Basics of Honeywell's HIH-4000 Humidity sensor
Measurement & controlling of Relative humidity finds applications in various industries from transportation to medical equipments. Various sensors are available in the market one such sensor that I would like to give you details of is Honeywell’s HIH-4000 Relative humidity Sensor. HIH-4000 has linear output voltage & draws only 200ua (yes micro ampere) current thus making it suitable for battery operated systems.
HIH-4000 humidity sensor is an industrial grade sensor specially designed for high volume OEM users. Since the output of the sensor is linear analog voltage it is possible to directly give the output of the sensor to Analog to Digital Convertor (ADC) or a controller with internal ADC. The Sensors sensing element's multilayer construction provides excellent resistance to most application hazards such as wetting, dust, dirt, oils and common environmental chemicals thus making it suitable for rugged industrial applications.
HIH-4000 humidity sensor has a capacitive sensing element and delivers instrumentation quality performance. The HIH-4000 does not require any external calibration or trimming to provide typical accuracies. The HIH-4000 low drain, linear output, and precise calibration make’s interfacing very easy to any micro-controller.
Features of HIH-4000 Humidity Sensor
- Molded thermoset plastic housing
- Near linear voltage output vs % RH
- Laser trimmed interchangeability
- Low power design
- Enhanced accuracy
- Fast response time
- Stable, low drift performance
- Chemically resistant
The main advantage if HIH-4000 humidity sensor is its output linearity. Below is the graph of output voltage of the sensor vs Relative humidity. As you can see the sensor output is linear right from 0% to 100% thus making it easy to calibrate on the controller side.
Specifications of HIH-4000 Humidity sensor
- Supply Voltage: 4-5.8 Volts
- Current: 200ua (Typically)
- Accuracy: ±3.5%RH
- Repeatability: ±0.5%RH
- Response Time: 5 Seconds
- Operating Temperature: -40°C to 85°C
- Operating Humidity: 0 – 100% RH
Interfacing of HIH4000
As you can see from the above image it is very simple to integrate this sensor into your project all you need is to connect a 80K ohm resistor between the output pin and ground. Since the output of the sensor is analog voltage it can be interfaced directly to any micro-controller which has internal ADC. It can also be interfaced directly to Arduino.
Alternative Sensors
Various types of Analog & digital Humidity sensors are available in the market. One of the most commonly used Analog Humidity sensors are SYHS220 Humidity sensor & SYHS230 Humidity sensor both are low cost as compared to Honeywell’s HIH4000. SYHS220 & SYHS230 also provide linear output but there operating range is limited from 30-90%RH with accuracy of ±5% RH and rated power is 3ma.
Digital Humidity Sensors with either I2C interface or SPI interfaces are also easily available in market. DHT11 & DHT22 are easily available Digital Humidity sensors. These sensors are very low cost and also have integrated temperature sensor. These sensors have operating range of 20-90% RH with accuracy of ±5% RH. But the biggest drawback of these sensors is that they do not have wide operating temperature range so they cannot be used in rugged industrial environment.
All in all I think because of cost & availability HIH-4000 is not used extensively by students & hobbyist. But it is a perfect sensor for industrial application & in battery operated systems.
Amol Shah
Founder of DNA Technology an Electronic Engineer by choice. Started working on this website as an Hobby and now its a full time venture. Very passionate about Electronics and like to learn new stuff. Want to make DNA Technology one of the best Online Store for Electronics Components in India.
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