RF4 RainFlow for Rain and Hail Monitoring
Non-mechanical rain and hail sensor
The RF4 RainFlow for Rain and Hail Monitoring is a non-mechanical rain and hail sensor. An acoustic instrument, the RF4 measures rain and hail precipitation. The RF4 also provides high-resolution disdrometry (number and size of raindrops). The RF4 is compatible with any SDI-12 logger or IoT Node (such as the MFR-Node or S-Node).
The RF4 RainFall Sensors is:
- Non obstructable
- Instrument with no mobile parts – totally sealed acoustic instrument
- Universal mounting kit available
- Omni-directional – even under the highest winds
- Corrosion free and resistant to the highest winds and the most extreme conditions
- Plug-and-Play or totally configurable – microcontroller inside
- Can be connected to almost any external unit
- SDI-12 and IoT compatible – internal memory
With the hemispherical surface, the measurements cannot be obstructed by dust, dirt, or leaf matter removing the need for ongoing maintenance.
Data output options include:
- SDI-12
- RS485 (accessory required)
- Analogue (0-2.5V or 0-5V)
Specifications
Measurement characteristics
| Measuring surface | 160 mm outer diameter hemisphere (402 cm2) |
| Precipitation detected by the sensor | Liquid (undifferentiated): rain, drizzle/rain, mixed rain/snow, sleet. Solid: hail. |
| Rain Intensity accuracy | 15% at 100% duty-cycle (most global precision and accuracy criteria) |
| Rain DSD | 27 classes from ≤ 0.75 mm to 7.0mm with a detection threshold (minimum detectable diameter) of about 0.5 mm |
| Measurement accuracy (liquid only) | A spatially distributed flux of controlled drops of a nominal diameter equal to the centre diameter of the class ± 20% produces an output centred in the corresponding class with typically ± 50% of the flux concentrated into the two lateral size-classes. |
| Hail detection* | Counting of the number of hailstone impacts up to 5 impacts per second and for hailstone diameter detection threshold of 0.5 cm. |
| Particle velocity | Not measured. |
*Note: For more specific hail detection, use the HailFlow HF4 sensor, variant of the RF4 specialised in hail detection.
Voltage ranges and measuring scales
| Voltage outputs | Continuous analogue voltage or pulse analogue voltage, user selectable +0 to +2.5V or +0 to +5V are available. Pulse threshold, integrator timeout and duration are also user selectable. The continuous analogue voltage persists on the outputs so that output voltages can be read at any time. |
| Rain intensity scaling | Sensitivity @voltage range +2.5V: [10 mV/(mm/h)] i.e. +2.5V corresponds to 250 mm/h |
| Sensitivity @voltage range +5V: [20 mV/(mm/h)] i.e. +5V corresponds to 250 mm/h | |
| Hail Sensitivity @voltage range +2.5V or +5V: 5 hit/s |
Construction and Dimensions
| Material | Stainless steel, plastic and anodized aluminium (breakdown voltage > 40 V/μm) |
| Installation | Universal mounting kit provided (ordering reference: RFBRA) |
| Weight | 1.4 kg without mounting kit |
| Dimensions (HxWxD) | 260 mm x 430 mm x 160 mm with mounting kit |
Power
| Voltage | 6 V to 30 V DC (9.6 V and 16 V DC in case of powering through the SDI-12 terminals) |
| Current | < 1 mA in stand-by mode and 20 mA max in acquisition mode. For a typical nominal duty-cycle of 10%: 2.1 mA (20 mA for duty-cycle of 100%). |
Outputs
| Analogue | Pulse and continuous (and persistent) voltages, 0-2.5V or 0-5V |
| SDI-12 | Yes, 1.3 certified (fully complies with the NR Systems SDI-12 Verifier) |
| Serial 3V3 TTL | Yes |
| Modbus RTU (RS485) | Yes, with the Modbus adapter accessory |
Environmental conditions
| Temperature range | -40°C to +80°C. (an even operate over this range.) |
| Relative humidity | 0 to 100% |
| Protection | IP67, survive to 1 m temporary immersion in salt water |
| Standards | EN 61326-1: 2013, CE compliant. 2014/30/EU, CE compliant |
Support Documents
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Case Studies and Application Notes
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