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Useful information on thermocouple multiplexers

Useful information on thermocouple multiplexers

Electrical devices like gas furnaces, water heaters and many other types use thermocouples. Thermocouple is a very sensitive part, and can be used for making a thermocouple multiplexer, also called a thermocouple conditioner. Thermocouple represents a device, which is comprised of two metal conductors (they usually are metal alloys). They produce voltage, which is dependent from the temperature difference. Their usage is mainly for temperature measurements. This article contains the most useful information on a thermocouple multiplexer.

Description of a thermocouple multiplexer

There are many thermocouple multiplexer units. One of them is the MRTM-3048C, which is a 48-channel thermocouple multiplexer. The MRTM-3048C provides electronic junction compensation, it accepts input thermocouple wiring, provides real-time linearization of data, and is compatible with thermocouple types J, E, K, and T. The data coming through the thermocouple wires is 12-bit long. The MRTM-3048C works as a remote unit, together with a CAIS master unit. The CAIS master unit controls the channel sample sequence and the conditioning parameters. It is worth mentioning that the CAIS master unit is user programmable through a serial connection to a PC. The computer must have Windows 95, Windows 98, or Windows NT installed, because the application needed for programming the CAIS master unit is compatible with these operating systems. The gathered and encoded data is then formatted as serial PCM (pulse-code modulation).

The MRTM-3048C is a fixed-volume unit, and can be used in low temperatures, and harsh conditions. The thermocouple wiring uses D-sub style connectors, which are highly reliable, while the CAIS signals use standard, CAIS compatible connectors. Power on the input uses circular, military-style connectors.

Features of the MRTM-3048C

As we said before, the MRTM-3048C is a 48-channel thermocouple multiplexer and encoder that uses 3 internal cards. Those cards include the overhead card, the conditioning card, and the power supply. The overhead card controls the internal sampling of the channel. The conditioning card provides the thermocouple conditioning, the electronic junction compensation, and the data linearization. The power supply of the thermocouple multiplexer provides multiple regulated outputs, and ground isolation. It is also comparable with various thermocouple types (T, J, E, and K), and every channel can be individually programmed. It weighs about 4 pounds, and there is a computer software included, used for programming the CAIS master unit. The MRTM-3048C has a ±0.3% system accuracy, a ±35V overvoltage protection, and it operates on +28V. The MRTM-3048C measures 5.8 inches in width, 4 inches in depth, and 3 inches in height.


There are many applications, where you can find the MRTM-3048C thermocouple multiplexer. One possible application is the distributed data acquisition systems. They use remote modules to measure, condition, linearize and transmit the variables of a process to a computer, which acts as a host. Then, with the data acquired from the computer, you can perform different calculations, write reports, and so on. Another possible application of the MRTM-3048C thermocouple multiplexer is for remote measurement of the temperature, because thermocouples are usually used as a part of thermocouple thermometers.

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