Friday, January 7, 2022 · 16 min read
How To Choose the Right Data Acquisition System For Your Measurement Application?
Choosing the right data acquisition system can be a challenge for even the most experienced test and measurement engineers and technicians. There are several important factors that must be taken into consideration during the DAQ selection process. This article will guide you through the process in a logical way, and then present you with a software tool that we have invented that automates the selection process.
5 essentials when choosing data acquisition hardware
To jump right in, these 5 metrics are essential when choosing the correct data acquisition hardware:
Scrolling further down we will break down all the important questions you need to ask yourself in order to choose the best data acquisition system for you. Questions are grouped into three mains sections:
What analog signals/sensors do I need to measure?
The essential function of a DAQ system is to make measurements from various sensors and electrical signals, e.g. to measure some kind of physical phenomenon. Therefore, making a comprehensive list of the types and quantities of signals and sensors that you need to measure is the first thing that you should do. This information will drive everything that follows.
There are numerous sensors and transducers for measuring temperature, vibration, pressure, strain, voltages, currents, resistance, and many more.
What digital and bus data do I need to record?
Today’s DAQ systems can measure much more than analog signals like voltages and temperatures. There are digital signals from encoders, RPM sensors, gear tooth, and tacho sensors, for example, that require a different kind of input. These “counter” inputs must be sampled much faster than the analog inputs.
There are also digital bus data that can be displayed and captured. Few examples:
CAN bus data found in every car and truck
Data transmitted across RS232 and Ethernet interfaces
Position data from GPS sensors, and 3D orientation data from IMU (inertial measuring units)
EtherCAT data found in countless industrial and process control environments
ARINC 429 and MIL-STD-1553 bus data found in commercial and military aircraft
Do you need to capture data from any of these?
Furthermore, there are industrial video cameras that can capture video in sync with your other data. Is this a requirement for you? Will it be in the future?
What measurement resolution do I need?
The most common measurement resolution today is 16-bit, but there are higher-end DAQ systems that provide 24-bit resolution, which is considered essential, especially for noise and vibration applications, and 12-bit resolution systems for low-end data logger applications.
Each bit doubles the possible resolution of the DAQ system. That means that 24-bit is not just 50% more resolution than 16-bit resolution. In fact, 24-bit ADCs provide 256 times greater possible resolution than 16-bit ADCs.
Theoretical maximum values based on bit resolution:
|Number of Bits||Max Values|
How much dynamic range do I need? 80 dB, 100 dB, 130 dB, or 160 dB?
Dynamic range is the difference between the smallest observable part of the signal and the largest. Systems that have higher dynamic ranges provide more vertical axis resolution. Another way of looking at this is to ask this next question…
What is the smallest change in a measured signal that I need to detect?
This goes hand-in-hand with dynamic range. You should have an idea of the smallest change in a signal that you want to see.
Systems with the highest dynamic range provide the best possible vertical axis measuring resolution. But you also have to consider the time axis, because if changes in amplitude fall between samples, they cannot be measured.
Systems with greater than 100 dB dynamic range and at least 200 kS/s sample rate can handle most applications. For shock, noise, and vibration applications, a dynamic range of 120 to even 160 dB is highly desirable.
Our DualCoreADC® technology in the SIRIUS data acquisition systems boosts dual 24-bit delta-sigma ADC converters with an anti-aliasing filter on each channel. This allows our DAQ modules to achieve an astonishing 160 dB of dynamic range in the time and frequency domains. Along with up to 200 kS/s/ch sampling rate per channel, these are unique amplifiers on the market.
What level of accuracy do I need?
In an ideal world, measuring systems would be 100% accurate, but perfection is not really possible. There will always be some inaccuracies introduced into the measurement chain, starting right at the sensor itself.
The most common factors contributing to the inaccuracy of any measuring system are gain errors, offset errors, and temperature drift errors in the analog domain and the time base accuracy of the ADC (analog-to-digital converter) and digital counters.
A good DAQ system will specify its accuracy in a clear and consistent way. For example, time base accuracy is normally expressed as “Typical 5 ppm, Max: 12 ppm,” meaning that the oscillator might typically deviate from its nominal value up to 5 parts per million, but the maximum deviation is 12, in this example.
Gain accuracy is normally written as a percentage, like “±0.05 % of reading.” So if the system is reading +1.000 V, the gain error could be as much as ±0.0005 V. It can also be written as a percentage of full-scale.
Offset accuracy is written as an absolute value, like “±0.02 mV,” which is easy to understand.
Temperature drift can affect both the gain and offset accuracy. Gain temperature offset is written like “±50 ppm/K of reading ±200 μV/K,” for example. This ties the error directly to the change in ambient temperature, in Kelvin.
What kind of noise performance do I need?
You’re probably thinking “I don’t want any noise!” Of course not, but in the real world, electrical and magnetic “noise” is bombarding DAQ systems constantly. Even when they are shielded properly, sensor cables are like antennas. In addition, there are nearby sources of EMI and RFI in most DAQ measuring environments.
The key is to find the system with the best isolation and the best grounding practices. Please see the next question for more details about isolation.
Does my DAQ system need isolation?
Electrical galvanic isolation is important for safety, for example, when you’re dealing with high voltages. But it also preserves the integrity of all measured data regardless of voltage level, by eliminating or reducing noise, crosstalk, and ground loops, which can either obscure or completely destroy your measurements. In general, we know two types of isolation:
Channel-to-channel isolation means that the noise or crosstalk between and among all channels is prevented.
Input-to-output isolation means that whatever the sensor or measuring wire is connected to in the outside world is isolated from the DAQ system.
Systems with both channel-to-channel and input-to-output isolation provide the most robust isolation.
SIRIUS DAQ systems from Dewesoft provide both channel-to-channel and channel-to-ground isolation, as shown in this short video:
Do I need filtering capabilities?
Filtering is one of the most important elements of analog signal conditioning. Filtering allows you to reduce or completely block frequencies above or below a selectable frequency component from being recorded. There are also band-pass and band-stop filters, allowing you to select a certain range of frequencies for inclusion or exclusion.
Filtering is sometimes needed to block 50 or 60 Hz noise created by nearby electrical power systems, or higher frequencies from electromotors, generators, power supplies, fluorescent lights, etc. There are many sources of electrical noise that can interfere with your measurements.
Ask yourself if you need non-destructive filtering. Would it be helpful if the filters applied before recording could be removed afterward, or changed completely? All Dewesoft data acquisition systems have filtering capabilities.
Do I need anti-aliasing protection?
An “alias” is a false signal that is created when the signal is moving too fast compared to the sample rate. Aliasing must be prevented before the measurement is made, otherwise, there is no way to recreate the real signal later.
There are two ways to prevent aliasing:
Always set the sample rate to be at least twice as fast as the highest frequency observed. (Sometimes this is not possible because the highest frequency cannot be predicted.)
Choose a DAQ system with a built-in anti-aliasing filter (AAF) system. Essentially this is a very steep low-pass filter that is set automatically to a percentage of the selected sample rate. This AAF filter blocks frequencies that are too high for the selected sample rate to reproduce, and thus prevent alias signals from being created.
Any DAQ system that is used for noise, shock, and vibration, or applications that involve AC waveforms should have robust, completely automatic anti-aliasing built-in, to ensure the integrity of your measurements.
How fast do I need to acquire or sample the signal?
The job of a DAQ system is to reproduce the character of the signal with as much fidelity as possible. A good rule of thumb is to pick a system that is capable of sampling at least 10 times faster than the fastest signal that you need to capture.
For example, if you need to capture signals that have 20 kHz content, your system should be capable of sampling at 200 kHz. You might read that you only need 2x over-sampling, i.e., the Nyquist frequency. Just note that only 2 samples per period cannot reproduce the appearance of the waveform.
The new HybridADC technology developed for the SIRIUS XHS product line allows the user to select three modes of operation, depending on the selected acquisition rate:
High Bandwidth Mode (Filter Off): 5 MHz bandwidth and 15 Ms/s sampling rate, the SIRIUS XHS can perfectly acquire impulse, step, and square signals without any ringing or overshoot. This mode is perfect for transient recording and power analysis. This behaviour is similar to typical SAR ADCs except for a higher sample rate and bandwidth.
Alias-free, High Dynamic Mode: Sampling up to 1.875 MHz and bandwidth up to 1 Ms/s, and 150 dB dynamic range. The data is totally alias-free, so all higher frequencies are fully rejected. This alias-free filter with a bandwidth close to the Nyquist criteria is used for frequency-domain analysis of signals such as sound and vibration. There is some ringing/overshoot on square waves and other impulse signals. This behaviour is similar to classical Sigma-Delta ADCs except with a much higher sample rate and bandwidth.
Ring-free filtering: in addition, Dewesoft offers ring-free filters with no overshoot on impulse signals while still maintaining alias-free acquisition. The measurement remains alias-free because the cut-off frequency is set automatically to 20% of the sampling frequency.
Will I need to upgrade or extend the DAQ system in the future?
Most engineers have a limited budget every year, and they tend to favor systems that are easy to upgrade or add on to next year, and in the years that follow.
Product lines that are built around a common “ecosystem” are easily interconnected and share modular elements. They can be synchronized together easily. They share a common software platform that integrates them all and eliminates having to learn to use completely different systems.
When looking at a manufacturer’s offerings, find out if they are built around such an ecosystem: can you interconnect them, and do they share common hardware and software?
Dewesoft data acquisition systems are modular by design. The input channel count and configurations can grow together with your testing need so you can easily expand the entire testing system at any time.
Do I need a portable, benchtop, or rack-mounting system?
This should be easy to analyze - it’s all about the environment in which the DAQ system is expected to work.
Certainly, any mobile environment, like inside a car, truck, train, etc., requires a portable system. Besides being generally smaller and lighter, portable systems typically run from either AC or DC power, so that they can be easily powered inside vehicles. Many of them also run from internal batteries, making them ideal for fieldwork. Battery-powered data acquisition systems have the added advantage of having a built-in UPS, and they don’t draw on the power system if that’s what you’re trying to measure.
If your environment is a nice clean laboratory or manufacturing floor then a benchtop system is generally fine. Benchtop systems are typically AC-powered and are larger than portable ones. If you intend to permanently mount your system in a 19” rack enclosure, then a rack-mounting system makes the most sense.
Dewesoft provides all kinds of data acquisition systems from handheld, benchtop, and portable, to rugged, high-channel rack-mounting systems.
Do I need a stand-alone instrument, or should it be connected to a PC?
This is a matter of your preference. PC-connected DAQ systems have the advantage of being smaller because they don’t have a computer, display, or hard disks inside of them. They are generally less expensive for the same reason. And, you can use your own computer.
But if you’re going to have to leave the system in a non-secure environment, a stand-alone system might be a better choice.
Do I need a rugged system that can withstand heavy shock or vibration?
If you’re bouncing around in cars and trucks, for example on test tracks, then there’s going to be a lot of shock and vibration. You know your environment better than anyone, so you probably already know the answer to this question.
It’s something worth thinking about. Most DAQ systems are not designed for high shock and vibration environments. Always check the shock and vibration ratings.
Systems rated in the 100 g range (EN 60068-2-27:2009) are considered rugged. Vibration is also a factor, particularly random vibration. Systems tested to MIL-STD-202G Method 214A, test conditions II-D and above are considered rugged.
Dewesoft DAQ systems are extensively tested in our state-of-the-art testing labs for shock and vibration. We install our systems on rocket launch platforms, use them in off-road proving grounds and all other types of environments where high ruggedness is needed!
Do I need a system with a wide temperature range or one that’s dust-proof or waterproof?
Another question worth thinking about is operating temperature, dust, and water protection. Environmental testing either in nature or in chambers always requires systems that can tolerate a much wider range of temperatures found in factories and laboratories.
Field testing of any type when you’re taking the instruments outside can lead to temperature extremes. It can also lead to salty air, heavy humidity, fog, dust, and even rain.
If this is your working environment, then a system rated IP65 or IP67 is a very good idea, since it will be sealed against the ingress of particles, including water. Systems rated to IP67 and with operating temperatures from -40° to 80°C (-40° to 185°F) provide excellent water and particle ingress protection and temperature performance.
KRYPTON and SIRIUS Waterproof are ultra-rugged DAQ systems for field testing in harsh environments that provide a wide operating temperature range, waterproof, and high shock protection.
Are the system’s specifications easy to understand?
DAQ manufacturers vary in terms of how much and which information is provided within their specifications. In addition to performance characteristics like a number of channels, selectable gain ranges, top sample rate, et al, it’s essential to look at the accuracy and isolation specifications.
It’s easy to be impressed by specification numbers with lots of precision, but that’s not the same thing as accuracy! For example, if you specify that the time is 2:00:0006437 PM, but it’s really 3:15 PM, that’s a lot of precision, but very poor accuracy.
It’s a good idea to look at how consistent specifications are given across different signal conditioners, for example. Is isolation of 1000V shown on several modules, but not mentioned at all with other signal conditioners? That could be a red flag. Always make sure that you know what the most important specifications to you really are, and how they apply to all important aspects of the product.
Ease of use, features, and support
Are operation manuals available and easy to read?
It’s great to have an operating manual, but only if you can understand it. It should be well-written in your language, and clear. Ideally, the manual will also be available as a searchable PDF file or even available online as a website with extensive search features.
And a great convenience is HELP built right into the software itself. When running the DAQ software, does pressing F1 to bring up context-sensitive help based on what you’re doing in the software? Is it searchable? Does it contain the entire manual?
Also check if there are any other training resources available like webinars, online training courses, and how-to guides, that will help you achieve your goals.
What technical support is available to me?
It’s always a good idea to ask about what kind of support you can expect after receiving your new DAQ system:
Is there someone to call?
Do they speak my language?
Is the support staff technically proficient?
What if there is a really deep question, will they go to engineering to get an answer for me?
Are there training classes or seminars available online or in person?
Can I get one-on-one training at my facility if I need that?
Are there any technical discussion forums available online?
You get the idea. No one expects all of these things to be free, but they should be available and performed at the most professional level, focusing on you, the customer.
Dewesoft offers a FREE global and local technical support line for our data acquisition solutions.
Is the user interface easy to read and learn?
This might be the most important thing to investigate before buying any DAQ system. Ideally, you will have had a product demonstration, but, it should be possible for you to download the software and run it in a demonstration model on your own computer.
Always ask for this, so that you can get the feeling of the interface, and gauge how long it will take you to achieve basic proficiency.
DewesoftX data acquisition software offers a very intuitive user interface with a short learning curve and no need to program in order to get great signal processing results. It really makes using the data acquisition system enjoyable again.
Is the system easily reconfigured for different applications?
It is a great probability that you will need your DAQ system for different measurement tasks and applications. System reconfiguration to fit your certain task may involve both hardware and software.
For example, if your DAQ system has plug-in signal conditioning modules, you may need to exchange some of them for different measurements. Is this easy to do in the hardware, and does the software automatically recognize the new modules?
Or, you may need to connect an external module or system to your main one - is this also easy to do? Does the software see the new channels and configure them in the software? Is synchronization handled?
Can I save setups for my applications?
The ability to freely name and save an unlimited number of setups should be a basic function of any good DAQ system. However, it’s always a good idea to check that this is supported, and how it is implemented.
This will save you a lot of testing preparation time and will enable you to easily repeat frequent measurements.
Can I analyze my data on the DAQ system? Can I also analyze offline?
Most DAQ systems provide some level of built-in data analysis that can be performed after the data has been acquired. It’s a good idea to find out exactly what can be done.
For example, if filtering was applied during measurement, can it be changed or even removed afterward? Can you create math functions and then run them on the recorded data? Can you make new displays and compare data easily?
Does the DAQ system allow you to put this software on your own computer and do all of these same analytical functions? Is it free of charge or are you required to have a paid license or a hardware dongle? Can the software be installed on other computers as well, either for free or with a paid license?
Obviously, you’d probably like to be able to do all of these things, and without any fees. But some DAQ makers do charge for this, so you should find out ahead of time.
Can data be exported easily to other analysis programs?
Unless your data will never require analysis outside of the DAQ system itself, it should be possible to export it in one or more common data formats. It should also be possible to select a portion of the data for exporting, and which channels are to be included.
Common data analysis formats include:
UNV / UFF (Universal File Format)
But there are many more, so you should verify that your DAQ system supports the specific format that you need. Also look at the import capabilities of your analysis software, because many of them can accept a number of file types.
Which analysis programs are supported?
As mentioned above, if there is a particular data analysis program that your company is using, you should verify that your DAQ system is capable of exporting to it. The most popular analysis programs include Excel® for limited data sets and Flexpro® and Matlab® for virtually unlimited data sets and a wide array of built-in analytical functions.
But there are other programs on the market. Some companies have even developed their own analysis tools in-house, and these are written to accept various file formats, almost always including a basic text format for universal compatibility.
DewesoftX data acquisition software includes in-depth math for digital signal processing in a single software package.
Investment cost and cost of the ownership
Is data acquisition software included or do I have to pay extra?
Some companies offer attractive pricing on their data acquisition hardware. But you need to be careful and check if the software that enables you to use that DAQ hardware is included in the offered price.
Also, make sure you know your software requirements! Check if the features you require are included in the included software package or require any upgrade options. Are those for free or require extra investment?
Dewesoft data acquisition systems are bundled with award-winning DewesoftX data acquisition software. The DewesoftX Professional version is always included for FREE. Furthermore, when your data is recorded into the Dewesoft data file, anyone can download the software and analyze the data for free. No additional seat licenses are required.
Are software updates free, or will I have to pay?
Software is never “done” - it’s always being improved and developed. There will be new releases that not only correct bugs but which add important new features and capabilities.
The majority of data acquisition companies require you to subscribe to an annual support contract, either for the software itself or for the entire system. This cost is often calculated as a percentage of the overall system cost. Or, they charge for new releases.
Dewesoft considers the software to be an essential living part of the data acquisition system and does not charge for its updates and new releases. All releases are free forever for all existing customers. Dewesoft releases 4 major software releases each year, adding new features, performance optimizations, new device support, and bug fixes.
Dewesoft offers FREE lifetime updates for all existing Dewesoft users. All new features are available for FREE by downloading our latest DewsoftX installer.
Is there an annual maintenance fee?
One of the “hidden” costs of owning a DAQ system may be an annual maintenance fee. You should ask right up front if there is a mandatory maintenance fee, and if so, what does it include and how is it priced? Ideally, there will not be one, but you should know upfront before you order the system, because it is an expense that will have to be budgeted ahead of time.
Dewesoft data acquisition systems do not require any yearly maintenance fees, except for recalibration if your company policy demands a recalibration of the systems on yearly basis.
How much does calibration cost? What Is included?
All measuring systems require calibration. You might assume that a brand-new system would arrive fully calibrated from the factory, and that “traceable” calibration certificates would be included. Don’t take that for granted and verify that with the manufacturer.
If they include them, that’s great. If not, how much do they cost? Now, what about next year? And the year after that?
Calibration is normally only valid for one year, so you should find out what your options are for future calibration. If your company has a calibration lab, they may be able to purchase a calibration kit from the DAQ manufacturer that will allow your company to do calibration in-house.
If not these are things to reconsider:
Is there a certified calibration lab in your area that can be hired to perform the service?
Does the DAQ manufacturer themselves offer an annual calibration service?
How quick is their turn-around, and where is it done?
If you need to send the unit halfway across the globe back to the manufacturer headquarters for recalibration, there will be costs and time associated with that. Ask these questions upfront.
All Dewesoft data acquisition systems are calibrated and checked for conformance tests before they leave our headquarters to you. Dewesoft has local factory calibration labs in Austria, Brazil, China, France, Germany, Hong Kong, Mexico, Russia, the United Kingdom, Sweden, and the United States of America. For more information see our DAQ Calibration Services page.
How long is the warranty?
The warranty period is another important thing to know about. One year is a good length for a warranty from the manufacturer, and Dewesoft includes this as standard. When comparing DAQ systems you should always ask about the warranty and what it provides.
Dewesoft offers an industry-leading 7-year warranty for its data acquisition systems. During the 7-year warranty period, Dewesoft guarantees to keep your equipment in working order by repairing or replacing it. The Dewesoft 7-year warranty is valid worldwide, no matter where the equipment is located. There are no hidden service costs or maintenance fees.
For more information check the Dewesoft Warranty page.
What technical support is available and for what cost?
As already answered earlier above in the question What Technical Support Is Available to Me? Good technical support is essential when it comes to data acquisition and similar systems. Ask yourself those questions. If technical support is available it is usually not free. Double-check the cost associated with it to see what cost could arise during the lifetime of your data acquisition system.
Dewesoft offers FREE worldwide and local technical support to our customers. Our global software and hardware technical support are available in the English language and our support agents are able to connect to your measurement unit with your allowance and help you troubleshoot your measurements. Our subsidiaries in all major countries also offer free technical software and hardware support in your local language.
Dewesoft offers a FREE global and local technical support line for our data acquisition solutions.