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pH METER CALIBRATION

Field Procedures 9thEdition, 2007

buffer differs with temperature, see thetable at the end of this protocol.]

7. Setting the midpoint:a. Press the ENTER key. The screen

will show CAL at the bottom,STAND will stop flashing and the pH

calibration value is shown with themiddle decimal point flashing.

b. When the meter decides the reading

is stable, the decimal point will stopflashing. Press and hold the ENTERkey until SAVE along with OFS isdisplayed and the display returns to

the main screen. SLOPE will nowappear on the display and beflashing. This indicates that the slopeis ready to be set using the secondpH buffer. Take the probe out of thepH 7 buffer solution and cap thebottle.

8. Setting the upper point:

a. Rinse the probe with purified water,then carefully dry the probe. Put thepH 10 buffer bottle into the foamholder and insert the probe into it,making sure the temperature sensoris immersed (top up if necessary).

b. Press ENTER. The screen will nowshow CAL at the bottom, SLOPEwill stop flashing, and the pH valuefor the pH 10 buffer is shown withthe right decimal point flashing.

c. When the reading is stable, the decimalpoint will stop flashing. Press and hold

ENTER until SAVE flashes on thedisplay along with SLP to indicate thesecond slope value has been saved.

9. [Special situations on ly; seeintroduction to this protocol:][Settingthe lower point:a. Rinse the probe with purified water,

then carefully dry the probe. Put the pH4 buffer bottle into the foam holder andinsert the probe into it, making sure thetemperature sensor is immersed.

b. Press ENTER. The screen will nowshow CAL at the bottom, SLOPE willstop flashing, and the pH 4 buffer valueis shown with the left decimal pointflashing.

c. When the reading stabilizes, the decimalpoint will stop flashing. Press and hold

ENTER to save the first slope untilSAVE is displayed along with SLP,and you return to a normal screen.]

10.Take out the probe and cap the buffer

bottle. The meter is now calibrated at 2 [or3] points.

(see next pages)

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pH METER CALIBRATION

Field Procedures 9thEdition, 2007

Removing the pH probe from its long-term buffer storage bottle: If you findthe pH probe stored in its long-term bufferstorage bottle, please follow the steps belowto remove it:

1. Remove the closed cap from the Velcro

at the bottom of the bottle.2. Holding the bottle upright, unscrew it

from the cap with the hole (open cap)and screw the closed cap onto it.

3. Rinse the probe and open cap withdistilled water.

4. Slide the open cap toward the cord toexpose the O-ring beneath the cap. Rolloff the O-ring, then slide the open capoff the end of the probe.

5.

Smush the O-ring into the Velcro at thebottom as you press the open cap into it.Thus, the bottle, both caps, and O-ringare all stored together in a single

package.6. Remove the tape thats covering the

probe chamber on the side of the meter,being careful not to lose the little spongethats inside.

7. Make sure that the little sponge is insidethe chamber, and add a few drops ofpurified water to moisten it.

pH Buffer Values at Various Temperatures (YSI 2002)

Temperature pH 4 pH 7 pH 10

0C 4.01 7.13 10.34

5C 4.00 7.10 10.26

10C 4.00 7.07 10.19

15C 4.00 7.05 10.12

20C 4.00 7.02 10.06

25C 4.01 7.00 10.00

30C 4.01 6.99 9.9435C 4.02 6.98 9.90

buffer

probe

cap withhole

closed cap

velcro

velcro O-ring

under

cap

Switch

these caps

when you

remove the

bottle from

the probe