How do zero calibrations differ between the TU5 series and legacy instruments like the 1720E and UltraTurb?

Document ID

Document ID TE9228

Version

Version 1.0

Status

Status Published

Published Date

Published Date 14/06/2018
Question
How do zero calibrations differ between the TU5 series and legacy instruments like the 1720E and UltraTurb?
Summary
TU5/ 1720/ UltraTurb - zero NTU calibration validation.
Answer
1. 1720E and TU5 instruments work with two different technical standards, therefore the turbidity values are not 100% comparable, especially around zero:
  • 1720E white light (EPA Method 180.1)
  • TU5 EPA red laser (EPA Method 10258)
  • TU5 ISO IR Laser (ISO Methode 7027)
2. With regards to turbidity as a physical phenomenon there is no absolute zero, as even the cleanest water will scatter light. Our instruments don’t perform a zero-point calibration, but a two point factory calibration with different standards and extrapolate down to zero at the point where the current is zero at the photodetector. Zero current would mean zero NTU.
Attachments