AMCI ANS1 ANYNET-I/O, User Manual

Page: 18 / 90

Limit Switch Functionality
ADVANCED MICRO CONTROLS INC.
2
18
Global Machine Position (continued)
Advanced Parameter Use
If your transducer completes less than one rotation for every part cycle on the machine, the Counts per Cycle
parameter can be used to force the Global Machine Position to return to zero before the transducer completes
a full rotation. Table 2.1 shows how the Counts per Cycle parameter affects the roll over position for a
resolver transducer.
Table 2.1 Roll Over Example 1: 4096 Count Transducer
The resolver will remain an absolute sensor if the Counts per Cycle parameter is programmed
to be a power of 2. (2, 4, 8, ... 1024, 2048, 4096). If any other value is used, the machine posi-
tion may be incorrect if the resolver shaft is rotated while power is removed from the machine.
Table 2.2 shows how the Counts per Cycle parameter affects the roll over position for a 2,000 count (500 line)
encoder.
Table 2.2 Roll Over Example 2: 2000 Count Encoder
Global Machine Speed
Global Machine Speed is the shaft speed in RPM. Global Machine Speed is updated every 14.6 milliseconds
and is averaged using an exponentially weighted moving average. A single parameter sets the smoothing fac-
tor for the filter.

RPM Filter:
[Range of 0 to 65,535, Default of 40,960] The smoothing factor ( k below) is a value that is
equal to the RPM Filter / 65,536. The formula below shows how the smoothing factor is used when cal-
culating the Global Machine Speed:

Where: S
t
= Next Global Machine Speed to be reported

S
t-1
= Last reported Global Machine Speed

k = RPM FIlter / 65,536

X
t
= Measured RPM Value
When the RPM Filter value, and therefore k, is near zero, the last reported Global Machine Speed is almost
completely eliminated and the latest Measured RPM Value is primarily what is reported. This is a signal
without much filtering and it quickly responds to changes in the machine speed.
As the RPM Filter approaches its maximum value, and k approaches 1, the latest Measured RPM Value is
attenuated more and more. The Global Machine Speed in more heavily filtered and more slowly responds to
changes in machine speed.
The default RPM Filter value yields a smoothing factor of 0.625.
Counts per Cycle Full Scale Count Results
4096 360 360 counts (0 to 359) over one turn of the transducer
3072 2700 2700 counts (0 to 3699) over 3/4 of a turn of the transducer
2048 360 360 counts (0 to 359) over 1/2 of a turn of the transducer
1024 90 90 counts (0 to 89) over 1/4 of a turn of the transducer
Counts per Cycle Full Scale Count Results
2000 1440 1440 counts (0 to 1439) over one turn of the transducer
1500 810 810 counts (0 to 809) over 3/4 of a turn of the transducer
1000 360 360 counts (0 to 359) over 1/2 of a turn of the transducer
500 90 90 counts (0 to 89) over 1/4 of a turn of the transducer
S
t
k S
t 1 –

1 k –
 
X
t

+ =