array(13, "Clark-type oxygen sensor", "A amperometric oxygen sensor with a sensing cathode and an internal Ag/AgCl reference anode submerged in an aqueous electrolyte chamber. Oxygen diffusing through a silicone membrane at the electrode tip is reduced at the cathode, which is polarized at -0.8V. The current produced is proportional to the oxygen partial pressure of the medium in which the sensor is immersed. The Clark-type microsensors sold by Unisense all contain a guard cathode within the electrolyte chamber to ensure a low zero-current", "", "", false); fb[7] = new Array(14, "Connector, general", "A standard BNC connector used to connect the signal cable to the measuring ampere meter or voltmeter", "", "", false); fb[8] = new Array(15, "Connector, mini", "A standard connector, used to connect electrodes to Landers for in situ measurements and remote control. Electrodes to be mounted in Landers must be purchased with mini connectors instead of the standard signal cables. Mini connectors cannot be attached to electrodes with signal cables", "", "", false); fb[9] = new Array(16, "Conversion sensor", "A sensor that indirectly senses the chemical of interest (the primary analyte) by converting it to or with a detectable chemical (the secondary analyte)", "", "", false); fb[10] = new Array(17, "Detection limit", "The concentration of primary analyte at which the sensor signal is twice the ambient noise level. As the ambient noise level may be different for different experimental setups and measuring matrices, the detection limit may vary. The detection limits indicated in the datasheets were obtained in distilled water under ordinary laboratory conditions", "", "", false); fb[11] = new Array(19, "Electrochemical", "The chemical reactions occurring at the cathode and at the anode surface that produce a current in the measuring circuit. The specific electrochemical reactions taking place in different electrodes are included as part of the detailed electrode descriptions", "", "", false); fb[12] = new Array(159, "Gel peeper", "A gel peeper is a plastic rod with a gel-filled groove. The rod is drilled in to the sediment and left there to equilibrate with the sediment. When the peeper is withdrawn protected by a special lid, the peeper is brought to the surface by the lander. Here, the gel can be cut into slices and analyzed for components such as iron and mangane, among others.
", "", "", false); fb[13] = new Array(160, "Gel peepers", "A gel peeper is a plastic rod with a gel-filled groove. The rod is drilled in to the sediment and left there to equilibrate with the sediment. When the peeper is withdrawn protected by a special lid, the peeper is brought to the surface by the lander. Here, the gel can be cut into slices and analyzed for components such as iron and mangane, among others.
", "", "", false); fb[14] = new Array(20, "General connector", "A standard BNC connector used to connect the signal cable to the measuring amperemeter or voltmeter", "", "", false); fb[15] = new Array(21, "Glass sensors", "Sensors where the sensing cathode and anode are mounted inside a tapered glass tube. All Unisense standard microsensors are glass sensors. However, glass sensors mounted inside hypodermic needles are available upon request", "", "", false); fb[16] = new Array(23, "Guard cable", "A guard electrode is frequently mounted behind the sensing electrode to electrochemically prevent interfering compounds within the electrode shaft from affecting the sensor signal. The guard electrode is usually polarized using a separate guard cable (yellow cable) that is connected to the meter using a standard banana plug.", "", "", false); fb[17] = new Array(24, "Guard cathode", "A guard cathode is mounted behind the sensing cathode in some sensors to electrochemically prevent oxygen within the electrode shaft from affecting the sensor signal. The guard cathode is usually polarized using a the separate guard cable that is connected to the meter using a standard mini-jack", "", "", false); fb[18] = new Array(25, "Guard connector", "The standard mini-jack connector which is used to connect the guard electrode to the meter. ", "", "", false); fb[19] = new Array(26, "Interfering compounds", "Compounds that interfere with the sensor signal. Some compounds may produce a false signal (e.g. sulfide interference for oxygen microelectrodes) whereas others may reduce the sensitivity of a given sensor. The effect may be temporary or permanent. The particular interfering compounds of relevance to a given sensor are described in the detailed sensor descriptions", "", "", false); fb[20] = new Array(27, "Internal guard: = guard cathode", "An internal guard electrode is frequently mounted behind the sensing electrode to electrochemically prevent interfering compounds within the electrode shaft from affecting the sensor signal. The guard electrode is usually polarized using a separate guard cable that is connected to the meter using a standard mini-jack", "", "", false); fb[21] = new Array(28, "Lifetime", "The lifetime of an electrode is the expected operational lifetime for a given type of electrode. The stated lifetimes apply to continuous measurement under normal laboratory conditions in distilled water. The lifetime may be reduced due to mechanical damage, exposure to adverse conditions, reactive chemicals, extreme temperatures etc. The shelf life of some sensor types usually vastly exceed the operational lifetime if the sensor is stored according to our specifications", "", "", false); fb[22] = new Array(29, "Measuring circuit", "The electrical circuit, which is usually composed of the microsensor, a reference electrode, ampere meter or voltmeter and the medium under investigation", "", "", false); fb[23] = new Array(30, "Mini-connector for in situ", "A standard connector, used to connect electrodes to Landers for in situ measurements and remote control. Electrodes to be mounted in Landers must be purchased with mini connectors instead of the standard signal cables. Mini connectors cannot be attached to electrodes with signal cables", "", "", false); fb[24] = new Array(31, "Needle diameter", "Outside diameter (mm) of the hypodermic needle, that surrounds a needle microsensor. - see sensor drawing", "", "", false); fb[25] = new Array(32, "Needle length", "Length (mm) of the hypodermic needle, that surrounds a needle microsensor - see sensor drawing", "", "", false); fb[26] = new Array(33, "Needle sensors", "Microsensors mounted inside a hypodermic needle to protect the electrode against mechanical damage and to facilitate insertion in living tissue. The standard sensors are all delivered as glass sensors but may be ordered as needle sensors when required", "", "", false); fb[27] = new Array(34, "Oxygen sensor", "Clark-type amperometric oxygen sensor with built-in guard cathode and reference anode. Must be connected to a picoammeter that can provide a stable polarization potential of -0.8 V to both the sensing cathode and the guard cathode", "", "", false); fb[28] = new Array(35, "Position of sensing tip", "Usually the sensing tip of the cathode is positioned as close to the sensor tip as possible to reduce the response time of the sensor. However, in some cases the sensing tip is withdrawn into a casing to provide additional mechanical protection in rugged environments. In other cases where a rapid response is desired, the sensing tip may be positioned exposed on the sensor surface", "", "", false); fb[29] = new Array(36, "Potentiometric sensor", "A sensor that measures the concentration of the analyte by the electrochemical potential generated by an electrochemical reaction involving the analyte. The electrochemical potential in the measuring circuit thus depends on the concentration of the analyte.", "", "", false); fb[30] = new Array(37, "Pressure sensitivity", "The sensitivity of a particular sensor to hydrostatic pressure will depend on pressure induced alterations in the physical and chemical properties of the components used to construct the sensor. The oxygen permeability of silicone membranes used in oxygen sensors may be reduced at elevated hydrostatic pressure", "", "", false); fb[31] = new Array(38, "Pressure tolerant sensing tip", "A special microsensor tip that is constructed to be able to withstand an elevated hydrostatic pressure. The signal may still be affected by the hydrostatic pressure and appropriate calibration of the sensor will be required", "", "", false); fb[32] = new Array(39, "Primary analyte", "The chemical compound of interest that may be detected directly by a sensor or through quantitative conversion to/by a measurable secondary analyte in a conversion sensor", "", "", false); fb[33] = new Array(41, "Response time", "When a microsensor is exposed to a different environment, the sensor signal changes exponentially to approach the new equilibrium value. The response time is defined as the time required for 90% of the change to occur. The response time does not depend on the magnitude of the change and thus indicates the minimal time required to make a measurement. The response time of some electrochemical microsensors is < 0.1s whereas for some biosensors it is several minutes", "", "", false); fb[34] = new Array(42, "Response type", "The standard microsensors available from Unisense have been designed with rapid response time and low stirring sensitivity. However, there is a tradeoff between response time and stirring sensitivity ( see Technical documentation: Stirring sensitivity and Response time), it is thus possible to produce faster electrodes (i.e. with quick response time) but a somewhat higher stilling sensitivity. Fast versions of most electrodes are available as build-to-order for a small surcharge. Sensors with a reduced stirring sensitivity are also available.
\nSee here for an explanation about the relationship between stirring sensitivity, response time, and signal-to-noise-ratio.
", "", "", false); fb[35] = new Array(43, "Salinity", "Even microsensors with tips that are not permeable to ions (like the oxygen electrode) may be sensitive to the salinity of the surrounding media. In case of the oxygen sensor, salinity will change the partial pressure in the surrounding media and for other sensors it may change important transport coefficients. Exact calibration of microsensors at the appropriate salinity should therefore always be attempted", "", "", false); fb[36] = new Array(44, "Secondary analyte", "A directly measurable chemical compound that is used in a conversion sensor to measure another compound, the primary analyte. The secondary analyte is either produced by or consumed by the conversion reaction of the primary analyte", "", "", false); fb[37] = new Array(45, "Sensor, amperometric", "A sensor that measures the concentration of the analyte by the current generated by an electrochemical reaction involving the analyte. The current in the measuring circuit thus depends on the concentration of the analyte", "", "", false); fb[38] = new Array(46, "Sensor, conversion", "A sensor that indirectly senses the chemical of interest (the primary analyte) by converting it to a detectable chemical (the secondary analyte).", "", "", false); fb[39] = new Array(47, "Sensor, potentiometric", "A sensor that measures the concentration of the analyte by the electrochemical potential generated by an electrochemical reaction involving the analyte. The electrochemical potential in the measuring circuit thus depends on the concentration of the analyte", "", "", false); fb[40] = new Array(48, "Shaft diameter", "The outside diameter of the electrode shaft. The maximum diameter of the electrode when the shaft protector is removed (e.g. effective diameter of microsensors when used in Landers for in situ measurements without shaft protection.). The shaft diameter is usually about 8 mm - see sensor drawing", "", "", false); fb[41] = new Array(49, "Shaft protection diameter", "The maximum outside diameter of the electrode shaft including the shaft protector. Usually about 10 mm - see sensor drawing.", "", "", false); fb[42] = new Array(50, "Shelf life", "The time a given type of microsensor can be stored safely without being connected to a measuring circuit. It is of paramount importance that the storage requirements indicated on the product specification sheets are met. In some cases the shelf life exceeds the expected operation lifetime as sensor performance may lessen during use", "", "", false); fb[43] = new Array(51, "Signal cable", "The electrical cable between the electrochemical sensor and the Ampere meter/Voltmeter. The sensor signal is usually transferred within a shielded coaxial cable as the currents and potentials generated by microsensors are easily disturbed by exterior electromagnetic fields. The coaxial cable is connected to the ampere meter/voltmeter using a standard BNC connector", "", "", false); fb[44] = new Array(52, "Spatial resolution of measurements", "The spatial resolution of a sensor is the size of the area of the environment that contributes to the sensor signal. For sensors that do not affect the environment by the measuring process, for instance pH and redox microelectrodes, the spatial resolution equals the dimensions of the sensitive area of the sensor. For these sensors, the horizontal spatial resolution is the tip diameter, and the vertical spatial resolution is the length of the pH-sensitive glass (see sensor drawing and pH sensor specifications).