26 Analog input module XN-322-10AI-TEKT
26.2 Wiring topic
191 XN300 slice modules 02/24 MN050002EN Eaton.com
26.2 Wiring topic
Two analog inputs can be wired to each of the connectors X1 to X5.
Remove the KTY sensor included as standard from the bottom of the
device.
Insert the thermocouple's positive pin into one of the + pins, e.g., "1+".
Insert the thermocouple's negative pin into one of the - pins, e.g., "1-".
If external cold junction compensation is used, the KTY sensor must be
placed at the reference junction and wired to one of the two measuring
inputs KTY1, KTY2. When parameterizing the device, each thermal
measuring input can be assigned a KTY measuring input for cold junction
compensation.
The reference point is the place where the transition of the
thermocouple lines to the supply line takes place.
26.2.1 Temperature measurements using thermocouples
Measuring temperatures with thermocouples takes advantage of the ability
of cables made of different alloys to produce a voltage at their point of
contact (junction) as a result of their electrochemical properties.
The magnitude of this voltage will be small, non-linear, and extremely
dependent on temperature, making this method ideal for measuring
temperatures across a wide temperature range. The module will adjust for
the corresponding non-linearity, representing values in °C / 10 (with one
decimal place).
The term "cold-junction compensation" refers to the action of correcting the
value measured with the thermocouple by removing the error resulting from
the corresponding pin. The reason this is necessary is that when a
thermocouple's individual lead is connected to the module connector's
copper, this will create a "parasitic" thermocouple, resulting in measuring
errors and requiring additional correction on behalf of the module.
Internal cold-junction compensation
On hardware version 3.03 and higher, internal temperature sensors for
cold-junction compensation are available. When thermo-wires are connected
directly on the module, It is recommended to select internal cold junction
compensation, since this will minimize the measurement error.
External cold-junction compensation
If external cold-junction compensation is selected and the wires of the
thermocouples are not directly connected to the module, the inputs KTY1
and KTY2 are used to detect the temperature at the junction of the
thermocouple cable and the copper wire. Nornmally compensation doses are
used for this purpose..
If the thermocouples are wired directly to the module, it is advisable to wire
the external KTY sensor directly to the module as well. This will ensure that
the temperature measured has a value that depends on the module's outside
and inside temperatures and reflects the temperature at the thermocouple
connector's pin. In fact, the conditions at the pin will be comparable,
To Next Page
Loading...
