Precipitation sensor IRSS88
IRSS88 / IRSS88T precipitation sensors – opto-electronic detectors for all types of precipitation, stainless steel housing, instantaneous detection, IRSS88T with integrated temperature measurement and RS232
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IRSS88 and IRSS88T precipitation sensors – Reliable detection of all types of precipitation
Why is a precipitation sensor used?
Reliable detection of precipitation is crucial in many areas of application – from traffic control technology to sewage treatment plants and building management. Incorrect or delayed precipitation detection can lead to accidents, inefficient processes or damage to property.
The IRSS88 and IRSS88T precipitation sensors from RLS Wacon are opto-electronic precipitation detectors that have been used successfully for years in traffic control systems, sewage treatment plants and building management worldwide. They reliably detect all types of atmospheric precipitation – rain, drizzle, hail and snow – and impress with their instantaneous response and extreme robustness. The IRSS88T also offers integrated temperature measurement with 0.1 °C resolution, potential-free relay outputs and an RS232 interface.
How do the IRSS88 / IRSS88T precipitation sensors work?
Based on a light barrier principle with high-performance infrared technology, the sensors generate an active detection area of approx. 120 × 25 mm. This area is sufficient to reliably detect even low precipitation densities with the smallest particle sizes.
The opto-electronic principle reacts instantaneously to particles that pass through the sensor zone. The highly sensitive microelectronics are insensitive to any kind of interfering light – even intense sunlight. The all-metal housing ensures effective shielding against HF radiation.
Signal outputs IRSS88
The IRSS88 has three signal outputs:
| Output | Designation | Function |
|---|---|---|
| POUT | Pulse output | Unweighted pulse output – behaves proportionally to the interruption time of the IR beam |
| SOUT | Evaluated output | Is activated if the set number of pulses (1-15) is exceeded within a time window of approx. 95 s |
| SACT | Sensor active signal | Signals the functionality of the sensor – goes LOW in case of contamination or permanent occupancy (> 4 s) |
All outputs are designed as PNP open collectors and require pull-down resistors (recommended: 1-10 kΩ). All outputs are short-circuit proof.
Additional functions of the IRSS88T
The IRSS88T contains a separate temperature sensor in an aluminum attachment on the core housing. This makes it possible to measure the ambient temperature to an accuracy of 0.1 °C and to control a potential-free switching output via a switching hysteresis function. The hysteresis can be set as required between 0 °C and 9 °C using two rotary selector switches.
| Output / Interface | Function |
|---|---|
| Temperature relay | Potential-free switching output – closes when the temperature falls below the set temperature threshold (T_ON), opens when T_ON + D_T_OFF |
| Precipitation relay | Potential-free switching output – closes when precipitation is detected (evaluation period approx. 95 s) |
| Analog temperature output | 10 mV per 1 °C, reference 2.73 V at 0 °C |
| RS232 interface | Serial output of status data in ASCII format (9600 baud, 8N1) |
Adjustable response threshold
The response threshold of the weighted output SOUT can be set to 1 to 15 pulses per time interval (approx. 95 s) using a rotary switch on the receiver circuit board. This allows the signaling of insignificant amounts of precipitation to be suppressed. The factory setting is 4 pulses.
Advantages of the IRSS88 / IRSS88T precipitation sensors
- Reliable detection of all types of precipitation
Rain, drizzle, hail and snow are reliably detected even with the smallest particle size
- Delay-free reaction
The opto-electronic principle reacts immediately to particles in the sensor zone
- Extremely robust stainless steel housing with protection class IP68
Waterproof all-metal housing made of stainless steel (V2A) – suitable for extreme environmental conditions
- Insensitive to interfering light
Reliable operation even in intense sunlight thanks to highly selective IR technology
- Alarm output for soiling
The SACT output informs the operator if the sensor windows are heavily soiled or iced up
- Connection cable up to 1000 m possible
Wide operating voltage range (9-18 V DC) and low current consumption enable long cable runs
- Adjustable response threshold
Rotary switch for 1-15 pulses per time interval – insignificant amounts of precipitation can be suppressed
- IRSS88T: Integrated temperature measurement with 0.1 °C resolution
Separate temperature sensor with adjustable switching hysteresis, analog temperature output and RS232 data protocol
Field of application
The IRSS88 precipitation sensor is used in the following areas:
| Area of application | Description |
|---|---|
| Traffic control systems | Automatic detection of precipitation to control speed displays, warning lights and road sensor systems |
| Sewage treatment plants | Monitoring of precipitation events to control stormwater overflow basins and sewer systems |
| Building management | Automatic control of awnings, skylights, irrigation systems and drainage systems |
| Meteorology | Use in weather stations for precise precipitation measurement under extreme environmental conditions |
Installation and commissioning
- Mount the sensor at the desired location – preferably in an exposed position with free access to the atmosphere
- Wire the connection cable according to the cable assignment: White (+9-18 V DC), gray (GND), brown (POUT), yellow (SOUT), green (SACT)
- Connect pull-down resistors (1-10 kΩ) to the outputs used after GND at the end of the line
- Apply operating voltage – the sensor is immediately ready for operation
- If necessary, adjust the response threshold of the SOUT output using the rotary switch on the receiver circuit board (1-15 pulses)
Tip for the installation
Mount the sensor so that the detection surface is free of obstacles and precipitation can pass through the sensor zone unhindered. The wide operating voltage range (9-18 V DC) and low power consumption enable connection cable lengths of up to 1000 m.
Important notes
- All outputs are PNP open collector and require pull-down resistors at the end of the line for proper function
- When the SACT alarm is triggered (sensor active signal on LOW), the infrared exit windows must be cleaned
- To change the factory rotary switch setting, the cover on the receiver side must be removed
- The sensor is designed for continuous outdoor operation under extreme environmental conditions (IP68, -25 to +60 °C)
Specifications at a glance
| Property | Value |
|---|---|
| Sensor principle | 2-channel IR sensor (light barrier principle) |
| Detection area | approx. 120 × 25 mm (approx. 3000 mm²) |
| Operating voltage | 9-18 V DC |
| Power consumption | max. 100 mA (typ. 88 mA) at 12 V DC |
| Operating temperature | -25 °C to +60 °C |
| Housing | Stainless steel (V2A), optionally powder-coated |
| Protection class | IP68 |
| Dimensions | approx. 275 × 185 × 85 mm |
| weight | approx. 2 kg |
| Output current per output | max. 50 mA |
| Output type | PNP open collector, active HIGH, short-circuit-proof |
| Signal level HIGH | min. 0.82 × VCC, max. VCC |
| Signal level LOW | 0 V (pull-down) |
| Pull-down resistor | 1-10 kΩ recommended |
| Evaluation time interval (SOUT) | approx. 95 s |
| Response threshold (SOUT) | 1-15 pulses / time interval (factory setting: 4) |
Additional specifications IRSS88T
| Feature | IRSS88 | IRSS88T |
|---|---|---|
| Operating voltage | 9-18 V DC | 9-32 V DC |
| Power consumption | max. 100 mA (typ. 88 mA) | type. 145 mA |
| Housing | Stainless steel (V2A) | Stainless steel / aluminum |
| Protection class | IP68 | IP65 |
| Dimensions | approx. 275 × 185 × 85 mm | approx. 170 × 250 × 85 mm |
| weight | approx. 2 kg | approx. 1.8 kg |
| Temperature sensor | – | -10 °C to +60 °C, resolution 0.1 °C |
| Temperature relay | – | Potential-free, switching hysteresis adjustable (T_ON: 0-9 °C, D_T_OFF: 0-9 °C) |
| Precipitation relay | – | Floating,Imax = 900 mA (resistive load) |
| Analog temperature output | – | 10 mV/°C, reference 2.73 V at 0 °C |
| RS232 interface | – | 9600 baud, 8N1, ASCII protocol |
Cable assignment IRSS88
| Wire color | Function |
|---|---|
| White | +9-18 V DC |
| Gray | GND |
| Brown | POUT (pulse output) |
| Yellow | SOUT (weighted output) |
| Green | SACT (sensor active signal) |
IRSS88T connection assignment (terminal strip)
| Clamp | Function |
|---|---|
| VCC | +9-32 V DC |
| GND | Ground |
| POUT | Pulse output (PNP open collector, pull-down required) |
| SOUT | Evaluated output |
| SACT | Sensor active signal |
| Temperature +/- | Potential-free relay output Temperature |
| Precipitation +/- | Floating relay output Precipitation |
| ANA (terminal 7) | Analog temperature output (10 mV/°C) |
| TX | RS232 Serial output |
| RX | RS232 Serial input (service only) |
Scope of delivery
| Component |
|---|
| 1 × IRSS88 precipitation sensor (in selected housing version) |
| Technical documentation |
Additional information
| Version |
|---|
