> For the complete documentation index, see [llms.txt](https://docs.echook.uk/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.echook.uk/circuit-schematics/temperature-inputs.md). # Temperature Inputs The thermistors form part of a potential divider. The resistance of each thermistor changes with temperature. As that resistance changes, the output voltage of the potential divider changes. ![](https://lh3.googleusercontent.com/dTmzH5MYW5Xj8Isw-SGnR_1u34sVLL_O2zmYcV4i6zEg_g0cZvfmK9op8tlo9R-367dwLYHgWkTaj_tbzzKKVIL-V53UfUgbPXsXuf8nvqEdvdpMYQDzUSF-5Muqz2rjxG4wXN-r) In the diagram above, the 'Therm' component to the left represents the three-pin connector on the eChook board. Thermistor 1 is connected between pins 1 and 3, and Thermistor 2 is connected between pins 2 and 3, completing potential dividers with R5 and R7 respectively. R6 and R8 are in place to protect the Arduino. The Arduino can be easily damaged by too much voltage, and without these resistors the pins would be directly connected to an external connector, making them vulnerable. The 1k resistor provides a little protection, although 24V applied to the connector will still damage the Arduino. They also do not affect the temperature reading, as the current flowing into the Arduino's analogue-to-digital converter (ADC) is so negligible that it can be assumed to be 0mA. The voltage drop across the resistor can be calculated using Ohm's law, (V = I \* R). In this case, the voltage drop is effectively 0V. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://docs.echook.uk/circuit-schematics/temperature-inputs.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.