Input Type Selection (Bits 0-3); Data Format Selection (Bits 4 And 5); Using Scaled-For-Pid And Proportional Counts Formats - Allen-Bradley SLC 500 1746-NR4 User Manual

Input Type Selection (Bits 0–3)
The input type bit field lets you configure the channel for the type of input
device you have connected to the module. Valid input devices are shown in
Table 5.A.

Data Format Selection (Bits 4 and 5)

The data format bit field lets you define the format for the channel data word
contained in the module input image. Valid data types are engineering units,
scaled–for–PID, and proportional counts. If you select proportional counts,
you have the option of using user–set scaling bits 13 and 14 (Table 5.A) to
define an optimum range for your application. Unless you specify otherwise,
the data will be scaled to the full scale range for that channel.
Table 5.B
Bit Descriptions for Data Format Select
Binary
Select
Value
00 engineering units x 1
01 engineering units x 10
10
scaled–for–PID
11 proportional counts
Using Scaled–For–PID and Proportional Counts Formats
The RTD module provides eight options for displaying input channel data.
These are 0.1 F, 0.1 C, 1 F, 1 C, 0.1Ω, 1Ω, Scaled–for–PID, and
Proportional Counts. The first six options represent real engineering units
and do not require explanation. The Scaled–for–PID selection allows you to
directly interface RTD Data into a PID instruction without intermediate scale
operations and Proportional Counts selection provides the highest display
resolution, but also require you to manually convert the channel data to real
Engineering Units.
Default scaling can be selected for scaled–for–PID data format and
proportional counts data format. User–set scaling can be selected for
proportional counts data format. For a description of default scaling, see
pages 5–6 (scaled–for–PID data format) and 5–7 (proportional counts data
format). For a description of user–set scaling using proportional counts data
format, see page 5–15.
The equations on page 5–8 show how to convert from Scaled–for–PID to
Engineering Units, Engineering Units to Scaled–for–PID, Proportional
Counts to Engineering Units, and Engineering Units to Proportional Counts.
To perform the conversions, you must know the defined temperature or
resistance range for the channel's input type. Refer to the Channel Data
Word Format in Table 5.C through Table 5.H. The lowest possible value for
an input type is S , and the highest possible value is S
LOW
Chapter 5
Channel Configuration, Data, and Status
Description
express values in 0.1 degree or 0.1W or 0.01W for 150W pot.,
only
express values in 1 degree or 1W or 0.1W for150W pot., only.
The input signal range for the selected input type is its full scale
input range. The signal range is scaled into a 0 to 16383
range, which is what the SLC processor expects in the PID
function.
The input signal range is proportional to your selected input
type and scaled into a –32768 to +32767 range (default) or
user–set range, based on the scaling select bits (13 and 14)
and scale limit words (O:e.4/O:e.5 or O:e.6/O:e.7).
.
HIGH
5–5