YSI 6 series User Manual page 51

Sondes
CALIBRATION TIP: Exposure to the high ionic content of pH buffers can cause a significant, but
temporary, drift in these ISE probes (ammonium, nitrate and chloride probes). Therefore, when calibrating
the pH probe, YSI recommends that you use one of the following methods to minimize errors in the
subsequent readings:
 Calibrate pH first, immersing all of the probes in the pH buffers. After calibrating pH, place the
probes in 100 mg/L nitrate or ammonium standard or 1000 mg/L chloride standard and monitor the
reading. Usually, the reading starts low and may take as long as 30 minutes to reach a stable value.
When it does, proceed with the calibration.
 When calibrating pH, remove ISE modules from the sonde bulkhead and plug the ports. After pH
calibration is complete, replace the ISE sensors and proceed with their calibration with no stabilization
delay.
TURBIDITY 2-POINT
Select Optic X –Turbidity-6136 or Optic X – Turbidity 6026 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
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 YSI turbidity sensor (Legacy 6026 or Current 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 126 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 carefully follow the instructions found above in
Section 2.6.1 to avoid interference from the bottom of the calibration cup. 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 1-8 above) of 0 NTU standard (clear
deionized or distilled water) into the calibration cup provided with your sonde. Immerse the sonde in the
YSI Incorporated Environmental Monitoring Systems Operations Manual
Section 2
TM
standards in various NTU
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