MQTT - the language that the Cloud can speak
Sensors in Building Automation
1. What sensor is and how it changes our comfort?
2. Most commonly used sensors in BAS.
Typical Monday, you finally get to your office after a few dozens of minutes of forcing your way through the morning traffic jam. At your full speed, with thoughts about tasks of the week, you are entering the entrance hall. You did not even slow down before the main door, because your brain learned that the door opens automatically. Ah, that’s just a motion sensor, not a big deal, you might think. Well, it is a big deal if you think about it in a technological sense. There is a device, mounted above the door, which constantly monitors the amount of thermal energy within its range. When you enter the ‘sensored’ area it detects the increase in infrared energy, which releases your body through heat. The sensor, therefore, changed the output to give the door controller signal that the motion was detected, and the door auto-magically opened. Such events most probably happen around you multiple times during the day, without you even noticing. And all of that because sensors of different types quietly do their job. Some of them may even save your life one day.
So what is a ‘sensor’? It is a device whose purpose is to detect changes in its environment and send the information to other electronic devices. In the case of Building Automation sensors typically used to monitor environmental conditions, ensure safety and save energy. ‘What you can measure you can control’ is often repeated truth among the BMS Engineers. When you get to your office, you expect a pleasant and safe environment. Sensors allow for controlling algorithms to compare current conditions to the predefined commonly known standards of comfort or defined specifically by the end-user. For example, if the temperature in a room is below 18 deg. C, the heating should be turned on, regardless, of the area is occupied or not. Also if the occupant prefers a higher temperature than the standard one and changes the setpoint, we need to know how to maintain the desired temperature most efficiently. For that, we have temperature sensors on the output of the Air Handle Unit, on the wall in the controlled room and the return of the air duct. Sensors give us information for precise and efficient control. Generally, the more sensors there are available, the more prices control we potentially can have and thus fewer energy losses.
Pic. 1. iSMA-B-LP (example of multi-sensor)
There are several ‘superstars’ among sensors, which are essential and thus very commonly used in building automation.
Lately, a large number of sensors are created according to IoT standards, have their IP address and are ready for integration to BMS wirelessly. But yet most of them are hard-wired to controllers or I/O modules that can read their values depending on the type of the sensor. For that purpose, I/O modules are equipped with Digital Inputs (signals true/false) and Analog Inputs (for measuring voltage, current or resistance values). There is also a common practice among BMS equipment manufacturers to implement Universal Inputs (they can act both as Digital or Analog) as it’s done in iSMA-B-MIX-38.
Pic 2. iSMA-B-MIX38 (example of I/O Module)
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