Types of temperature probes for thermostat and solar thermal equipment
15 MARCH 2021
Ptc or Ntc type temperature probes
They are temperature sensitive resistors.
Its functionality is based on the change of internal resistance as the external temperature rises or falls, the voltage does internally.
Obviously this is completely analog technology.
It is the type of sensor or thermal probe used in today's consumer electronics.
It is easy to find in the electronic components market.
Advantages of analog Ntc or Ptc probes
They are easy to find in electronics stores.
They do not need a special thermostat and can be tested with an electronic multimeter.
Disadvantages of analog Ntc or Ptc probes
The reading is not very accurate.
The quality and length of the cable may vary the sensor reading.
The passage of natural time can vary the accuracy of the sensor.
The thermostats that use these probes can be configured in order to fine-tune their accuracy, but it won't be easy if the probe is already installed in a hard-to-reach location.
If several comparative probes are used, as is the case with a solar heater, the difference in accuracies can make life relatively difficult.
Digital temperature probes
They are not resistors like the previous ones.
It looks very similar to a transistor.
They are pure digital devices as if they were micro computers.
The device that manages it literally asks you what your temperature is, and this digital probe responds with the exact data.
They are widely used in the recreation and learning of domestic electronic uses and home automation applications. The most popular among digital probes is the DALLAS B18B20.
It is exceedingly popular in the arduino world.
The Dallas Ds18b20 digital probe looks like this:
These tiny devices are made up of 3 legs. Two of them are to deliver the voltage (5v).
The 3rd leg is the one you use for digital communication with your thermostat or any similar device that manages it.
Here the identification of the legs of the sensor ds18b20:
Advantages of the Dallas 18B20 digital probes
Today they are easy to find in the digital market, usually in stores such as Aliexpress, Amazon, Ebay, etc.
Poor quality aging or excess length of your wiring will not affect your reading accuracy at all.
Thermostats do not need to calibrate or fine tune the readings from these probes, because they are real and truly accurate data.
Generally, its minimum and maximum temperature range is wider than analog probes.
Many probes can be put in parallel on the same cable, since they function internally as a telecommunications network. (You could even put several probes in a place that is difficult to access, to be able to select another alternatively in case of failure)
The device that manages the probes can configure the order of the probes without performing physical operations, since each probe has an internal digital address.
Disadvantages of Dallas 18B20 digital probes
They need special thermostats for the use of these digital probes.
They cannot be tested with an electronic multimeter, a compatible device is needed, or an arduino or raspberry with the code loaded for this use.
The reading is much slower than an analog probe. If you use a lot of probes and configure them with high precision, the latency time can be a bit high.
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