Analog PLC Programming

[Meyers Mills]

I am beginner in plc programming, I want to know the salient points /topics in analog PLC programming a starter must know .

Meyers Mills

 

[tarik1978]

https://www.plcacademy.com/plc-analog-input-output/

 

[ndzied1]

Here is a chart that helps show all the bits and pieces of analog input signals.

 

[parky]

The last post is a good representation of how it works. the analog output is just the reverse.
It depends on the PLC on how the value is received or sent to/from the PLC (code-wise). for example, Siemens use Peripheral words (PW) so the card converts it into a value i.e. 0-2048 and then in your code you load the PW and scale it to what you want. Mitsubishi uses FROM/TO instructions to retrieve the raw data and store it in a memory word, from there you can scale it as required. Many PLC platforms have either functions to retrieve & scale the data or the card can be configured via the programming utility to process the data into meaningful values. You really need to read the datasheet on each particular platform to understand the ways to read/send values from/to cards.

 

[cardosocea]

Siemens use Peripheral words (PW) so the card converts it into a value i.e. 0-2048.

Small remark, that is a tiny range for any PLC. Even PLC5s went to 4095.

 

[parky]

If I remember correctly in S5 the value was 16384 but the lower bits were diagnostic bits for the card so you had to shift right. I could be mistaken as it was some time ago and it could be 4096, however, they were 12-bit conversion in a 16-bit word and as the lower 3 bits were diagnostic and there was of course the sign bit and this was just the siemens older cards. just remembered they were 2047 max.

 

[ndzied1]

It is very specific to what hardware you are using. Even with one piece of hardware, there are sometimes options to configure it in different ways to provided different numbers and diagnostic information in the input table.

These are the possible configurations for a Phoenix Contact
IB IL AI 2/SF-PAC (2861302)
For the 0-10V input range.

This card can also be configured for +/10V, 0-20mA, +/-20mA, 4-20mA.

So you really have to read the data sheet for hardware as mentioned above.