Back in my days as a full-time experimentalist, my group would make copious use of precision meters for gathering a large number of sensitive electrical measurements simultaneously. Data gathered from these systems were critical for helping to answer basic scientific questions and evaluating new electronic and optoelectronic devices. Even if you’re not a scientist, you’ll still need to use similar techniques as part of your tests and measurements, requiring systems for logging data in real time and storing it on a local desktop.

Many instruments can interface with your desktop via USB, RS232, or GPIB, but this eliminates the use of many different sensors that are too compact to include these standard interfaces. Some examples include environmental sensors, electrochemical sensors, optical detectors, and compact RF sensors. This is where a data logger board can expand your measurement capabilities and make your testing systems much more flexible.

Why Use a Data Logger Unit?

If you’re working in a lab gathering a large number of sensitive measurements, it helps to funnel your data back to your desktop for further analysis. Many instruments offer a USB, RS232, and/or IEEE 488 GPIB interface for gathering data from precision electronic meters. These interfaces can also be used to control certain functions on your meters through a custom computer program (usually something like LabVIEW). However, not all precision measurement units provide this type of interface, leaving many important sensors unable to interface with your measurement system.

This is where a small data logger board comes into play. These boards function exactly as their name suggests; they use an ADC to convert a voltage/current reading to a digital bit stream, which is then sent to a desktop or other processor for storage and further processing. These boards expand the capabilities of your sensing system beyond those provided by precision meters and are critical for providing a direct comparison between DUTs and bulky precision measurement systems. This route is preferable to buying larger, more costly measurement units that include the digital interfaces you need to send data to a desktop. Data logger units provide greater flexibility for a large number of sensors with a single low-power device.

 

 

Choosing a Data Logger Unit

The primary device that makes your data logger work is an ADC. This converts your analog measurements into a digital number, which is then sent via your interface to a PC or mobile device. Most ADCs in data logger units are 8, 10, or 12-bit ADCs. There are some important points to consider when selecting a data logger unit:

• Bit depth and resolution: This refers to the bit depth in the ADC the device's analog front end. There is a tradeoff between measurement resolution (the minimum difference between two voltage levels that can be reliably measured) and sensitivity to noise.
• Input voltage range: Your ADCs will saturate at some input level. If one of your devices outputs at too high a level, then you will need to step down the voltage; a simple voltage divider network is usually sufficient. Note that you’ll need to connect the ground of your voltage divider to the common ground point on your data logger. This is an extremely important point as ground loops can create a large amount of noise in your measurement system; keeping your sensors and data logger tied to a common ground helps suppress noise in your readings.
• Interface type: Data loggers will typically connect to a PC via RS232 (D-Sub connector) or USB (usually a USB-A connector). Some newer data loggers for use in the field will include Bluetooth or WiFi access for communication between a phone, tablet, or PC.
• Sample rate: This tells you how often data is gathered. Some development boards will allow you to select this through your control program. For DC measurements, this is not much of a concern as you’ll essentially be gathering time-averaged data. For purely AC data logger measurements, you’ll need to consider the Nyquist sampling rate. In general, your sampling rate should be much larger than the AC frequency you’re trying to measure.
• Available software: Some companies that manufacture data logger units will supply a convenient software program that allows you to capture and save data from the unit. Companies that don’t offer these programs should give you a LabVIEW VI or an SDK that helps you develop your own application.
• Onboard storage: If you’re building a system for remote monitoring, you’ll need some onboard memory to store data.

Here are some options for low-cost data logger units with small footprints.

Advantech PCIE-1812-AE

The PCIE-1812-AE data logger board from Advantech is a heavy duty data acquisition module for use in rack-mounted units or custom enclosures. This module connects to a motherboard as a PCI-E card and provides 32 digital I/O connections. This module supports 8 differential analog input changes with 16-bit resolution and 250 kS/s maximum sample rate. This card is ideal for any application that requires simultaneous acquisition and monitoring of a very large number of external devices. This module is rather expensive, although Advantech offers other data logger modules with similar capabilities and a lower price.

 

 

Keysight DAQM907A

The DAQM907A multifunctional data logger is designed for a variety of sense and control applications. It provides two 8-bit digital input and output ports, a 100 kHz gated totalizer, and two 12 V/24 mA analog outputs. Keysight provides an SDK for this module and a number of useful whitepapers for gathering precision measurements.

 

 

Pico Technology DrDAQ

The DrDAQ data logger is an excellent standalone module for gathering data from instruments via BNC cables. This data logger can connect to a desktop/laptop via USB-A for data acquisition and power. Onboard features include built-in light, temperature, and sound sensors. There are also 4 digital I/O pins on the device.

Pico Technology provides a software application that allows the module to act as an oscilloscope/spectrum analyzer, arbitrary waveform generator, and pH/redox sensor with standard reference electrodes. Users can also download an SDK for building a custom application.

 

 

Designing a Custom Data Logger PCB

vThe data logger units shown here are just a few examples. For specialized applications, you may find that an off-the-shelf data logger does not meet all of your requirements. In this case, designing a custom data logger PCB can provide the exact functionality needed for your system. This approach allows you to tailor the hardware to specific sensor types, power constraints, and communication protocols.

When designing a custom data logger PCB, consider the following core requirements:

• Analog-to-Digital Converter (ADC): Choose an ADC that matches your resolution and sampling rate needs. Typical options range from 10-bit to 24-bit resolution, with sample rates that vary depending on whether you’re measuring DC or high-speed AC signals.
• Sensor Interfaces: Plan for the sensor connections you'll need, such as single-ended or differential inputs, current loops (e.g., 4-20 mA), or specialized sensor protocols like I2C or SPI.
• Embedded MPU or FPGA: Use an MPU or FPGA to manage data acquisition, timing, and communication with external systems. If DSP steps are implemented in the application, FPGAs or a dedicated DSP are often the best option.
• Data Storage: Include onboard storage such as SD cards, flash memory, or SRAM if remote operation or large data collection is required.
• Power Management: Design appropriate power regulation, including low-dropout regulators (LDOs) or switching regulators to supply stable voltage to analog and digital circuits. If battery-powered, consider energy efficiency and low-power design techniques.
• Communication Interfaces: Decide how the board will communicate with a host system. This could include USB, RS232, Bluetooth, WiFi, or even LoRaWAN for remote data collection.
• Clock Source: Stable reference oscillators are often used provide timing for ADC sampling and data logging intervals, especially in time-critical applications. In some applications, such as RF signal sampling with JESD204C, source-synchronous clocking is used as the reference for timing and data capture.
• PCB Layout Considerations: Keep analog and digital ground planes properly separated and use careful routing to minimize noise coupling. Place decoupling capacitors near power pins to stabilize voltage and reduce EMI.

Designing a custom data logger allows you to optimize your system for specific performance criteria, cost targets, and form factor requirements. It’s a valuable option for embedded systems engineers looking to build flexible and scalable monitoring solutions.

 

 

Whether you're designing an ultra-rugged aerospace system or feature-rich embedded computing products, make sure your design firm understands how to coordinate with electronics manufacutring services and contract manufacturers to help you produce and scale with maximum quality. NWES helps aerospace OEMs, defense primes, and private companies in multiple industries design modern PCBs and create cutting-edge embedded technology, including power systems for high reliability applications and precision control systems. We've also partnered directly with EDA companies and advanced ITAR-compliant PCB manufacturers, and we'll make sure your next high speed digital system is fully manufacturable at scale. Contact NWES for a consultation.

 

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