DS-TACHO-4
TECHNICAL REFERENCE MANUAL
3. Introduction
Always keep in mind that the Tacho-4 sensors are threshold sensors. This is important especially for the
proximity detection mode, the most commonly used for rotating: working distance could change with
the albedo and/or the form and distance of the target, also, contrast appears as an important
parameter: teeth-no teeth, black and white marks.
The recommended distance for encoding application is a few millimetres: put the probe close to the
target to avoid an incorrect reading resulting from rocking and wagging of the turning part (Descartes
optical law); on the other hand, the reflective tape allows for much more than 100 mm. It is highly
recommended that you use the adhesives encoders for optimal results.
A few phenomena may affect the detection function, such as a drop of liquid on top of the probe,
excessive dust covering the top, more generally, a non transparent environment for our light source
such as diesel engine sump film (i.e. carbon is not transparent for the near I.R.). Patented concept
implemented in the sensors strongly simplifies mounting and set-ups. 152 sensor lights sources are not
dangerous: No Laser inside. Prior to measurement, it is recommended that a detection test be
performed, even at low speed, to ensure detection feasibility and determine detection distance required
for the sensor.
If it is impossible to perform a test due to technical reason or mounting specifics, a theoretical method
would be to fix the probe at a distance equivalent to the width of the black and width strips to detect- in
any event, without exceeding 4mm.
Important
Fixing and support of the probe will influence acquisition of the reading. Please be careful
regarding vibration. We recommend that you design your supports including appropriate
vibration orders studies. The further the probe will be away from the target, the more the TTL
amplitude signal will decrease.
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