Calibration and Maintenance Procedures: YSI ProDSS rev 8/31/15

Transcription

1 Calibration and Maintenance Procedures: YSI ProDSS rev 8/31/15 These procedures are to be performed by program staff or people who have been trained by staff. Calibration frequency will depend upon the sensor and sampling needs. Our first year of using this meter (summer spring 2016) will be a secondary deployment alongside our regular field equipment, and we will be experimenting with acceptable recalibration intervals. Initially, our plan is to calibrate the meter for all sensors before every month-long quarterly monitoring session, and to see if the sensors will adequately hold their calibration during that period. We expect this to be an iterative process, with some data needing to be qualified or rejected as a result. We hope to make this meter our standard equipment in summer Table of Contents - Putting the unit together Cable connection Pre-Sensor Installation Sensor installation - Calibration Barometer Conductivity ph Turbidity Dissolved oxygen - Maintenance - Short term storage - Long term storage K:\Streamkeepers\Monitoring\Eqpt & supplies\calibration-maintenance\sops\ysi ProDSS maint-cal SOP's 1

2 A FEW NOTES BEFORE GETTING STARTED The instrument/cable connectors, bulkhead ports, and sensor connector ends are not wetmateable and can become damaged if they come into contact with moisture. Never connect the cable connector to the handheld unit, or install a sensor if they are wet! Carefully follow sensor tightening instructions during installation. If any resistance is felt during any tightening (sensor, sensor guard, port plug), stop tightening, loosen nut or guard, and start again. Cable Connection PUTTING THE UNIT TOGETHER Make sure the connectors are clean and dry before connecting! If connecters are clean and dry, align the keys on the male cable connector with the female slots on the instrument connector. Push together firmly, and then twist the outer ring clockwise until it locks into place. The metal pin should snap into place and be visible through the small hole in the outer ring (see image below). Metal pin showing through outer ring of connector piece. Sensor Installation NOTE: There are two different storage procedures for the sensors and unit: short term (sensors are still attached to the unit), and long term (sensors have been removed and individually stored). If the unit has been stored under the short term procedures, continue to the Calibration section below. The ports on the ProDSS bulkhead are universal; therefore, you can install any sensor into any port. For highest accuracy, always install a conductivity/temperature sensor to compensate all measurement data for temperature and dissolved oxygen data for conductivity. Similar to the cable connection, the sensor and bulkhead ports are not waterproof, therefore always make sure the ports are clean and completely dry before installation. Any moisture in the ports will result in damage to the unit not covered under its warranty. Avoid sensor installation in the field at all costs. K:\Streamkeepers\Monitoring\Eqpt & supplies\calibration-maintenance\sops\ysi ProDSS maint-cal SOP's 2

3 Dissolved Oxygen 1. Remove the DO sensor from the container. Slide the plastic protective cover off of the end of the sensor; you may need to wiggle it back and forth to get it off. NOTE: Do not remove the black DO cap (this cap will twist off in a counter clockwise direction)! 2. Inside the plastic protective cover is a yellow sponge, inspect the sponge and take note if it appears dry. Also inspect the tip of the sensor for fouling or other debris, if dirty clean with a moist non-abrasive lint-free cloth. NOTE: Clean the tip carefully to prevent scratches. Do not use organic solvents to clean the ODO sensor or sensor cap. 3. Inspect the bulkhead ports for moisture or debris, clean with a dry lint-free cloth if need be. If moisture can t be reached with a cloth, ask staff to assist with an air compressor. Remove the red connector cap and apply a thin coat of Krytox o-ring lubricant to the sensor o-rings (maintenance kit). Wipe off any extra lubricant with a lint-free cloth (see image below). 4. Carefully align the sensor into the bulkhead port rotate the sensor gently until you can feel it align with the bulkhead. Once aligned, push the sensor into the bulkhead until it is firmly seated in the port (see image below). 5. Carefully tighten the retaining nut, if any resistance is felt loosen the nut and try again. Finger tighten as much as you can, then use the sensor installation tool to tighten until snug (see image below). DO NOT OVER TIGHTEN! Conductivity (NOTE: Use care when handling this sensor to prevent damage to the exposed thermistor (at tip of sensor). 1. Remove the conductivity sensor from the container. Slide the clear plastic cap from the tip of the sensor and store in container. Inspect the tip of the sensor for debris or fouling, look into the two holes for debris or fouling. If the tip is dirty, refer to the Maintenance section below for cleaning techniques. 2. Inspect the bulkhead ports for moisture or debris, clean with a dry lint-free cloth if need be. If moisture can t be reached with a cloth, ask staff to assist with an air compressor. Remove the red connector cap and apply a thin coat of Krytox o-ring lubricant to the sensor o-rings (maintenance kit). Wipe off any extra lubricant with a lint-free cloth (see image below). 3. Carefully align the sensor into the bulkhead port rotate the sensor gently until you can feel it align with the bulkhead. Once aligned, push the sensor into the bulkhead until it is firmly seated in the port (see image below). 4. Carefully tighten the retaining nut, if any resistance is felt loosen the nut and try again. Finger tighten as much as you can, then use the sensor installation tool to tighten until snug (see image below). DO NOT OVER TIGHTEN! If not all ports on the bulkhead will be filled, a port plug must be installed to prevent damage to the unit. ph K:\Streamkeepers\Monitoring\Eqpt & supplies\calibration-maintenance\sops\ysi ProDSS maint-cal SOP's 3

4 1. Remove the ph sensor from the container. Holding the bottle upright, remove the bottle covering the tip of the sensor and replace the open cap and o-ring with the storage cap and store in container. If the tip of the ph sensor appears dirty, refer to the Maintenance section below for cleaning techniques. 2. Carefully rinse the sensor tip with clean tap or distilled water, TAKE EXTREME CARE to not get the sensor connector end of the sensor wet. If you do get moisture in the connector end, completely dry the sensor with a lint-free cloth, or ask staff for assistance with an air compressor. 3. Inspect the bulkhead ports for moisture or debris, clean with a dry lint-free cloth if need be. If moisture can t be reached with a cloth, ask staff to assist with an air compressor. Remove the red connector cap and apply a thin coat of Krytox o-ring lubricant to the sensor o-rings (maintenance kit). Wipe off any extra lubricant with a lint-free cloth (see image below). 4. Carefully align the sensor into the bulkhead port rotate the sensor gently until you can feel it align with the bulkhead. Once aligned, push the sensor into the bulkhead until it is firmly seated in the port (see image below). 5. Carefully tighten the retaining nut, if any resistance is felt loosen the nut and try again. Finger tighten as much as you can, then use the sensor installation tool to tighten until snug (see image below). DO NOT OVER TIGHTEN! Turbidity 1. Remove the turbidity sensor from the container. Slide the clear plastic cap from the tip of the sensor and store in container (you may need to wiggle it off). 2. If the tip is dirty, refer to the Maintenance section below for cleaning techniques. 3. Inspect the bulkhead ports for moisture or debris, clean with a dry lint-free cloth if need be. Remove the red connector cap and apply a thin coat of Krytox o-ring lubricant to the sensor o-rings. Wipe off any extra lubricant with a lint-free cloth 4. Carefully align the sensor into the bulkhead port, rotate the sensor gently until you can feel it align with the bulkhead. Once aligned, push the sensor into the bulkhead until it is firmly seated in the port. 5. Carefully tighten the retaining nut, if any resistance is felt loosen the nut and try again. Finger tighten as much as you can, then use the sensor installation tool to finish tightening. You will not need to tighten the retaining nut much more, only a ¼ to ½ turn, DO NOT over tighten. If not all ports on the bulkhead will be filled, a port plug must be installed to prevent damage to the unit. K:\Streamkeepers\Monitoring\Eqpt & supplies\calibration-maintenance\sops\ysi ProDSS maint-cal SOP's 4

5 Installing the Sensor Guard 1. Carefully slide the sensor guard over the bulkhead and attached sensors/port plugs. Push the sensor guard toward the bulkhead until the sensor guard threads align with the bulkhead threads (see image right). 2. Carefully finger-tighten the sensor guard clockwise. NOTICE: If any resistance is felt, loosen the sensor guard completely to prevent cross-threading. Incorrect installation may cause damage to the sensor guard or bulkhead that is not covered by the warranty. Battery Life Use YSI designated charging equipment only! If the battery is not charged, the meter must be charged from the AC power adapter (strongest charge source), directly from a computer USB connection or from an external, portable USB battery pack. For the instrument to recognize that it is using AC power, you must start charging the ProDSS while on. After the instrument recognizes it is being charged, it can be turned off to finish charging. When using the AC adapter, it takes approximately 14 hours to charge the ProDSS battery when the instrument is turned off during the charge. The amount of time required to completely charge the battery pack when the ProDSS is initially turned on during the charge is approximately 9 hours. Expected battery life: ProDSS instrument only - 48 hours ProDSS with fully loaded cable assembly and 25% (Default) LCD brightness - 20 hours ProDSS with fully loaded cable assembly and 100% LCD brightness - 14 hours For maximum battery life, keep the battery 40% to 80% charged. Also, a larger discharge (e.g. to 50%) is better than a small discharge (e.g. to 90%) between recharges. Check Sensor Readings After installing all the sensors turn the unit on. In the Run screen (main display screen, image right) make sure all parameters are being displayed and are displaying the proper units: temperature C barometer inhg dissolved oxygen DO mg/l conductivity SPC-µS/cm salinity SAL-ppt ph ph units turbidity FNU If any of these are not right, do the following: Select the probe button and scroll down to Display submenu and hit enter. Scroll down and select the desired parameter. A submenu will appear with multiple unit options, select the proper unit and return to the Run Screen. K:\Streamkeepers\Monitoring\Eqpt & supplies\calibration-maintenance\sops\ysi ProDSS maint-cal SOP's 5

6 CALIBRATION These procedures are to be performed by Streamkeepers staff or trained volunteers. Calibrate all parameters before every quarterly monitoring session. If the instrument is used between seasonal sampling months, additional checking is recommended. Be sure the primary reference standards used in the office for calibration are within their expiration dates (last day of listed month), The YSI ProDSS will automatically store calibration information into a GLP (good lab practices) file. This includes what was calibrated, who calibrated it, and when it was calibrated. To prevent contamination, always calibrate the sensors in the following order: Barometer (if necessary), conductivity, ph, turbidity, dissolved oxygen Pre-sensor calibration: Make sure all sensors, sensor guard, and calibration cup are clean. For proper cleaning procedures, see the Maintenance section below. Make sure the sensor guard is in place before installing the calibration cup. Fill the calibration cup with a moderate amount of water and rinse the sensor guard and sensors by gently shaking the sealed cup. Discharge the water and repeat if necessary Below is a schematic of the calibration cup (note the different fill lines), and a picture of the sensor tips. You may need to reference this image during calibration. Temperature sensor Calibration Data Sheet and Meter Login A copy of the calibration data sheet is attached at the end of this protocol. Fill out the top part now, then fill out the other parts as you go along. Remember to log in to the meter with your UserID (indicated by your initials). Button Navigation Tips K:\Streamkeepers\Monitoring\Eqpt & supplies\calibration-maintenance\sops\ysi ProDSS maint-cal SOP's 6

7 If the display has darkened and you hit any key, the display will brighten, but the key will not execute as a key. To get to a prior screen, try pressing the left arrow first; if that doesn t work, press Esc. When navigating with the Up/Down/Left/Right arrows, when you reach the end of the screen, if you keep going, it will circle back around to the other side. Barometer Calibration The YSI ProDSS has a built in barometer that has been factory calibrated and rarely needs to be recalibrated. The accuracy of the barometer is essential for dissolved oxygen calibration. Before and after each season, check the barometer readings for accuracy by testing against the weather station located in the Roads Department upstairs. (You may have to hold the probe facing down and loosen the calibration cup to equalize the pressure.) Record on Barometer data sheet the weather station location, the weather station barometric pressure reading to 0.01 inches Hg, and the ProDSS barometer reading to 0.01 inches Hg. If the ProDSS s barometer does not match the value of the weather station within our QAPP specifications, it will need recalibration. Calibration: 1. If barometer units are not in inhg, refer to Check Sensor Readings on page 4 to change units. 2. Select the calibration button, and select Barometer. 3. Select Calibration Value then enter the correct true barometric pressure by pressing Enter, then the value, then Enter again. 4. Record the pre-calibration reading, then Select Accept Calibration Barometric Unit Conversions: BP in mmhg=25.4 x BP inhg BP in mmhg= x BP mb BP in mmhg= x BP psi BP in mmhg= x BP kpa BP in mmhg=760 x BP atm Conductivity Calibration With this conductivity/temp sensor, once specific conductance is calibrated, all other parameters measured by this sensor will be calibrated. Equipment Needed: Purified water Mild solution of dish soap and tap water Cleaning brush found in maintenance kit Conductivity standard solution *Check date if opened. The solution expires one month after opening. If expired, get new solution. NEVER REUSE CALIBRATION SOLUTION. CHECKING PRIOR CALIBRATION STABILITY: K:\Streamkeepers\Monitoring\Eqpt & supplies\calibration-maintenance\sops\ysi ProDSS maint-cal SOP's 7

8 1. Record the date, your initials, season, and conductivity standard strength on the conductivity calibration data sheet. 2. Thoroughly rinse the calibration cup with a small amount of conductivity standard solution and then discard. 3. Fill the pre-rinsed calibration cup with the conductivity solution to the second fill line (225 ml) 4. Carefully immerse the sensors (with sensor guard on) into the cup, make sure the solution is above the vent holes on the side of the conductivity sensor. To remove bubbles, gently rotate the sensors, or move the sensors up and down. Allow at least one minute for temperature equilibration. 5. On the Run Screen check and record the pre-calibration conductivity reading with the probe in the conductivity solution (make sure it s in µs/cm, if not see Check Sensor Readings above for correction). Record this value in the Pre SP.C column on the data sheet. If the meter s value does not match the reference value within our QAPP specifications, it will need recalibration. 6. Now you will clean the conductivity cells prior to calibration. Cleaning Procedures: Remove the sensor guard. Dip the probe into a beaker of mild solution of dish soap and clean tap water. Let it sit for about 30 seconds. Use the cleaning brush from the maintenance kit to scrub the inside of the chamber; insert in holes and scrub back and forth about times. Rinse the probe in clean tap water thoroughly. Replace the sensor guard. CALIBRATING SPECIFIC CONDUCTANCE: 1. Thoroughly rinse the calibration cup and sensors with a small amount of conductivity standard solution and then discard. 2. Fill the calibration cup with the conductivity solution to the second fill line (225 ml). 3. Carefully immerse the sensors (with sensor guard on) into the cup, make sure the solution is above the vent holes on the side of the conductivity sensor. To remove bubbles, gently rotate the sensors, or move the sensors up and down. Allow at least one minute for temperature equilibration. 4. Select the calibration button, select Conductivity, then select Specific Conductance 5. Select Calibration Value; enter the calibration value of the calibration solution. Calibration value should be displayed on the solution bottle, it should read: 1,000 C Note: umhos = µs/cm 6. Confirm stabilization by watching the actual readings on the screen; if µs/cm has not significantly changed in 40 seconds, the sensor is stable. 7. After observing stabilization, record the pre-calibration reading, then press Accept Calibration. A message will appear: Calibration Successful. 8. The meter should now be calibrated. For added assurance, rinse the probe in purified water, shake off excess water and take a reading in air only. It should be 1 µs/cm. If not, repeat calibration steps. K:\Streamkeepers\Monitoring\Eqpt & supplies\calibration-maintenance\sops\ysi ProDSS maint-cal SOP's 8

9 9. Record the post-calibration conductivity reading and temperature on the data sheet. 10. Rinse the sensors and calibration cup with clean water and proceed to ph calibration. If data does not stabilize after 40 seconds: - Gently rotate the sensor, or remove/reinstall the calibration cup to make sure that no air bubbles are in the conductivity cell - If the actual measurement data is about 1/2 if the expected calibration value, the conductivity sensor is not completely submerged. Add more calibration standard to the calibration cup - If you get calibration error messages, check for proper sensor immersion, verify the calibration solutions is fresh, the correct value has been entered into the ProDSS, and/or try cleaning the sensor (reference the Maintenance section below on proper cleaning techniques for the conductivity sensor) Equipment Needed: Purified water Kimwipes ph 4, 7 and 10 buffer solutions ph Calibration Perform a 3-point calibration of the ph meter before every monitoring session. Replace buffer solutions as needed so as not to exceed expiration dates. Solutions are good until the last day of the month listed. Anytime a new lot number of buffer is put into use, calibrate the instrument with the new lot and check the old lot to compare the results. A breakdown of the calibration screen for ph. Calibration: Setting the midpoint (ph buffer 7) 1. Rinse sensors once with distilled water, once with old buffer solution, and twice with new solution. To rinse, fill cup ~2, attach cup to unit and lightly shake the unit while tilting it K:\Streamkeepers\Monitoring\Eqpt & supplies\calibration-maintenance\sops\ysi ProDSS maint-cal SOP's 9

10 back and forth. Shake and tilt the unit until all sensors and guard have been rinsed. 2. Fill the calibration cup with the buffer 7 solution to the first fill line (170 ml) 3. Carefully immerse the unit into the calibration cup, allow at least one minute for temperature stabilization. 4. Check for any air bubbles on the sensor tip, if any are present, tap the side of the unit until the bubbles are removed. 5. Allow the sensor to stabilize (doesn t vary by more than 0.01 for 2 min.) record the date, mvs, and the ph 7 before calibration reading in the calibration notebook. 6. Press the calibration button, select ph, and then select Calibration Value. 7. Enter the ph buffer value that corresponds to the temperature value that you can see under Actual Readings (e.g., 21.2 C in the above picture). This value can be found on the bottle of most ph buffers (e.g., the value of most ph 7 buffer solution at 20 C is 7.02). 8. Confirm stabilization by watching the actual readings on the screen; if ph remains within ± 0.01 for 2 minutes, the sensor is stable. 9. After observing stabilization, record the pre-calibration reading, then press Accept Calibration. A message will appear: Calibration Successful. A second message will then appear: Ready for cal point 2. You are now ready to calibrate with the next buffer solution. DO NOT back out to the Run screen by hitting the left arrow button or the Esc button. If you don t finish the three point calibration, the unit will register this as a one point calibration and you will have to start over again with the ph calibration. A note about ph millivolts (mv): Millivolts (mv) are a way to troubleshoot calibration problems, they can help identify if the buffer solutions are bad, or if the sensor needs replaced. Below is the proper range for mvs in the designated buffers: o Buffer 7: -50 to +50 mv o Buffer 4: +165 to 185 above buffer 7 mv value o Buffer 10: -165 to -185 below buffer 7 mv value If these values are not being produced during calibration, do the following: - Remove the sensor from the calibration cup and rinse the sensor and calibration cup with clean water - To rule out that the buffer is bad, get a fresh ph 7 buffer, rinse the sensor with a small amount of buffer and re-calibrate - If mvs are still not showing accurate readings, the sensor may need to be replaced, check the purchase sticker on the long term storage bottle (ph sensor has a 1-2 year life expectancy) Setting the lower point (ph buffer 4) 1. Rinse sensors once with distilled water, once with old buffer solution, and twice with new solution. To rinse, fill cup ~2, attach cup to unit and lightly shake the unit while tilting it back and forth. Shake and tilt the unit until all sensors and guard have been rinsed. 2. Fill the calibration cup with buffer 4 solution to the first fill line (170 ml) 3. Carefully immerse the unit into the calibration cup, allow at least one minute for temperature stabilization. 4. Check for any air bubbles on the sensor tip, if any are present, tap the side of the unit until the bubbles are removed. 5. Observe the mv and wait for stabilization (ph doesn t vary by more than 0.01 for 2 min.), record value on data sheet. K:\Streamkeepers\Monitoring\Eqpt & supplies\calibration-maintenance\sops\ysi ProDSS maint-cal SOP's 10

11 6. Enter the ph buffer value that corresponds to the buffer temperature reading (value should be located on ph buffer bottle) 7. Confirm stabilization by watching the actual readings on the screen; if ph remains within ± 0.01 for 2 minutes, the sensor is stable. 8. After observing stabilization, record the pre-calibration reading, then press Accept Calibration. A message will appear Ready for cal point 3. If doing a 3-point calibration, proceed to Setting the upper point below; if you are doing a 2-point calibration, select Finish Calibration and proceed to the next calibration parameter. DO NOT back out to the Run screen by hitting the left arrow button, or the Esc button. If you don t finish the three point calibration, the unit will register this as a two point calibration and you will have to start over again with the ph calibration. Setting the upper point (ph buffer 10) 1. Rinse sensors once with distilled water, once with old buffer solution, and twice with new solution. To rinse, fill cup ~2, attach cup to unit and lightly shake the unit while tilting it back and forth. Shake and tilt the unit until all sensors and guard have been rinsed. 2. Fill the calibration cup with buffer 10 solution to the first fill line (170 ml) 3. Carefully immerse the unit into the calibration cup, allow at least one minute for temperature stabilization. 4. Check for any air bubbles on the sensor tip, if any are present, tap the side of the unit until the bubbles are removed. 5. Observe the mv and wait for stabilization (doesn t vary by more than 0.01 for 2 min.), record value on data sheet. 6. Enter the ph calibration value that corresponds to the buffer temperature reading (value may be located on ph buffer bottle) 7. Confirm stabilization by watching the actual readings on the screen, if ph remains within ± 0.01 for 2 minutes, the sensor is stable. 8. After observing stabilization, record the pre-calibration reading, then press Accept Calibration. Select Finish Calibration and proceed to the next calibration parameter. 9. Rinse the sensors and calibration cup with clean water and proceed to turbidity calibration. The date and time of calibration will be stored in the GLP file. For sensor storage, refer to the Short Term Storage or Long Term Storage sections below. Always check amounts and dates for all ph buffer solutions to ensure there is enough for the next calibration check. If not, notify staff. K:\Streamkeepers\Monitoring\Eqpt & supplies\calibration-maintenance\sops\ysi ProDSS maint-cal SOP's 11

12 Turbidity Calibration For proper calibration, you must use standards that have been prepared according to details in Standard Methods for the Treatment of Water and Wastewater (Section 2130 B). The standard Streamkeepers uses is: YSI 6073G Turbidity Standard 124 FNU for an EXO Turbidity Sensor Do not use any other standards or it will result in calibration errors and inaccurate field readings. Never mix standards together, i.e. formazin and the above standard This standard will expire 1 year after opening! If you open a fresh gallon of the YSI 6073G turbidity standard, write the date it was opened on the label in permanent marker Equipment Needed: YSI 6073G turbidity standard (124 FNU) Calibration: NOTE: The sensor guard must be installed on the unit to calibrate the turbidity sensor. When calibrating turbidity, the first point must be zero. The following is a 2-point calibration with clear deionized water, and the turbidity solution. 1. Make sure that the sensors and calibration cup have been rinsed 2-3 times with distilled or clean tap water since the previous calibration procedure (should have been ph). 2. Rinse the sensors and calibration cup with zero standard, or deionized water. Shake off the unit and cup after rinse. 3. SLOWLY pour the deionized water down the side of the cup (like you re pouring a beer), fill the cup to the first fill line (170 ml). Immerse the sensors and the guard into the cup. A few air bubbles are ok but you don t want a lot. 4. Select the calibration button, then select Turbidity. 5. Select Calibration Value and enter 0.0 (if it isn t already). 6. Confirm stabilization by watching the actual readings on the screen; if the readings don t change by > ±0.1 FNU for 40 seconds, the sensor is stable. 7. After observing stabilization, record the pre-calibration reading, then press Accept Calibration. Ready for cal point 2 will be displayed in the message area; you are now ready to calibrate the second point. DO NOT back out to the Run screen by hitting the left arrow button, or the Esc button. If you don t finish the two point calibration, the unit will register this as a one point calibration and you will have to start over again with the turbidity calibration. 8. If you open a new YSI turbidity standard, write the date on the label in permanent marker. 9. Empty, shake off, rinse once with old turbidity standard (if available; if not, use distilled water again), and twice with new solution. To rinse, fill cup ~2, attach cup to unit and lightly shake the unit while tilting it back and forth. Shake and tilt the unit until all sensors and guard have been rinsed. 10. SLOWLY pour the standard down the side of the cup (like your pouring a beer), fill the cup to the first fill line (170 ml). 11. Check Calibration Value at top of screen and change to 124 FNU if needed. 12. Confirm stabilization by watching the actual readings on the screen; if the readings don t change by > ±0.1 FNU for 40 seconds, the sensor is stable. 13. After observing stabilization, record the pre-calibration reading, then press Accept K:\Streamkeepers\Monitoring\Eqpt & supplies\calibration-maintenance\sops\ysi ProDSS maint-cal SOP's 12

13 Calibration. Ready for cal point 3 will be displayed in the message area. Select Finish Calibration (unless you have the proper calibration solution for an additional upper point). 14. Rinse the sensors and calibration cup with distilled or clean tap water and proceed to dissolved oxygen calibration. Dissolved Oxygen Calibration The following must be done before and after each sampling session: Pre Monitoring Session: Confirm DO sensor is clean DO zero-point calibration DO calibration DO calibration check (Winkler side-by-side) Post Monitoring Session: DO drift check (Winkler side-by-side) Equipment Needed: Sodium sulfite powder Purified water, lint-free tissues for cleaning Goggles or safety shield, gloves, lab apron Pre-Monitoring Session Calibration Procedures The DO sensor should have already been inspected for cleanliness during sensor installation, but if the sensor is visibly dirty, refer to the Maintenance section below for proper cleaning procedures. DO Zero-Point Calibration 1. Put on safety equipment: goggles, gloves, lab apron. 2. Make a solution using ~ 3g sodium sulfite/375 ml DI water. Stir to dissolve and allow to sit for at least 60 min. 3. Pour the sodium sulfite solution into a 1000 ml graduated cylinder 4. Place DO probe in the sodium sulfite solution. 5. Select the calibration button, then select ODO, then Zero. 6. Confirm stabilization by watching the Actual Readings on the screen; if DO% and Temp remain within ± 0.1 for 2 minutes, the sensor is stable. 7. After observing stabilization, record the pre-calibration reading, then press Accept Calibration. Calibration Successful! will be displayed on the screen. 8. Record results on the data sheet. 9. Rinse the probe thoroughly with DI water before placing it back in the calibration cup - this is important or it could interfere with future calibrations. 10. Proceed to DO% calibration. DO% Calibration Calibrating in DO% automatically calibrates the mg/l measurement. There is no reason to K:\Streamkeepers\Monitoring\Eqpt & supplies\calibration-maintenance\sops\ysi ProDSS maint-cal SOP's 13

14 calibrate both parameters. 1. Make sure the sensors and calibration cup have been rinsed following the preceding calibration. 2. Make sure there are no water droplets on the sensor cap or temperature sensor. With a Kimwipe or lint-free cloth, carefully wipe off any large droplets from the DO sensor tip and the temperature sensor by inserting the Kimwipe through the open slots in the sensor guard. If large droplets cannot be removed by wiping them away through the guard, remove the sensor guard to get to the sensors. Note that the temperature sensor does not need to be completely dry; drying the sensor at its base is hard to do and is not necessary. 3. Pour a small amount of clean water (1/8 th inch) gently down the side of the calibration cup 4. Gently insert the sensor and guard into the calibration cup and partially tighten the calibration cup to the bulkhead. NOTE: Do not fully tighten the cup; atmospheric venting is required for accurate calibration. Make sure the DO and temperature sensors are not submerged in water. 5. Set the unit aside right side up and wait 5 to 15 minutes for complete air saturation in the cup chamber. 6. Select the calibration button, then select ODO, then DO%. 7. Confirm stabilization by watching the actual readings on the screen; if DO% and Temp remain within ± 0.1 for 2 minutes, the sensor is stable. 8. After observing stabilization, record the pre-calibration reading, then press Accept Calibration. Calibration Successful! will be displayed on the screen. NOTE: If you see a calibration error message, verify the barometer reading and inspect the sensor cap. Clean and/or replace the sensor cap as needed (see the Maintenance section below). DO Calibration Check (Winkler side-by-side) We test the validity of the meter s DO calibration at the beginning and end of each quarter by doing a side-by-side Winkler titration. Equipment needed: 1 or 2 large plastic bucket(s) - depends on method used below Purified water, lint-free tissues for cleaning Aquarium air pump and aeration stone Graduated cylinder burette with stopcock at bottom, 25 ml/ with 3-way stopcock Volumetric burette, 10 ml with 3-way stopcock or 10 ml pipette with bulb on the end 3 Erlenmeyer flasks, 250 ml (number them-sample 1, 2, & 3) Volumetric pipette 10 ml stored in Streamkeepers cardboard tube at back of counter 3 BOD bottles and glass stoppers Manganous sulfate solution with its eyedropper (2 ml pipette) Alkali-iodate-azide reagent with its eyedropper (2 ml pipette) Pipette suction/dispenser bulb Magnetic stirrer Stirring bars (one for each sample) 203 ml Volumetric flask (plastic flask cut to hold exactly 203 ml when completely filled above the top; a rubber gasket around the top helps to deliver this flask s contents into the Erlenmeyer flasks) Concentrated sulfuric acid K:\Streamkeepers\Monitoring\Eqpt & supplies\calibration-maintenance\sops\ysi ProDSS maint-cal SOP's 14

15 2 ml disposable pipette stored in glass jar, for acid transfer Aqueous starch solution preserved with salicylic acid Squirt bottle (250 ml) with starch solution Sodium thiosulfate, M (Check pull date shelf life critical) Potassium bi-iodate, M (Check date good 18mos from mfr.) Rubber apron, nitrile gloves, acid face shield Ensure all liquids are within the expiration date and there is enough quantity to complete all 3 Winkler samples. First prepare the 100% oxygen-saturated environment in the lab: Method 1 (preferred) 1. Fill a bucket with DI water in the lab. 2. Place the aeration stone on the bottom of the bucket and turn on pump. 3. Loosely cover the bucket and set aside for approximately 24 hours. Method 2 1. Fill one of the buckets with DI water in the lab. 2. Pour this water into the other bucket and repeat 20 times. 3. Let this water sit with a lid on it until the following day. If the temperature does not change, it will stabilize and remain at 100% oxygenation. Preparing Winkler samples: 1. Put on safety equipment: face shield, gloves, apron. 2. Take out BOD bottle #1 and fill it with the air saturated water previously prepared - fill to neck; a clean beaker can be used to transfer water from the sample bucket you prepared earlier. 3. Put on the glass stopper. 4. The BOD bottles need to have the DO stabilized immediately by adding two chemicals as follows: a. Take the 1st pipette out of the manganous sulfate solution. Check and make sure it is filled with approximately 2 ml of solution and then add it to the BOD #1 bottle by immersing the tip of the pipette into the sample before injecting the solution. Make sure when you add solution you do not squeeze any air bubbles into the sample. Keep squeezing the top of the pipette when you replace it in the sulfate solution so that it will be filled for the next time. b. Take the 2nd pipette out of the alkaline-azide solution, check and make sure it has approximately 2 ml of solution and add it to the BOD #1 bottle using the same procedure as before. c. Adding these solutions turns the water brown and chemically converts the free oxygen into a manganese precipitate which falls to the bottom of the bottle. Put the glass stopper in the BOD bottle and invert slowly a couple of times to mix the contents. The solution is now stable. 5. Repeat all the sampling steps for the other two BOD bottles. 6. Record the time the samples were taken on the data sheet. Winkler titration steps: K:\Streamkeepers\Monitoring\Eqpt & supplies\calibration-maintenance\sops\ysi ProDSS maint-cal SOP's 15

16 NOTE: Dilute the chemicals going into the sink during the process with a continuous stream of tap water to prevent damage to plumbing. 1. Pour off the water seal and invert the bottle several times to mix the floc. 2. Remove the glass stoppers and put sample bottles in sink. 3. Using a pipette, draw and add 2 ml of sulfuric acid to each sample bottle. Keep the tap water running. 4. Rinse the pipette and put the cap securely on the acid bottle. 5. Put the stoppers back on the bottles and invert them several times over the sink until the precipitate has completely dissolved. 6. To transfer the liquid to the 203 ml volumetric flask, place the flask on top of BOD bottle number 1 and invert over sink. Once the flask is full, quickly remove the BOD bottle. The liquid should appear slightly convex on the top of the flask. Transfer the sample to the #1 Erlenmeyer flask. Repeat for samples # 2 and Carefully uncover the sodium thiosulfate burette (a purple cover on it for protection and storage.) 8. Ensure there is enough thiosulfate solution to complete the three trials in the burette. Add solution to the reservoir if necessary. 9. Empty any of the sodium thiosulfate left in the burette. 10. Turn the stopcock valve so the handle faces the burette body (directly away from you toward the wall). 11. Tighten the valve on the rubber bulb and pressurize the reservoir. Pump the rubber bulb gently to raise the solution, drain, refill and drain twice more to rinse, then fill the burette until the sodium thiosulfate escapes from the top nipple. 12. Turn the stopcock 90 degrees and loosen the valve on the bulb to allow the excess solution to return to the reservoir. 13. Drop a stir bar in the first sample flask and place it centered on the magnetic stirrer. Place the stirrer and flask centered under the burette valve to ensure drips fall cleanly into flask. 14. Turn the stirrer on the lowest setting. 15. Turn the stopcock valve handle toward you (there is a guide mark) and begin adding the sodium thiosulfate drops. You can add drops somewhat quickly at first but slow down when the sample starts turning a pale yellow. 16. Now, SLOWLY add one drop at a time until the sample turns very pale yellow and stop titrating. (It helps to place white paper between the burette and sample bottle.) 17. Add 1 to 2 ml of the starch solution into the flask using the squirt bottle until the sample turns a dark purple. 18. Continue to titrate the sample, adding drops VERY SLOWLY until the purple color just disappears and the sample is clear. Record the volume of solution used for each sample, to the nearest 0.1 ml. If ANY doubt about the end point, you can check the titration of the sample. 19. Check the end point by adding a drop of potassium bi-iodate into the flask with a dropper that delivers 20 drops per ml, identical to the burette. If the end point is correct, the purple color should reappear. If more than one drop is required, then the end point was overrun. 20. If the end point was overrun, back-titrate the sample with the bi-iodate standard (1 drop = 0.05 mg/l using a disposable 2 ml pipette) and correct the final value and data sheet. (For values halfway between the 0.1 ml marks, round down even numbers and round up odd numbers.) 21. Sodium Thiosulfate Normality Check: When the sample has been titrated to its end point, K:\Streamkeepers\Monitoring\Eqpt & supplies\calibration-maintenance\sops\ysi ProDSS maint-cal SOP's 16

17 add 10 ml of the bi-iodate standard to the sample using the pipette in the cardboard box. This is the nominal value that you ll record on the data sheet. Then record the correction factor for that pipette (i.e., how many actual ml are delivered for 10 ml nominal value on the pipette, as measured by repeated tests with purified water, an accurate balance, and factoring in air temperature). Refill the burette with sodium thiosulfate and re-titrate. Record the volume of the sodium thiosulfate normality check volume needed to back-titrate to clear. 22. Titrate the other two samples following the same steps as the first. Make sure you refill the burette and dab any excess fluid from the burette tip between each sample. 23. Wash the glassware and put away all liquids and equipment. Check the dates and amounts of all solutions used to ensure there are adequate unexpired chemicals for the next calibration activity. If not, inform the office staff immediately. Meter Samples 1. Place the bucket of prepared DI water in the sink 2. Record the time and take water temp, DO, and conductivity readings from the meter in the bucket as follows: 3. Place the probe in the bucket of DI water and allow the temperature to stabilize. 4. Wait for the readings to stabilize: DO sat ±.5% & Temp ± 0.1 for 30 sec., and then record the readings. 5. Remove probes. 6. Repeat for a second trial if necessary. 7. After all trials are done, rinse probe with DI water, shake off the probe and place back into the calibration cup. Post Winkler Meter Drift Check 1. Record time on data sheet under Post-sampling cal-. 2. Rinse the calibration cup with clean tap water; fill the cup with 1/8th in. of clean tap water. 3. Place unit into calibration cup, slightly tighten the calibration cup onto the bulkhead but do not fully tighten, allow for atmospheric venting. 4. Set the unit upright for 5-15 minutes and allow meters to stabilize: for 2 minutes, both DO% and Temp. ( C) remain within ± 0.1 of their initial readings. Record time, temp, and DO%. This text is in abeyance for now: Once you have finished calibrating the equipment, YOU are responsible for entering the new data into the database. Once the data has been entered, the database will automatically tell you if the instruments have passed their quality control criteria. Print this report and staple it to the front of the data sheet, 3-hole punch these pages and place them in the back of the calibration notebook behind the data sheet tab. Put the most recent data sheet on top. K:\Streamkeepers\Monitoring\Eqpt & supplies\calibration-maintenance\sops\ysi ProDSS maint-cal SOP's 17

18 MAINTENANCE When performing maintenance on the ProDSS and its sensors, follow the specified procedures in this section, which have been taken directly out of the manual, or it could void the warranty. For more information on the warranty, consult the manual. Handheld Unit, Cable, and Bulkhead The handheld unit, consisting of the screen, keypad, and the unit itself, can be cleaned with a wash cloth dampened with a mild solution of clean water and dish soap. DO NOT clean handheld unit, cable, or bulkhead if they are detached or the sensor ports are exposed (on bulkhead). If these connectors are exposed to any moisture the unit can be damaged and would not be covered under warranty. Sensor Guard For a quick cleaning of the sensor guard, use a cloth dampened with clean water and dish soap. To remove resistant dirt or heavy bio-fouling, soak the guard in a solution of clean water and dish soap and then scrub with a plastic scrub brush. For a stronger soak, use vinegar. DO NOT use a brush that could scratch the finish on the guard, DO NOT sand or polish the guard. Removal of the guard coating can affect turbidity data. Conductivity Sensor NOTE: Be careful when handling this sensor, the tip has a temperature sensor that is fragile. 1. Dip the cleaning brush from the maintenance kit in distilled or clean tap water, insert the brush at the top of the channels and sweep the brush back and forth times. 2. If heavy build up has occurred on the electrodes, use a mild solution of dish soap and clean water. If build up is still present, soak the sensor in white vinegar and then clean with the brush and a mild soap and water solution. 3. Rinse the sensor after cleaning. 4. Gently pat dry with Kimwipes and proceed to the Storage section below. ph Sensor NOTE: ph and ph/orp sensors require periodic maintenance to clear contamination from the sensing elements. These contaminants can slow sensor response time. Clean the sensors when deposits, bio-fouling or other contamination appears on the glass or when the sensor response time is noticeably slow. Try to avoid using deionized water when cleaning or storing (short term) the ph sensor, clean tap water will suffice. DO NOT physically scrub or swab the glass bulb, the bulbs are fragile and can break with a small amount of force. 1. Remove the sensor from the bulkhead and soak the end of the sensor in a mild solution of clean tap water and dish soap in a glass beaker. Soak for ~10 to 15 minutes. 2. After soaking, rinse with clean tap water and inspect the glass probe, if the probe is visibly clean then proceed to storage. 3. If the glass bulb appears to still be dirty, soak the sensor in 1 molar HCl for 30 to 60 minutes, if HCl is not available, use white vinegar. After soaking in HCl rinse with clean tap water, K:\Streamkeepers\Monitoring\Eqpt & supplies\calibration-maintenance\sops\ysi ProDSS maint-cal SOP's 18

19 then soak the sensor in clean tap water for 60 minutes, stir occasionally. 4. If dirt or bio-fouling is still present, soak the sensor in a 1:1 dilution of clean tap water and chlorine bleach for 60 minutes. Rinse the sensor with clean tap water; soak the sensor in clean tap water for 60 minutes. 5. Gently pat dry with Kimwipes and proceed to the Storage section below. Turbidity Sensor Clean the sensing window with a non-abrasive, lint-free cloth. Clean the window carefully to avoid scratches. If necessary, use a mild solution of dish soap and water. Gently pat dry with Kimwipes and proceed to the Storage section below. Dissolved Oxygen Sensor ODO sensor caps are warranted for 1 year but have a typical working life of 18 to 24 months. As the ODO sensor caps ages, large scratches in the paint/dye layer and changes in the dye layer can reduce measurement stability and response time. Periodically inspect the sensor cap for damage and large scratches in the paint/dye layer. Replace the cap when readings become unstable and cleaning the cap and DO recalibration do not remedy the symptoms. The sensor cap should be kept clean since some types of fouling may consume oxygen which could affect the dissolved oxygen measurements. To clean the sensor cap, gently wipe away any fouling with a lens cleaning tissue that has been moistened with water. NOTICE: Do not use organic solvents to clean the sensor cap. Using an organic solvent to clean the sensor cap may cause permanent damage to the cap. For example, alcohol will dissolve the outer paint layer and other organic solvents will likely dissolve the dye in the cap. Sensor Cap Replacement YSI recommends replacing the sensor cap once a year, but can last up to 2. It is VERY important to keep the instruction sheet that is shipped with the new sensor and cap, or a new replacement cap. Calibration coefficients are on the instruction sheet and must be loaded onto the ProDSS; keep the coefficients in case you need to reload them into the ProDSS. It is also important to keep the sensor cap in a 100% humid environment, the storage sections below instruct on how to keep the sensor under these conditions. If receiving a new cap, do not remove it from its shipping chamber until ready for installation. Replacing the DO Sensor Cap NOTE: Use extreme care to not damage the threads at the end of the sensor 1. Turn the old cap on the sensor counterclockwise and remove, do not use any hand tools to remove this cap as it could damage the sensor threads. If cap cannot be removed without a hand tool, a small pair of pliers can be used with care until the cap breaks loose. Never use the pliers on the sensor itself. 2. Remove and discard the old o-ring without using any tools, clean the threads with a clean lint-free cloth. 3. Inspect the new o-ring for any nicks, tears, or particles/contaminants. If the o-ring is compromised, discard and get a new one from the maintenance kit. 4. Install the new o-ring over the threads and into the o-ring groove, DO NOT twist the o-ring. 5. Skillfully apply a thin coat of Krytox to the o-ring only, if excess lubricant is applied to the threads or sensor body, gently wipe it off with a lint-free cloth. 6. Make sure the new sensor cap cavity is completely dry, then carefully finger-tighten the cap clockwise onto the sensor. The o-ring should be compressed between the sensor cap and body and not pinched. If the o-ring is pinched, discard and repeat the above steps with a new K:\Streamkeepers\Monitoring\Eqpt & supplies\calibration-maintenance\sops\ysi ProDSS maint-cal SOP's 19

20 o-ring. Do not over tighten the cap. After the new sensor cap has been successfully installed, the sensor cap coefficients must be updated on the ProDSS unit. You will need the instruction sheet that was shipped with the new sensor cap. Attach the sensor to the bulkhead; refer to the Sensor Installation section above for proper sensor installation techniques. Updating the ODO Sensor Cap Coefficients: 1. Select the probe button, then Setup, then ODO, then Sensor Cap Coefficients 2. Using the coefficient values from the instruction sheet, enter the coefficient # into the proper coefficient slot in the handheld. After all the coefficients have been entered, select Update Sensor Cap Coefficient. 3. Hit Yes on the prompt screen to override the old coefficient #s. After updating the Coefficients, the Serial # in the Sensor Cap menu will be updated automatically based on your entries. If errors are made in entering the Sensor Cap Coefficients, the instrument will block the update and an error message will appear on the display. If you see this error message, re-enter the coefficients and check them carefully for correct transcription from the Calibration Code Label prior to selecting Update Sensor Cap Coefficients. If you receive an error message after several entry attempts, contact YSI Technical Support for assistance ( ). Calibrate the sensor after cap replacement and coefficient update; refer to the DO Calibration section above. IF THE CAP EVER GETS DRIED OUT (left dry for longer than 8 hours), rehydrate the cap by soaking it in room temperature tap water for 24 hours. After the soak, recalibration the sensor. Installing a Port Plug 1. Apply a thin coat of Krytox o-ring lubricant to the o-rings on the plug port. 2. Remove any excess lubricant from the o-rings and port plug with a lint-free cloth. 3. Insert the port plug into the empty port and press until firmly seated. 4. Finger-tighten the port plug clockwise to install. If necessary, use the sensor installation tool to make sure that the plug is fully seated into the port. NOTICE: The o-rings will not be visible if a port plug is correctly installed. Do not overtighten the port plug. Over-tightening can cause damage K:\Streamkeepers\Monitoring\Eqpt & supplies\calibration-maintenance\sops\ysi ProDSS maint-cal SOP's 20