User manual

Chapter 1 Introduction to the 2762-17
ADVANCED MICRO CONTROLS INC.
9
Transducer Setup Parameters (continued)
Number of Turns
Use this parameter, along with the Scale Factor parameter, to set the correlation between
the transducer position and the load position. This parameter is usually set to the number of
rotations the transducer makes for the expected linear travel of the load. Its minimum value is
0.1 turns. Its maximum value is equal to the number of turns of the transducer, 100 or 180
turns, with 0.1 turn resolution. When using it with a 1000 or 1800 turn transducers consider it
programmable from 1 turn to 1000 or 1800 turns with 1.0 turn resolution.
Scale Factor
Use this parameter, along with the Number of Turns parameter, to set the correlation
between the transducer position and the load position. The Scale Factor sets the position
resolution and must be set to the number of counts needed over the programmed Number of
Turns parameter. The range of values that can be programmed for the Scale Factor is 2 to
(4096 * Number of Turns).
Counts per Turn and Full Scale Count
The Scale Factor divided by the Number of Turns is the number of counts per turn. The
2762-17 uses this ratio when calculating the position values. Therefore the actual values for
Number of Turns and Scale Factor can be any convenient numbers. For example, assume
150.7641 turns corresponds to 9.000 inches of travel. Therefore, the counts per turn ratio is
9000 / 150.7641 ! 59.6958. Setting the Number of Turns to 150.8 results in a significant error,
9000 / 150.8 ! 59.7213. Using successive approximation techniques to arrive at different
values, setting the Number of Turns to 138.1 and the Scale Factor to 8244 results in a much
better approximation. {8244 / 138.1 ! 59.6958. Its accuracy to the actual ratio is greater than
five decimal places}.
The 2762-17 uses the counts per turn
ratio to calculate the Full Scale Count
(FSC). The Full Scale Count is the largest
number the position value will attain
before the transducer completes its multi-
turn cycle. (100 or 180 turns.) See Figure
1.5.
The Full Scale Count sets limits on the
values that can be programmed into the
other transducer setup parameters as well
as some of the positioning setup
parameters.
LOAD
2.000 in
1.250 in
Expected
Travel
20 inches
112.5 Turns
20,000 Counts
Full Scale
Travel
32 inches
180 Turns
Full Scale
Count
((20,000/112.5) * 180) - 1
= 31,999
Counts range from
0 to 31,999
Figure 1.5 Full Scale Count Example