DBK19 Measurement Computing 14-Channel High-Accuracy Thermocouple Expansion Card

The Measurement Computing / IOtech DBK19™ 14-Channel High-Accuracy Thermocouple Expansion Card provides IOtech’s LogBook, DaqBook, DaqBoard, and Daq PC-Card data acquisition systems with the ability to measure up to 14 thermocouple inputs. Each thermocouple input is attached to the unit via convenient screw terminal blocks.

To ensure precise measurements over a wide range of operating temperatures, two of the unit’s 16 on-board channels are reserved for auto-zero and cold-junction compensation. As a result, the user can attach up to 14 thermocouples of different types (J, K, S, T, E, B, R, and N) to one DBK19 card. As many as 16 DBK19 cards can be attached to one LogBook, DaqBook, DaqBoard, or Daq PC-Card, for a total of 224 channels.

The DBK19’s input stage features a 16-channel multiplexer, and a low-noise instrumentation amplifier. All thermocouple measurements are made differentially to minimize common-mode noise pick-up. The amplifier’s gain is automatically selected by the software driver to maximize A/D resolution based on the type of thermocouple attached to the channel being measured.

Once the DBK19 has amplified the signal, the LogBook, DaqBook, DaqBoard, or Daq PC-Card data acquisition system’s A/D converter digitizes it and passes it on to the PC for further processing. The system then automatically measures the DBK19’s cold junction temperature sensor to determine the temperature of the thermocouple connection block. In addition, the LogBooks, DaqBooks, DaqBoards, and Daq PC-Cards automatically correct for system offsets by measuring the auto-zero input channel.

After these three measurements are complete, the DBK19’s software performs cold-junction compensation and zero-offset compensation to determine the actual temperature reading.