Post process

Input processing acts on data as it arrives. The post process module acts on feed data that is already recorded. Use it to create a feed you forgot to set up, rebuild a feed after a fault, or clean up bad data.

The module is installed on the emonPi and emonBase. Open it from Setup > Post Process.

Create a process

1. Go to Setup > Post Process.

2. Select a process from Process. A description appears below it.

3. Fill in the parameters. For an output feed, choose Create new and enter a tag and name, or select an existing feed.

4. Set Run on to All data, from the start or New data only.

5. Click Create and run.

The process appears in the Processes list. Status shows Queued, Running, Finished or Error. Hover over the status for details. A large feed can take several minutes.

An output feed does not update by itself when new data arrives. To update it once, run the process again with New data only. To keep it updated, add an input process that writes to the same feed. See Example: cumulative kWh from power.

Example: cumulative kWh from power

Many apps and daily kWh graphs need a cumulative kWh feed. Use this example if you only have the power feed.

1. Select Power to kWh.

2. Select the power feed.

3. Choose Create new and name the output feed, for example use_kwh.

4. Set Run on to All data, from the start and click Create and run.

5. To keep the feed updated, go to Setup > Inputs. On the power input, add a Power to kWh process that writes to the new feed.

Optional limits on power values can remove spikes, or create import only or export only feeds.

Example: grid import from solar and use

Import calculation calculates grid import from a solar feed and a use feed. Run Power to kWh on the result to get a cumulative import feed.

Example: formula

Basic Formula combines feeds with +, -, * and /, constants and brackets, for example:

f1+2*f2-f3/12

f1 is the feed with id 1. Use Feed finder to look up feed ids.

Processes

Group	Process	Description
Calibration	Scale feed	Multiply a feed by a constant
Calibration	Offset feed	Add a constant to a feed
Power & Energy	Power to kWh	Create a cumulative kWh feed from a power feed
Limits	Allow positive	Keep only positive values
Limits	Allow negative	Keep only negative values
Limits	Limit more than/less than	Limit values above or below a set value
Limits	Remove more than/less than	Remove values above or below a set value
Feeds	Add feeds	Add two feeds together
Feeds	Average	Average a feed to a longer interval
Feeds	Downsample	Reduce a feed to a longer interval
Feeds	Upsample	Increase a feed to a shorter interval
Feeds	Merge feeds	Fill gaps in one feed from another. Average where both have data
Formula	Basic Formula	Combine feeds with a formula
Solar	Import calculation	Grid import from use and solar
Solar	Export calculation	Grid export from use and solar
Solar	Solar direct calculation	Solar used directly from use and solar
Solar	Solar battery kWh flows	Energy flows between solar, battery, grid and home. Used by My Electric Flow
Simulation	Battery simulator	Simple solar battery simulation
Simulation	Carnot COP simulator	Heat pump heat output and COP from flow and outside temperature
Data cleanup	Remove resets	Remove resets from a cumulative feed, such as a pulse count
Data cleanup	Remove missing values	Fill gaps by interpolation
Data cleanup	Replace missing values with last value	Fill gaps with the last value
Misc	Accumulator	Running total of a feed
Misc	Constant flow to kWh	Heat from flow and return temperature at a constant flow rate
Misc	Liquid or airflow to kWh	Heat from flow and return temperature and a flow rate feed
Misc	To signed	Convert unsigned values to signed values

Source code

emoncms/postprocess on GitHub.