ATI
Q46UV UV254/Turbidity Monitor
Part 6 - Calibration
43
O&M Manual
Rev-D (11/19)
Stock turbidity solution of 4000 NTU is also available from ATI (part #51-0077). This stock
solution is good for 1 year and may be diluted to 20 NTU for calibration. A 1 liter volumetric flask
and an accurate 5 ml. pipette should be used for dilution of the 4000 NTU standard.
To set the span of the turbidity monitor, dilute the 4000 NTU stock solution by 200:1 to give you a
20 NTU standard or dilute the 400 NTU standard by 20:1. Once your standard is prepared,
proceed as follows.
1. Refer to Figure 9 on page 16. 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 18” of silicon tubing is provided for use in
feeding standard into the flowcell.
2. Prior to feeding calibration 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 Turbidity standard solution. Turbidity
standard may be a third party solution or it may be Formazin standards prepared using ATI
supplied solutions. 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.
4. Allow the sensor to sit in the Turbidity standard for 5 minutes to get a stable reading. Once a
stable reading is displayed, press the Menu key
to get to the CAL menu. Use the ▲ key to
access “Cal NTU”.
5. Press Enter and you will be prompted to enter the value of the standard you are using for
calibration. Enter either the value of your third party standard or the value from your ATI
calibration solution. Use the
▲ key to adjust the flashing digit and the ◄ key to move to the
next digit.
6.
Press the Enter key and the message “Wait” will flash. Note that the message will flash for 3-
4 minutes while the sensor makes all of its internal adjustments. If the sensor is not able to
adjust to the value entered, a “Cal Fail” message will appear and the “Fail” icon on the display
will light up.
7. Once the span adjustment is complete, pull the syringe plunger back again to suck out the
standard 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.
6.3
Temperature Calibration
The temperature calibration sequence is essentially a 1-point offset calibration that allows
adjustments of approximately ± 5°C.
The sensor temperature may be calibrated on line, or the sensor can be removed from the
process and placed into a known solution temperature reference. In any case, it is critical that the
sensor be allowed to reach temperature equilibrium with the solution in order to provide the
highest accuracy. When moving the sensor between widely different temperature conditions, it
may be necessary to allow the sensor to stabilize as much as one hour before the calibration
sequence is initiated. If the sensor is on-line, the user may want to set the output HOLD feature
prior to calibration to lock out any output fluctuations.
