FC 7 - Square Root

This function computes the square root of the input signal in engineering units. The output equals a factor (k) times the

square root of the input. The equation for this function is:

 

NOTES:

  1. When function code 7 is utilized as a shaping algorithm for function code 222 (analog in/channel), its tunable specifications are not adaptable.

  2. When function code 7 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 7 should not be referenced by function blocks other than function code 222 utilizing it as a shaping algorithm.

  3. Multiple instances of function code 222 function blocks may utilize the same function code 7 function block as a shaping algorithm. The function code 7 shaping algorithm function block is not required to be in the same segment as the function code 222 blocks.

 

Outputs:

Blk

Type

Description

N

R

Output value equals square root of input value

multiplied by the gain value (k)

 

 

Specifications:

Spec

Tune

Default

Type

Range

Description

S1

N

6

I

Note 1

Block Address of input

S2

Y

1.000

R

Full

Gain value (k) in engineering units (EU)

 

 

NOTES:

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

 

7.1 Applications

Specification S2 is the gain (k) applied to the value and can be any real number. It is used to scale an input signal to a meaningful or easy to work with output signal. Figure 7-1 shows an example of how function code 7 can be used. In the example, a flow rate of zero to 50,000 pounds per hour is being measured by a differential pressure transducer whose output range is zero to 200 inches of water. The flow is a function of the square root of the differential pressure multiplied by some constant (k). The equation for this example is:

 

If it is known that the flow is 50,000 pounds per hour at a transmitter output indicating 200 inches of water differential pressure, the required constant (k) can be calculated as follows:

 

 

 

 

Many nonlinear inputs need to be converted to linear outputs. Figure 7-2 illustrates converting a nonlinear pressure signal to a linear flow signal using function code 7.