Vout
t
In the case that disturbing lights (DC lights) are present
Vout(OFF)
≒
Vout influenced by disturbing lights
＊
The time till the sensor output becomes stable is 400 micro sec. or less.
Vout
t
In the case of no disturbing lights
(2) Sampling timing for sensor output
Considering the sensor response time, the recommended sampling timing of sensor output is shown below;
-
Vout(OFF)
: Output voltage when LED is turned off
*The sampling timing for Vout(OFF) : 1,000 micro sec. after the end point of LED pulse
-
Vout(ON)
: Output voltage when LED is turned on
*The sampling timing for Vout(ON): 1,600 micro sec. after the end point of LED pulse
(3) Cancellation processing for external disturbing light interference (DC lights)
Next procedure is to calculate the difference of the two output voltage (Vout(ON) and Vout(OFF)) in order to
cancel the influence of external disturbing lights. This voltage difference can be regarded as the voltage
generated by sensing the object, in the absence of external disturbing lights.
Radical output voltage without disturbing lights = Vout(ON) - Vout(OFF)
(4) Optimum threshold level setting
The analog output model of the B5W-LB series detects objects using the above recommended external circuits.
In order to stably detect the objects to be sensed, proper evaluation should be performed considering the
potential worst case conditions of the actual application. For example, the threshold level should be properly
set using actual object samples that have the lowest reflection factor out of all of the actual objects to be
sensed.
Worst case design methods considers all factors that will change the sensor output voltage, such as; variations
in sensing distance, angle, size, surface conditions of objects, and ambient temperature. If there are any
objects or background surfaces which should not be detected in the sensing area, then the proper threshold
level should be set, considering the potential influence they’ll have on the output voltage.
Vout(ON)
Vout(ON)
B5W-LB Light convergent reflective type sensor User’s manual (E592)
7
