Parenthesis

Emoncms
1

Hi,

Sorry but I’m newbie with emoncms, I have some inputs taht are generating some feeds and are working correctly, but now I need to create some additional feeds as a result of other feed with some calculs,for example one of them " Exchanger Power = 1.163 * V1 * (tV1 - tR1)"

My question i how to do this, my question is realted with parenthesis and also how to create a new feed with this output

Thanks

2

Reverse the order of the calculations, so the subtraction is done first:

For example, as a virtual feed:

  • Source feed: tV1
  • subtract feed: tR1
  • multiply feed: V1
  • multiply factor: 1.163

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You could also do this with inputs if you want to create an actual feed of results.

3

Hi, first of all thanks for your answer

the problem is that I need this

Exchanger Power = 1.163 * (V1*0.001 ) * (tV1 - tR1)"

0.001 is a unit conversion, I have tried changing order but no sucess, what is wrong

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Other question is how can I make a newfeed with this result to be available to be used in any option emoncms

Otherissue is this virtual feed is not available to be used, any requirements to be used forexampel on a graph orother emoncms option?

Thanks

4

Welcome, @klxout , to the OEM forum.

In emonCMS, a Feed is the database. Values sent to a Feed are stored for ever. This is what you need if you want to see the data in a graph tomorrow, next week or next year.

This might help you with understanding Virtual Feeds:
https://openenergymonitor.github.io/forum-archive/node/10977.html
The important part is in the second line: “no disc space is used.” This means data is stored only for a limited time.

To send data to a (real) Feed, use Log to Feed.

5

Hi, great! thanks for this information

One additonal question I’m trying to use a conditional to reocver some values only if mode is =1, I’m trying this but is not working, how can I dothis?

if mode is =! 1 then absolute value 0,andwhen 1calculate from 5 to steps 7, how cna Ido this?

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Thanks

6

You need one more GOTO as step 5.
What comes after step 9 (now step 10)? if it is Log to feed then the new GOTO is to step 11: Log to Feed, so you record a Zero value if you came via the GOTO, else you record the result after × 0.001 (step 10).

7

Hi,

not sure ifthisiscorrect, always reutnrs 0,andnow for exampel I have mode =1 and in this case I expect a value != 0,
in thiscase 6/7/8 are really executed on any case? about log to feed hwo can I do this I can find this options

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using this seems that returns values

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i sthis correct?

How can I save to disk with log to feedor similar this virtual feed?

Thanks

8

Step 3 should be GOTO 6. When you inserted a step, all those below moved down one step.

If you need to save the data in a Feed, my understanding is you should be doing this as part of the processing for one of your Inputs on an Input page, not in a Virtual Feed.

Choose the last input that appears on the Inputs page for Node hpsu508. When the last input is processed, all the others will have the latest value - if you use the first, all those down the page will not yet be processed and some data could be 10 s or more old.

Do Reset to ZERO, then use + Input to read again the input in whose process list you are working on and those you have not logged to a Feed, and + Feed to read all the others that have already been processed and logged to a Feed.

Then at the end, you can Log to Feed and create a new Feed with the result.