Troubleshooting Guide 109
© 2018 Nortek AS
Boundary interference: If there are any obstructions in the beam path, the result may look like this.
Little scattering material / low power: The curve showing the sampling volume is "too low" in
terms of counts. If the scattering level is sufficient, increase the output power.
Too little scattering m aterial or pow er level too low
Bent receiver arm: Take a look at the location (range) of the peak in amplitude on the probe check
for each receiver. If it is significantly shifted closer or further away, then it is usually an indication of a
bent receiver arm. In the figure below, the red and blue curve (representing beam 1 and 2) are not
aligned with the other two curves, In this case, beam 2 was bent a bit out, beam 1 a bit in.
Check to confirm: Gently place the probe on a flat surface and confirm that all beams touch the
surface at the same time.
A bent receiver arm will change the calibration since the receiver arm geometry has changed. If it is
only minor changes, then you may not not notice much difference, but it will introduce a bias to the
measurements. Contact Nortek for further guidance.
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