ATI
Q46UV UV254/Turbidity Monitor
Part 6 - Calibration
42
O&M Manual
Rev-D (11/19)
6.13 Cal Turbidity Zero
Adjustment of the turbidity measurement in the UVA/Turbidity sensor requires the use of distill
water for zero and a Formazin standard for span. To zero the sensor, proceed as follows. Note
that the procedures for turbidity zero and turbidity span are essentially the same as for UVA zero
and span adjustments.
1. Refer to Figure 9 on page 15. The 3-way valve supplied with the flowcell provides a convenient
port for draining the flowcell and introducing a calibration standard into the flowcell. As part of
the system, a 60 cc syringe and a short length of silicon tubing is provided for use in feeding
standard into the flowcell.
2. Prior to feeding zero solution, the flowcell must be drained. Turn the yellow valve handle so
that the OFF position is facing the sample inlet tube. This will stop sample flow and open the
side port. Allow water from the flowcell to drain out this port. Note that you may need to
disconnect the outlet tube for water to flow out of the open port.
3. With the syringe is a short length of tubing and a luer fitting that mates with the end of the
syringe. Place the end of the tube into a bottle of distilled water and pull the plunger back to fill
the syringe with 40-50 cc. Connect to the open side of the 3-way valve and depress the
plunger to fill the flowcell with distilled water. Pull the plunger back out to suck out the distilled
water and discard that first fill. Refill the syringe with fresh distilled water and fill the flowcell a
second time. (the first fill is meant to rinse out any contaminants that might remain in the
flowcell.)
4. Press Menu to access the Cal Menu. Press the
arrow to access “Cal NTU Zero”.
5. Press the Enter key and you will be prompted enter a zero value for turbidity. Since turbidity
values of exactly zero are only theoretical, enter a value of 00.04 NTU. Use the
key to adjust
the flashing digit and then use the
◄ key to move to the next digit. Press Enter and a “Wait”
message will appear. As with the UVA adjustments, this message will flash for 3-4 minutes.
6. Once the zero adjustment is complete, pull the syringe plunger back again to suck out the
distilled water or simply move the valve to the normal operate position and allow the standard
to flow to drain. If the outlet tube was disconnected, be sure to reconnect prior to turning on
flow. At this point, a span check or calibration can be done if desired.
6.14 Cal Turbidity Span
Adjustment of the turbidity measurement in the UVA/Turbidity sensor requires the use of a
turbidity standard. Formazin standards are commonly used. Standards less than 10 NTU are not
recommended. Standards from third party suppliers may be used for Q46 turbidity calibrations or
solutions are available from ATI.
Formazin turbidity standards can be prepared using reagent solutions available from ATI or other
lab supply companies. The chemicals required are Turbidity Standard 1 (Formazin Sulfate, 1%,
ATI #51-0052) and Turbidity Standard 2 (Hexamethylenetetramine, 10%, ATI #51-0053).
Stabilized turbidity standards available commercially may also be used for this purpose.
Mixing a turbidity standard takes 24 hours. First, place 5 cc. of Turbidity Standard 1 and 5 cc. of
Turbidity Standard 2 in a 100 cc volumetric flask. Allow to stand for 24 hours at about 25 C.
Then dilute to 100 cc. with distilled water. This will provide a stock solution with a turbidity value
of 400 NTU. This solution should be discarded after about 15 days.
