Table of Contents The dew point depends on how much water vapor is present in the air. If the air is very dry with
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Dew Point Sensor
Monitoring the dew point of compressed air or gas systems helps extend equipment service life and reduce maintenance costs. Installing a dew point sensor provides accurate dew point measurements for factory pipelines. We offer two models: RS-DEW-N01-S-EX and RS-DEW-N01-2-*-EX. These sensors are suitable for open environments such as meteorology and agriculture, and can also accurately monitor dew point inside equipment such as air compressors, refrigerated dryers, desiccant dryers, and air storage tanks.
- Model: RS-DEW-N01-2-*-EX/RS-DEW-N01-S-EX
- MOQ: 1 PCS
- Delivery date: within 24 hours
- Price:$25.2/$167.7
About - Dew Point Sensor
Dew point is the lowest temperature at which water vapor is allowed to remain in a gas without condensing into a liquid. As the temperature of air or gas decreases, its capacity to hold water vapor decreases until it becomes fully saturated, and below this dew point temperature, water droplets will begin to form. Typically, a dew point sensor is installed downstream of a dryer to provide information when the dryer starts to malfunction and moist air enters the distribution system. When the dew point reaches a preset value, an alarm is triggered, notifying professionals to take swift action. This can save significant costs resulting from damage and production losses caused by water ingress.
RS-DEW-N01-S-EX
This dew point sensor features a 304 stainless steel housing, with a fully sealed cable outlet for waterproof protection. It achieves an IP65 protection rating, ensuring stable operation even in harsh conditions such as high temperature or high humidity.
The internal circuit uses an industrial grade microprocessor and a high accuracy temperature sensor to guarantee excellent performance.
With a sleek appearance and compact dimensions, the dew point sensor is equipped with a G1/2 threaded interface, allowing easy installation on various mechanical pipelines. It supports standard Modbus protocol and outputs through RS485, making it suitable for secondary development.
| Power Supply | DC 10-30V | |
| Max. Power Consumption | 0.4W | |
| Accuracy | Dew Point | ±0.8°C (25°C) |
| Temperature | ±0.4℃ (25℃) | |
| Operating environment | -40℃~+60℃, 0%RH~95%RH (Non Condensation) | |
| Dew Point Range | -30℃-100℃ | |
| Dew Point Resolution | 0.1℃ | |
| Temperature Resolution | 0.1℃ | |
| Refresh Time | 1s | |
| Long-term Stability | Temperature | ≤0.1℃/y |
| Response Time | Temperature | ≤25s(1m/s Wind Speed) |
| Output Signal | RS485(ModBus Protocol) | |
| Installation | G1/2 Thread Installation | |
RS-DEW-N01-2-*-EX
This dew point sensor integrates an internal temperature and humidity sensor, calculating the dew point by measuring the ambient temperature and relative humidity. It can therefore output three parameters: temperature, relative humidity, and dew point. Designed for wall-mounted installation, it is suitable for measuring atmospheric dew point. The housing is fully waterproofed and rated IP65, ensuring long-term durability.
To meet the requirements of different application environments, we offer a variety of probe options, such as PE probes, waterproof probes, metal probes, high-temperature probes and so on. This dew point sensor is widely used in applications that require reliable monitoring of dew point temperature and ambient temperature and humidity.
| Power Supply | DC 10-30V | |
| Max. Power Consumption | 0.4W | |
| Accuracy | Relative Humidity | ±3%RH(60%RH,25℃) |
| Dew Point | ±1℃（25℃） | |
| Temperature | ±0.5℃（25℃） | |
| Operating environment | -40℃~+80℃, 0%RH~95%RH (Non-condensing) | |
| Dew point temperature range | -30℃~100℃ | |
| Dew Point Resolution | 0.1℃ | |
| Temperature Resolution | 0.1℃ | |
| Humidity Resolution | 0.1%RH | |
| Refresh Time | 1s | |
| Long-term Stability | Relative Humidity | ≤1%RH/y |
| Temperature | ≤0.1℃/y | |
| Response Time | Relative Humidity | ≤8s(1m/s Wind Speed) |
| Temperature | ≤25s(1m/s Wind Speed) | |
| Output Signal | RS485(ModBus Protocol) | |
FAQs - Dew Point Sensor
What is dew point? How is it different from relative humidity?
Dew point is the temperature at which the water vapor in the air becomes saturated. That is, when the air cools to this temperature, water vapor begins to condense into liquid water.
Relative humidity indicates the percentage of water vapor currently in the air compared to the saturated water vapor amount at the same temperature (0-100%).
Their relationship is: dew point reflects the absolute moisture content and is independent of temperature (under a given water vapor content), while RH changes significantly with air temperature (the same amount of water vapor will result in lower RH at higher temperatures). Therefore, in many control/monitoring applications, dew point is more stable and intuitive in indicating the moisture content of the air than RH.
What is the difference between dew point and frost point?
Dew point is based on the formation of liquid water, while frost point is based on the direct deposition of ice. When the ambient temperature is below 0 °C, water vapor may actually form ice directly on a surface, and in this case the corresponding “saturation pressure” is with respect to ice rather than liquid water. For the same water vapor partial pressure, the frost point temperature is usually slightly higher than the dew point corresponding to a liquid water surface (the difference must be calculated using the precise relationship between the saturation vapor pressures of the ice/water phases). In engineering applications, when the temperature is below 0 °C, it should be clearly specified whether the “frost point” or “dew point” standard is being used.
Why measure dew point?
Industrial compressed air and gas systems can be directly damaged due to water contamination or subsequent freezing and expansion of water. The presence of water vapor in the air or gas can also affect process or product quality. It is common practice to remove water contamination through filters and drying systems, but due to the dew point (and potential destructive condensation) varying with pressure changes, the risk of damage to the entire factory can also differ.
Which industries need to monitor dew point?
- Medical and Respiratory Air
When it comes to most regulations for medical gases and respiratory air, dew point monitoring is necessary to ensure compliance and safe breathing conditions for everyone from patients to firefighters. - Plastic Drying
Maintaining adequate dryer performance prevents material waste and production downtime while ensuring product quality. - Food and Pharmaceutical Industry
Many applications in the food and pharmaceutical industry use compressed air. Standard applications include coating quality control, filling, and packaging. - Rail Transportation
Brakes, doors, and air conditioning systems on trains, buses, and other public transportation vehicles rely on dew point measurements in compressed air to ensure safety and reliability.
How to measure dew point?
Dew point is typically measured using a dew point sensor or hygrometer. There are several methods to measure dew point, including: Chilled Mirror Hygrometer, Capacitive Hygrometer, Resistive Hygrometer, Infrared (IR) Hygrometer, Psychrometric Charts, Electronic Sensors.
What is dew point sensor?
Dew point sensor is a specialized instrument used to measure the dew point temperature in a gas or air mixture.
How does the dew point sensor work?
Working principle of dew point sensor: When the ambient temperature falls below the dew point, water vapor in the air condenses into liquid. Conversely, when the ambient temperature is above the dew point, the air contains saturated water vapor and forms dewdrops. In an environment with a relative humidity of 100%, the water vapor content in the air is directly proportional to the humidity of the ambient air.
How accurate is the dew point sensor?
The data sheet for the dew point sensor will provide you with the accuracy specifications. This is usually given as a range, for example ±0.8°C. This means that the sensor accuracy is expected to be within plus or minus 0.8 °C of the actual dew point.
What is the difference between humidity sensor and dew point sensor?
Dew point is an absolute measurement, while humidity is a percentage. Therefore, dew point is considered a more accurate method of measuring air humidity and comfort. Additionally, humidity depends on air temperature, while dew point does not.
How to choose a dew point sensor for a compressed air system? What should be considered?
The dryness of compressed air is often expressed as “pressure dew point.” System characteristics: high temperature, high pressure, and the presence of oil, particles, or chemical contaminants. Key selection points:
- Measurement range: Industrial compressed air often requires specifications such as -40 °C DP or -70 °C DP, confirm the target dew point.
- Contamination resistance: Choose sensors with filtration/sample interfaces, external filters, or pre-treatment (condensate separation, oil mist filtration).
- Pressure range/isolation: If the dew point sensor cannot withstand high pressure, use a sampling pressure-reducing system or a sensing probe with pressure isolation.
- Output and interface: 4-20 mA and RS485 are common, facilitating integration with PLC or monitoring systems.
- Calibration and maintenance cycle: In high-contamination environments, shorten the calibration interval; it is recommended to retain replaceable probes or spare parts.
How should a dew point sensor be installed?
- Avoid direct sunlight, heat sources, or strong cold air, install the sensor in a representative airflow location.
- Keep the measurement point temperature stable and avoid sudden changes. When measuring inside pipelines, use an appropriately sized probe and an anti-vibration mounting bracket.
- In dusty or oil-mist environments, install a filter and replace the filter element regularly.
- When measuring in high pressure gas, use a suitable pressure-reducing device or select a model that can be directly connected to high pressure.
Why do dew point readings fluctuate?
Common causes include:
Contamination on the probe surface
Inaccurate temperature measurement
Unstable power supply or wiring
Probe aging, requiring recalibration
Why does the response time slow down?
Possible reasons include clogged filters, overly thick protective sleeves, excessively long sampling tubes, or slower water absorption/desorption of the probe material. Cleaning, shortening the sampling path, or replacing the probe with a faster model can improve response time.
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