Splitting A Thermocouple Signal

Thermocouple in heater, temperature measurement equipment

Thermocouples are simple and easy sensors use to measure temperature for a wide variety of uses. The way they work is pretty simple. Thermocouples are made up of two different alloys that create voltage when touched together. The voltage is increased based on the difference in temperature between the two metals, due to a natural phenomenon called the Seeback effect. One of the alloys is kept at a consistent reference temperature, and the other one is placed on whatever it is that you're trying to figure out the temperature of. You can then measure the voltage created when the alloys are touched together, and use that information to figure out the temperature. Pretty simple, right? Because thermocouples are so small, cheap, and accurate, they are often used to measure temperature in devices like thermometers, as well as safety features in ovens and water heaters.

In general, wiring a thermocouple sensor to an instrument is pretty easy. Thermocouples usually have two wires: a red negative output wire, and a black positive output wire. Hooking these wires up to an instrument is pretty much like hooking up a car battery for a jump start. Just connect the negative output wire of the sensor to the negative terminal of the instrument, and the positive output wire to the positive terminal. Easy-peasy. However, if you're trying to connect a single thermocouple sensor to two different instruments, the process becomes a bit more complicated. If you just repeat the process twice and hook up two instruments to the same thermocouple, you could end up with inaccurate temperature readings due to the resistance, or "impedance", of the wires. However, there are a few ways you can hook up a single sensor to two receivers. There are two main methods for this.

The first and simplest way to do this is just to get a dual thermocouple sensor. These sensors have two different junctions that are both connected to whatever you're trying to measure the temperature of, and each of those junctions can be hooked up to a separate receiver. This is probably the simplest and easiest way to hook a thermocouple to two different receivers, and it's a good idea to try this one first. However, it is limited in that you can only hook it up to two instruments at once. If you need to hook the sensor up to any more, you'll have to try a different method.

The other way to hook up a thermocouple to two different instruments is to use a thermocouple transmitter. Instead of connecting the sensor to multiple instruments that can measure the output, a transmitter just takes the output from a single sensor and converts it into voltage or a current signal. This information can be broadcast from the transmitter to any number of instruments, making it a more versatile method. However, it's also a little trickier, and requires some programming effort. You're going to have to make sure that every instrument you send the signal to is properly scaled, otherwise the measurements could be inaccurate.