Calibrated differential pressure sensors will find usage in industry and also in every smart home.
Ventilation, air conditioning (HVAC), or any other applications, where a pressure or a flow of air (gas) is essential, can be precisely regulated only if we know a real pressure/ flow conditions. Monitoring of fans functionality, status of filters, …, even for this purpose are very suitable differential pressure sensors from Swiss company Sensirion with an excellent accuracy and long-term stability.
As SDP sensors are differential, they have 2 nozzles. The base of these sensors is a miniature heating element and two temperature sensors. Difference of pressures will cause a small air flow through a component and it will cause a temperature difference in these built-in sensors. Temperature difference is directly depending on the amount (weight) of air flowing through a sensor and it naturally depends just on a pressure difference. A great advantage against membrane pressure sensors is a long-term high accuracy even at measuring of small pressure and maintaining of accuracy of a “zero point”.
As an air specific weight depends on temperature, measurement based only on a temperature difference of two internal sensors wouldn´t be accurate. That´s why SDP sensors have a built-in temperature compensation and linearization, thus an output of a sensor is directly a value usable for further processing. Resolution of sensors is very high and is user selectable in a range of 9-16 bits. Resulting binary value read-out through I2C interface can be divided by a constant shown in a tab. 2.1 on page 3 of the SDP6xxv1.7 datasheet and we´ll get a resulting value in desired units (Pa, bar, inch).
Universal and price-attractive series is the SDP600 (6xx) series, in which we´ll find types optimized for measurement of pressure (SDP 600/610), mass flow (SDP601/611) and types with a minimal power consumption suitable even for battery-operated devices (SDP606/616). All these types are able to measure “bidirectionally” i.e. positive and even negative values. For applications, where we know, that a pressure difference will be always positive (flow by only one direction), it´s possible to use more price-affordable types SDP 500/510 (in fact even these types measure bidirectionally, but their accuracy is not guaranteed in this range). For the most of applications no additional compensation is necessary, only it can be necessary to multiply a resulting value by a constant for an altitude compensation shown in a table 5.4 on page 6 in the datasheet.
How can be this small sensor used to measure flow of a big amount of air?
Relatively simply. All that is necessary is to make a small orifice in a pipe and this way to create a “resistance” as described in the SDPxxx_Bypass_Configuration application note. In an electronics analogy the differential pressure measurement is similar to measurement of voltage on a resistor, which depends on a current flowing through a resistor. SDP sensors can be used even for measurement of a pressure difference in a given pipe against a surrounding environment, in such a way, that one nozzle of sensor will be left “unconnected”. Naturally, such a configuration can only be used if a small leakage of a measured “gas” (air) is acceptable.
Sensirion SDP sensors measure pressure but even a flow - [Link]
Felix of LowPowerLab writes:
I’m calling it MotionMote because it detects motion and because pretty much every type of wireless sensor or Moteino node name ends in “mote“. The possibilities for home security are endless, put this little guy in a corner near a door or on top of a cabinet somewhere and detect them intrudaz! Did I say there’s no wires?
Read on for details and source code and case design.
MotionMote – Moteino motion sensor - [Link]
BH1750FVI Is a Digital Light sensor , which is an digital Ambient Light Sensor IC for I2C bus interface. This IC is the most suitable to obtain the ambient light data for adjusting LCD and Keypad backlight power of Mobile phone. It is possible to detect wide range at High resolution.( 1 – 65535 lx ).
BH1750 Digital Light Sensor - [Link]
cbrittain1 @ instructables.com writes:
I’ve been working on re-making the the Open Hardware Pulse Sensor so it’d be “easy” to send off to OSHPark and make at home. I’m not sure but I think I started this project in March (2013) and I’ve just now finished it.
Homemade Arduino Friendly Pulse Sensor - [Link]
Nix is a breakthrough smartphone accessory. Just scan an object and instantly view the color on your iPhone, Android, PC, or Mac.
Nix is a patent pending device that allows anyone to become a color expert. Just grab Nix from your pocket, purse, or bag, touch it to an object and magically watch the exact color appear on your iPhone, Android, PC, or Mac. Once scanned, you can keep palettes of your favorite colors, match the color to real life pigments, and even receive directions to the nearest store where you can purchase the color.
Nix Color Sensor - [Link]
Humidity can be measured by various sensors, but sensors SHT from company Sensirion add many benefits moreover.
To be exact, a word „sensors“ is not a suitable expression in this case. As SHT series sensors contain on one chip humidity and temperature sensor, precise supply, low noise linear amplifier, AD converter and a serial interface, they represent a ready-made “device”. Moreover, they´re calibrated, thus to get an exact value it´s only necessary to read out data through a serial interface. In case of SHT2x series, it´s a standard, easy-to-implement I2C interface.
Sensirion sensors SHT2x series was more in detail introduced to you in our article „New sensors Sensirion will take you only 3x3mm on PCB!”, that´s why we´d like to bring you mainly few tips for simplification of development now.
Area of relative humidity and physics of water vapors is quite ample and into its introduction will initiate you the document Introduction_to_Relative_Humidity. Don´t be scared of many quotations, which you´ll find there – fortunately in common praxis we usually manage it with values of relative humidity and a dew point, which can be found together with code examples in Humidity_at_a_Glance.
As humidity sensors are very often used in residential places for regulation of heating and ventilation, also useful can be information about influence of humidity on a thermal comfort. For a practical usage of sensors it´s also important their placement on a PCB and a good access of air, what is in detail described in the document Sensirion_Humidity_Design_Guide. SHT2x are intended for 3VDC power supply, that´s why when using in 5V applications, you can face a problem of different voltage levels. This can be easily solved for example by a circuit described in the document SHT2x_5V_Supply_Embedding.
The program itself doesn´t need to be developed “from zero”. Examples can be found in the document SHT21_Sample_Code and SHT2x_Electronic_Identification_Code. Detailed information about testing and specification of SHT sensors can also be found in documents Sensirion_Humidity_Sensor_Specification_Statement and Sensirion_Humidity_Testing_Guide.
SHT25 – humidity and temperature precisely in every season – [Link]
Maxim’s Collection of temperature sensor and thermostat ICs
These temperature sensors offer good accuracy (±1.5°C) over the range of -25°C to +125°C and feature a 2-wire digital output with bus lockup protection and external reset.
Here is a small collection of circuits that provide an interface to sensor transducers including pressure, temperature, and others.
This circuit provides a highly integrated analog sensor signal conditioner targeted for automotive applications. The device provides amplification, calibration, and temperature compensation. Output is digital. Read the rest of this entry »
Epson has combined the reliability of quartz crystals with the tiny dimensions of MEMS devices to create a tiny high-resolution six degree-of-freedom inertial measurement unit that can track motion for everything from aerospace to oil-well drilling. [via]
Epson Downsizes Inertial Measurement Units - [Link]
Digital Temperature Sensor in TO-92 Package Ideal for Measuring Ambient Temperature.
The MAX31820 ambient temperature sensor provides 9-bit to 12-bit Celsius temperature measurements with ±0.5°C accuracy over a +10°C to +45°C temperature range. Over its entire -55°C to +125°C operating range, the device has ±2.0°C accuracy.
MAX31820 – 1-Wire Ambient Temperature Sensor - [Link]