How to mirror Float Tag to a scaled Short Tag

Ignition
1

I feel like I am making something that should be simple way more complex than it needs to be.

I have a memory tag that is a float and I want another tag (short) to have that value but multiplied by 1000.

Example:
The below is what I want..
MemoryTag = 3.125
OPCShortArray[3] = 3125

What is the best way to accomplish this?

I have attempted putting a change script into the Memory Tag, but I have had no success with that. When I run the script in the script console it works but nothing happens when I put the same script in the change script for the memory tag. I have tried changing it to tell it that the path is [Edge]Path, [~]Path, and [Gateway Scripting Project Name]Path.. none of the above is working.

2

Ignition Edge doesn't do gateway-scope scripts unless you have the compute plug-in licensed.

You probably want a derived tag.

3

Do you need an additional tag at all? With scaling, the tag appears to have the larger value at all times, but is silently read/written as the scaled value.

If you truly want a separate tag, use a Derived Tag.

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4

I have the compute plug-in, so I would think it should still work.

5

Actually, your problem may be the use of a short array. OPC array tags are notoriously fickle when it comes to writing to single elements (or anything less than the entire array). Test with a simple integer tag.

6

I got it working with a derived Tag, but I feel like I am doing it incorrectly:

I have my memory tag that has the float value

Then I have my OPC array which has the value I want to write to.

I made a separate derived tag with the read/write using the memory tag * 1000, then the source is set to the OPC array element I want to work with. However to get the tag to update I have to set the value of the derived tag to any arbitrary value and it will then read/write the memory tag...

I feel like I am setting something up incorrectly, but it is doing what I want it to do..

7

Ok, I will test with a integer tag.. should I set that up as a memory tag also?

8

No, break your OPC array into individual tags. They your original script idea should work (using system.tag.writeBlocking...) without an intervening tag.

9

The issue is that the OPC server is set up by another device which I don't have any control over.

I was attempting to break the array into individual tags by using reference tags which reference specific elements in the array that I want to be able to use. However I had the same issue when using the reference tag.

10

Let's back up. Please show your script that you originally tried, that worked in the script console. In a tag's value change, that would likely work if indented properly, and there was no reliance on any project defaults.

11

system.tag.writeBlocking('[Edge]Robot/IO/Length',10)

In the change script I had the 10 replaced with currentValue. However when I ran into issues I attempted to use a constant and it still wasn't working.

I also attempted to put [~] and [Gateway Scripting Project Name] (not that actual value but the value I have in the gateway settings for that value)

12

You realize that currentValue is a fully qualified value meaning it has timestamp and quality values too. You should use currentValue.value to get just the value from the qualified tag value.

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13

Thank You,

I must've had something else incorrect when I tried the constant value because after I got that to work I attempted using a constant value again and it worked.

Thanks to everyone for all the help

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