FC 182 - Analog Input Definition (CBC01, SLC01-02)

The analog input definition function code defines the input type and the engineering units for the batch command controller (CBC). Input types include thermocouple, millivolt, resistance temperature detector (RTD) and high level. Engineering units include degrees Celsius and degrees Fahrenheit.

 

This function code outputs the input voltage and its status. The corresponding block of the batch I/O module (function code 180) and the Type SLC controller I/O module (function code 230) outputs the equivalent engineering units.

 

The analog input definition function code allows the selection of a square root or polynomial function. This function can be applied to a reading before or after conversion to engineering units.

 

 

 

Outputs:

Blk

Type

Description

N

R

Analog terminal block reading in millivolts with quality

N+1

R

Analog input status

 

 

 

Specifications:

Spec

Tune

Default

Type

Range

Description

S1

N

0

I

0 - 139

Input type:

0 = undefined block

0XX = 2-wire RTD (or non-RTD)

1XX = 3-wire RTD

001 = S type TC

002 = R type TC

003 = E type TC

004 = J type TC

005 = K type TC

006 = T type TC

007 = Chinese E TC

008 = Chinese S TC

009 - 019 = not implemented

X20 = U.S. laboratory standard 100 W platinum RTD

X21 = U.S. industry standard 100 W platinum RTD

X22 = European standard 100 W platinum RTD

X23 = 120 W chemically pure nickel RTD

X24 - X39 = not implemented

040 = high level (+1 V to +5 V, 4 mA to 20 mA)

041 - 063 = not implemented

064 = millivolt input (-20 mV to +80 mV)

S2

N

2

I

0 - 4

Engineering units type:

0 = °C

1 = °F

2 = engineering units conversion

3 = square root after engineering units conversion

4 = square root before engineering units conversion1

S3

Y

0

I

Full

Reserved (calibration)2

S4

Y

0.000

R

Full

Engineering units zero value

S5

Y

100.000

R

Full

Engineering units span value

S6

Y

0.000

R

Full

Lead wire resistance

S7

Y

1800.000

R

Full

Offset correction factor2

S8

Y

40.000

R

Full

Gain correction factor2

S9

N

5

I

Note 3

Block address of the polynomial block

S10

N

5

I

Note 3

Block address for the remote cold junction value

S11

Y

0

I

Full

Polynomial correction option

S12

Y

1.000

R

Full

Lag filter time (secs)4

S13

Y

0.000

R

Full

Spare

 

NOTES:

1. Differential pressure to flow square root conversion in Type SLC controller.

2. Not relevant in Type SLC controller.

3. Values are 0-1023 for Type SLC controllers and 0-2046 for Type CBC controllers.

4. S12 active for low level inputs in Type CBC revision A controllers. Active for all input types in Type SLC revision B controllers.

 

 

182.1   Explanation

 

128.1.1  Specifications

 

S1

Specification S1 identifies the input type. Thermocouple, RTD, millivolt and high-level are the available types of inputs. For RTD inputs, this specification also selects between a two or three-wire RTD.

 

S2

Specification S2 defines the engineering units that the batch I/O module block uses. This specification can also apply a square root function to the analog input.

0 = degrees Celsius

1 = degrees Fahrenheit

2 = engineering units conversion (use with millivolt and high level inputs only)

3 = apply square root function to engineering units after conversion (use with millivolt and high level inputs only)

4 = apply square root function to engineering units before conversion (use with millivolt and high level inputs only)

 

Function code 182 converts the analog input to millivolts. When S1 equals 040 (high level) or 064, one of three paths is taken for the engineering units conversion.

 

If S2 equals two, only the engineering unit conversion is executed.

 

 

If S2 equals three, the engineering unit conversion is executed, followed by the square root subroutine.

 

If S2 equals four, the square root subroutine is followed by the engineering unit conversion subroutine. This selection represents a zero based differential pressure to flow conversion.  In the Type CBC batch command controller, function code 182, the conversion is:

 

where:

Xn = analog input in millivolts

Xmin = 1,000 millivolts

 

The Type CBC batch command controller performs function code 182 conversion in millivolts.

 

In Type SLC Strategic Loop Controller revision B firmware, function code 182 performs the following conversion:

 

However, if S4 equals zero, the output further reduces to:

 

 

S3

Reserved for calibration.

 

S4

Specification S4 is the engineering units zero value. This value corresponds to a one-volt or four-milliamp input when using the high level input type. With the selection of the millivolt input, this value corresponds to a -20-millivolt input.

 

S5

Specification S5 is the engineering units span. This span is equal to the difference between the engineering units value at maximum (five volts or 20 milliamps) and the engineering units zero value. Thermocouple and RTD inputs do not require the engineering units span specification.

 

S6

Specification S6 is the lead wire resistance in ohms. High level inputs do not require the lead wire resistance specification.

 

S7

Specification S7 is the offset correction factor. The batch command automatically calculates this value during calibration.  The batch command then stores this calculated value in this location. High level inputs do not require the offset correction factor specification.

 

S8

Specification S8 is the gain correction factor. The batch command automatically calculates this value during calibration.  The batch command then stores this calculated value in this location. High level inputs do not require the gain correction factor specification.

 

S9

Specification S9 is the block address of the polynomial block (function code 167). This polynomial applies to the input.  Specification S11 determines whether the polynomial applies before or after conversion to engineering units. If the configuration does not use S9, it must link to system constant block five that has an output of 0.0.

 

S10

Specification S10 is the block address of the block that outputs the remote cold junction value. This link supplies the temperature of the remote terminal block. This value functions

as the cold junction compensation for this temperature input. If the configuration does not use S10, it must link to system constant block five that has an output of 0.0.

 

S11

Specification S11 selects the option of applying the polynomial to the input before or after conversion to engineering units (if S9 is not linked to system constant block five). Setting

S11 to zero applies the polynomial to the input after conversion to engineering units. Setting S11 to one applies the polynomial to the input before conversion to engineering

units. Refer to S9.

 

S12

Specification S12 represents the lag filter time in seconds.

 

S13

Spare parameter.

 

 

 

182.1.2  Outputs

 

N

High level input - millivolt reading at the terminal block.

 

RTD input - millivolts of the input adjusted for lead wire resistance.

 

Thermocouple input - millivolts of the input with lead wire and cold junction adjustment.

 

Millivolt input - millivolts of the input adjusted for lead wire resistance.

 

Quality of output N is bad if one of the following conditions exist:

  • Conversion error.

  • A/D error.

  • Cold junction error.

  • Not calibrated or aborted calibration.

  • Start-up.

 

N+1

Analog input status.

0.0 = reliable analog input reading

1.0 = bad status or unreliable analog input reading

2.0 = input not calibrated

3.0 = input type undefined or function block 182 not linked to batch I/O module block (function code 180)

 

 

 

182.2   Applications

 

Figure 182-1 illustrates how the analog input definition block links to the polynomial block for polynomial adjustment. Specification S9 is the block address of the polynomial block.  The polynomial defined by function code 167 applies to the input of the analog input definition block. Specification S11 determines whether the polynomial applies before or after conversion to engineering units.

 

 

Figure 182-2 illustrates how the analog input definition blocks link to the batch I/O module block to monitor the remote cold junction input.

 

The lower analog input definition block monitors the temperature of the remote terminal block. The output of this analog input definition block is linked to S7 of the batch I/O module block. The corresponding output of the batch I/O module block feeds back to S10 of the two remaining analog input definition blocks. This allows the two thermocouple temperature inputs which are terminated remotely to have the remote cold junction compensation applied in order to maintain accuracy.