Red-lion TCU User Manual download pdf (Page 45)

Square Root Linearization (root) (Cont’d)

As a result of the scaling and square root linearization, the following

represents the readings at various inputs:

Delta P

(PSI)

Transmitter

(mA)

Flow

(Ft

)

0.00 4.00 0

15.63 4.50 1099

31.25 5.00 1554

62.50 6.00 2198

125.00 8.00 3108

187.50 10.00 3807

250.00 12.00 4396

312.50 14.00 4914

375.00 16.00 5383

437.50 18.00 5815

500.00 20.00 6216

Decimal Point Position (dPt2)

For Remote Setpoint operation, the decimal point position is normally

programmed to be the same as the main input. For Internal Cascade operation,

the decimal point may be different from the main input.

Example:

If main input = 500 degrees FS,

Second Input = 15.00 PSI FS,

then dCPt = 0 and dPt2 = 0.00.

Second Analog Input Scaling Points (dSP1, INP1, dSP2, INP2)

Prior to installing and operating the indicator, it may be necessary to

change the scaling to suit the display units particular to the application.

The indicator is unique in that two different scaling methods are available.

The operator may choose the method that yields the easier or more accurate

calibration. The two scaling procedures are similar in that the operator keys in

the display values and either keys in or applies a signal value that corresponds

to those d isplay value points. The location of the scaling points should be near

the process end limits, for the best possible accuracy.

Once these values are programmed, the indicator calculates the slope and

intercept of the signal/display graph automatically. No span/zero interaction

occurs, making scaling a one-pass exercise.

Before programming the indicator, organize all the data for the

programming steps to avoid confusion.

To scale the indicator, two signal values and two display values that

correspond to the signal values must be known. These four values are used to

complete the scaling operation. An example is listed below.

Example:

Scaling Point #1 Scaling Point #2

0.00% @ 4.00 mA AND 100.0% @ 20.00 mA

Display Values (dSP1 & dSP2)

Key-in the display value for Scaling Point 1 and Scaling Point 2.

dSP1 -999 to 9999 (Ex. 0.0%)

dSP2 -999 to 9999 (Ex. 100.0%)

Signal Input Values (INP1 & INP2)

The signal input value can either be keyed via the front panel buttons or an

input signal can be applied to the appropriate signal input terminals. Initially,

the unit is in the key-in mode.

Key-in Method

Key-in the signal value for Scaling Point 1 and Scaling Point 2.

INP1 -999 to 9999 (Ex. 4.00 mA DC)

INP2 -999 to 9999 (Ex. 20.00 mA DC)

Signal Input Method

To change to the apply signal method press the DSP button. Front panel

annunciators %PW and SEC flash and the display indicates the signal value

applied to the input terminals. The unit can be toggled to the key-in method by

pressing the DSP button again.

When the desired value is indicated on the display, press the PAR button to

store the value and advance to the next parameter.

The scaling of the Remote Setpoint and Internal Cascade units are

normally made equal to the physical range of the system.

Example: If the temperature control range of the process is 100 to 400

degrees, the Remote Setpoint is normally scaled to 100 and 400 degrees.

Example: The Secondary variable under internal cascade control is steam

pressure over the range of 0.00 to 60.00 PSI. The Second Analog input is

normally scaled to 0.00 and 60.00 units.

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Red-lion TCU User Manual Page 45

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