Before starting the verifications procedures, make sure that you have a PR‑21‑S sample holder at hand. Check the condition of your standard refractive index liquids. You need a cleaning solution (ethanol) to clean the sensor prism and the sample holder.
The sample holder is kept in place by a rubber link.
The verification of the PR‑21‑S sensor calibration is made using a set of standard refractive index liquids with the nominal values at +25 °C (+77 °F):
- 1.330
- 1.350
- 1.360
- 1.370
- 1.390
- 1.410
- 1.430
- 1.450
- 1.460
- 1.470
- 1.490
- 1.500
- 1.520
The accuracy of the certified standard refractive index liquids is ±0.0002 and they can be traced back to national standards: N.I.S.T Standards # 1823 and # 1823 II.
The repeatability of PR‑21‑S sensor, that is the deviation from the latest nD calibration, is within ±0.0004.
As the specified accuracy of PR‑21‑S is ±0.0004, then the representative level is the root sum square of the three accuracy specifications, that is ±0.0006.
Vaisala provides a set of standard R.I. liquids, PR‑2000, containing these five liquids. The set can be ordered directly from Vaisala or through your nearest representative.