> For the complete documentation index, see [llms.txt](https://faq.growsensor.co/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://faq.growsensor.co/substrate-probes/what-do-the-substrate-probes-measure.md). # What do the substrate probes measure? All of our supported substrate probes measure three key factors, giving you valuable insights into your root zone. * **Water Content (VWC)** – Measures how much water is in your substrate, helping you fine-tune irrigation. * **Electrical Conductivity (pwEC)** – Indicates the salt/nutrient concentration in your substrate, ensuring optimal feeding levels. * **Substrate temperature** – Tracks how warm your substrate is, which affects root health and nutrient uptake. ### **Why is this important?** Measuring Water Content and pwEC is essential for crop steering. It allows you to make data-driven decisions about when to water and when to feed your plants. You can access dedicated graphs for each measurement in the Grow App, and set limits and alerts for all three to stay in complete control of your grow. --- # 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 by asking a question. Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters: ``` GET https://faq.growsensor.co/substrate-probes/what-do-the-substrate-probes-measure.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case. 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.