node-red-contrib-pt1

A Node-RED PT1 first-order low-pass filter for smoothing noisy measurement values.

Formula: y(t) = y(t-1) + (dt / (T1 + dt)) * (x(t) - y(t-1))

Installation

npm install node-red-contrib-pt1

Inputs

• payload number: Raw measurement value to filter.
• T1 (optional) number: Override T1 in seconds for this message only.
• reset (optional) boolean: Reset filter state; next input passes through directly.

Outputs

• payload number: Filtered (smoothed) value.
• pt1 object: { input, output, T1, dt, decimals, initialized }

Configuration

• Time Constant T1: Smoothing constant with unit s/min/h. Larger = more smoothing, slower response.
• Decimal Places: Output precision 0-4 (default: 2).

Tips

• First message always passes through unfiltered (initialization).
• T1 = 0 disables filtering (passthrough mode).
• Uses actual elapsed time between messages - no fixed interval required.
• Tip: use the 24h moving average as input for best predictive results.

License

MIT (c) sr.rpo