Our question is if the thermocouple inputs on the amplifier are EMC protected
or if external components are required. If so, please advice a solution that
has no effect on the performance of the amplifier.
The inputs of the AD594 have standard ESD protection diodes to protect the
device during normal handling and manufacturing events ( approx 2kV to the
Human Body Model).
The inputs are not protected for the purposes of EMC. If you require your
product to pass CE mark – radiated immunity, fast transient burst, IEC4000 ESD
levels, you will need to provide external protection circuitry. OF course the
AD594 is typically connected to a long cable thermocouple and is therefore
placed in a particularly sensitive position.
Remember that the AD594 cold junction thermocouple compensation will only work
if the AD594 and the cold junction (where the thermocouple metals meet the
copper PCB) are at exactly the same temperature and places on the same thermal
gradient. Bear this in mind when laying out your circuit board.
Also think about parasitic thermocouples on your board – the effects can be
minimized by ensuring symmetry in both thermocouple signal paths.