FAQ

What are the best practices for calibrating the HL series ISE sensors?

Rebuild the reference if needed, and calibrate conductivity and pH before calibrating any ISE sensor.
Calibrate ISE sensors with standards that either bracket your expected measurements or that are close to what you expect to measure.
The ISE sensors need frequent maintenance and calibration compared to other water sensors. ISE calibrations do not last as long and will drift faster. Bio-fouling and water conditions will affect maintenance and calibration frequency. A difficult to calibrate ISE sensor indicates that it needs to be replaced.
Before calibrating a new sonde with ISE sensors, soak the sensors in the calibration cup with a high conductivity standard, like 47.6 mS/cm, for 2 to 4 hours to condition the reference electrode. When the reference mV is stable, it is ready.
Soak a new ISE sensor in any of its standards overnight to condition it. It will calibrate more easily.
To calibrate an ISE sensor reliably will take a minimum of 20 minutes per sensor. ISE sensors need more time to stabilize than other sensors during calibration as well as during measurements in the field.
For best results, calibrate the ISE sensor at or near the water temperature it will be sampling. In any case, be consistent in your calibration temperatures.
When calibrating sensors, it is important to use deionized (DI) water to rinse between calibration steps.
If at all possible, use a stir plate to calibrate ISE sensors. Keeping the standard well-mixed improves calibration stability.