±2% accuracy in a whole range of relative humidity measurement – that´s just one of several improvements brought by the third generation of miniature calibrated sensors from company Sensirion.
Even the actual series like SHT1x and SHT2x belong to a top in this segment. Forthcoming series SHT3x (SHT30, SHT31 and soon also SHT35) addresses mainly those of you, requiring maximum accuracy even in limit values (humidity below 10% and above 90%), miniature dimensions and ultra low power consumption. So a main difference of a new SHT31 compared to SHT21 is, that a typical +-2% is maintained in a whole range. Together with a precise temperature measurement in element we still have a possibility to simply compute a dew point, what´s one of the key parameters for ventilation control (HVAC, heat recovery). If it´s “only” necessary to guide a humidity not to exceed certain level, then you´ll probably also use the output „Alert“ pin, able to start interrupt in a host MCU for instance or directly control further devices. Output of the SHT3x sensor is the linearized value, which can be easily transformed to a final value (%RH, °C).SHT31 is available in 2 versions – SHT31-DIS-B with a digital output via well-proven I2C bus (2 selectable addresses) and also in a version SHT31-ARP-B with a linearized analogue (proportional) output. That´s why SHT31-ARP-B is an interesting alternative for direct processing in analogue circuits, as it contains 2 independent outputs with output voltage of 10-90% Vdd, responding to 0-100%RH and -45 to +130°C temperature. Digital output version also features wide possibilities of setting regarding measurement frequency, communication speed and other parameters.
Even the humidity & temperature sensors can be “3G” – [Link]
Measurement and control of temperature and relative humidity finds applications in numerous areas. These days devices are available which have both temperature and humidity sensors with signal conditioning, ADC, calibration and communication interface all built inside them. The use of such smart sensors greatly simplify the design and reduces the overall cost. We discussed in past about Humidity and temperature measurements with Sensirion’s SHT1x/SHT7x sensors. These sensors are capable of measuring both temperature and relative humidity and provide fully calibrated digital outputs. While SHT1x/SHT7x are very accurate sensors, they are still expensive for hobbyists use. This articles discusses the DHT11 sensor which also provides calibrated digital outputs for temperature and humidity but is relatively lot cheaper than the Sensirion sensors. The DHT11 sensor uses a proprietary 1-wire protocol which we will be exploring here and implementing with the PIC16F628A microcontroller that will receive the temperature and humidity values from the sensor and display them on a 16×2 character LCD.
Measure temperature and humidity using DHT11 sensor and PIC – [Link]