node-red-contrib-scale

Node-RED Scale Node - maps values from one range to another using linear interpolation.

Features

• Linear mapping from input range to output range
• Works with inverted ranges (e.g. 100→0)
• Optional clamping to output range
• Runtime overrides via msg properties
• Configurable decimal places (0-10)

Formula

output = (input - inMin) / (inMax - inMin) * (outMax - outMin) + outMin

Examples

0-10 → 0-100:

Input 0  → Output 0
Input 5  → Output 50
Input 10 → Output 100

4-20mA → 0-100%:

Input 4  → Output 0
Input 12 → Output 50
Input 20 → Output 100

Inverted 0-10V → 100-0%:

Input 0  → Output 100
Input 5  → Output 50
Input 10 → Output 0

Configuration

| Property | Description | Default | |----------|-------------|---------| | Input Min | Lower bound of input range | 0 | | Input Max | Upper bound of input range | 10 | | Output Min | Lower bound of output range | 0 | | Output Max | Upper bound of output range | 100 | | Clamp | Limit output to range bounds | false | | Decimals | Number of decimal places | 2 |

Input

• msg.payload - Numeric value to scale

Runtime Overrides

| Property | Description | |----------|-------------| | msg.inMin | Override input minimum | | msg.inMax | Override input maximum | | msg.outMin | Override output minimum | | msg.outMax | Override output maximum |

Output

{
  "payload": 50,
  "scale": {
    "input": 12,
    "output": 50,
    "inMin": 4,
    "inMax": 20,
    "outMin": 0,
    "outMax": 100,
    "clamped": false,
    "decimals": 2
  }
}

Use Cases

| Application | Description | |-------------|-------------| | 4-20mA | Sensor signal to percentage | | 0-10V | Analog signal to engineering units | | Inverted | Reverse valve position (100%=closed) | | Temperature | Celsius to Fahrenheit |

Node Status

• 12 → 50.00 - Scaled value
• 22 → 100.00 (clamped) - Output was clamped
• Invalid range - inMin equals inMax

Author

sr.rpo

License

MIT