What are the steps to calibrate the Solitax sc sensor for turbidity or suspended solids?

Document ID

Document ID TE2323

Version

Version 5.0

Status

Status Published

Published Date

Published Date 04/18/2019
Question
What are the steps to calibrate the Solitax sc sensor for turbidity or suspended solids?
Summary
Solitax sc and calibrating for turbidity or suspended solids
Answer
Turbidity calibration requires the use of two 800 NTU turbidity standard solutions and a calibration kit.  A zero point calibration using deionized water is also recommended.
  1. Place the sensor in the calibration cylinder with deionized water, mounting it with the supplied clamp. The tip of the probe should be approximately 1-inch below the surface of the water
  2. Press the Menu button > select the sensor (if more than one) > calibrate > sensor measure. This display shows a live reading. Record the reading.
  3. Press"back" to return to the calibrate menu. Go to the Offset Menu. Multiply the reading obtained in #2 by -1, and enter that value here. For example, if the reading obtained in #2 was 10 NTU, you would enter -10. Press "enter" to save this value.
  4. Gently invert both Stablcal standard bottles a minimum of 50 times. Remove the lid and seal from each bottle. To avoid creating bubbles, slowly pour the contents of both bottles into the calibration cylinder. Immediately place the tip of the probe into the positioning bracket in the calibration cylinder. The tip of the probe should be approximately 1-inch below the surface of the standard.
  5. Scroll up to the"Sensor Measure" menu again. Allow the reading to become stable on the "Sensor measure screen". Record the value. This will be referred to as the "measured value" below.
  6. Calculate the factor: New Factor = 800 NTU Standard / measured value
  7. For example, if a sample measures 750 NTU using the sensor and the standard is 800 NTU, the new factor would be calculated as: New Factor = 800 / 750 = 1.07
  8. Go to the main menu > sensor set up > calibrate > factor menu and enter the factor. Then press enter. Go home to see the corrected measurement. The sensor is now calibrated.
Suspended solids calibration requires calibration to the customer's actual sample. This optimizes the compensation for particle size and shape typical at a measuring site. Calibration is best performed by mounting the sensor as usual for normal measurement, and then collecting grab samples to be evaluated by laboratory methods. While a single point calibration is usually sufficient to provide excellent accuracy, the Solitax does offer the ability to calibrate with up to 5 calibration points.
  1. Press the"Menu" button > select the sensor (if more than one) > calibrate > configure. Choose the number of points desired for calibration. Select "factor" for a single point calibration.
  2. Mount the sensor as it will be during normal operation.
  3. Press sensor measure. This display gives you a live reading uncorrected by response time or existing calibration settings. Record this reading.
  4. Immediately take a grab sample. Determine the total suspended solids using a gravimetric method such as Method 2540 D in Standard Methods for the Examination of Water and Wastewater
  5. If doing a single point "Factor" calibration, calculate the new factor: New Factor = Determined gravimetric value / measured value
    • For example, if a sample measures 23 mg/L using the Solitax sensor and the gravimetric value was 20 mg/L, the new factor would be calculated as: New Factor = 20 / 23 = 0.86 mg/L
  6. Go to the main menu > sensor set up > calibrate > factor menu and enter the factor. Then press enter. Go home to see the corrected measurement. The sensor is now calibrated.
If doing a multi-point calibration, repeat steps 3-6 at different times to obtain different measurements. Then, enter the menu "2 point" or other point menu. Within this menu, enter your pairs of values for each reading, the target value being the laboratory determined value, and the actual value being the reading that the Solitax produced in step 4. The pairs should be entered in order from lowest to highest values. The sensor is now calibrated. Press "Home" to see the corrected measurement.