# Geiger Counter Radiation Chart UI for iOS > By Lawrence Arya, Founder & CEO of VP0. Published 2026-06-27. 7 min read. > Source: https://vp0.com/blogs/geiger-counter-radiation-chart-ui-ios A radiation chart app reads an external sensor over Bluetooth and plots the dose rate. Here is how to wire Core Bluetooth and Swift Charts, with honest units. **TL;DR.** An iOS Geiger counter chart reads from an external radiation sensor, since the phone has no radiation hardware, usually over Bluetooth with Core Bluetooth, and plots the dose rate over time with Swift Charts. The honest core is units and framing: show microsieverts per hour clearly, mark a sensible reference band, and never present a hobby sensor as a calibrated safety instrument. Handle the disconnected state truthfully and keep the chart smooth as readings stream. Build the dashboard from a free VP0 design and wire the sensor and chart yourself. A Geiger counter chart on iOS reads from an external radiation sensor, because the phone has no radiation hardware, and plots the dose rate over time. In practice that means connecting to a Bluetooth Geiger counter with Core Bluetooth and rendering the readings with Swift Charts, with one non-negotiable: honest units and framing. The instrument dashboard is fastest to start from a free [VP0](/explore) design, and it shares the live-reading chart craft of a [CGM glucose chart in SwiftUI](/blogs/cgm-glucose-chart-ui-swiftui/). ## The phone cannot measure this on its own Start from the truth that shapes the whole app: the iPhone has no radiation detector. Any credible radiation app is a front end for a separate sensor, so the first design decision is the connection, not the chart. Most hobby and prosumer Geiger counters expose their readings over Bluetooth Low Energy, which is exactly what [Core Bluetooth](https://developer.apple.com/documentation/corebluetooth) is for: you scan for the device, connect, discover its service, and subscribe to the characteristic that streams the dose rate. That framing also rules out a whole category of fake apps. Anything claiming to detect radiation using only the phone is not measuring anything, and your honest app should make clear it reads a real external sensor. ## Charting the dose rate Once readings stream in, [Swift Charts](https://developer.apple.com/documentation/charts) turns them into a dashboard: a line of dose rate over time, with a reference band drawn behind it so a viewer sees context, not just a bare number. Bind the chart to a bounded, recent window of readings, label the axis with the unit, and let it update as new values arrive. Keep the parsing off the main thread and the visible window bounded so the chart stays smooth, the same performance discipline a [Buienradar-style rain map overlay](/blogs/buienradar-rain-map-overlay-clone-swiftui/) needs when frames stream in. ## Units, honestly The single most important thing on the screen is the unit. Ambient dose rate is typically shown in microsieverts per hour, and the US Environmental Protection Agency's [radiation basics](https://www.epa.gov/radiation/radiation-basics) explains the sievert as the unit that captures the health-relevant dose, which is why labeling the axis and the headline number in those terms matters. Mark a sensible reference band for typical background so the chart reads as context rather than a frightening bare figure. Showing a number people may react to emotionally puts a duty on the design: state the unit, give the reference, and never imply more precision than a hobby sensor has. ## Connection and limits Two honesty points finish the app. Handle the disconnected state truthfully: show a clear reconnecting or stale indicator rather than freezing the last reading as if it were live, the same connection honesty a [Bet365-style odds display](/blogs/bet365-odds-display-ui-react-native/) owes its users at the integrity moment. And frame the whole thing as informational: a hobby sensor and app can show trends and relative changes, but calibrated safety decisions belong to proper equipment and the authorities, and the app should say so and point to official guidance. ## What to choose For a Geiger counter chart on iOS, build it as a Bluetooth sensor front end: connect with Core Bluetooth, subscribe to the dose-rate stream, and render it with Swift Charts over a bounded, recent window. Label the unit, microsieverts per hour, on the axis and the headline, mark a background reference band, and keep the chart smooth by parsing off the main thread. Be honest in two places: show a real disconnected state instead of a frozen value, and frame the app as informational rather than a calibrated safety instrument, pointing to official guidance. Start the dashboard from a free, $0 VP0 design and wire the sensor and chart yourself. ## Frequently asked questions ### How do I build a Geiger counter chart on iOS? Read from an external radiation sensor, because the iPhone has no radiation hardware. Most hobby and prosumer Geiger counters expose their readings over Bluetooth, so you connect with Core Bluetooth, subscribe to the dose-rate characteristic, and plot the values over time with Swift Charts. Show the units clearly, mark a reference band, and handle disconnection honestly. Build the dashboard layout from a free VP0 design and wire the Bluetooth and chart code yourself. ### Can an iPhone measure radiation without a sensor? No. The iPhone has no built-in radiation detector, so any radiation app either reads an external sensor or is not actually measuring anything. Apps that claim to detect radiation using only the phone are not credible. A real radiation chart app is a front end for a separate Geiger counter or dosimeter, connected over Bluetooth, and the app's job is to read, chart, and label that sensor's data honestly. ### What units should a radiation chart use? Dose rate is typically shown in microsieverts per hour for ambient readings, and you should label the unit on the axis and the headline number so there is no ambiguity. Mark a sensible reference band for typical background levels so a viewer can read context, not just a bare number. Being explicit about units and reference levels is what makes the chart informative rather than alarming, especially for a measurement people may react to emotionally. ### Is a hobby Geiger counter app safe to rely on? Treat it as informational, not as a calibrated safety instrument. A hobby sensor and app can show trends and relative changes, but real safety decisions belong to properly calibrated equipment and the relevant authorities. The app should say so plainly and avoid implying it can certify an area as safe. Honest framing, show the data, state the limits, point to official guidance, is what keeps a radiation app responsible. ### Can VP0 give me a free template for the radiation dashboard? Yes. VP0 is a free iOS design library where each screen has an AI-readable source page, so you copy a link and Claude Code or Cursor builds the dashboard, the live reading, the chart, the connection status, in SwiftUI. You wire the Core Bluetooth sensor and the Swift Charts data yourself. The design gives you a clear, honest instrument layout to start from at no cost. ## Frequently asked questions ### How do I build a Geiger counter chart on iOS? Read from an external radiation sensor, because the iPhone has no radiation hardware. Most hobby and prosumer Geiger counters expose their readings over Bluetooth, so you connect with Core Bluetooth, subscribe to the dose-rate characteristic, and plot the values over time with Swift Charts. Show the units clearly, mark a reference band, and handle disconnection honestly. Build the dashboard layout from a free VP0 design and wire the Bluetooth and chart code yourself. ### Can an iPhone measure radiation without a sensor? No. The iPhone has no built-in radiation detector, so any radiation app either reads an external sensor or is not actually measuring anything. Apps that claim to detect radiation using only the phone are not credible. A real radiation chart app is a front end for a separate Geiger counter or dosimeter, connected over Bluetooth, and the app's job is to read, chart, and label that sensor's data honestly. ### What units should a radiation chart use? Dose rate is typically shown in microsieverts per hour for ambient readings, and you should label the unit on the axis and the headline number so there is no ambiguity. Mark a sensible reference band for typical background levels so a viewer can read context, not just a bare number. Being explicit about units and reference levels is what makes the chart informative rather than alarming, especially for a measurement people may react to emotionally. ### Is a hobby Geiger counter app safe to rely on? Treat it as informational, not as a calibrated safety instrument. A hobby sensor and app can show trends and relative changes, but real safety decisions belong to properly calibrated equipment and the relevant authorities. The app should say so plainly and avoid implying it can certify an area as safe. Honest framing, show the data, state the limits, point to official guidance, is what keeps a radiation app responsible. ### Can VP0 give me a free template for the radiation dashboard? Yes. VP0 is a free iOS design library where each screen has an AI-readable source page, so you copy a link and Claude Code or Cursor builds the dashboard, the live reading, the chart, the connection status, in SwiftUI. You wire the Core Bluetooth sensor and the Swift Charts data yourself. The design gives you a clear, honest instrument layout to start from at no cost. --- *Published on the [VP0 Journal](https://vp0.com/blogs). Free to read, index and cite with attribution.*