Turbidity uses a two-point calibration; one point is zero turbidity and the other point should be a
standard approximating the turbidity of the water you intend to monitor. Care must be taken
during calibration to ensure that external effects are kept to a minimum and that enough
calibration standard to cover the sensor’s “optical volume” - imagine tennis ball stuck on the end
of the sensor; make sure there are no objects in the volume represented by that ball. One
common method is keeping calibration solutions in one-liter, dark, wide-neck bottles with a non-
reflective finish (such as Nalgene® 2106 bottles in amber). For the zero calibration:
1) Make sure the Turbidity sensor is fully immersed (i.e. at least an inch of solution over the
sensor) in zero-turbidity standard and has an unobstructed optical path.
2) Follow the Manta 2 Control Software’s calibration instructions.
For the other calibration point:
1) Rinse your sensors several times with the standard you’ll use for calibration.
2) Make sure the Turbidity sensor is fully immersed (i.e. at least an inch of solution over the
sensor) in the standard and has an unobstructed optical path.
3) Follow the Manta 2 Control Software’s calibration instructions.
A clean wiper means better measurements. If the wiper pad is deteriorating or is clogged with
debris from your water (algae, silt, etc.), you should change the wiper pad. For best results, you
might consider changing the wiper pad prior to each long term deployment:
Please do not over-tighten the set screw (that’ll strip the threads) or rotate the wiper arm
manually (that’ll strip the gears).
1) Loosen the small set screw on the wiper with the 1.5mm hex key provided.
2) Remove the wiper from the wiper shaft.
3) Place a new wiper on the shaft so that the set screw faces the flat spot on the wiper shaft
4) Gently press the wiper against the face of the probe until the foam pad is compressed to
roughly three quarters of its original thickness. It is important that the wiper arm body
does not make contact with the probe face – only the pad should be in contact. A gap of
0.5mm between the wiper body and the probe face is typical when a new pad has been
installed.
5) Tighten the set screw.
Eureka recommends the polymer-bead calibration solutions, as they are stable and safe. You
can use formazin standards, but these are not as stable, require stirring and are a suspected
carcinogen.
E14 Chlorophyll, Rhodamine, and Blue-Green Algae
Eureka’s chlorophyll, rhodamine, and blue-green algae sensors are fluorometric sensors, with
each tuned to the slightly different wavelengths. Fluorescence occurs when a molecule absorbs
light at one wavelength and then emits that energy at a different wavelength. More molecules of
analyte produce a higher level of that different-wavelength light. Fluorometric sensors emit light
at a certain wavelength, and look for a very specific, different wavelength in return. The
magnitude of the return light is relatable to the amount of analyte present.
Maintenance and calibration are sensor-specific; please follow the instructions provided by
Eureka’s sensor vendor.
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