A Review of 11 Temperature and Humidity Sensors

You’ve been working on a project that requires temperature and humidity data, and Google.com returned your dozens of different models.

If choosing the right temperature/humidity sensor baffles you, we hope this review of 11 different temperature and humidity sensors will 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     The 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 Temperature 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.

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.

Part III. Response Time

This part compares the response time between the MCU sending a request and receiving 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 the single bus is shared by multiple modules, which can only be time-division multiplexing, may result in a 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 outdoors then retrieve back (It’s winter), to observe how long it takes for the temperature to achieve stable results after the dramatic change. First, let’s take a look at two IR temperature sensors, and get a rough idea of the high precision.

Whatmore, since they work without contacting the object, they can be very useful in measuring moving objects, small objects/low specific heat objects, drastic temperature changes 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

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

Cheaper. The smaller size (found it really suitable for thermometer pen). Nice curve with high precision and compensator. Resolution options. No library is needed. Digital output. Low signal loss. Soldering headers are needed. Inadequate measurement range. Need 3 digital interfaces. Applications?Same as above. Now it’s time to compare three temperature & humidity sensors at the same time.

It seems that SHT1x is the most sensitive one and achieves stable output quickly. DHT11...However, suffers from errors in humidity. DHT22 is a capacitive moisture temperature measuring sensor which uses an NTC thermistor.

DHT11

No soldering is needed. Cheapest of the 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

No soldering is needed. Adding a few bucks to DHT11 and getting 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

No soldering. Smooth curve. Small error. Quick response. Low power consumption. Auto sleep. Extraordinary long-term stability and consistency. Two digital interfaces. Humidity error. Same measuring range as DHT11. Library needed.

Applications: Heavy duties and longtime installations. Following are three relatively cheap choices.

LM35 Analog Linear Temperature Sensor

Super user-friendly–one analog cable is enough! Fast response time. Large temperature measurement range. Cheap. No resolution option. Low precision. 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

Resolution options from 9~12bit. IIC Protocol. Maximum 8 sensors on the bus. Supports IDC10 interface. Short stabling time. Soldering needed. Jumper cable manual setup. Don’t forget to change address in the program. Library needed. Application?Power supply system monitoring, Computer overheating, Thermo control system.

18B20 Temerature Sensor

All-around player. Cheap. Resolution options (9-12bit). No soldering is needed. Easy connection. Long measurement range. 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, and 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, and keep making.