# ADC in Digital Temperature Sensor DS18B20

1. According to the datasheet of DS18B20 temperature sensor, it is clear that the sensor is digital so the output is in digital form.

The resolution of the temperature sensor is 9, 10, 11, or 12 bits, corresponding to increments of 0.5°C, 0.25°C, 0.125°C, and 0.0625°C, respectively, and by default it is 12-bits. Which means, for 12-bits, a change of 0.0625°C in temperature causes an increment of 1-bit.

But there is no information given on how much change in voltage will result from a change in Temperature (i.e. scale factor). For example, there is an analog temperature sensor in which a change of 10mV in the output voltage is equal to a change of 1°C of temperature.

Is there any way to calculate the scale factor of the digital temperature sensor like the way we do for analog?
2. I've only used the analog 3-wire temperature sensors and, as you already stated, you simply take the voltage measurement, do your own D/A, and then multiply the resulting digital value by a fixed number.

The unit you are looking at does its own D/A and provides you with a digital number. From that point, you do the same exact thing as you do with the analog sensor.

I'm not sure I understand your question because once you have the digital number that is sent over the one-wire serial connection, you'll have that in the register of your Stamp controller (or whatever you are using), and you'll multiply by the number given in the datasheet. I'm sure you'll find lots of application notes online that should give you a "cookbook" description of how to proceed.

(BTW, my work was with the now-ancient LM-35, which I used to sense the cold water inlet temperature on my hot water heater, in order to get a proxy for whether hot water was flowing. If the pipe was hot, then no water was flowing, because the heat from the water heater caused the cold water to get warm. When the pipe gets cold, that meant water was flowing from the cold water supply. It has worked great, every day, for almost a quarter century. There is about a five second delay between the time when water flows and when the sensor reacts to the cold pipe, but that's OK for my application which is to turn the instant hot water recirculator on and off.)
3. Originally Posted by makiyoung
Is there any way to calculate the scale factor of the digital temperature sensor like the way we do for analog?
Not unless they tell you how it works internally. Why would you need to know that anyway? The whole point of a digital temperature sensor is to shield you from dealing with analog data.

And why are you asking this in a video help forum?
4. Definitely you should carefully read datasheet - table 1 provide answer for your question and this is directly as expressed by jagabo - this is digital temperature sensor with approx 9 bit accuracy not analog one - if you search for analog one go for other part.

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