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 resistorshe diagram below shows the temperature profile and the corresponding switching points.If 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 CPU
● Distributed operation on PROFINET IO in an ET 200MP system
● Distributed operation on PROFIBUS DP in an ET 200MP system
When assigning parameters in the user program, use the WRREC instruction to transfer the
parameters to the module by means of data records; refer to the section Parameter
assignment and structure of the parameter data records (Page 54).
The following parameter settings for the channels are possible:
Table 4- 2 Configurable parameters and their defaults
quence The recorded input data of a data cycle (send clock) is copied into the interface module in the next data cycle and is available for the module in the data cycle after that. The figure below shows the chronological sequence for oversampling with 10 sub-cycles.
Fixed reference
temperature
• Dynamic reference
temperature
• Internal reference
junction
• Reference channel
of the module
Only for measurement type Resistance, Resistance Thermometer RTD: If "Wire break" diagnostics and "Value status"
are deactivated, the module reports overflow or underflow (7FFFh or 8000h) in case of a wiring error. The alarm depends
on whether the connected cables are faulty.
Recommendation: Activate the "Wire break" diagnostics. The active check for wire break reliably detects wiring errors and
the module reports overflow (7FFFH).
2) When "Wire break" diagnostics is disabled, the current limit of 1.185 mA applies to the value status. For measured
values below 1.185 mA, the value status is always: 0 = fault.
3) If you enable diagnostics for multiple channels, you will receive an alarm surge on failure of the supply voltage because
each enabled channel will detect this fault.
You can prevent this message burst by assigning the diagnostics function to one channel only.
4) You can set the effective range of the diagnostics for each channel in the user program with data records 0 to 7.
5) You can set the current limit for wire break diagnostics, the setting "Fixed reference temperature" and "Reference channel
of the module" as well as the limits for hardware interrupts in the user program with data records 0 to 7.
Parameters of the reference channel
You cannot configure the reference channel with GSD file. You have to transfer the
reference channel to the module with data record 8.
If you want to change the default settings, you have to transfer the parameters to the module
with data record 8, see chapter Parameter assignment and structure of the parameter data
records (Page 54).
The diagnostics "Common mode error" and "Reference channel error" cannot be configured
for the reference channel.Enabling of the diagnostics, with missing or too little supply voltage L+.
Overflow
Enabling of the diagnostics if the measured value violates the high limit.
Underflow
Enabling of the diagnostics when the measured value violates the low limit.
Common mode error
Enabling of diagnostics if the valid common mode voltage is exceeded.
Enable the Common mode error diagnostics when 2WMT is connected, for example, to
check for a short circuit to MANA or a wire break. If you do not need the Common mode error
diagnostics, disable the parameter.
Reference channel error
● Enable diagnostics for an error at the temperature compensation channel, e.g. wire
break.
● Dynamic reference temperature compensation type is configured and no reference
temperature has been transferred to the module yet.
Wire break
Enabling of the diagnostics if the module has no current flow or the current is too weak for
the measurement at the corresponding configured input or the applied voltage is too low.
Current limit for wire break diagnostics
Threshold for reporting wire breaks. The value can be set to 1.185 mA or 3.6 mA, depending
on the sensor used.
Temperature coefficient
The temperature coefficient depends on the chemical composition of the material. In Europe,
only one value is used per sensor type (default value).
The temperature coefficient (α value) indicates by how much the resistance of a specific
material changes relatively if the temperature increases by 1 °C.
The further values facilitate a sensor-specific setting of the temperature coefficient and
enhance accuracy.At analog input modules, this suppresses interference caused by the frequency of the AC
network.
The frequency of the AC network may corrupt measurements, particularly in the low voltage
ranges and when thermocouples are being used. For this parameter, the user defines the
mains frequency prevailing on his system.
Smoothing
The individual measured values are smoothed using filtering. The smoothing can be set in 4
levels.
Smoothing time = number of module cycles (k) x cycle time of the module.
The following figure shows the number of module cycles after which the smoothed analog
value is almost 100%, depending on the set smoothing. It is valid for each signal change at
the analog inputThe following settings can be configured for the reference junction parameter:
Table 4- 3 Possible parameter assignments for the reference junction parameter TC
Setting Description
Fixed reference temperature The reference junction temperature is configured and stored in the module as
a fixed value.
Dynamic reference temperature The reference junction temperature is transferred in the user program from the
CPU to the module by data records 192 to 199 using the WRREC (SFB 53)
instruction.
Internal reference junction The reference junction temperature is determined using an integrated sensor
of the module.
Reference channel of the module The reference junction temperature is determined using an external resistance
thermometer (RTD) at the reference channel (COMP) of the module.
Hardware interrupt 1 or 2
Enabling of a hardware interrupt at violation of high limit 1 or 2 or low limit 1 or 2.
Low limit 1 or 2
Specifies the low limit threshold that triggers hardware interrupt 1 or 2.
High limit 1 or 2
Specifies the high limit threshold that triggers hardware interrupt 1 or The module can be configured differently in STEP 7; see following table. Depending on the
configuration, additional/different addresses are assigned in the process image of the inputs.
Configuration options of AI 8xU/I/RTD/TC ST
You can configure the module with STEP 7 (TIA Portal) or with a GSD file.
When you configure the module by means of the GSD file, the configurations are available
under different abbreviations/module names.
The following configurations are possible:1 x 8-channel without value status AI 8xU/I/RTD/T
C ST
V12 or higher X
1 x 8-channel with value status AI 8xU/I/RTD/T
C ST QI
V12 or higher X
8 x 1-channel without value status AI 8xU/I/RTD/T
C ST S
V13 Update 3 or higher
(PROFINET IO only)
X
(PROFINET IO only)
8 x 1-channel with value status AI 8xU/I/RTD/T
C ST S QI
V13 Update 3 or higher
(PROFINET IO only)
X
(PROFINET IO only)
1 x 8-channel with value status for moduleinternal
shared input with up to 4 submodules
AI 8xU/I/RTD/T
C ST MSI
V13 Update 3 or higher
(PROFINET IO only)
X
(PROFINET IO only)
Value status (Quality Information, QI)
The value status is always activated for the following module names:
● AI 8xU/I/RTD/TC ST QI
● AI 8xU/I/RTD/TC ST S QI
● AI 8xU/I/RTD/TC ST MSI
An additional bit is assigned to each channel for the value status. The value status bit