c) We Recommend using TruRead
TM
Measurement Mode
Turbidity measurement is a complex analytical measurement. Its error and stability are related
not only to the design of the instrument, but also many other factors such as solution uniformity
and precipitation, stray light, air bubble interference, sample vial contamination, optical errors,
operation technology and more. Therefore, using normal measurement mode will obviously result
in a larger error. For this reason, we recommend using TruRead
TM
measurement mode with 5
times continuous measurement for regular tests, that is, set the continuous measurement to 5
times in parameter setting P2, and read the average value each time to improve the measurement
accuracy. Compare the maximum and minimum values at the same time. If the difference is too
large, it means that the measured value is not reliable, the solution may be unstable or there
might be other factors affecting the measurement. You need to check the root-cause and measure
again. For rapid-settling or continuously changing solutions, set continuous measurement for 10,
15 or 20 times.
5.4 Notes for Measurement
a) Keep the sample stable: After the vial is placed into the sample cell, it is recommended to wait for
1 to 2 minutes before calibration, as the solution will experience some shaking when the vial moves,
which may result in inaccurate measurements.
b) Sample Vial cleaning requirement: Sample vial must be rigorously cleaned and free from smudges
and scratches. When wiping, user should grip the cap and bottom to avoid leaving fingerprints on
the surface of the vial. Its surface should be applied with a drop of silicone oil be wiped with a micro-
fiber cloth. After that, please clean with filter paper or high-quality tissue paper. See section 4.1(c)
for details.
c) Mixing and Degassing: Samples should not be vigorously shaken or vibrated. It is recommended
that users gently shake the sample vial to make solution evenly distributed. Air bubbles in solution
will cause big error to turbidity measurement. So, the vial should be left stand still for 2 to 5 minutes
to eliminate potential air bubbles before measuring. But mixing and degassing simultaneously is a
difficult process to handle, especially for solution with precipitates, which requires some operating
experience or make some limits in test conditions. For example, limit the mixing condition and waiting
time for degassing to be the same before comparing measurements.
d) Other Requirements
On the premise of ensuring evenly distributed samples, sample solution should be measured
immediately to prevent temperature changing and precipitates from affecting measurements.
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