When using the AD59x, the thermocouple should be grounded at one place, and
place. The grounding can occur at the negative input of the AD59x, the positive
the AD59x, or at the thermocouple tip.
Where the thermocouple is grounded will change the behaviour of the AD59x
open thermocouple condition. If the negative input is grounded, the part’s
will rail high during an open thermocouple event. If the positive input is
part’s output voltage will rail low during an open thermocouple event.
undefined if grounding at the thermocouple tip.
Special Case: Non-isolated thermocouples
For good measurements, it is critical to only have one ground point. The vast
thermocouples have an electrically isolated sheath around the sensing end, so
there is no
electrical contact between the material being sensed and the thermocouple.
some types of thermocouples (such as those designed to respond very quickly)
an electrical connection between the material being measured and the
this case, if the material being measured is grounded, this connection counts
thermocouple’s “ground” and the AD59x should not be grounded at one of the
With long thermocouple connections the “ground” at the tip may be considerably
different than the ground at the AD59x. In these cases it is recommended to run
AD59x with a dual supply, so that if the “ground” at the thermocouple deviates
somewhat from the AD59x’s ground, it will still be in the common mode range of