Operation Manual

13
How does liquid affect the signal?
There are a few considerations to take into account if your application requires
measuring distances to, or within, liquid:
• Reectivity and other characteristics of the liquid itself
• Reectivity characteristics of particles suspended in the liquid
• Turbidity
• Refractive characteristics of the liquid
Reectivity of the liquid is important when measuring distance to the surface of
a liquid or if measuring through liquid to the bottom of a container(“How does
the device work with reective surfaces?”, page 12).
It is important to note that measuring distance with the device depends on
reected energy from the transmitted signal being detected by the receiver
in the sensor. For that reason, the surface condition of the liquid may play an
important role in the overall reectivity and detectability of the liquid. In the
case of a at, highly reective liquid surface, the laser’s reected energy may
not disperse adequately to allow detection unless viewed from the normal. By
contrast, small surface ripples may create enough dispersion of the reected
energy to allow detection of the liquid without the need to position the sensor
so that the transmitted beam strikes the liquid’s surface from the normal.
Reectivity of suspended particles is a characteristic that may help or hinder
depending on the application.
Turbidity, or the clarity of a liquid created by the presence or absence of
suspended particles, can similarly help or hinder measurement efforts. If
the application requires detecting the surface of the liquid, then suspended
particles may help by reecting more of the transmitted beam back to the
receiver, increasing detectability and permitting measurements to be taken.
It is important to note that, attempting to measure through suspended particles
in a liquid will only be successful if the transmitted beam is allowed to reect
off of the desired target without rst being absorbed or reected by the
suspended particles.
When the near infrared energy transmitted by the device transitions from the
atmosphere to a liquid, the energy may be bent, or refracted, and absorbed
in addition to being dispersed. The degree to which the transmitted beam is
refracted and absorbed is dened by its refraction index. That being said, the
most important criteria impacting successful measurement through a liquid
is the amount of dispersion of the transmitted beam and whether any of the
dispersed beam makes its way back to the receiver on the device.
Remember that electromagnetic energy travels slower through a liquid and
may affect accuracy of the nal measurement output.