Instruction Sheet. Calibration of Multiple 1720 and FT660 Turbidimeters

Transcription

1 Instruction Sheet Calibration of Multiple 1720 and FT660 Turbidimeters Overview This instruction sheet describes the calibration of up to eight 1720C, 1720D, or 1720E turbidimeters, or up to three FilterTrak 660 (FT660) instruments with a single calibration standard. Additional instruments can be calibrated using fresh calibration standards. The calibration procedures in this instruction sheet are separated by instrument model. Highlight the calibration procedure pertaining to the instrument model to be calibrated. It is important to follow all instructions pertaining to cleaning equipment and preparing standards before calibrating instruments. Required Items Calibration Solutions StablCal Turbidity Standards are stabilized formazin standards that are recognized by the U.S.E.P.A. (U.S. Environmental Protection Agency) as primary standards for turbidity calibration. StablCal standards require no dilution or any preparation other than mixing. Use a StablCal Standard to minimize contamination and dilution errors that can occur when preparing a standard by dilution. StablCal Standards are manufactured with rigorous controls that provide extremely accurate calibration for low-level turbidity monitoring. The 20.0 NTU calibration standard for 1720 series turbidimeters can also be prepared from dilution of a well-mixed 4000 NTU stock solution. If the standard is prepared, two calibration cylinders must always be used; one for dilution water and one for the 20.0 NTU standard. The FilterTrak 660 laser nephelometers are calibrated with an 800 mntu (0.800 NTU) StablCal standard. Extra care must be taken to avoid contamination or evaporation of this standard during use. The 800 mntu standard cannot be prepared by dilution. The FT660 calibration requires a special calibration cylinder (different from the 1720 series calibration cylinder) that is designed to minimize stray light at very low NTU values. It is important that this calibration cylinder and 800 mntu standard only be used for calibration of FT660 instruments. Wash and Dilution Water Wash water is necessary to clean apparatus such as calibration cylinders before calibration. Dilution water is necessary when preparing standards by dilution. Prepare wash and dilution water by filtering through a 0.2 µm filter. Effluent water having turbidity below 0.05 NTU can also be used. Store dilution water in clean polyethylene containers or similar containers that will not contribute turbidity to the water. Item List using StablCal for 1720C and 1720D (V 2.1 or earlier) Obtain the items in Table 1 when calibrating a 1720C or 1720D (software version 2.1 or earlier) turbidimeter using StablCal standards. Table C and 1720D (V 2.1 or earlier) Calibration Items List Description Quantity/Calibration Unit Cat. No. Calibration Cylinder 2 each <0.1 NTU StablCal Standard Solution 1 L 1 L NTU StablCal 1 L 1 L Wash Water 3 L 3 L N/A Filter, 0.2 µm, for preparing wash water 1 10/pk

2 Item List using StablCal for 1720D (V 2.2 or later) and 1720E Obtain the items in Table 2 when calibrating a 1720D (software version 2.2 or later) or a 1720E turbidimeter using StablCal standards. Table D (V 2.2 or later) and 1720E Calibration Items List Description Quantity/Calibration Unit Cat. No. Calibration Cylinder 1 each NTU StablCal 1 L 1 L Wash Water 3 L 3 L N/A Filter, 0.2 µm, for preparing wash water 1 10/pk Item List using StablCal for FT660 Obtain the items in Table 3 when calibrating a FilterTrak 660 nephelometer using StablCal standards. Table 3 FT660 Calibration Items List Description Quantity/Calibration Unit Cat. No. Calibration Kit (800 mntu StablCal, calibration cylinder, dust cover) 1 each Wash Water 3 L 3 L N/A Filter, 0.2 µm, for preparing wash water 1 10/pk Cleaning the Turbidimeter Item List using Formazin Dilutions Obtain the items in Table 4 when using formazin dilutions for calibration of any 1720 series turbidimeter. Table 4 Dilution Calibration Items List Description Quantity/Calibration Unit Cat. No. Calibration Cylinder 2 each L Class A Volumetric Flask 2 each TenSette Pipet, 1 to 10 ml NTU Formazin Standard Solution 5 ml 500 ml Dilution/Wash Water 3 L 3 L N/A Filter, 0.2 µm, for preparing wash water 1 10/pk It is important to clean all instruments, materials and the surrounding area before calibration. Use a laboratory detergent such as Liqui-Nox (1 part detergent to 20 parts water) and a soft brush. Use wash water to rinse the turbidimeter body, bubble trap, detector, glassware, calibration cylinders, and containers. Be sure to: Clean the calibration cylinder(s) and the photodetector on each turbidimeter according to the instructions in the User Manual. Clean the turbidimeter body and bubble trap, even if they are not used for calibration. Use care in cleaning the photodetector. Use only a soft brush and use care to avoid scratching the surface of the detector. Perform a final rinse of all components with wash water. 2

3 Cleaning and Filling the Calibration Cylinder Prevent contamination of the turbidity standard after it is poured into the calibration cylinder by placing a dust-free cover over the cylinder when not in use. Keep the cover on the cylinder during transport between instruments. Using StablCal Turbidity Standards 1. Clean the calibration cylinder(s). Rinse the inside and outside of the cylinder with wash water. Place on a dust-free surface. Immediately proceed to the next step. 2. Rinse the outside of the StablCal Solution bottles with wash water. 3. Follow the mixing steps below for the standard(s): <0.1 NTU StablCal: DO NOT INVERT OR MIX. 800 mntu StablCal: Gently invert the 800 mntu StablCal bottle at least 50 times NTU StablCal: Gently invert the 20.0 NTU StablCal bottle at least 50 times. 4. Carefully remove the seal from the StablCal bottles and slowly pour the contents of the 20.0 NTU or 800 mntu StablCal into the calibration cylinder. Cover the cylinder with a dust-free material such as aluminum foil or plastic wrap. 5. If the <0.1 NTU StablCal Standard is required for the instrument model to be calibrated, slowly pour the contents of the <0.1 NTU Standard into the second calibration cylinder. Cover the cylinder with a dust-free material such as aluminum foil or plastic wrap. Preparing Formazin Dilutions 1. Clean the calibration cylinders and volumetric flasks. Rinse the inside and outside of the cylinder with wash water. Place on a dust-free surface. Immediately proceed to the next step. 2. Pour dilution water into a clean 1-liter Class A volumetric flask and fill to the 1-liter mark. 3. Slowly pour the entire contents of the flask into one of the clean calibration cylinders. Protect from contamination by covering with a dust-free material such as aluminum foil or plastic kitchen wrap. 4. Mix the 4000 NTU standard by inverting at least 50 to 100 times. 5. Pipet 5.0 ml of well-mixed 4000 NTU formazin standard into another clean 1-liter Class A volumetric flask. Dilute to the 1-liter mark with dilution water. Stopper and invert several times to mix. 6. Slowly pour the entire contents of this flask into one of the clean calibration cylinders. Protect from contamination by covering with a dust-free material such as aluminum foil or plastic wrap. 3

4 Calibrate the Turbidimeters 1720C Calibration Procedure The calibration procedure differs for each instrument model due to software differences. Ideally, refer to the respective User Manual for specific instructions regarding calibration of these instruments. The cleaning steps and filling of the calibration cylinder should be completed right before beginning the calibration procedure. Perform all turbidimeter calibrations concurrently and within one hour after opening the StablCal bottle. Discard the StablCal solution after calibration. Do not return the StablCal to the original container for reuse. Cover the calibration cylinders when transporting them between calibration sites. 1. Remove the cover from the cylinder containing the <0.1 NTU StablCal turbidity standard. Place the cleaned turbidimeter head into the cylinder. 2. Tap the side of the cylinder several times to dislodge any air bubbles. Wait 2 to 5 minutes. 3. On the 1720C Control Module, press SYS RESET. 4. Press 6, then SIG AVE. Wait for the reading to stabilize to a value less than 0.1 NTU. 5. Enter 0.0 and then press STD. 6. Remove the turbidimeter head from the cylinder. Tap the head a few times to remove any dripping water. 7. Remove the cover from the cylinder containing the 20.0 NTU turbidity standard. Use a stir rod to re-suspend this standard. Stir 20 to 30 times. Place the cleaned turbidimeter head into the cylinder. 8. Tap the side of the cylinder several times to dislodge any air bubbles. Wait one minute for the reading to stabilize. A stable reading is achieved when the measured value does not change by more than NTU for 30 seconds. 9. Enter 20.0 and then press STD. The calibration is complete. 10. Remove the sensor head, rinse, and return to the turbidimeter body. Return to the measurement mode. 11. Cover the calibration cylinders and immediately proceed to the next turbidimeter for calibration. When a total of eight turbidimeters have been calibrated, discard the calibration standards. Clean the calibration cylinders, obtain new StablCal Turbidity Standards, and continue with calibration until all turbidimeters have been calibrated. 1720D StablCal Calibration Procedure Using the Aquatrend Controller 1720D, Software Version V2.1 or Earlier: 1. Remove the cover from the cylinder containing the <0.1 NTU StablCal turbidity standard. Place the cleaned turbidimeter head into the cylinder. 2. Tap the side of the cylinder several times to dislodge any air bubbles. Wait 2 to 5 minutes. 4

5 3. On the Aquatrend Controller, press the MENU key. Select SENSOR MENU and press the ENTER key. 4. Select the sensor to be calibrated using the arrow keys and press ENTER. 5. Select CALIBRATION and press ENTER. 6. Select NORMAL CAL and press ENTER. The instrument will read the <0.1 NTU standard. When the reading is stable, press ENTER. A stable reading is achieved when the measured value does not change by more than NTU for 30 seconds. 7. Remove the cover from the cylinder containing the 20.0 NTU turbidity standard. Use a stir rod to re-suspend this standard. Stir 20 to 30 times. Place the cleaned turbidimeter head into the cylinder. 8. Tap the side of the cylinder several times to dislodge any air bubbles. 9. Use the arrow keys to enter Press ENTER. 10. Wait one minute for the reading to stabilize. 11. Press ENTER. The calibration is complete. Press DISPLAY to return to the measurement mode. 12. Remove the sensor head, rinse, and return to the turbidimeter body. 13. Cover the calibration cylinder and immediately proceed to the next turbidimeter for calibration. When a total of eight turbidimeters have been calibrated, discard the calibration standards. Clean the calibration cylinders, obtain new StablCal Turbidity Standards, and continue with calibration until all turbidimeters have been calibrated. 1720D, Software Version V2.2 or Later: 1. Remove the cover from the cylinder containing the 20.0 NTU turbidity standard. Use a stir rod to re-suspend this standard. Stir 20 to 30 times. Place the cleaned turbidimeter head into the cylinder. 2. Tap the side of the cylinder several times to dislodge any air bubbles. 3. On the Aquatrend Controller, press the MENU key. Select SENSOR MENU and press the ENTER key. 4. Select the sensor to be calibrated using the arrow keys and press ENTER. 5. Select CALIBRATION and press ENTER. 6. Select STABLCAL/COMPARATIVE CAL and press ENTER. The display will show ENTER CALIBRATION STANDARD VALUE. 7. Use the arrow keys to enter Press ENTER. 8. The instrument will read the standard. Wait one minute for the reading to stabilize. A stable reading is achieved when the measured value does not change by more than NTU for 30 seconds. 5

6 9. Press ENTER. The calibration is complete. Press ENTER to store the calibration. Remove the sensor head, rinse, and return to the turbidimeter body. Press DISPLAY to return to the measurement mode. 10. Cover the calibration cylinder and immediately proceed to the next turbidimeter for calibration. When a total of eight turbidimeters have been calibrated, discard the calibration standards. Clean the calibration cylinders, obtain new StablCal Turbidity Standards, and continue with calibration until all turbidimeters have been calibrated. 1720E and FT660 StablCal Calibration Procedure Using the sc100 Controller 1. On the sc100 Controller, press the MAIN MENU key. 2. Select SENSOR MENU and press the ENTER key. 3. Select the sensor to be calibrated using the arrow keys and press ENTER. 4. Select CALIBRATE and press ENTER. 5. Select STABLCAL CAL and press ENTER. 6. The display will show OUTPUT MODE. Use the ARROW keys to select ACTIVE, HOLD, or TRANSFER. Press ENTER. 7. Remove the cover from the cylinder containing the turbidity standard. Use a stir rod to re-suspend this standard. Stir 20 to 30 times. Place the cleaned turbidimeter head into the cylinder. 8. Tap the side of the cylinder several times to dislodge any air bubbles E: The display will show POUR 20 NTU STD INTO CYL/BODY. REPLACE HEAD. Press ENTER. Wait one minute for the reading to stabilize. FT660: Wait 5 minutes for stabilization. Press ENTER. Use the ARROW keys to adjust the displayed turbidity to match the assigned value on the 800 mntu bottle. Note: A stable reading is achieved when the measured value does not change by more than NTU for 30 seconds. 10. The display will show the turbidity reading. Press ENTER. 11. The display will show GOOD CAL! GAIN: X.XX ENTER TO CONTINUE. Press ENTER to store the calibration. 12. The display will show VERIFY CAL? Press EXIT. 13. Enter initials. Press ENTER. 14. Remove the sensor head, rinse, and return to the turbidimeter body. 15. Press the HOME key to return to the measurement mode. 16. Cover the calibration cylinder and immediately proceed to the next turbidimeter for calibration. 6

7 When a total of eight 1720 turbidimeters or three FT660 instruments have been calibrated, discard the calibration standards. Clean the calibration cylinders, obtain new StablCal Turbidity Standards, and continue with calibration until all turbidimeters have been calibrated. Calibration using a Dilute Formazin Standard When using a formazin dilution: Two calibration cylinders are always required for calibration, one for dilution water and the other for the 20.0 NTU formazin standard. 1720C and 1720D (V2.1 or earlier): the same calibration steps can be followed whether using a standard prepared through dilution or StablCal standards. 1720D (V2.2 or later): On the Aquatrend menu, select USER PREPARED CAL. 1720E: Select USER PREPD CAL on the sc100 menu and follow the instructions in the 1720E User Manual for User-prepared Calibration. Additional instructions are available in the User Manual for each turbidimeter under User Prepared Calibration. Calibration Verification If verification is to be performed after calibration, pour the mixed verification standard into a clean calibration cylinder. Rinse the turbidimeter sensor with dilution water prior to placing it into the verification standard. Read the value of the standard in the measurement mode. A correct value indicates that the turbidimeter is calibrated properly. General Information Note: The 1720E and FT660 instrument software includes a wet verification menu. Use of 20 NTU Turbidity Standard for 1720 Turbidimeter Calibrations When the sample water is of extremely low turbidity, it may appear advantageous to use a turbidity standard of extremely low NTU value for calibration of the 1720 series turbidimeters. There are several practical reasons why the 20 NTU standard should be used and why calibration using a standard less than 20 NTU is not recommended: Contamination is a significant concern at low turbidity levels. Any contamination in a low NTU turbidity standard during calibration or preparation would significantly alter the NTU value. However slight contamination would not significantly alter the value of a 20.0 NTU standard. The 1720 calibration cylinder allows stray light to reach the detector at very low NTU values. At 20.0 NTU, however, the light is effectively scattered before reaching the bottom and does not reflect back to the detector as an interference. A 20.0 NTU turbidity standard is easy to prepare and is stable long enough for accurate calibration. Contamination and bubble errors have less effect on the calibration accuracy at 20.0 NTU than at a lower NTU value. The calibration curve is linear from 0 to 40 NTU. Therefore, calibration at 20.0 NTU is valid in the ultra-low measurement range of 0 to 1 NTU. StablCal Storage Store standards between 0 and 25 C. Allow the standard to acclimate to ambient instrument conditions before use, not to exceed 40 C. StablCal can be frozen for short durations such as during shipment. Allow the standard to thaw at room temperature and mix well before use. 7

8 Do not transfer the standard from the calibration cylinder to another container for storage. Store standards away from direct sunlight. StablCal Use The 1-liter volume of StablCal in the bottle has been pre-measured. It is not necessary to measure this volume when transferring the standard into the calibration cylinder. The <0.1 NTU StablCal standard should never be mixed. The 800 mntu and 20.0 NTU turbidity standards remain in suspension for 30 to 60 minutes. After 30 minutes, gently swirl the cylinder or use a clean glass stir rod to re-suspend the polymer. Use care not to contaminate the standards. Never shake the standards. FOR TECHNICAL ASSISTANCE, PRICE INFORMATION AND ORDERING: In the U.S.A. Call toll-free Outside the U.S.A. Contact the HACH office or distributor serving you. On the Worldwide Web techhelp@hach.com HACH COMPANY WORLD HEADQUARTERS Telephone: (970) FAX: (970) Hach Company, All rights reserved. Printed in the U.S.A. jk September 2005 Edition 2