Principles of Operation
61
The channels are read in order from the first entry to the last entry in the channel list. Refer to
for more information on the supported conversion modes.
Cold Junction Compensation
One cold-junction compensation (CJC) circuit is provided for all thermocouple input channels.
The software reads the value of the CJC input and applies it to the value of the thermocouple
input to correct for errors based on the specified thermocouple type.
The conversion time for the CJC circuitry is 240 ms, typical. The software takes care of
correlating the CJC measurements with the analog input measurements.
Note:
When using the DT-Open Layers for .NET Class Library, the software provides the
option of returning CJC values in the data stream. This option is seldom used, but is provided
if you want to implement your own temperature conversion algorithms in software when
using continuous operations. Refer to
for more information on this feature.
Open Thermocouple Detection
A 10 M
Ω
pull-up resistor is provided on the high side input of each differential thermocouple
channel for open thermocouple detection. When an open thermocouple is detected, a positive,
full-scale input voltage is returned.
The software returns the value SENSOR_IS_OPEN (99999 decimal) for any channel that was
configured for a thermocouple input and has either an open thermocouple or no
thermocouple connected to it.
Input Ranges and Gains
The DT9828 module supports an input range of ±156 mV. In software, specify a gain of 1.
If a voltage is measured on the input that is outside of the range for the selected thermocouple
type, the channel may be configured for the wrong type of thermocouple or something other
than a thermocouple may be connected to the channel.
In addition, if the input voltage is less than the legal voltage range for the selected
thermocouple type, the software returns the value TEMP_OUT_OF_RANGE_LOW (–88888
decimal). If the input voltage is greater than the legal voltage range for the selected
thermocouple type, the software returns the value TEMP_OUT_OF_RANGE_HIGH (88888
decimal).
Summary of Contents for DT9828
Page 1: ...DT9828 User s Manual UM 24984 A Title Page ...
Page 4: ......
Page 8: ...Contents 8 ...
Page 12: ...About this Manual 12 ...
Page 13: ...13 1 Overview Features 14 Supported Software 16 Accessories 18 Getting Started Procedure 19 ...
Page 20: ...Chapter 1 20 ...
Page 21: ...Part 1 Getting Started ...
Page 22: ......
Page 30: ...Chapter 2 30 ...
Page 49: ...Verifying the Operation of a Module 49 ...
Page 54: ...Chapter 4 54 ...
Page 55: ...Part 2 Using Your Module ...
Page 56: ......
Page 57: ...57 5 Principles of Operation Analog Input Features 59 Digital I O Features 67 ...
Page 80: ...Chapter 6 80 ...
Page 86: ...Chapter 7 86 ...
Page 92: ...Chapter 8 92 ...
Page 106: ...Appendix A 106 ...
Page 112: ...Appendix B 112 ...