Sondes
Section
2
YSI Incorporated
Drinking Water Monitoring Systems Operations Manual
2-34
TURBIDITY 2-POINT
Select
Optic T (or Optic C) –Turbidity-6136
from the Calibrate Menu and then
2-2-Point
.
NOTE:
Before calibrating your 6136 turbidity sensor, pay particular attention to the following cautions:
•
To properly calibrate YSI turbidity sensors, you MUST use standards that have been prepared
according to details in
Standard Methods for the Treatment of Water and Wastewater (Section 2130 B)
.
Acceptable standards include (a) formazin prepared according to
Standard Methods
; (b) dilutions of
4000 NTU formazin concentrate purchased from Hach; (c) Hach StablCal
TM
standards in various NTU
denominations; and (d) AMCO-AEPA standards prepared specifically for the 6026 and 6136 by either
YSI or approved vendors who are listed on the YSI website (www.ysi.com). STANDARDS FROM
OTHER VENDORS ARE
NOT
APPROVED FOR THE YSI TURBIDITY SYSTEM AND THEIR
USE WILL LIKELY RESULT IN BOTH CALIBRATION ERRORS AND INCORRECT FIELD
READINGS.
•
For AMCO-AEPA standards, the value entered by the user during the calibration protocol is
DIFFERENT depending on which sensor (6026 or 6136) is being calibrated. This reflects the
empirically determined fact that 6026 and 6136 sensors that have been calibrated to the same value in
the primary standard formazin, will have different responses in suspensions of the AEPA-AMCO
beads.
This effect is likely due to the larger optical cell volume of the 6136.
Thus, for example, the
label of the YSI 6073 turbidity standard bottle indicates that the value of the standard is
100 NTU
when used for calibration of the 6026 sensor, but 123 NTU when used to calibrate the 6136.
Note that the phenomenon of a sensor-specific formazin/AEPA-AMCO ratio is well known for sensors
other than the 6026 and 6136.
•
When calibrating a 6136 turbidity sensor you MUST use either a modified calibration cup arrangement, an
extended length calibration cup or laboratory glassware with the probe guard installed for the calibration.
See section 2.6.1 above for details. Failure to carry out the calibration properly can result in inaccurate
readings, particularly water of very low turbidity.
•
Before proceeding with the calibration, be certain that the probe compartment of the sonde has been
cleaned and is free of debris. Solid particles from this source, particularly those carried over from past
deployments, will contaminate the standards during your calibration protocol and cause either
calibration errors and/or inaccurate field data.
•
One standard must be 0 NTU, and this standard must be calibrated first.
To begin the calibration, place the correct amount (see Tables 1-5) of 0 NTU standard (clear deionized or
distilled water) into the calibration cup provided with your sonde. Immerse the sonde in the water
.
Input
the value 0 NTU at the prompt, and press
Enter
. The screen will display real-time readings that will allow
you to determine when the readings have stabilized. Activate the wiper 1-2 times by pressing
3-Clean
Optics
as shown on the screen, to remove any bubbles. After stabilization is complete, press
Enter
to
“confirm” the first calibration and then, as instructed, press
Enter
to continue.
Dry the sonde carefully and then place the sonde in the second turbidity standard (100 NTU is
suggested) using the same container as for the 0 NTU standard. Input the correct turbidity value in
NTU, press
Enter
, and view the stabilization of the values on the screen in real-time. As above,
activate the wiper with the “3” key or manually rotate the sonde to remove bubbles. After the
readings have stabilized, press
Enter
to confirm the calibration and then press
Enter
to return to the
Calibrate menu.
NOTE CAREFULLY:
If you are calibrating a 6136 turbidity sensor you MUST use either a modified
calibration cup arrangement or laboratory glassware with the probe guard installed for the calibration. See
