Rockwell Automation 1762-IT4 Thermocouple/mV Input Module - Manual (Page 38)

Publication 1762-UM002A-EN-P - July 2002
3-8 Module Data, Status, and Channel Configuration
Engineering Units x 10
When using a thermocouple input with this data format, the module
scales the input data to the actual temperature values for the selected
thermocouple type. With this format, the module expresses
temperatures in 1°C or 1°F units. For millivolt inputs, the module
expresses voltages in 0.1 mV units.
The resolution of the engineering units x 10 data format is dependent
on the range selected and the filter selected. See Determining Effective
Resolution and Range on page 3-14.
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 1200 and other Allen-Bradley controllers (e.g. SLC). For
example, if type J thermocouple is used, the lowest temperature for
the thermocouple is -210°C, which corresponds to 0 counts. The
highest temperature in the input range, 1200°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 type J thermocouple, the range -210°C to +1200°C is
represented as 0% to 100%. See Determining Effective Resolution and
Range on page 3-14.
Selecting Input Type (Bits 11 through 8)
Bits 11 through 8 in the channel configuration word indicate the type
of thermocouple or millivolt input device. Each channel can be
individually configured for any type of input.