SLC Analog I\O

bfranklin · Mar 8, 2013

In a SLC 500 PLC I have noticed some some the raw 4-20ma analog inputs are configured to be 0% an 4000 and 100% at 20000.
How do you go about doing this?
Also can you do the same thing for 4-20ma analog outputs?

Thanks

Bit_Bucket_07 · Mar 8, 2013

Module level scaling configuration is dependent upon the type of analog I/O modules installed.

bfranklin · Mar 8, 2013

say we had an analog I\O modules capable of scaling. Where in rs logix 500 is this typically done?

Thanks

sthompson · Mar 8, 2013

Perhaps you could tell us which Analog I/O Module you are talking about.

Stu....

Bit_Bucket_07 · Mar 8, 2013

Either in the I/O configuration dialog, or by manually assigning appropriate values to the I/O associated with the module's configuration data table within the user program. Some SLC analog I/O modules cannot be configured -- they have a fixed configuration depending upon model number.

bfranklin · Mar 18, 2013

Analog Input- 1746-NI8

Analog Output- 1746-N08I

Anirban Hazra · Mar 18, 2013

First configure the Data type of the module.How that can be done is shown in the attached picture.

Anirban Hazra · Mar 18, 2013

Refer to the Table attached below to know about the data values corresponding to the data format that you have chosen.

If Scale(SCL) instruction is available in SLC 500 then use that, otherwise just construct a " y = mx + c " equation using math and scale those data values to whatever range you need.

Lancie1 · Mar 18, 2013

If Scale (SCL) instruction is available in SLC 500 then use that,

Yes, SCL it is available in the RSLogix500 software, but SCP (Scale with Parameters) would probably be a better choice. With SCL, you have to manually calculate and enter the Rate and Offset, but SCP does that internally.

SCP [Scale with Parameters]

Description
This output instruction consists of six parameters. Parameters may be integer, floating point, or immediate data values or addresses containing values. The Input value is scaled to a range determined by creating a linear relationship between input min and max values and scaled min and max values. The scaled result is returned to the address indicated by the output parameter.

You can use indexed addressing (with SLC only) or indirect addressing.
Data filetypes MG (message) and PID are available to indirectly address parameters when using the MicroLogix 1200 or 1500 controller.

Entering Parameters
Input - Enter a value to be scaled. This can be a word address or an address of floating point data elements.
Input Min - Enter a minimum value for the input (low end of range). This value can be a word address, a long (double-word) address, an integer constant, floating point data element, or a floating point constant.
Input Max - Enter a maximum value for the input (high end of range). This value can be a word address, a long (double-word) address, an integer constant, floating point data element, or a floating point constant.
Scaled Min - Enter a minimum scaling value representing the low end of the range to which you want to scale the input. The scaling relationship is linear. The value can be a word address, a long (double-word) address, an integer constant, floating point data element, or a floating point constant.
Scaled Max - Enter a maximum scaling value representing the high end of the range to which you want to scale the input. The scaling relationship is linear. The value can be a word address, a long (double-word) address, an integer constant, floating point data element, or a floating point constant.
Output - Enter an address for the scaled value that is returned after the instruction is executed. This value can be a word address, a long (double-word) address or an address of floating point data elements. If any floating-point file types or floating-point constants are encountered in the above parameters, then the entire instruction is treated as floating point, and all immediate integer data values are converted to immediate floating-point data values.

Note The input minimum, input maximum, scaled minimum, and scaled maximum are used to determine the slope and offset values. The input value can go outside of the specified input limits and no ordering is required. For example, the scaled output value will not necessarily be clamped between the scaled minimum and scaled maximum values.
Rockwell Software

bfranklin · Mar 18, 2013

that's exactly what I needed to know.

Thanks!!!

Lancie1 · Mar 18, 2013

Great. You can use the SCP instruction for both analog inputs and analog outputs.

Anirban Hazra · Mar 19, 2013

Lancie1 said:
Yes, SCL it is available in the RSLogix500 software.

I know that it is present in RSLogix 500 software but what I meant to ask was whether it was available for the SLC that he was using because I think in the really old ones(I think SLC 5/01) it's not available.Also, I said SCL intstead of SCP because I think it is available in later models(ie. from SLC 5/03) than even for which the SCL is first available.

Bit_Bucket_07 · Mar 19, 2013

Anirban Hazra said:
I know that it is present in RSLogix 500 software but what I meant to ask was whether it was available for the SLC that he was using because I think in the really old ones(I think SLC 5/01) it's not available.Also, I said SCL intstead of SCP because I think it is available in later models(ie. from SLC 5/03) than even for which the SCL is first available.

You are correct. Older models of the SLC do not support the SCP function.

Bit_Bucket_07 · Mar 19, 2013

bfranklin said:
Analog Input- 1746-NI8

Analog Output- 1746-N08I

You'll notice that after you configure one of these modules as in Anirban's example, rungs will be added to your PLC program. The I/O Configuration dialog establishes the correct numerical values for the data tables that will be written to your module upon the PLC entering run mode. For your NI8 input module's input addresses, there are corresponding output addresses to which the configuration data tables will be written.

SLC Analog I\O

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