1. Remove the four Phillips screws from the back of the ChemTester and lift off the back cover.

2. Carefully remove battery from battery holder but leave the battery attached to the battery terminals.

3. Remove the four Phillips screws from each corner of the green circuit board.

4. Remove the circuit board from the case by pulling firmly on the black sample well until the board comes loose from the case. (The black holding ring will come off the front of the unit).

5. Detach one of the battery terminals from the battery but leave the other terminal connected. (It doesn't matter which one).

6. You can now swivel the battery terminal connector and touch the battery terminal to activate the unit.

7. Hold down the left black square switch and swivel the loose battery connector until it contacts the battery terminal.

8. The display will now read "430 nm" and a number. (Note: If you get a row of rectangles, repeat step 7).

9. Push the right switch two times. The lower number is the calibration number and should read "120". (If it reads "120", skip to step 11). NOTE: FOR THE CM-600-AS1 TURBIDOMETER, SKIP TO STEP 11.

10. If it doesn't read "120", insert a small screwdriver into the left yellow POT (potentiometer) and turn slowly to adjust the number to 120. If the numbers drift during this adjustment, there is too much light on the underside of the circuit board. Cover the underside with a towel before adjusting and the numbers should not drift.

11. Press the left button three times to read "565 nm Value".

12. Press the right button one time to read "565 nm" and a number below it. If it reads 120 skip to step 14.

13. Turn the right yellow POT to adjust the number to 120.

14. Calibration is complete. Reconnect the battery clip. The meter should self-test and display the Ammonia Test. If it does not reboot, disconnect the battery clip and attach it again.

15. Reassemble the colorimeter by repeating steps 1 to 4 in reverse order. Replace holding ring on front of unit.