Faulty Ssi Query; Display/Controller For Ssi - Balluff BML Información Básica

Interfaces for BML Magnetic Encoder System
2
Interfaces (continued)
2.2.2

Faulty SSI query

Clocking too fast
This error is described in the guide for the
sensor.
Underclocking
If there are too few clock edges, the current data level will
be maintained for the time t
from +Clk. If, however, another positive edge occurs within
the t time, the next bit will then be output. If the t
m
has expired, the +Data output goes high. The high level is
maintained until the next clock burst.
Overclocking
If there are too many clock edges, the data output will
switch to low after the correct number of cycles has been
completed. With each additional negative edge of +Clk the
t time is restarted. The +Data output switches back to
m
high after the time t has elapsed.
m
Calculated resolution adjustment
Intentional over- and underclocking allows the calculated
resolution of the sensor to be doubled or halved.
Example
Assume the sensor has a resolution of 1 µm and the
number of bits is 25.
– The data bit for the 25th Clk has a value of 1 µm
– The data bit for the 24th Clk has a value of 2 µm
– The data bit for the 23rd Clk has a value of 4 µm
– etc.
If the controller only outputs 24 clock pulses, the sensor
can only output 2-µm increments. To the controller it
appears the sensor has a resolution of 2 µm. In other
words for a travel distance of 1 mm the position does not
change by 1000 increments, but rather by only 500
increments.
If the controller outputs too many clock pulses, the
calculated resolution of the sensor is reduced.
– The data bit for the 25th Clk has a value of 1 µm
– The data bit for the 26th Clk is null and has a value of
1/2 µm
– The data bit for the 27th Clk is null and has a value of
1/4 µm
– etc.
If the controller outputs 27 clock pulses, to the controller it
appears the sensor has a resolution of 1/4 µm. When
traveling over 1 mm the position changes by 4000
increments in 4-increment steps.
If a controller does not support the configurable number of
bits, a different clock count can be used. To ensure correct
processing of the measured value the resolution per bit
must be adjusted.
8 english
after the last negative edge
m
time
m
2.2.3

Display/controller for SSI

The following display units are available for the
SSI interface:
BDD Touch Display
Order code: BAE010N
96
Housing depth 105 mm
– SSI master (see Fig. 2-3) or slave interface (see
Fig. 2-4)
– 2 programmable relay outputs
– 8 directional switching points possible
– Multi-color display
BDD BDD
Fig. 2-3: Use as SSI master
Controller
BDD BDD
Fig. 2-4: Use as slave
BML-S1G BML-S1G
BML-S1G BML-S1G