38
6.
Repeat Step 5 until the desired
amount of turbidity-free water has
been collected.
TESTING TIPS
1.
Samples should be collected in a clean glass or polyethylene container.
2.
Samples should be analyzed as soon as possible after collection.
3.
Gently mix sample by inverting before taking a reading but avoid introducing air
bubbles.
4.
For the most precise results, follow the recommended procedure for wiping a fi lled
tube before placing it in the meter chamber. Invert tube very slowly and gently three
times to mix the sample. Surround the tube with a clean, lint-free cloth. Press the
cloth around the tube. Rotate the tube in the cloth three times to assure that all areas
of the tube have been wiped. Place tubes in the chamber with the same orientation
each time.
5.
Discard tubes that have signifi cant scratches and imperfections in the light pass
zones. (Central zone between bottom and fi ll line).
6.
When reading very low turbidity samples, do not use tubes or caps that have been
used previously with high turbidity samples.
7.
Use the averaging option for low level measurements of turbidity.
8.
The meter should be placed on a surface that is free from vibrations. Vibrations can
cause high readings.
9.
Turbidity readings will be aff ected by electric fi elds around motors.
10. Carbon in the sample will absorb light and cause low readings.
11. Excessive color in a sample will absorb light and cause low readings. The user should
verify if a certain level of color will cause a signifi cant error at the level of turbidity
being tested. Use of the Ratiometric calibration curve is recommended for highly
colored samples.
12. Observe shelf life recommendations for turbidity standards.
13. Do not use silicone oil on tubes when testing turbidity with the
2020t/i.
14. When testing at low concentrations use the same tube for the blank and the sample.
15. Always insert tube into the meter chamber with the same amount of pressure and to
the same depth.
16. Occasionally clean the chamber with a damp lint-free wipe, followed by a Windex
®
dampened wipe. A clean chamber and tubes are essential for reliable results.
17. For the greatest accuracy during the calibration procedure, be sure that after the
meter is blanked and the blank is scanned as a sample, the reading is 0.00. If not,
reblank the meter and scan the blank again until it reads 0.00. When scanning the
calibration standards as the sample, scan the calibration standard three times
removing the tube from the chamber after each scan. The readings should be
