40
4.5.2
S
TANDARDIZE
Leave the sensor in the process solution or in the air, take a grab sample from the process and determine the
dissolved oxygen concentration or enter the temperature and pressure corrected value for air.
Action
Prompt
Double Press any Button
MENU HOME, Hold is OFF
Press HOLD
Hold freezes 4-20 mA Output and locks Alarm Relays during Calibration
Press CAL
Place Sensor in Air or with the sensor in the process solution
Press STAND
Enter Value
Press
▲
▼
NEXT
xx.xx ppm or % SAT (use arrows and NEXT to enter process value)
Press OK
xx.xx ppm, Accept Value?
Press YES
CALIBRATING, SAVING CAL, CURRENT VALUE: x.xx ppm, DESIRED VALUE: x.xx
ppm, OFFSET xxx ppb or ppm
Press OK
Back to Cal Menu
Press HOME
Hold is ON (Press HOLD to turn off Hold)
Press HOLD
Turn off Hold
Press EXIT
Main Display
4.6
TRITON®
TR6
T
URBIDITY
/S
USPENDED
S
OLIDS
S
ENSOR
The TRITON® TR6 turbidity sensors are dual range sensors available in four different ranges. The TR6 turbidity
sensors have a non-linear output. The calculation of the turbidity is accomplished using a 2
nd
order polynomial of
the millivolt output, NTU = ax
2
+ bx + c, where x = millivolt output of the sensor. A three point calibration is
required to define the shape of the curve. The Model T80 turbidity analyzer was calibrated at the factory before
shipment in three Formazine solutions using the values listed below. The calibration was performed with the
three solutions specific for the NTU range of the sensor ordered.
Changing the range of the sensor (Hi to Low or Low to Hi) or changing the measurement unit will require a new
three point calibration. The calibration points for the three point calibration are 0%, 50% and 100% of the
measurement range, NTU, FNU, ppm, mg/L or % Solids. Calibrations of NTU or FNU can be made with formazine
solutions diluted from the 4000 NTU stock solution to the values listed in the table below. Calibrations of ppm,
mg/L, and % Solids require the actual process solutions to be used for the calibration. The 100% solution for the
ppm, mg/L and % solids should be near the high point of the measurement, it does not need to be the maximum
value but it should be in the upper range of the measurement. The value of the solution must be known or
determined by another method such as a grab sample and laboratory measurement. Then make the 50%
solution from 1 part of the high sample to one part deionized water, its value is half of the high value and finally
use deionized water for the 0% solution.
Calibrations should be performed in a vessel with similar characteristics to the actual process installation. Black
plastic containers work best, minimizing reflectance problems in lower NTU solutions. ECD offers a TRITON® TR6
Turbidity Calibration Kit that includes a TR6 Calibration Cup, 250 ml, 100 ml and 50 ml graduated cylinders and a
1 liter volumetric flask. The kit provides the necessary laboratory equipment to make calibration standards from
a 4000 NTU formazine stock solution and an easy to use calibration cup. This kit is ideal for calibration of inline
pipe mounted TR6 turbidity sensors.
Example of a mg/L Calibration: The process solution ranges around 3000 mg/L. A 2 liter sample was taken from
the process and tested, it was determined to be 2850 mg/L. Keep one liter of the 2850 mg/L solution for the
(100%) solution calibration and mix 500 mls of the 100% solution with 500 mls of deionized water, making the
