Applications of Temperature and Humidity Sensors in Machine Room Monitoring Products

For delicacy management of places with higher requirements on data security, like large-scale data centers, IDC or power distribution cabinets, monitoring temperature and humidity in their computer room only is not enough. In practice, there are cases when every checking point in the machine room shows that temperature and humidity are normal, while operation environment of  internal facilities cant be guaranteed. Internal heat dissipation of equipment has become a major source of equipment fault, so temperature and humidity monitoring inside machine rooms and cabinets is urgently required.


At present, most machine rooms and their environmental units are 24-hour safeguarded and regularly inspected by staff. With heavier management burden, it can neither shoot troubles in advance nor implement scientific management on time and liability of happened accidents. Therefore, it is necessary to monitor temperature and humidity and add video surveillance in machine room and paths between servers. Here is the recommended structure chart of monitoring system:


In relatively larger computer rooms, temperature and humidity differs between each checking points due to airflow and equipment distribution. Amount of sensors to be mounted should be determined by the actual area and locating positions of facilities in the machine room. Real-time onscreen display of temperature and humidity in the machine room can be realized by the interaction between sensors and IPC in main monitoring room. When the measurement value reaches the preset point, the system will make an alarm to warn on-site administrative staff. Moreover, a communication interface for wireless modem can be preserved for further expansion. The card slot for wireless modem preserved on the hardware can be useful in the future when SMS alarm is needed.

In this article we recommend a digital temperature and humidity sensor – HTU21D. With its unique design and process, this type of sensors can measure and display ambient RH and temperature within a high accuracy and relatively low cost.

Miniature Digital Relative Humidity and Temperature Sensor
  1. Brief instructions of HTU21D:

HTU21D Digital Relative Humidity and Temperature Sensor DESCRIPTION 
HTU21D, the new humidity and temperature sensor of MEAS is about to set new standards in terms of size and intelligence: Embedded in a reflow solderable Dual Flat No leads (DFN) package of 3 x 3mm foot print and 1mm height it provides calibrated, linearized signals in digital, I2C format.

HTU21D sensors are dedicated humidity and temperature plug and play transducers for OEM applications where reliable and accurate measurements are needed. Direct interface with a micro-controller is made possible with the module humidity and temperature digital outputs. HTU21D sensors are low power consumption designed for high volume and cost sensitive applications with tight space constraints.

Every sensor is individually calibrated and tested. Lot identification is printed on the sensor and an electronic identification code is stored on the chip – which can be read out by command.

Furthermore, the resolution of HTU21D sensor can be changed by command (8/12bit up to 12/14bit for RH/T), low battery can be detected and a checksum improves communication reliability.

With made improvements and the miniaturization of the sensor the performance-to-price ratio has beenimproved – and eventually, any device should benefit from the cutting edge energy saving operation mode.

HTU21D Digital Relative Humidity and Temperature Sensor Characteristic

• DFN type package
• Relative Humidity and Temperature Digital Output, I2C interface
• Fully calibrated
• Lead free sensor, reflow solderable
• Low power consumption
• Fast response time

HTU21D Digital Relative Humidity and Temperature Sensor FEATURES
• Full interchangeability with no calibration required in standard conditions
• Instantaneous desaturation after long periods in saturation phase
• Compatible with automatized assembly processes, including Pb free and reflow processes
• Individual marking for compliance to stringent traceability requirement

HTU21D Digital Relative Humidity and Temperature Sensor APPLICATIONS 
• Automotive: defogging, HVAC
• Home Appliance
• Medical
• Printers
• Humidifier


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