the user manual for full specifications
Contents
1. 0 to 20 000 uS Note If you are not sure which setting to use start with the high setting to get a sense of what region you may want to narrow into Once this value is determined then select the appropriate setting for your measurements 2 Initiate the calibration procedure in the software 3 Low Conductivity Standard Solution Calibration Point Place the Conductivity Probe into a standard solution with a low conductivity value such as an accurately prepared dilution of the sodium chloride standard that is supplied with your probe Be sure the entire elongated hole with the electrode surfaces is submerged in the solution and that there are no bubbles along the electrode surface Wait for the displayed voltage to stabilize Enter the value of the standard solution in the appropriately chosen units Note Performing a zero point calibration is not recommended with conductivity sensors It is preferred that you use a low standard calibration standard instead of a zero point This is particularly important if you plan to use the low range of the sensor where the low calibration point is most critical 4 High Conductivity Standard Solution Calibration Point Place the Conductivity Probe into a standard solution with a high conductivity value such as the sodium chloride standard that is supplied with your probe Be sure the entire elongated hole with the electrode surfaces is submerged in the solution and that there are no bubbles along the elec2. add 4 60 g of NaCl to enough distilled water to prepare liter of solution e A high standard 10 ppt salinity add 9 20 g of NaCl to enough distilled water to prepare liter of solution More about Conductivity Conductivity is an easy and informative water quality test It is sometimes used as a watchdog environmental test any change in the ionic composition of a stream or lake can quickly be detected using a conductivity probe Conductivity values will change when ions are introduced to water from salts e g Na Cl acids H bases OH hard water Ca2 HCO37 CO32 or soluble gases that ionize in solution CO2 NO or SO2 However a conductivity probe will not tell you the specific ion responsible for the increase or decrease in conductivity It simply gives a general indication of the level of total dissolved solids TDS in the stream or lake Subsequent tests can then help to determine the specific ion or ions that contributed to the initial conductivity reading e g a pH test for H a titration for hard water as Ca or a colorimetric test for NO37 State and local regulations often place upper limits on the level of total dissolved solids in drinking water These levels vary from state to state but often must be at a level less than 1100 mg L TDS A conductivity probe can give a quick and accurate reading for such a determination Since there is a nearly linear relationship between a ere conductivi
3. Public Health Association American Water Works Association and Water Environment Federation Standard Methods for the Examination of Water and Wastewater Washington DC American Public Health Association 1998 Warranty Vernier warrants this product to be free from defects in materials and workmanship for a period of five years from the date of shipment to the customer This warranty does not cover damage to the product caused by abuse or improper use 10 11 Measure Analyze Learn Vernier Software amp Technology 13979 S W Millikan Way e Beaverton OR 97005 2886 Toll Free 888 837 6437 e 503 277 2299 e FAX 503 277 2440 info vernier com e www vernier com Rev 8 13 2012 Logger Pro Logger Lite Vernier LabQuest 2 Vernier LabQuest Vernier LabQuest Mini Vernier LabPro Go Link Vernier EasyLink and other marks shown are our trademarks or registered trademarks in the United States CBL 2 TI Nspire CBL 2 and CBL TI GRAPH LINK and TI Connect are trademarks of Texas Instruments All other marks not owned by us that appear herein are the property of their respective owners who may or may not be affiliated with connected to or sponsored by us ae tae Printed on recycled paper 12
4. 2000 uS cm 5 566 g 5566 mg L 5000 mg L as TDS 10 000 wS cm Automatic Temperature Compensation Your Vernier Conductivity Probe is automatically temperature compensated between temperatures of 5 and 35 C Note that the temperature of a solution is being read by a thermistor that extends into the space between the graphite electrodes Readings are automatically referenced to a conductivity value at 25 C therefore the Conductivity Probe will give the same conductivity reading in a solution that is at 15 C as it would if the same solution were warmed to 25 C This means you can calibrate your probe in the lab and then use these stored calibrations to take readings in colder or warmer water in a lake or stream If the probe was not temperature compensated you would notice a change in the conductivity reading as temperature changed even though the actual ion concentration did not change Using the Conductivity Probe with Other Vernier Sensors Some combinations of sensors interfere with each other when placed in the same solution The degree of interference depends on many factors including which combination of sensors is being used which interface is being used and others For more information see www vernier com til 638 Sampling in Streams and Lakes It is best to sample away from shore and below the water surface if possible In free flowing streams there will usually be good mixing of the water so that samples taken near
5. Conductivity Probe Order Code CON BTA The Conductivity Probe can be used to measure either solution conductivity or total ion concentration of aqueous samples being investigated in the field or in the laboratory Conductivity is one of the most common environmental tests of aquatic samples Even though it does not tell you specific ions that are present it quickly determines the total concentration of ions in a sample It can be used to perform a wide variety of tests or planned experiments to determine the changes in or levels of total dissolved ions e Allow students to qualitatively see the difference between the ionic and molecular nature of electrolytes in aqueous solution This can include differences in strength of weak acids and bases or the number of ions that an ionic substance dissociates into per formula unit e Use the probe to confirm the direct relationship between conductivity and ion concentration in an aqueous solution Concentrations of unknown samples can then be determined e Use this probe for an accurate on site measurement of total dissolved solids TDS in a stream or lake survey e Monitor the rate of a chemical reaction in which dissolved ions and solution conductivity varies with time due to an ionic species being consumed or produced e Use the Conductivity Probe to determine the rate at which an ionic species diffuses through a membrane such as dialysis tubing Collecting Data with the Conductivity Prob
6. d with LabQuest 2 LabQuest LabQuest Mini LabPro Go Link SensorDAQ TI Nspire Lab Cradle EasyLink or CBL 2 the data collection software identifies the sensor and uses pre defined parameters to configure an experiment appropriate to the recognized sensor Specifications Range of Conductivity Probe Low Range 0 to 200 uS cm 0 to 100 mg L TDS Mid Range 0 to 2000 uS cm 0 to 1000 mg L TDS High Range 0 to 20 000 uS cm 0 to 10 000 mg L TDS 13 bit Resolution with SensorDAQ Low Range 0 05 uS cm 0 025 mg L TDS Mid Range 0 5 uS cm 0 25 mg L TDS High Range 5 uS cm 2 5 mg L TDS 12 bit Resolution with LabQuest 2 LabQuest LabQuest Mini LabPro Go Link EasyLink TI Nspire Low Range 0 1 wS cm 0 05 mg L TDS Mid Range 1 uS cm 0 5 mg L TDS High Range 10 uS cm 5 mg L TDS 10 bit Resolution with CBL 2 Low Range 0 4 wS cm 0 2 mg L TDS Mid Range 4 wS cm 2 0 mg L TDS High Range 40 wS cm 20 mg L TDS Accuracy using factory calibration 8 of full scale reading for low range 3 of full scale reading for mid range 4 of full scale reading for high range Accuracy using custom calibration 2 of full scale reading for each range 98 of full scale reading in 5 seconds 100 of full scale in 15 seconds Response time Temperature compensation automatic from 5 to 35 C Temperature range probe can be placed in 0 to 80 C Cell constant 1 0 cm Description ABS body para
7. e This sensor can be used with the following interfaces to collect data e Vernier LabQuest 2 or original LabQuest as a standalone device or with a computer e Vernier LabQuest Mini with a computer e Vernier LabPro with a computer or TI graphing calculator e Vernier Go Link e Vernier EasyLink e Vernier SensorDAQ e CBL 2 o TI Nspire Lab Cradle Here is the general procedure to follow when using the Conductivity Probe 1 Connect the Conductivity Probe to the interface 2 Start the data collection software 3 The software will identify the Conductivity Probe and load a default data collection setup You are now ready to collect data Data Collection Software This sensor can be used with an interface and the following data collection software e Logger Pro 3 This computer program is used with LabQuest 2 LabQuest LabQuest Mini LabPro or Go Link e Logger Lite This computer program is used with LabQuest 2 LabQuest LabQuest Mini LabPro or Go Link e LabQuest App This program is used when LabQuest 2 or LabQuest is used as a standalone device e DataQuest Software for TI Nspire This calculator application for the TI Nspire can be used with the EasyLink or TI Nspire Lab Cradle e EasyData App This calculator application for the TI 83 Plus and TI 84 Plus can be used with CBL 2 LabPro and Vernier EasyLink We recommend version 2 0 or newer which can be downloaded from the Vernier web s
8. ite www vernier com easy easydata html and then transferred to the calculator See the Vernier web site www vernier com calc software index html for more information on the App and Program Transfer Guidebook e DataMate Use DataMate with LabPro or CBL 2 and TI 73 TI 83 TI 84 TI 86 TI 89 and Voyage 200 calculators See the LabPro and CBL 2 Guidebooks for instructions on transferring DataMate to the calculator e LabVIEW National Instruments LabVIEW software is a graphical programming language sold by National Instruments It is used with SensorDAQ and can be used with a number of other Vernier interfaces See www vernier com labview for more information NOTE Vernier products are designed for educational use Our products are not designed nor recommended for any industrial medical or commercial process such as life support patient diagnosis control of a manufacturing process or industrial testing of any kind Taking Measurements with the Conductivity Probe e Rinse the tip of the Conductivity Probe with distilled water Optional Blot the inside and outside of the electrode cell dry to avoid water droplets diluting or contaminating the sample to be tested e Insert the tip of the probe into the sample to be tested Important Be sure the electrode surfaces in the elongated cell are completely submerged in the liquid and that there are no bubbles around the electrode surface If you are using Logger Pro 2 with either a ULI
9. llel graphite electrodes Dimensions 12 mm OD and 150 mm length Factory Calibration Values intercept all ranges 0 0 slope low range 65 7 slope mid range 960 slope high range 9000 How the Conductivity Probe Works The Vernier Conductivity Probe measures the ability of a solution to conduct an electric current between two electrodes In solution the current flows by ion transport Therefore an increasing concentration of ions in the solution will result in higher conductivity values The Conductivity Probe is actually measuring conductance defined as the reciprocal of resistance When resistance is measured in ohms conductance is measured using the SI unit siemens formerly known as a mho Since the siemens is a very large unit aqueous samples are commonly measured in microsiemens or US Even though the Conductivity Probe is measuring conductance we are often interested in finding conductivity of a solution Conductivity C is found using the following formula C Geke where G is the conductance and ke is the cell constant The cell constant is determined for a probe using the following formula ke d A where d is the distance between the two electrodes and A is the area of the electrode surface Figure I For example the cell in Figure 1 has a cell constant ke d A 1 0 cm 1 0 cm 1 0 cm The conductivity value is found by multiplying conductance and the cell constant Since the Vernier Conductivity Pr
10. nal Calibration Procedure You do not have to perform a new calibration when using the Conductivity Probe for most experiments in the classroom Each Conductivity Probe is programmed with an experimentally determined calibration before shipping it This calibration is unique for each setting on the sensor The factory calibrations work best if each setting 1s used in the appropriate range 1 e use low for 0 uS cm to 200 uS cm use middle for 200 uS cm to 2 000 uS cm and use high for 2 000 uS cm to 20 000 uS cm However if your experimental application requires more accurate readings you should calibrate your sensor The Conductivity Probe can be easily calibrated at two known levels using any of the Vernier data collection programs The calibration units can be uS cm dS cm mg L ppm or ppt For best results it is recommended that the two point calibration be performed using two standard solutions that bracket the expected range of conductivity or concentration values you will be testing For example if you expect to measure conductivity in the range of 600 mg L to 1000 mg L TDS you may want to use a standard solution that is 500 mg L for one calibration point and another standard that is 1000 mg L for the second calibration point Make sure the correct switch setting is used for the middle range of conductivity To Calibrate 1 Select the conductivity range setting on the probe box low 0 to 200 uS medium 0 to 2000 uS and high
11. obe also has a cell constant of 1 0 cn its conductivity and conductance have the same numerical value For a solution with a conductance value of 1000 uS the conductivity C would be C Geke 1000 uS x 1 0 em 1000 uS cm A potential difference is applied to the two probe electrodes in the Conductivity Probe The resulting current is proportional to the conductivity of the solution This current is converted into a voltage Alternating current is supplied to prevent the complete ion migration to the two electrodes As shown in the figure here with each cycle of the alternating current the polarity of the electrodes is reversed which in turn reverses the direction of ion flow This very important feature of the Conductivity Probe prevents most electrolysis and polarization from occurring eee at the electrodes Thus the solutions that are being measured for conductivity are not fouled It also greatly reduces redox products from forming on the relatively inert graphite electrodes One of the most common uses of the Conductivity Probe is to find the concentration of total dissolved solids l or TDS in a sample of water This can ee be accomplished because there is generally a direct relationship between conductivity and the concentration of ions in a solution as shown here The relationship persists until very large ion concentrations are reached lon Concentration TOS mg L Optio
12. or SBI the sensor will not auto ID Open an experiment file for the Conductivity Probe in the Probes amp Sensors folder e While gently swirling the probe wait for the reading on your data collection device to stabilize This should take no more than 5 to 10 seconds Note Do not completely submerge the sensor The handle is not waterproof e Rinse the end of the probe with distilled water before taking another measurement e If you are taking readings at temperatures below 15 C or above 30 C allow more time for the temperature compensation to adjust and provide a stable conductivity reading e Important Do not place the electrode in viscous organic liquids such as heavy oils glycerin glycerol or ethylene glycol Do not place the probe in acetone or other organic solvents such as pentane or hexane Storage and Maintenance of the Conductivity Probe e When you have finished using the Conductivity Probe simply rinse it off with distilled water and blot it dry using a paper towel or lab wipe The probe can then be stored dry e If the probe cell surface is contaminated soak it in water with a mild detergent for 15 minutes Then soak it in a dilute acid solution 0 1 M hydrochloric acid or 0 5 M acetic acid works well for another 15 minutes Then rinse it well with distilled water Important Avoid scratching the inside electrode surfaces of the elongated cell This sensor is equipped with circuitry that supports auto D When use
13. t concentration comprised mostly of Na and Cl ions Even though there are smaller quantities of other ions in seawater e g K Mg2 or SOq2 sodium and chloride ions represent about 91 percent of all seawater ions Salinity is an important measurement in seawater or in estuaries where freshwater from rivers and streams mixes with salty ocean water The salinity level in seawater is fairly constant at about 35 ppt 35 000 mg L while brackish estuaries may have salinity levels between 1 and 10 ppt The salinity range of the Conductivity Probe is 0 to 10 ppt Seawater has a salinity of 35 ppt so any seawater samples will need to be diluted before making measurements with this sensor We recommend that you dilute seawater samples or other samples that initially give readings above 10 ppt to 1 4 of their original concentration then multiply their measured salinity reading by 4 to obtain a final salinity value in ppt Brackish water in coastal estuaries is often in the range of 0 to 10 ppt well within the high range of the probe Note Vernier also sells a Salinity Sensor order code SAL BTA with a range of 0 to 50 ppt Since there is no stored salinity calibration for a Conductivity Probe perform a two point calibration using 5 ppt and 10 ppt salinity standards Make sure your sensor switch is on the high conductivity setting You will need to prepare two standard solutions to calibrate for salinity e A low standard 5 ppt salinity
14. the current will be quite representative of the stream as a whole If you are sampling an impounded stream or a lake there will be very little mixing therefore it is important to sample away from shore and at different depths if possible Do not drop the Vernier Conductivity Probe so that the entire electrode is submerged The electrode is not constructed to withstand higher pressures so seepage into electronic components of the electrode will result Although it is better to take readings at the collection site readings of total dissolved solids or conductivity should not change significantly if you collect samples and take readings at a later time However be sure that samples are capped to prevent evaporation If sample bottles are filled brim full then a gas such as carbon dioxide which is capable of forming ionic species in solution is prevented from dissolving in the water sample Since the probe has built in temperature compensation you can do your calibration in the lab This means that even though you will be sampling in water that has a different temperature than your calibration temperature the probe will take correct readings at the new sampling temperature Sampling in Ocean Water or Tidal Estuaries Salinity Salinity is the total of all non carbonate salts dissolved in water usually expressed in parts per thousand 1 ppt 1000 mg L Unlike chloride Cl concentration you can think of salinity as a measure of the total sal
15. trode surface Wait for the displayed voltage to stabilize Enter the value of the standard solution 5 You may wish to store this custom calibration if your software has this option Maintaining and Replacing the Sodium Chloride Standard Calibration Solution If you choose to calibrate the Conductivity Probe you will want accurate standard solutions The 1000 uS cm Standard that shipped with the Conductivity Probe will last a long time if you take care not to contaminate it with a wet or dirty probe as well as reduce its exposure to air This is a good concentration to calibrate your Conductivity Probe in the middle range O 2000 uS cm Vernier sells three Conductivity Standards one appropriate for each range of the Conductivity Probe These standards are available in 500 mL bottles Order codes are Low Range 150 uS cm CON LST Medium Range 1413 uwS em CON MST High Range 12880 uS cm CON HST You can also prepare your own standard solutions using solid NaCl Use a container with accurate volume markings e g volumetric flask and add the amount of solid indicated in Table 1 Table 1 dd this amount of TDS and Conductivity values equivalent to aCl to make the NaCl concentration in the first column 1 liter of solution Total dissolved solids Conductivity TDS microsiemens cm 0 0474 g 47 4 mg L 50 mg L as TDS 100 uS cm 0 491 g 491 mg L 500 mg L as TDS 1000 uS cm 1 005 g 1005 mg L 11000 mg L as TDS
16. ty and concentration of a specific ion or salt the Conductivity Probe can be used to determine conductivity the concentration of an ion A curve similar to the 3 one shown here can be obtained if you prepare or 700 maL purchase standard solutions solutions with known TD 5 concentration concentrations Note in this figure the 2 1 ratio between conductivity in uS cm and TDS concentration in mg L Even though total dissolved solids is often defined in terms of this 2 1 ratio it should be understood that a TDS reading of 500 mg L can have a different meaning in a sample that is mostly NaCl than in another sample that is composed primarily of hard water ions such as Ca2 and HCO37 The relationship between conductivity and sodium chloride concentration is approximately a 2 1 ratio and is very nearly a direct relationship Table 2 shows the relationship for sodium chloride concentration in mg L to TDS to conductivity Table 3 shows some conversion values for conductivity uS cm to concentration mg L for various ions 100 105 210 150 158 315 200 208 415 500 510 1020 1000 995 1990 1500 1465 2930 2000 1930 3860 5000 4482 8963 10250 9000 18000 Table 3 Conversion from Conductivity uS cm to Total dissolved solids mg L Total dissolved solids mg L Bicarbonate Calcium Carbonate Chloride Magnesium Nitrate Potassium Sodium Sulfate American
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