Building a Multichannel Data Logger with Raspberry Pi – Part 1: Requirements & Architecture

For the full build, see Part 2 (hardware) and Part 3 (software). In this article, we outline the core concepts behind a multichannel data logger that records voltage, current, and temperature at configurable intervals.

The goal is to demonstrate that a Raspberry Pi can transition from an educational toy to a robust, field‑ready instrument capable of handling professional measurement tasks. According to Wikipedia, a data logger is "an electronic device that records data over time, or in relation to location either with a built‑in instrument or sensor or via external instruments and sensors."

System Requirements

As a field or service engineer, you’ll need a device that offers the following capabilities:

• Eight temperature inputs covering 0–260 °C (32–500 °F)
• Eight versatile inputs that can measure either voltage (30 mV – 30 V, ±2 mV accuracy) or current (10 mA – 500 A)
• Configurable sampling interval from 1 s to 60 s
• Persistent configuration storage across restarts
• Intuitive data retrieval and graphical representation

Desired features:

• Battery‑powered, lightweight, and portable
• Operational in both field and laboratory environments
• No reliance on an external desktop or laptop for data acquisition

These specifications enable a wide range of applications—from tuning electric vehicle circuits and monitoring incubators to assessing solar batteries and greenhouse conditions.

Architecture & Design Overview

The core platform is a Raspberry Pi running Raspbian Linux. We’ll augment it with a custom carrier board that hosts an ADC, shunt connectors, temperature sensors, a power stabilizer, and a power‑failure notifier to support battery operation.

Connectivity is Wi‑Fi based. A USB Wi‑Fi dongle will be configured in AP (host) mode, making the logger appear as a network access point on any phone or tablet. In laboratory settings, an Ethernet cable can turn the Pi into a free Wi‑Fi router or extender.

Software architecture centers on a web‑based UI. Users can configure logging intervals, select channels, and set trigger conditions through a browser. Real‑time data appears as dynamic graphs, while full datasets can be exported as CSV for external analysis (e.g., Excel).

Key components include:

• ADC interfaced via GPIO for high‑precision readings
• A background service that polls the ADC at user‑defined intervals, stores raw data, and manages configuration persistence
• A RESTful API that exposes configuration and data endpoints for the web UI
• Two primary UI screens: Configuration (set parameters) and Status (view data, graphs, and export options)

For deeper insights, refer to Part 1 of the "Multichannel Professional Data Logger on Raspberry Pi" series.