thermocouples for external/internal compensation and the connection of a resistance
thermometer (RTD) at the reference channelWiring of a thermocouple (non-grounded) for internal compensation
CHx Channel or 9 x channel status
(green/red)
② Wiring of a thermocouple (non-grounded) for external compensation
RUN Status display LED (green)
③ Wiring of a resistance thermometer (RTD) at the reference
channel
ERROR Error display LED (red)
④ Analog-to-digital converter (ADC) PWR LED for power supply (green)
⑤ Backplane bus interface
⑥ Supply voltage via power supply element
⑦ Equipotential bonding cable (optional)
Figure 3-6 Block diagram and pin assignment for non-grounded thermocouples and resistance thermometersThe following figure shows an example of the pin assignment for grounded thermocouples
for internal compensationWiring of a thermocouple (grounded) for internal compensation
CHx Channel or 9 x channel status (green/red)
② Analog-to-digital converter (ADC) RUN Status display LED (green)
③ Backplane bus interface ERROR Error display LED (red)
④ Supply voltage via power supply element PWR LED for power supply (green)
⑤ Equipotential bonding cable (optional)
Figure 3-7 Block diagram and pin assignment for grounded thermocouplThe module is set to voltage measurement type with measuring range ±10 V by default. You
need to reassign the module parameters with STEP 7 if you want to use a different
measurement type or range.
Deactivate the input if it is not going to be used. The module cycle time is shortened and the
interference factors that lead to failure of the module (for example, triggering a hardware
interrupt) are avoided.
The following table shows the measurement types and the respective measuring range.
Table 4- 1 Measurement types and measuring rangesPTC resistors are suitable for temperature monitoring of electrical devices, such as motors,
drives, and transformers.
Use Type A PTC resistors (PTC thermistor) in accordance with DIN/VDE 0660, part 302. In
doing so, follow these steps:
1. Choose "Resistor (2-wire terminal)" and "PTC" in STEP 7.
2. Connect the PTC using 2-wire connection technology.
If you enable the "Underflow" diagnostics in STEP 7, it will be signaled for resistance values
<18 Ω. In this case, this diagnostic signifies "Short-circuit in the wiring".
The following figure shows the address space assignment for the AI 8xU/I/RTD/TC ST
module with PTC resistorThe diagram below shows the temperature profile and the corresponding switching poIf faults occur (for example supply voltage L+ missing) that make it impossible to acquire
measured values with PTC resistors, the corresponding channels (IR x/IR x+1) report
overflow (7FFFH). If the value status (QI) is enabled, the value 0 = incorrect is output in the
corresponding bit.
4.2 Parameters
AI 8xU/I/RTD/TC ST parameters
When you assign the module parameters in STEP 7, you use various parameters to specify
the module properties. The following table lists the configurable parameters. The effective
range of the configurable parameters depends on the type of configuration. The following
configurations are possible:
● Central operation with a S7-1500 CPU
● Distributed operation on PROFINET IO in an ET 200MP system