Why One Wire Temperature Humidity Sensor (RS485 Modbus)

One wire temperature humidity sensor refers to temp. humidity sensor with 1 wire only that contains signal output wire and power supply wire together. Such design makes it convenient to wire and can reduce installing cost and installing space.

However,because integrated in one wire,  the whole design is met with several hard points,e.g. must be ultra low power consumption design,otherwise released heat by working will effect the accuracy seriously, also because it is one wire, the signal interference will be very difficult to process, and other problems available.  With strong power and rich experience, we have worked for several years and have a good result.

The typical one wire output is RS485 Modbus protocol and I2C  output, but Modbus is better than I2C. If possible, RS485 Modbus protocol should be the first consideration. Except digital output, many projects also require analog output,e.g. 4-20mA, 0-5vdc, 0-10VDC,etc. This will be more difficult because analog outputs will require more power consumption with more  heat released. We have a special model with one wire which can meet such requirement

Why Our Temperature and Humidity Sensor Transmitter

Our temperature and humidity sensor transmitters are manufactured on advanced digital IC chips which have been developed for over 3 generations. When working as temperature humidity sensor, it can support I2C or similar customizing port. If you are good at electronic design, you may select the port to integrated into your system. Of course, we have developed temperature humidity transmitters with 4-20mA,0-5Vdc,0-10Vdc and digital RS485(Modbus). These signal outputs belong to standard industrial communication, users can operate and use them easily even though not expert in electronic designing.

The sensors can be used for measurement of temperature and relative humidity.For humidity measurement,they are mainly for air test. One complete system of temp. humidity transmitter usually includes measuring sensors, single processing chip and protection enclosure. For probe protection cover, there are mainly two kinds: plastic and metal. Metal has a longer life and can be used in rugged application.

The temperature humidity sensors have been tested and calibrated independently, and each sensor is processed with electrical aging before sale. Low voltage input checking and verification can help to improve signal stability. Our temp. and humidity sensors are equipped with 10k pull-up resistor and 0.1uf filtering capacitor, that can well improve the data performance. Meanwhile, water-proof is designed and made for the sensors.

Protection Encased Material of Probe

Generally, there are two kinds of enclosure materials: plastic and metal. Plastic enclosures mainly have PVC and PE. Metal enclosure is mainly sintered copper. This is our advantage product and its core technology is firstly to make copper material become ultra-fine particles, and then shaped by sintered mold.

Sintered copper enclosure provide many good advantages-strengthening sensor capability of temperature resistance, pressure resistance and loss resistance. This makes our temp. humidity sensors widely used for checking and monitoring in external wall insulation of building, and other industrial class application.

Sintered Copper Enclosure

PE+Sintered Copper

Double Water-Proof Technology

Our probe protection enclosure is sintered copper or PE material, and the feature is water proof and breathability. Water molecule can go into the enclosure, but water drops can't because of its surface tension force. When used under application with heavy humidity, the water molecule in enclosure will be condensed into water because environmental temperature is down. If water drop adhere to the wiring PCB, it may be damaged. Thus, in order to solve the problem, we will do glue sealing protection for the PCB, and this glue is special material which has no influence to the measured value.

Because of this processing, our sensors can be used in water and won't be faulty. When become dry again, the sensor can still be normal work.

Several Problems Available from Other Brand Products

As we know, some companies are not professional and their temp. humidity sensors will have several problems as below:

  • Sealing glue is moisture absorption, especially heavy humidity condition. Once humidity is up, it can't become down, because sealing glue holds water.
  • Don't re-do moisture process after welding. As a result, the error becomes bigger. Many factories even didn't know such process.
  • Glue sealing layer is not well processed. As a result, the layer is fracturing because of long-term temperature and oxidizing. Then water drop will cause electrophoresis, fault is up.

We have successfully solved all of problems above by our unique production technique. When you inquire temp. humidity meters from other suppliers, please be sure that you can learn these details completely. Because you will find there are many products which looks almost the same in market, but in fact, their performance may vary. Don't be cheated by several suppliers.

Featured Products

RS485 Modbus/1-Wire I2C


Analog 5V/10V Optional

Main Specification:

  • Accuracy: Temp.:±0.3℃;Humidity:±3%RH. Higher accuracy available
  • Outputs: 0-5V/10VDC,I2C and RS485 Modbus(with dial switch)
  • Power supply: 5VDC or 12-30Vdc(0-10Vdc output)
  • Meas.range:Temp.:-20-80℃;Humidity:0-100%RH
  • Installing way:Insertion or Wall Mounted


Signal Outputs(RS485 Modbus,Analog,I2C)

The temperature humidity sensors have digital and analog outputs: RS485(Modbus),one wire I2C and 0-5Vdc,0-10Vdc.The following will give a brief introduction about them for your reference.

1.RS485(Modbus): Rs485 is one of serial port which has two wire terminals. It is digital output and support longer distance communication. Modbus is a kind of popular standard industrial communication protocol. By this protocol,users can easily collect required value and easily make a network management.

2.One wire I2C: It features small size and good performance. On hardware design, I2C just requires two wires: data wire and clock time wire, and doesn't need external special port diagram. Thus, it can simplify PCB circuit layout, reduce system cost and improve system reliability.Comparing with RS485 Modbus, its communication distance is shorter.

3.Analog 0-5Vdc/0-10Vdc: This is analog voltage output. It features easy to use and many older equipment are supplied with such signal communication. But comparing with digital output, its accuracy is worse and it has weaker signal anti-interference capability.

Warm Tip: RS485(Modbus) has better performance than I2C, so recommend RS485 Modbus.

OEM Customizing Available:

We are glad to supply OEM customizing service for your unique requirement. We have provided such for many customers from different industries. If you have such requirement, please feel free to contact us. For example, we have developed wholly metal version temperature and humidity sensors for a tobacco equipment company,and they have purchased about 1,000 sets each month.