Spectrum Controls 1769sc-IR6I - Manual (Page 37)

Chapter 4: Module, Data, Status, and Channel Configuration 4-5
User’s Manual Pub. 0300241-01 Rev. A
lowest temperature of -200°C corresponds to -32767 counts. The highest temperature of
850°C corresponds to +32767.
Engineering Units x1
When using this data format for a RTD or resistance input, the module scales the RTD or
resistance input data to the actual engineering values for the selected RTD or resistance
input type. It expresses temperatures in 0.1°C or 0.1°F units for RTDs. For resistance
inputs, the module expresses resistance in 0.01Ω increments.
Note: Use the engineering units x 10 setting to produce temperature readings in whole
degrees Celsius or Fahrenheit.
Engineering Units x10
When using a RTD input with this data format, the module scales the input data to the
actual temperature values for the selected RTD type. With this format, the module
expresses temperatures in 1°C or 1°F units. For resistance inputs, the module expresses
resistance in 0.1 Ω increments.
Scaled for PID
The value presented to the controller is a signed integer with 0 representing the lower
input range and +16383 representing the upper input range.
To obtain the value, the module scales the input signal range to a 0 to +16383 range,
which is standard to the PID algorithm for the MicroLogix 1500 and other Allen-Bradley
controllers (e.g. SLC). For example, if a Pt 385 RTD is used, the lowest temperature for
the RTD is -200°C, which corresponds to 0 counts. The highest temperature in the input
range, 850°C, corresponds to +16383 counts.
Percent Range
Input data is presented to the user as a percent of the specified range. The module scales
the input signal range to a 0 to +10000 range. For example, using a Pt 385 RTD, the
range -200°C to +850°C is represented as 0% to 100%.
4.2.5 Selecting Input Type (Bits 8 through 11)
Bits 8 through 11 in the channel configuration word indicate the type of RTD or
resistance input device. Each channel can be individually configured for any type of
input.
4.2.6 Selecting Temperature Units (Bit 7)
The module supports two different linearized/scaled ranges for RTDs, degrees Celsius
(°C) and degrees Fahrenheit (°F). Bit 7 is ignored for resistance input types, or when
raw/proportional, scaled-for-PID, or percent data formats are used.
4.2.7 Determining Open-Circuit Response (Bits 5 and 6)
An open-circuit condition occurs when an input device or its extension wire is physically
separated or open. This can happen if the wire is cut or disconnected from the terminal
block.
Bits 5 and 6 define the state of the channel data word when an open-circuit condition is
detected for the corresponding channel. The module overrides the actual input data
depending on the option that you specify when it detects an open circuit. The open-
circuit options are explained in the table below.