Turbidity Sensors

We have turbidity sensors permanently mounted at each laboratory workstation for use in pilot scale drinking water treatment plants. The turbidity sensors were acquired with a generous educational discount from hfscientific. The operators manual is available online.

The turbidimeters can transmit data to the computer using a serial communication cable. The turbidimeters use a RS 485 protocol and the computers use a RS232 protocol. We use a serial converter to facilitate communication between the two serial protocols. This converter should be plugged directly into the serial port on the back of the computer.

To acquire data using the Process Controller software you will need to configure a set point as a variable and then load a piece of external code that acquires data from the turbidimeter. Here are the steps

  1. Open Process Controller software
  2. GO to the Configuration tab
  3. Click on the "Edit Rules" icon
  4. Click on the last set point in the "Set points and variables list".
  5. Click on "Add set point after"
  6. Type "turbidity unit ID" in the name box of the new set point
  7. Enter "1" in the value of the new set point (this is the default ID number of the turbidimeters). The only reason to change this is if multiple units are connected together for communication across a single serial port.
  8. Click on "Add set point after"
  9. Type "turbidity meter" in the name field of the new set point
  10. Type "NTU" in the unit field
  11. Select Variable as the type
  12. click on the file browse icon to find the external code in enviro\Software\Process Controller methods\HF turbidimeter\HF turbidimeter (com2).vi
  13. Note that the code is specific for the communication port that the turbidimeter is connected to. Select the version that corresponds to the port you are using.
  14. In the selected set points select the turbidity unit ID.
  15. The turbidity should display in the value field. A value of -999 signifies that the function was unable to get a valid reading from the turbidimeter. If that occurs it may be because the unit ID is not 1 or because it is connected to a different serial port. And, of course, you could verify that the turbidimeter is on and is displaying the turbidity on its screen.

The turbidity data will be logged to file (if you have enabled datalogging) and it is also available for viewing in the graph tab of the process controller.