FAQ - USB Digital Accelerometer

Getting Started
Basic Usage
Measurement Specifics
Sensor Overview

Creating Scripts and Apps
ASIO Questions

Getting Started

How do I get started?

See our Quick Start Guides to help you get started.

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What are the specifications for the 333D01?

Information for specifications of the 333D01 can be found on the Specifications page.

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Basic Usage

What is the Model 333D01?

The 333D01 is a plug and play USB digital accelerometer. Instead of outputting a voltage or current signal proportional to acceleration, it outputs digital samples.

Why would I use a Digiducer USB Digital Accelerometer?

By directly outputting digital samples from the sensor over USB, you bypass the need for a separate acquisition system, cables and adaptors, or specialized software. Because the 333D01 USB digital accelerometer appears as a USB microphone to the audio driver, any software that works with sound recording via USB (USB microphones, headsets) will work with the USB digital accelerometer.

Who is Digiducer?

Please visit our About Us page to learn more.

How do I start measuring vibration?

All you need to do is attach the sensor to the vibrating test surface of interest via the ¼ -28 mounting threads (or adhesive), plug the sensor into a computer or mobile device (via USB On-The-Go) USB port, open your data capture software of choice, and you’re ready to go!

How do I mount the sensor?

The easiest way is with a temporary adhesive such as cyanoacrylate for smooth surfaces and “dental cement” for rough surfaces. Take care not to fill the stud mount hole by either filling it with wax or putty or using a stud mounted adhesive mounting base. *For more tips, an overview of mounting techniques can be found here.

What mounting accessories are available?

The 333D01 has a ¼-28 thread in the center. Mounting studs and adhesive mounting bases can be purchased from a variety of vendors, for example PCB. Multiple thread adaptors are available to attach to other screw threads via mounting studs. Magnetic mounts are also available. Refer to the online sensor manual section on mounting for more details and best mounting practices.

How can I record my vibration signal data?

After plugging the sensor into a computer or mobile device, simply select the 333D01 in the software’s interface and hit the record or capture button. You can also specify a specific sample rate or bit depth. The software should detect the 333D01’s capabilities from the device itself.

How do I save my vibration signal data?

The 333D01 sends a stream of audio formatted data. The software you choose will need to have saving capabilities to store the data after capture. Typically, this will be in an audio format such as a .WAV file or an application specific format.

What sample rate should I use?

For general purpose use, a sample rate of 48000Hz will work for most applications. For specific frequency measurements, make sure the sample rate is at least twice the maximum expected frequency. For low frequency (< 20 Hz) applications the 8000 Hz rate is ideal.

Which channel should I use?

The device is a single vibration sensing axis and the same signal can be found on both channels. Channel A is suitable for measurements up to ±20 g full scale while Channel B is the same signal scaled ±10 g full scale.

How many sensors can be supported?

Because the sensor identifies as a USB audio device, multiple sensors can be active simultaneously though they WILL NOT BE synchronized. To use more sensors, simply plug in multiple USB hubs. The limit for the maximum number of USB device attached to a computer is 128, according to the USB specification.

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Measurement Specifics

What sample rate does the sensor support?

The 333D01 USB digital accelerometer supports standard audio sampling rates – 48 kHz, 44.1 kHz, 32 kHz, 22.05 kHz, 16 kHz, 11.025 kHz, and 8 kHz.

What bit depth does the sensor support?

The 333D01 has 24-bit resolution, but can also output 16-bit resolution samples. This is selectable in audio driver software.

What is the sensor frequency range?

The 333D01 has a flat response from 2-8000 Hz within ±5% deviation of the calibrated sensitivity at reference frequency.

What is the low frequency capability of the 333D01?

The 333D01 is within ±5% deviation from 100Hz down to 2 Hz. The -3 dB limit is typically 0.75 Hz.

What is the high frequency capability of the 333D01?

The 333D01 is within ±5% deviation from 100 Hz up to 8000 Hz. The +3 dB limit is typically 15 kHz.

What is the amplitude measurement range?

The 333D01 can nominally measure up to 20 g (196 m/s2) of acceleration through Channel A. Channel B is the same signal scaled to nominally measure up to 10 g (98 m/s2) of acceleration.

What are the maximum frequencies for accurate recording and analysis?

The maximum useable frequency depends on the select sample rate – cutoff occurs at ½ of the sample rate. For example, if the sample rate is 8 kHz, you can accurately measure and analyze frequencies up to 4 kHz.

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Sensor Overview

Does the sensor have internal memory?

Yes, for storing self-identifying information and calibration information. It cannot store vibration data.  It is similar in concept to the IEEE 1451.4 TEDS (Transducer Electronic Data Sheet) standard.

What is the sensor weight?

The 333D01 weighs 131 grams (4.62 oz), cable not included.

What is the sensor’s communication method?

USB 2.0 full speed, using audio class device protocols.

What is the length of the cable?

The integrated cable is 2.9 m (9.6 ft).

How is the cable connected to the sensor?

The cable for the sensor is integrated into a sealed housing.  It is not removable.

What is the operating temperature range for the sensor?

The 333D01 can operate between -10° C and 70° C (14° F to 158° F).

Is the sensor susceptible to static electricity?

The sensor is not susceptible to static electricity generated and conveyed through the human body.  The design has been tested as part of susceptibility in CE mark testing.

What connector terminates the cable?

USB type A

What are the power requirements for the sensor?

The sensor operates off of the 5V USB bus and consumes less than 50 mA.

What certifications does the sensor comply with?

The 333D01 has been tested for and is compliant with CE mark standards.

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How do I scale my sampled data to get engineering units (g or m/s2)?

The 333D01 comes with both a calibration certificate and calibration data stored in its internal memory. Software can access this internal data by reading the USB Serial Number descriptor. 333D01 optimized software can perform this task automatically, directly translating the sensor output to engineering units.  See the Software Page for a list of supporting software and features.

What is a nominal calibration value?

36750 counts / (m/s2) (Channel A) and 71974 counts / (m/s2) (Channel B)

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How do you connect to a mobile device?

Simply plug the 333D01 USB cable into a USB On-The-Go (OTG) adaptor cable.

How do you connect to a laptop or PC?

Simply plug the 333D01’s integrated USB cable into any USB port.

Can I use a USB extender cable?

Yes, you can use one or multiple USB extender cables or USB hubs. The maximum length able to be reached is 10km using Fiber Optic cabling, 100m using Copper, and, roughly, 5m using a passive(just wires) extender cable.

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What versions of Windows can be used?

Windows® 7 and 8 offers full compatibility with the 333D01. Windows® XP is compatible, though limited to 16-bit resolution with standard Windows audio drivers.

Can the sensor be used on Android tablets and phones?

Yes – the 333D01 is compatible with both Android phones and tablets, through the use of a USB OTG cable.

Can the sensor be used on Mac and iPhone?

The 333D01 works with Macintosh operating systems and iOS mobile platform. For iOS devices with a lightning connector, Apple’s Lightning to USB Camera Adapter can be used.

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Creating Scripts and Apps

Can I build my own scripts or applications for collecting and processing vibration signals from the 333D01?

Yes – on this site there are examples of MATLAB® scripts, as well as LabView® and LabWindows® applications that interact with the 333D01.

What module of MATLAB® should I use?

The base MATLAB® package can read data from the sensor using Windows® DirectSound drivers. However, more functionality can be obtained with the DSP Toolbox using the dsp.AudioRecorder object.

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When I plug in my sensor, it does not appear in my audio device list.

Sometimes when first plugging in the sensor, the device information is not properly transmitted. If unplugging and replugging the sensor does not fix the problem, you can try restarting the computer. If that does not resolve the problem, uninstall the device through the Device Manager window (may require a restart).

Why do I have an abnormal frequency cut off?

If you are using Windows built-in drivers, make sure that the correct sample rate is selected in the Windows Recording Devices interface. This should match the sample setting in your software application.

What are the units being output from the sensor? How do I convert them into useful units?

The raw data coming from the sensor is a 16-bit or 24-bit sample (depending on software settings), sent a byte at a time. Depending on the application this may be displayed as a digital count from -223 to +223 (leading bit is a sign bit) or represented as a full scale value (FSV). To convert from FSV to digital counts, multiply the full scale value by 223 or 215 for 24-bit samples and 16-bit samples, respectively. To convert from a digital count to engineering units of m/s2, divide the digital count value by the calibration value for the channel in question. To convert from m/s2 to g, divide by 9.80665.

One of the channels is displaying signal clipping – what does this mean?

If the clipping is in Channel B, the input acceleration being measured has likely reached it the Channel B maximum measurement range (normally 10 g). Switching to Channel A should solve the problem.  If clipping is still present , the acceleration measured is likely beyond the max range of 20 g and cannot be accurately measured by this device.

The Windows recording interface states that 24-bit depth is available for only two sample rates (44100 and 48000) – what do I do?

Default Windows sound drivers do not permit 24-bit samples below 44100 Hz sample rates. However, using another sound driver such as ASIO will allow full use of the sensor’s bit depth and sample rate capabilities.

I’ve dropped my sensor, is it broken?

The 333D01 is rated up to 7000 g of shock without damage. Your sensor should still work – however if you are concerned about performance impacts, you can have your sensor recalibrated by a regional instrument calibration lab or by www.digiducer.com. Email us at info@digiducer.com for details.

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ASIO Questions

What does ASIO stand for? (What is ASIO?)

ASIO stands for Audio Stream Input and Output. (ASIO is a low latency, high fidelity interface directly between software and the sound card, or in this case the 333D01 hardware. A free implementation can be found in ASIO4All.)

What does ASIO do?

ASIO allows you to utilize the full features of the sensor by bypassing Windows restrictions and directly accessing the hardware. Specifically, it allows you to choose any combination of bit depth and sample rate supported by the 333D01.

Why should I use ASIO?

Though you can operate with the standard Windows DirectSound drivers, it requires you to match the sample rate chosen in software with the sample rate listed in the Windows Recording Devices interface. If these sample rates do not match, Windows resamples incoming data which will corrupt the integrity of the data. In addition, Windows DirectSound only permits the use of 24-bit samples with 44.1kHz and 48kHz sample rates. The sensor itself allows any of its 7 available sample rates to be used with either 24-bit or 16-bit resolution.

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