Temperature and humidity sensor is refers to the amount of temperature and humidity can be converted into easy to measure electrical signal processing equipment or device. The temperature and humidity on the market in general is measuring the temperature and relative humidity. And, temperature and humidity sensor is a kind of sensor which only just, just the temperature and humidity in the air by certain detection device, the measured temperature and humidity, according to certain rules to transform electrical signal output, or other form of information needed to meet user needs. And in practical application, we consider the environmental requirements of more complex, so to the choose and buy of temperature and humidity sensor also to have certain requirements. 1. Select measuring range and measuring weight, temperature, choose the humidity sensor to determine the measurement range in the first place. In addition to weather, outside the department, temperature and humidity measurement and control of generally don't need the wet process ( 0 - 100% rh) Measurement. 2. Choose measurement precision accuracy of measurement is the most important indicator of humidity sensor, per - Percentage for humidity sensor is a higher level, or even better. Because to achieve different precision, the manufacturing costs vary widely, the price also differs very far. So the user must act according to actual circumstances, should not blindly pursue 'high, refined, sharp'. As at different temperatures using a humidity sensor, and its value to consider the influence of temperature drift. As is known to all, is a function of temperature, relative humidity temperature greatly affects the relative humidity within a specified space. In most cases, if there is no precise temperature control means, or measured space is sealed, the precision of + / - 5% RH is enough. Accurate control for the local space of constant temperature, constant humidity, or need to track humidity change Settings at any time, to choose more than + / - 3% RH precision humidity sensor. And the accuracy is higher than the requirements of + / - 2% RH even sensor calibration standard humidity generator also hard to do, what's more, the sensor itself. 3. When considering drift and temperature drift in be used actually, because of the influence of the dust, oil pollution and harmful gas, use a long time, electronic moisture transfer device can produce aging, precision, electronic humidity sensor in scatter is generally in the plus or minus 2%, even higher. In general, the effective use of production vendors will indicate one calibration time is 1 year or 2 years, due to calibration. 4. Other matters needing attention of humidity sensor is sealing, to protect the measuring accuracy and stability, and should be avoided in the atmosphere of the acid, alkali and organic solvent. Also avoid using dust in the larger environment. For the correct reflection to measure the humidity of the space, also should avoid sensors placed too close to the walls or the flow of air is not blind Angle. If the room is too large to be measured, it should be placed more sensors. Some humidity sensor to power supply requirement is higher, otherwise will affect the accuracy of measurement. Or mutual interference between sensors, even unable to work. When using, should according to the technical requirements to provide appropriate, conform to the requirements of the precision of power supply. Sensor need for remote signal transmission, to pay attention to the attenuation of the signal problem. When the transmission distance of more than 200 m or more, the proposal chooses humidity sensor output signal frequency.