IC-LO_16 Datasheet, PDF (15/25 Pages) IC-Haus GmbH – TRIANGULATION SENSOR

iC-LO
TRIANGULATION SENSOR
RECEIVED SIGNAL MONITORING
preliminary
Rev B3, Page 15/25
Two sum comparators have been integrated to monitor
the system and evaluate the intensity of the received
light pulse. A switching threshold can be configured
separately for each of the comparators. The warning
threshold is configured by using VTHSW and an error
threshold by using VTHSE. If the received light pulse
undershoots the relevant set threshold, the correspond-
ing comparator output (KSw and KSe, see block dia-
gram) is set to low. It makes sense to set the warning
threshold higher than the error threshold. The warning
threshold could indicate that the sensor is contaminated.
If the intensity of the received light pulse undershoots
the error threshold, the switching output is deactivated
as a decision cannot be safely made (see table 21).
THSW
Addr. 0x05; bit 4:0
RW
THSE
Addr. 0x06; bit 4:0
RW
Code
Description
0x00
VTHSx = 2.8 mV
0x01
VTHSx = 5.6 mV
..
0x1F
VTHSx = 89.6 mV
Table 17: Thresholds Sum Comparators, x = W, E
SAMPLE POINT, DIGITAL SIGNAL CONDITIONING, AND OUTPUT CONFIGURATION
The signal conditioning chain between the comparator ^FIN
Addr. 0x09; bit 3:0
RW
outputs and the switching outputs is shown in figure 4. ^Code
Description
0x0
1
0x1
2
0x2
3
...
0xF
16
Figure 4: Digital processing and signal output
Table 18: Number of Measurements Per Cycle
Digital filter
To improve noise immunity a measurement cycle (see
figure 5), which results in an update of the switching
and warning outputs, can consist of several individual
measurements (see figure 6). The number of individual
measurements in a measurement cycle is set using FIN.
After each individual measurement the last individual
measurements set through FIN are collated to form a
measurement cycle and evaluated.
FIM
Addr. 0x09; bit 7:4
RW
Code
Description
0x0
1
0x1
2
0x2
3
...
0xF
16
Table 19: Number of Measurements Complementary to
Current Comparator State
Update
switching
output
Single measurement
Measurement cycle consisting of FIN-single measurements
Figure 5: Measurement cycle
Sample point in time
The point in time at which the outputs of the three com-
parators are sampled during an individual measurement
(t_sample, see figure 6) can be shifted using parameter
SKO. This shift is always referenced to the rising edge
of the light pulse generated in the LED driver.
In doing so, each comparator output (KD, KSw, and
KSe) is separately filtered. There must then be a
minimum number of individual measurements comple-
mentary to the current filtered comparator output (KDF,
KSwF, and KSeF) so that the corresponding filtered
comparator output changes its state. This number is
configured using FIM.
Light pulse
t
sample
t(SKO)
Single measurement
Figure 6: Single measurement