Campbell Scientific - Model AM25T -25-Channel Solid-State Thermocouple Multiplexer

• Greatly increases the number of thermocouples a data logger can measure
  
• Multiplexes up to 25 thermocouples
  
• Includes an on-board PRT that serves as a reference junction
  
• Allows several AM25Ts to be controlled by one data logger, increasing the number of thermocouples that can be measured
  
• Uses a metallic, internal ground plane to reduce thermal gradients, which ensures more accurate measurements
  
• Provides a vertical package for a smaller “footprint” that makes it easier to fit in a crowded enclosure
  
• Supports a maximum cable length of 152.4 m (500 ft) when lightning protection is used

Up to 25 thermocouples are sequentially connected to a common differential channel on the AM25T. (Note: Other low-level voltage output sensors that do not exceed the common mode range of the data logger can also be measured. The AM25T should NOT be used to measure resistive bridges or configured with a voltage divider between the AM25T and the data logger; ask about our AM16/32B multiplexer for these applications.) The output from this channel is wired to a differential input channel on the data logger. As the AM25T sequentially changes channels, the data logger measures the output from each thermocouple in sequence.

A PRT attached to the AM25T’s grounding bar provides a temperature reference for the thermocouple measurements. The heat capacity of the grounding bar and an insulated aluminum cover reduce thermal gradients along the length of the multiplexer. Reducing the thermal gradients allow more accurate measurements.