So you’ve been working on a project which requires temperature/humidity data, and Google.com returned you dozens of different models. If choosing the right temperature/humidity sensor baffles you, we hope this review on 11 different temperature/humidity sensors would help you out a bit.
Products & Quick Comments

	Waterproof DS18B20 Digital Temperature Sensor   Waterproof, long range, affordable
	TMP100 Temperature Sensor (Gadgeteer Compatible)   Mid price range, high performance, versatile, IIC digital output
	Sparkfun Evaluation Board for MLX90614 IR Thermometer   Expensive, long range, smooth curve
	DHT22 Temperature and Humidity Sensor   Mid-price range, Long range, nice cost performance
	Steam Sensor   Low cost, easy to use water detector
	Soil Moisture Sensor (Arduino Compatible)   For plant uses, oxidation-proof
	Infrared Thermometer Module   Cost-efficient, high sensitivity, long range, easy to be embedded, non-contact
	SHT1x Humidity and Temperature Sensor   High-end heavy duty sensor, quick response, high reliability and stability, auto sleep, low power consumption
	DHT11 Temperature and Humidity Sensor   Cost-efficient, for less demanding jobs
	LM35 Analog Linear Temperature Sensor   Cost-efficient, analog linear sensor
	18B20 Temerature Sensor (Arduino Compatible)   good cost-performance?digital sensor

  Part I. Basic Specs This part mainly deals with basic specs such as the interface, size, working voltage, soldering and price, to help you with preliminary screening with physical space, interface and budget.

Product	Size	Price	Interface	Voltage	Need Soldering?
TMP100 Temperature Sensor (Gadgeteer Compatible)	32 x 27mm	$11.50	IIC(Analog4,5?/IDC10	2.7V~5V	Y
Sparkfun Evaluation Board for MLX90614 IR Thermometer	31 x 23mm	$49.95	IIC(Analog4,5?	3V/5V	Y
DHT22 Temperature and Humidity Sensor	38 x 20mm	$9.50	1 analog (can also be digital via converter cable)	+5V	N
SHT1x Humidity and Temperature Sensor	32 x 27mm	$21.00	2 digital	3.3V-5.0V	N
Infrared Thermometer	12x13.7x35mm	$49.00	3 digital	3V/5V	Y
DHT11 Temperature and Humidity Sensor	22 x 32mm	$5.20	1 digital	3.3V-5.0V	N
LM35 Analog Linear Temperature Sensor	22 x 30mm	$4.50	1 analog(can also be digital via converter)	+5V	N
18B20 Temerature Sensor (Arduino Compatible)	22 x 30mm	$4.00	1 digital (1-Wire)	3.3V/5.0V	N

  Part II. Range & Precision If you insist toasting the sensor on fire, it might not taste as good as kebab…So please stay within the temperature scope when using the sensor. The first thing you need to do is to determine the measurement range, then the precision. Precision refers to the value at a certain temperature. It varies with different segments, so please remember checking the datasheet as well. If a constant temperature is hardly achievable in some situations, high measurement precision is not appropriate, because it will change with humidity/temperature drift.

Sensor	Error	Resolution Option	Range
TMP100 Temperature Sensor (Gadgeteer Compatible)	±2°C @-25°C ~85°C±3°C @-55°C ~125°C	Y	-55°C to 125°C
Sparkfun Evaluation Board for MLX90614 IR Thermometer	±0.5°C	N (0.02°C)	-55°C to 125°C?Working?  -70°C to 380°C?Measurement?
DHT22	Temp±0.5°C /Humid±2%RH	N (Temp 0.1°C /Humid 0.1%RH?	Temp -40°C-80°C /Humid 0-100%RH
Infrared Thermometer Module	±0.6?	Y (Max1/16?)	-10~50??Working?       -33~220??Measurement?
SHT1x Humidity and Temperature Sensor	Temp±0.5°C/Humid±4.5%RH	N	Temp 0-50?/Humid 20-90%RH
DHT11 Temperature and Humidity Sensor	Temp±2°C/Humid±5%RH	N	Temp 0-50?/Humid 20-90%RH
LM35 Analog Linear Temperature Sensor	±0.75?	N	-55 to 150°C
18B20 Temerature Sensor (Arduino Compatible)	±0.5°C	N(0.5??  A/D Precision Switch	-55 to 125°C

  Part III. Response Time This part compares the response time between the MCU sends a request and receives from different sensors. The network used is RTT. This value varies greatly with the program (such as delays) and means of communication. The fastest response comes from LM35, which has an output voltage proportional to the temperature. Bus communication is related to the communication protocol, while 1 - Wire communication takes longer time than IIC. Also because of the single bus shared by multiple modules, and can only be time-division multiplexing, may result in large time delay. As a result, it is not recommended to connect multiple devices on the same single bus.   Part IV. Performance (Temperature tracking ability) The way I used is really simple and may not be so scientific: place outdoor then retrieve back (It’s winter), to observe how long it takes for the temperature to achieve stable result after dramatic change. First let’s take a look at two IR temperature sensors, and get a rough idea of the high precision. Whatsmore, since they work without contacting the object, they can be very useful in measuring moving objects, small objects/low specific heat objects, drastic temperature change on object surfaces and 

In a word, these two IR temperature sensors react sensitively to temperature change, and adapt quickly to environmental temperature. Compared with the Infrared Thermometer Module, the MLX90614 IR Thermometer has a smoother curve with less jitter.  
MLX90614 IR Thermometer                                                    Rating??????
Pros: Smooth curve, long range. Has eco mode, non-contact. IIC interface. Quick response. Multiple sensors via single bus. Cons: Costy. Soldering needed. Not very easy to use (IIC Protocol doesn’t support the Arduino Wire Library). Applications: Medical instruments, office equipment (printers, scanners, etc), long range data transmission (over 20m).  

Infrared Thermometer Module                                          Rating??????

It seems that SHT1x is the most sensitive one and achieves stable output quickly. DHT11...However, suffers from error in humidity. DHT22 is a capacitive moisture temperature measuring sensor which uses NTC thermistor.  
DHT11                                        Rating??????
Pros?No soldering needed. Cheapest among three. Get stable output quickly. Transmission over 20m. Strong interference. Cons?Library! No resolution option. Errors: Temp+/-2°C; Humid+/-5%RH. Inadequate measuring range(0-50°C). Applications?Gardening, Agriculture.  
DHT22                                   Rating??????
Pros?No soldering needed. Adding a few bucks to DHT11 and get an upgrade. Smooth curve. Smallest error. Large range. Transmission over 20m. Strong interference. Cons?Can be more sensitive. Slow temperature tracking. Library needed. Applications?Environmental Monitoring.  
SHT1x                                   Rating??????
Pros?No soldering. Smooth curve. Small error. Quick response. Low power consumption. Auto sleep. Extraordinary long term stability and consistency. Cons?Two digital interfaces. Humidity error. Same measuring range with DHT11. Library needed. Applications?Heavy duties and longtime installations.   Following are three relatively cheap choices.

LM35 Analog Linear Temperature Sensor                          Rating??????

Pros?Super user-friendly – one analog cable is enough! Fast response time. Large temperature measurement range. Cheap. Cons?No resolution option. Low precision. Errors… Application?General occasions that do not require high precision.   I also gathered temperature sensors that I think to be high performance: DS18B20, TMP100, SHT1x and DHT22.  
TMP100 Temperature Sensor                                                 Rating??????
Pros?Resolution options from 9~12bit. IIC Protocol. Maximum 8 sensors on bus. Supports IDC10 interface. Short stabling time. Cons?Soldering needed. Jumper cable manual setup. Don’t forget to change address in program. Library needed. Application?Power supply system monitoring, Computer overheating, Thermo control system.  

18B20 Temerature Sensor                                                   Rating??????

Pros?All-around player. Cheap. Resolution options (9-12bit). No soldering needed. Easy connection. Long measurement range. Cons?Library needed. Changing resolution not mentioned in sample code. Single bus. Takes a while to stabilize. Application?Wide. Home appliances, automotive electronics, instrumentation, medical equipment, industrial productions.   Epilogue Still got no idea of which one to use for your project after reading? That’s the exact feeling I got as well. Anyway, hope it might aid just even a tiny little bit, and keep making.