Product Overview
The OHTS1121 is a qualitative detection sensor based on AC impedance measurement principles, designed to detect rainfall or snowfall states in outdoor natural environments. The sensor employs AC excitation technology to prevent oxidation of the sensing plate surface, ensuring long-term detection sensitivity and measurement stability even under continuous outdoor exposure.
The device features dual output modes, supporting both RS485 digital communication with ModBus-RTU protocol and traditional relay switch output, making it compatible with modern IoT monitoring systems as well as conventional industrial control equipment. An optional automatic heating module can be equipped for low-temperature, high-humidity environments to prevent surface icing and condensation, ensuring reliable operation in winter conditions.
With IP68 protection rating and wide operating temperature range, the OHTS1121 is suitable for rain/snow monitoring applications in environmental monitoring stations, agricultural greenhouses, building automation systems, traffic infrastructure, and smart city deployments.
Features
- AC Impedance Measurement - Utilizes AC excitation technology to prevent electrode oxidation, maintaining long-term measurement stability and sensitivity in outdoor environments.
- Dual Output Interface - Supports both RS485 ModBus-RTU digital output and relay normally-open contact, providing flexible integration options for various system architectures.
- IP68 Protection - Rugged enclosure design with IP68 protection rating ensures reliable operation during long-term outdoor deployment in harsh weather conditions.
- Fast Response - Detection response time less than or equal to 0.5 seconds enables real-time monitoring of precipitation events.
- Automatic Heating Option - Configurable heating module prevents ice formation and condensation with adjustable start temperature and upper limit controls.
- Configurable Sensitivity - Detection threshold adjustable from 500 ~ 3500 to optimize detection for different precipitation intensities and environmental conditions.
- Alarm Delay Function - Configurable delay from 0 ~ 60000 seconds prevents false alarms from transient interference or brief precipitation events.
- Wide Voltage Range - Operates from 10 ~ 30 V DC power supply, compatible with standard industrial and solar power systems.
Applications
The OHTS1121 rain/snow sensor is designed for diverse environmental monitoring applications including meteorological and environmental monitoring stations, agricultural greenhouse environmental control systems, and livestock breeding facility monitoring. It is also suitable for building peripheral rain/snow detection, building automation environmental control systems, and outdoor equipment protection status monitoring.
Additional applications include traffic infrastructure meteorological monitoring, photovoltaic and wind farm environmental monitoring, warehousing and logistics facility environmental control, and smart city environmental sensing nodes where reliable precipitation detection is required for operational safety and efficiency.
Technical Specifications
| Parameter | Specification | Remarks |
|---|---|---|
| Power Supply | 10 ~ 30 V DC | - |
| Operating Temperature | -40 ~ 60 °C | - |
| Storage Temperature | -40 ~ 80 °C | - |
| Normal Operating Power | 0.4 W | - |
| Heating Operating Power | 7.5 W | Typical value |
| Relay Load Capacity | 250 VAC 1 A / 30 VDC 1 A | Normally-open contact |
| Heating Start Temperature | < 15 °C | Default threshold, configurable |
| Heating Temperature Upper Limit | 40 °C | Default, range 0 ~ 70 °C |
| Communication Interface | RS485 | ModBus-RTU protocol |
| Default Baud Rate | 4800 bit/s | Optional 2400/4800/9600 |
| Data Format | 8 data bits, no parity, 1 stop bit | - |
| Default Device Address | 0x01 | Configurable |
| Supported Function Codes | 0x03, 0x06 | Read/Write holding registers |
| Detection Response Time | <= 0.5 s | - |
| Sensitivity Setting Range | 500 ~ 3500 | Default 800 |
| Alarm Delay Range | 0 ~ 60000 s | Default 1 s |
Physical Specifications
| Parameter | Specification |
|---|---|
| Protection Rating | IP68 |
| Mounting Method | Wall-mounted, expansion plug fixation |
| Accessories | Expansion plugs φ 6 mm x 4, self-tapping screws 4 pcs |
FAQ
Q: What measurement principle does the OHTS1121 use?
A: The sensor uses AC impedance measurement principles with AC excitation technology to detect rainfall or snowfall states qualitatively. This approach prevents oxidation of the sensing plate surface, ensuring long-term detection sensitivity.
Q: What output interfaces does the sensor support?
A: The device supports dual-mode output including RS485 digital interface with ModBus-RTU protocol and relay normally-open contact switch output, suitable for both digital monitoring systems and traditional control circuits.
Q: How does the optional automatic heating function work?
A: The optional heating module activates when temperature drops below the configurable threshold (default less than 15 °C) and maintains heating up to an upper limit (default 40 °C) to prevent dry burning, effectively preventing surface icing and condensation.
Q: What is the detection sensitivity range and how does it affect performance?
A: Sensitivity is configurable from 500 ~ 3500 with a default of 800. The sensitivity setting and detection threshold exhibit an inverse relationship; lower values increase detection sensitivity but may increase false alarm risk, while higher values decrease sensitivity.
Q: What are the wiring requirements for the RS485 interface?
A: RS485 bus device addresses must not conflict and A/B wire sequence must not be reversed. When bus length exceeds 100 meters, terminal matching with 120 ohm resistor is recommended to ensure signal integrity.