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S7-1200 CPU 12xx -- Setting up and parameterizing hardware -- Initializing and parameterizing modules
Which settings do you have to make in the TIA Portal to read out messages and status information over the CPU's web server and display them in the web browser?
What is the meaning of the system constants in STEP 7 (TIA Portal) with S7-1200/1500?
How can the CPU analog inputs of the SIMATIC S7-1200 also measure currents of 0-20mA?
How do you program the "GET" and "PUT" instructions in the user program of the SIMATIC S7-1200 CPU in order to transfer more than 160 bytes of data?
Why must you never remove a memory card when the S7-300/S7-400/S7-1200/S7-1500 CPU is in operation (RUN)?
How does startup work in an S7-1200?
What is the connection between subnet masks and IP addresses with regard to subnetting and supernetting (Classless Inter Domain Routing CIDR)?
How can you prevent data loss of runtime-generated parameters when updating your S7-1200 PLC program?
How can you share runtime-generated parameters between several S7-1200 PLCs with a KTP Basic Panel?
How can you change the IP address of an S7-1200 without using STEP 7 Basic?
How can you delete the IP address and reset your S7-1200 to factory settings using the SIMATIC MC memory card (2MB or 24MB)?
How can you download to a network of several S7-1200 PLCs with the same IP address?
How can you reset the IP address of your S7-1200 PLC using STEP 7 Basic software?
How can the CPU analog inputs of the SIMATIC S7-1200 also measure currents of 0-20mA?
Part number:

Description
The two analog inputs of the S7-1200 CPUs are factory-set for voltage measurement (0..10V).
In order to be able to use the inputs as current inputs as well you must incorporate a 500 Ohm resistor between terminals "0" and "2M" (or "1" and "2M").


Fig. 01: Connection of a sensor to a voltage source as a 2-conductor connection


Fig. 02: Connection of a sensor to a voltage source as a 3-conductor connection


Fig. 03: Connection of a sensor to a voltage source as a 4-conductor connection


Fig. 04: Connection of a measuring transducer with voltage output to a current source as a 4-conductor connection

Note
To avoid damage you must ensure that the external current source has short-circuit protection in all conductor cases.

The external resistor is a source of error because of its dependency on temperature and its inaccuracy.
In order to obtain measuring results that are as precise as possible it is recommended to use resistors with tolerances that are as small as possible.

With a 500 Ohm resistor you must pay attention to the measurement of the power dissipation.
With a power supply of 24V the resistance should be configured for at least 1.16W.
Commercially available resistors have a power dissipation of 0.25W to 0.5W.

Additional Information
The SIMATIC S7-1200 provides analog signal modules for measuring currents.
These are available in the system manual Entry ID: 36932465:

How you connect a sensor to the analog signal modules of the SIMATIC S7-1200 is described in Entry ID 40913432.

Additional Keywords
Current measuring, Measuring transducer

 Entry ID:67396370   Date:2013-01-23 
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