The document introduces the use of the pNa HI 98202 soft water tester. The instrument uses a sodium ion-selective electrode to determine the activity of free sodium in solution (pNa = -log aNa). In dilute solutions, the activity coefficient is nearly 1 and in such solutions pNa is a good indicator of the sodium ion concentration. The relationship between the pNa scale and the g/L Na+ scale is explained in the chart below. A double junction reference is used to ensure a highly stable reading. If you suspect that the calibration has drifted, you can recalibrate the meter by using a solution of known concentration. Adjust the reading with the calibration trimmer.
The Hanna Instruments HI 98202 is a soft water tester that utilizes a sodium ion-selective electrode to determine the activity of free sodium in solution. It displays measurements in pNa units and includes a chart to calculate g/L values. The device features a double junction reference for stable readings and requires manual calibration using a known concentration solution.
| Resolution | 0.1 pNa |
|---|---|
| Accuracy | 0.2 pNa |
| Calibration | Manual, 1 point |
| Environment | 0 to 50°C (32 to 122°F) |
| Battery Life | approx. 800 hours |
| Dimensions | 75x 41 x23 mm |
| Weight | 95 g |
Immerse the tester in HI 7080 calibration solution and turn the calibration trimmer until the display shows "1.0" pNa.
You should immerse it in HI 7080 solution up to the maximum immersion level at least once a week to improve performance.
Pull out 2 mm (1/8") of the cloth junction to renew the electrode reference and recalibrate the meter.
The cloth junction can be pulled out approximately 20 times before the electrode should be replaced.