HF4 HailFlow sensor for Hail Monitoring

Name: HF4 HailFlow sensor for Hail Monitoring
Brand: ISAW
SKU: HF4

Non-mechanical hail sensor

The HF4 HailFlow sensor for Hail Monitoring is a non-mechanical hail sensor. An acoustic instrument, the HF4 enables the detection of hail and characterisation of hailstone size. The sensor is able to distinguish between 15 classes of hailstone diameter, ranging from 0.5 to 8 cm, with a capability of counting up to 25 solid impacts per second. The HF4 is compatible with any SDI-12 logger or IoT Node (such as the MFR-Node or S-Node).

The HF4 HailFlow 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	200 mm outer diameter disc
Precipitation detected by the sensor	Solid only (hail). 15 classes, from 0.5 cm (minimal detectable diameter) to >7.5 cm (possible saturation of the instrument). Counting of the number of hailstone impacts up to 25 impacts per second.
Measurement Accuracy	For a given controlled elastic momentum impact (such as spheres of equal diameter, density, Young modulus, falling speed and incidence angle), the response of the sensor varies typically by ± 10%, depending on the spatial position of the impact on the disc and on the sensor (± 10% variability between two sensors).

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 +2.5V: [100 mV/(hits/s)] i.e. +2.5V corresponds to 25 hits/s
	Sensitivity @voltage range +5V: [200 mV/(hits/s)] i.e. +5V corresponds to 25 hits/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	3.2 kg without mounting kit 5.4 kg with mounting kit
Dimensions (HxWxD)	260 mm x 450 mm x 200 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