FC 1 - Function Generator

This function approximates a nonlinear output to input relationship. The input range is divided into five sections and a linear

input to output relationship is set up for each of the five sections. This function then computes an output that is related to the

input according to the five linear relationships.

 

          

NOTES:

1. When function code 1 is utilized as a shaping algorithm for function code 222 (analog in/channel), its tunable specifications are not adaptable.

 

2. When function code 1 is used as a shaping algorithm, it can not at the same time also be used as a logic function because the block output will not respond to the specification S1 input. Function code 1 should not be referenced by function blocks other than function code 177 or function code 222 blocks utilizing it as a shaping algorithm.

 

3. Multiple instances and combinations of function code 177 and 222 function blocks can utilize the same function code 1 function block as a shaping algorithm. The function code 1 shaping algorithm function block is not required to be in the same segment as the function code 177 or function code 222 blocks.

 

Outputs:

Blk

Type

Description

N

R

Output Value of Function

 

Specifications:

Spec

Tune

Default

Type

Range

Description

S1

N

5

I

Note 1

Block Address of Input

S2

Y

9.2E18

R

 

Input Coordinate

S3

Y

0.000

R

 

Output Coordinate for S2

S4

Y

9.2E18

R

 

Input Coordinate

S5

Y

0.000

R

 

Output Coordinate for S4

S6

Y

9.2E18

R

 

Input Coordinate

S7

Y

0.000

R

 

Output Coordinate for S6

S8

Y

9.2E18

R

 

Input Coordinate

S9

Y

0.000

R

 

Output Coordinate for S8

S10

Y

9.2E18

R

 

Input Coordinate

S11

Y

0.000

R

 

Output Coordinate for S10

S12

Y

9.2E18

R

 

Input Coordinate

S13

Y

0.000

R

 

Output Coordinate for S12

 

NOTES:

1.Maximum values are: 9,998 for the BRC-100, IMMFP11/12,  31,998 for the HAC.

 

1.1 Explanation

To set up this function, first determine what the output should be for a given range of input and draw a graph to show this

relationship. Divide the graphed relationship into five sections, preferably into sections where straight lines can closely

approximate the graph as shown in Figure 1-1.

 

 

The coordinates of the end points of the sections are used as entries for S2 through S13. The even-numbered

specifications are the X-axis coordinates and the odd-numbered are the Y-axis coordinates. Consequently, when the X-axis

input value is at S2, the output will be the value of S3 as shown in the graph. This divides the graph into five linear (straight line)

sections, with each section having its own particular slope as shown in Figure 1-2.

 

 

If the input value is between two X-axis points, the output will be determined by the equation:

 

 

Where:

X         =    Present input value.

Xn       =    X-axis specification point just to the right of the present input value.

Xn-1    =   X-axis specification point just to the left ofthe present input value.

Yn        =   Y-axis coordinate that corresponds to Xn.

Yn-1     =   Y-axis coordinate that corresponds to Xn-1.

 

=    Slope of the particular graph segment between (Xn,Yn) and (Xn-1,Yn-1). This is the unit output change per unit input change.

 

 

X - Xn-1    =  Amount that the input is above the next lower specification point.

 

 

For example, suppose the graph shown in Figure 1-1 is a graph of desired output values for input values. These values may

represent any engineering units.

 

First, the graph is divided into five sections as shown in Figure 1-2. The coordinates of the end points of these segments are

then entered into the module.

 

Suppose the input <S1> to the function block represented by Figure 1-2 is six units. This corresponds to point S4.

Therefore, the output will be two units (S5). If the input is ten units (which corresponds to S6), the output will be five units

and so on. If the input is between six units and ten units (for example, seven units), the output is determined according to

the function equation. The values for the equation become:

 

1.1.1 High and Low Limits

If the input <S1> goes higher than the S12 value, the output will remain at the S13 value for the high limit. If the input goes

below the S2 value, the input will remain at the S3 value for the low limit.

 

1.2 Applications

Five possible applications of function generators are illustrated in Figures 1-3, 1-4, 1-5, 1-6 and 1-7. Figures 1-6 and 1-7

illustrate the use of multiple function generators to achieve good resolution when representing a complex function.