Product overview
KL3311, KL3312, KL3314 and KL3302
12
Version: 4.2
Fig. 3: Principle of the thermocouple
Example:
In the following example, the voltage U
th
is given which is present at a type-K thermocouple at the
temperature Tm.
U
th
= (k
NiCr
- k
Ni
) x ΔT
with
ΔT = T
m
- T
v
A type-K thermocouple consists of a junction of a nickel-chrome alloy and nickel, where k
NiCr
and k
Ni
represent the thermoelectric coefficients of nickel-chrome and nickel respectively. By adapting the equation
according to T
m
, the sought-after temperature can be calculated from the voltage measured across the
thermocouple. Based on the difference to the cold junction temperature, the temperature at the
measurement point can be determined to an accuracy of better than one tenth of a Kelvin with the aid of the
above thermocouple equation.
Sensor circuit
A modification of the sensor circuit with additional devices such as change over switches or multi-
plexer decreases the measure accuracy. We strongly advise against such modifications.
