From inputs, you should ‘log to feed’ sensor A and sensor B to another feed.
Then create a new virtual feed and add “source feed” referring to previous created feed A and next “+ source feed” referring feed B.
I have two feeds (A and B) 'Logged to Feed". If I try to create a New Virtual Feed using ‘Source Feed’ and Feed A I get the following error message: ERROR: Could not save processlist. Cannot use virtual feed as source.
Am I missing something or do you think this might be a bug of some kind?
After messing with this for a while I realized that Virtual Feeds may only be created from physical inputs, as Dan also discovered.
Processes created from a physical input (such as power to kwh/d) can’t [currently] be used in Virtual Inputs. I don’t see any reason why one should not be able to used ‘calculated inputs’ such as kWh/d if they are logged.
A work-around: If I send data from Node-Red to EMONCMS it shows up in the Inputs list and these data can be used in Virtual Inputs -even though they are not real ‘physical inputs’- so, to calculate kwh$/d, I can send kwh/d to Node-Red, calculate kwh$/d and return this value to EMONCMS. This value then shows up on the Inputs list and can be used in Virtual Inputs. I do not recommend this method for critical or robust systems, but it works.
So why not the ability to create a virtual feed from a kwh/d process? I see no reason why Virtual Feeds could not be created from any input, physical or calculated. However my knowledge of EMONCMS programming is essentially zero so I defer to the experts.
Hello.
My software is and fresh install of 9.9.8 version.
In this fresh install I can’t make a virtual feed when the source feed is an calculated feed.
This give the following error already report:
ERROR: Could not save processlist. Cannot use virtual feed as source
No “OK” button. Strangely, the problems encountered with the Post Processing module differ at random. (I know the [Return] key has to be pressed for the [OK] button to appear.)
Also, unable to use Virtual Feeds to create calculated feeds as only physical inputs may be used as inputs to the Virtual Feed and many calculated data need virtual feeds as input.
To conclude Post Processing and Virtual Feeds come up short and I don’t have the knowledge to resolve this myself.
In my opinion not having the ability to create ‘calculated feeds’ is a ‘dent in the armour’ of EmonCMS and greatly reduces its usefulness in converting Data to Information. I must also say that EmonCMS is great and the work that has been put into it is commendable, I hope I’m not perceived as being too critical.
Currently the only way I know how to do what I need to do is to use Node RED for the UI, send any data needed back to EmonCMS via MQTT for data storage only, and do all calculations in Node RED.
