16804212 Calibration Guidelines

7/29/2019 16804212 Calibration Guidelines

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Calibration Guidelines

pH Meter

Introduction:

You can calibrate the pH meter for three pH levels, but pH7 is most important. If youhave limited time and/or resources, its OK if you just test for pH7 only. If you are testing

all three solutions, test pH7 first, and then pH4 and pH10 in any order following. It is best

to calibrate the pH meter(s) up to 24-48 hours before the water monitoring event, or less.Record your calibration on the provided sheet for pH7 only, not pH4 or pH10. Check for

a BAT symbol flashing on the pH meter, which indicates low batteries. Be sure to

record low batteries on the calibration sheet, and notify a San Diego Coastkeeper water

monitoring staff member. Be aware that the meters will automatically turn off after 3-5min. as a battery saving precaution, so dont leave the meter sitting for more than 5 min.

or it will turn off.

Materials:pH meters you wish to calibrate

Calibration solutions pH4, pH7 & pH10Three 80mL beakers fill with enough calibration solution to submerge the instruments

electrodes

De-ionized DI H2O for rinsing electrodes

Step-by-Step Instructions:

1) Pour the pH7 calibration solution into an 80mL beaker. You want to be able tosubmerge the entire electrode, so be sure to pour enough to make this possible,

but not so much that there is a lot of excess so we dont waste calibration solution.2) Rinse the electrode with DI H2O and gently shake off excess H2O.3) Insert the pH meter into the pH7 calibration solution, deep enough so the entire

electrode is submerged.

4) Swirl the electrode for a few seconds, and then leave still in the solution for up to2 minutes.

5) Wait until the pH value stops fluxuating and settles on one value; record that

value on the calibration sheet under current reading.

6) Now, you are ready to calibrate. Press and release the CAL button. On thepHTestr3 instruments, the value will start to blink, however on the pHTestr30

instruments the value does not blink. Once settled, press the HOLD button.

7) The value will settle at the calibrated value, which should take no longer than 30seconds. [The pH meter will automatically settle at the pH value closest to the

pre-calibration value. Ex: If the pre-calibration value was 7.25, the pH meter

should calibrate to 7.00, or something very close to that. is this correct? Or is it

] The value should then read 7.00.

8) Record the value after calibration on the provided sheet under reading after

calibration, even if its not exactly 7.00. You only have to record the pre and postcalibration values for the pH7 calibration, not the subsequent pH4 and pH10

San Diego Coastkeeper Calibration Guidelines, courtesy of SDSU 1


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calibrations.

9) Its a good idea to check the calibrated reading again. It should read the exact

same calibrated value, even if the calibrated value wasnt exactly 7.00.10) If the up/down fluxuation is 1.0 or greater (ex: reading 1 = 7.5; reading 2 = 6.4),

recalibrate. If the problem persists, record in the notes, dont use the pH meter and

notify a San Diego Coastkeeper water monitoring staff member.11) Rinse with DI H2O if continuing the calibration process with the pH4 and pH10

calibration solutions and follow the same procedure you did for calibrating pH7.

12) Now that the pH meter is calibrated, you need to complete a control chart. To dothis, you will record the pH level of the same solution (use the pH7 calibration

solution to complete these tests because its a known value) seven times. Be sure

to rinse the electrode with DI H2O in between each reading. Once this procedure

is complete, plot your results on the provided charts (pH values on the Y axis,reading number on the X axis). This will help us see if the pH meter is taking

accurate readings, or if it needs to be replaced. If the readings are going up and

down slightly each time (a horizontal zigzag), that is optimal. If the readings are

going consistently up or down from readings 1 to 7, the pH meter needs to be re-calibrated. If the problem persists you should not use the pH meter, as it probably

needs to be replaced. You do notneed to complete a control chart for pH4 orpH10, only pH7.

13) Once calibration is complete, store the electrode damp. To do this, rinse the

electrode with DI H2O, gently shake the excess H2O off and cap to store. If

necessary, you can wipe the pH meter with a cloth, but do not touch the electrodewith the cloth. Storing the electrode wet helps to keep the circuit closed and

prolong the pH meters life and accuracy.

Clean-up:

You can safely pour all pH calibration solutions down the sink drain; they are not

hazardous.

Return the pH calibration solutions and DI H2O squeeze bottle(s) to the appropriate

cabinet for storage.

Wash all beakers and dry on the drying rack; return to the appropriate cabinet once dry

for storage.

Make sure all calibrated pH meters are turned off and put in the correct monitoring

box(es), or stored all together and clearly dated and labeled calibrated.

Make sure youve filled out all the fields on the calibration sheet and return to the

clipboard on the wall to the right of the sink.

Conductivity Meter



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Introduction:

You can calibrate the conductivity meters for up to 3 standards, but we only calibrate 1standard (1,413). You should change the calibration solution after every 5 instruments

calibrated. It is best to calibrate the conductivity meters on the same day as the water

monitoring event, or at least within 24 hours.

Materials:

Conductivity meters you wish to calibrateTraceable Conductivity Calibration Standard Solution (1,413)

One 80mL beaker fill with enough calibration solution to submerge the instruments

electrodes

De-ionized DI H2O for rinsing electrodes


1) Rinse electrode with DI H2O and gently shake off excess H2O, you can gently

towel off the excess water if needed just dont towel off the electrodes.2) Turn on the instrument and insert the Conductivity meter into the calibration

solution, deep enough so the entire electrode is submerged.3) Swirl the electrode for a few seconds, and then leave still in the solution for up to

2 minutes.

4) Wait until the conductivity value stops fluxuating and settles on one value; record

that value on the calibration sheet under reading before calibration.5) Hold down the CAL button for a few seconds and release. It will immediately

start blinking 1,413 a few times, and then will settle on the actual calibrated

value.6) Record the value after calibration on the provided sheet under reading after

calibration, it should be exactly 1,413.

7) Now that the conductivity meter is calibrated, you need to complete a controlchart. To do this, you will record the conductivity level of the same solution (use

the same calibration solution you calibrated the conductivity meter with) seven

times. Be sure to rinse the electrode with DI H2O in between each reading. Youcan test in the same solution because you are testing the same instrument. Once

this procedure is complete, plot your results on the provided charts (conductivity

values on the Y axis, reading number on the X axis). This will help us see if the

conductivity meter is taking accurate readings, or if it needs to be replaced. If thereadings are going up and down slightly each time (a horizontal zigzag), that is

optimal. If the readings are going consistently up or down from readings 1 to 7,

the conductivity meter needs to be re-calibrated. If the problem persists, youshould not use the conductivity meter, as it probably needs to be replaced.

8) A 5% swing on either side of 1,413 is generally bad and should be recorded in the

notes section of the calibration sheet. However, you will likely see a swing greaterthan that on the control chart (around 10-15%), as the conductivity meters are

highly variable. Still make a note of it on the calibration sheet.

9) Once calibration is complete, store the electrode damp. To do this, you do not

need to rinse the electrode with DI H2O, simply take out of the calibration



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solutions and gently shake the excess solution off and cap to store. If necessary,

you can wipe the conductivity meter with a cloth, but do not touch the electrode

with the cloth. Storing the electrode wet helps to keep the circuit closed andprolong the conductivity meters life and accuracy.

Clean-up:You can safely pour the Traceable Conductivity Calibration Standard Solution down the

sink drain; it is not hazardous.

Return the Traceable Conductivity Calibration Standard Solution and DI H2O squeeze

bottle(s) to the appropriate cabinet for storage.

Wash all beakers and dry on the drying rack; return to the appropriate cabinet once dryfor storage.

Make sure all calibrated conductivity meters are put in the correct monitoring box(es), or

stored all together and clearly dated and labeled calibrated.

Make sure youve filled out all the fields on the calibration sheet and return to theclipboard on the wall to the right of the sink.

Dissolved Oxygen Meter



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Introduction:

This meter reads dissolved oxygen (DO) in solution, or the oxygen in the air. The DO

in natural/healthy spring water is usually around 8 or 9 (the value is variable dependingon several conditions such as aeration, bacteria levels, etc.), and the oxygen in air (20.9

moles per liter). Therefore, we calibrate using the air because its a known value. Its

important to look for indicators that the membrane may need to be replaced, or the probetip is cracked/broken. Those indicators are 1) if the value doesnt settle on one particular

value when trying to calibrate and 2) if the value is reading 0 when trying to calibrate

or test. You can also check the probe tip each time you calibrate or use it to look forcracks. Be sure to mark this on the calibration sheet and notify a San Diego Coastkeeper

water monitoring staff member. It is best to calibrate in an open, well aerated/circulated

room 24-48 hours before the water monitoring event, or less.

Materials:

DO meters you wish to calibrate

New membranes (only if you need to change the membranes should only be performed

by a San Diego Coastkeeper water monitoring staff member)


1) Make sure the DO meter is reading O2, not mg/L. This will allow you to

calibrate using air.

2) Without attaching the probe, turn the meter on. It should read 0.

3) Plug in the probe and take off the cap. Be very careful to remove the cap gently,easing off from the bottom of the cap. Never pull from the top or twist, which are

the motions that tend to break the membrane and/or crack the probe tip. Leave

probe open to the air in the room for a few minutes (can prop up on something tokeep the DO meter stable) until the value settles on one value.

4) Once the value is stable, press the Ox Cal button and release to calibrate.

5) You do not need to complete a control chart, or fill out the calibration sheet. Youdo need to check off and date the calibration event on the checklist provided to

record that the calibration was completed.

6) Once the calibration is complete, turn off the DO meter. Be sure to change thereading units to mg/L to set the DO meter to test water during the upcoming

water monitoring event.

7) Unplug probe before storing.

Clean-up:

Make sure all calibrated DO meters are put in the correct monitoring box(es), or stored all

together and clearly dated and labeled calibrated.

Make sure youve completed the calibration checklist and return to the clipboard on the

wall to the right of the sink.

Return the membranes to the appropriate cabinet if necessary.


16804212 Calibration Guidelines

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