Go Direct^® Salinity Sensor (GDX-SAL)
Specifications and User Guide

TROUBLESHOOTING
-Primary Test: Connect the sensor and start up the data-collection program. Place the sensor in distilled water. The reading should be at or near 0 ppt. Place the sensor in a 35 ppt salinity standard solution. The reading should be at or near 35 ppt. Note: This standard solution can be purchased from Vernier or made by adding 33.03 g reagent grade NaCl to enough distilled or deionized water to make 1.00 liter of solution.
-Secondary Test: Connect the sensor and start up the data-collection program. Place the sensor in distilled water and then move the sensor to a container of tap water. The readings should change from 0 ppt to a salinity value that is appropriate for your region of the country.

RELATED TIL ENTRIES
–Can I use Vernier water quality sensors in salt water or in a salt water aquarium?
–What is the difference between salinity and conductivity?

CALIBRATION
-Calibrate? For many experiments, calibrating the Salinity Sensor is not required. We store a
calibration equation on each sensor before shipping it, which is used as a
default by our software.

For the most accurate measurements with this sensor above 35 ppt, we recommend calibration.
It is a simple process that takes only a few minutes. For instructions for Salinity Sensor calibration, select the link that matches your software…
• How do I manually calibrate my sensor in LabQuest App?
• How do I manually calibrate my sensor in Graphical Analysis and Graphical Analysis Pro?
• How do I manually calibrate my sensor in Graphical Analysis and Graphical Analysis Pro for iOS/Android?

Making Standard Calibration Solutions
If you choose to calibrate the Salinity Sensor, you will want an accurate
standard solution. Vernier sells a 35 ppt standard solution (order code SAL-ST).
To prepare your own 35 ppt standard solution using solid NaCl, use a container
with accurate volume markings (e.g., volumetric flask). Add 33.03 g NaCl to
enough distilled water to make 1 liter of solution. Use reagent grade NaCl.
Note: The Practical Salinity Scale 1978 was developed relative to a KCl
solution. Standard Methods for the Examination of Water and Wastewater
states that “A seawater with a conductivity at 15°C equal to that of a KCl
solution containing a mass of 32.4356 g in a mass of 1 kg of solution is defined
as having a practical salinity of 35.”

RELATED VERNIER PRODUCTS
Salinity Standard (SAL-ST) (Salinity Standard, 35 ppt, 500 mL)