There are many considerations when choosing a Michigan Scientific thermocouple (TC) amplifier product; mounting, channel count, TC type, input range, and accuracy are the main concerns. In Part Two of our two-part blog series, we will discuss how to choose the correct thermocouple amplifier for your application.
Most MSC TC amps are small enough to be mounted with a cable tie, epoxy, or a single mounting screw, even in rotating applications. The exceptions to this mounting configuration would be the AMP-TC units, which are designed to be mounted on the rotating side of an end-of-shaft slip ring assembly and the Short S-Series slip rings that have thermocouple amplifiers built directly into the rotors.
Channel Count and Linear/Non-linear Output
The MSC TC amplifiers that provide a linear output, such as the AMP-TC-LIN and MicroTC, are only available in single channel configurations. If multiple channels in a single unit are required, only MSC amplifiers with a non-linear output can be used. The AMP-TC-M1 is available in 1-3 channels, while the AMP-TC can provide up to 9 channels. Keep in mind that multiple single-channel units can be powered from a single source and they can even share their signal ground connections.
Our smallest and most cost-effective TC amplifier, the MicroTC, is only available for K-type thermocouples. If J-type with a linear output is required, the AMP-TC-LIN is available in K and J. Our non-linear units, such as the AMP-TC and AMP-TC-M1, are available in K, J, T, and E. Other TC types may be available on request.
Input Range and Output Scale
The AMP-TC and AMP-TC-M1 offer a wide input range of -260 °C to 1000 °C. The outputs are amplified to approximately 10 mV/°C. The output is “approximately” 10 mV/°C because it is not a linear 10 mV/°C. MSC provides polynomial equations for converting the output to a linear scale.
The AMP-TC-LIN provides a linear 10 mV/°C output and will measure up to 1000°C, but the low end of the measurement range stops at -80°C.
The MicroTC offers the widest input range of -200 °C to 1360 °C, but it does not provide a linear output over that entire range. The output is scaled to a linear 5 mV/°C over the input range of -50 °C to 400 °C. Inputs outside of that range can still be measured, but a polynomial equation must be applied to accurately calculate the output.
In normal ambient temperature conditions, accuracy will be either ±2 °C or ±3 °C, depending on model. The worst-case accuracy for any MSC thermocouple amplifier is ±5 °C. This will occur when the case temperature of the amplifier gets too high or too low and is different for each amplifier model. Please refer to the product datasheets for more information.