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How to Estimate iTestSystem TDMS Data File Size

When streaming high speed data over a long period of time it is important to estimate data file size to avoid filling up your drive and also to prevent producing large, unwieldy data files. I usually try to keep file sizes less than one (1) gigabyte (FAT 32 maximum file size is 4 gigabytes) to minimize potential data losses and to make sure data transfers, analysis, and plotting don’t take too long. Whether you are using the free version of iTestSystem to manually control data file size or the paid version to automatically control file size, it is important to estimate your file size before collecting data.

iTestSystem uses the standard binary TDMS file format to stream high speed data to disk. Estimating file size depends on five (5) things.

  1. Header Size (Negligible for large files)
  2. Number of Channels
  3. Data Type Size in Bytes
  4. Sample Rate
  5. Logging Duration

File Size Formula = ((Number of Channels) x (Data Type Size (bytes)) x (Sample Rate (Samples/Second)) x (Logging Duration (Seconds))) + Header Size

TDMS File Size Estimator Spreadsheet

File Size Example: Eight (8) Accelerometer Channels sampled at 2560 Samples/Second are logged as a double (8 Bytes) for 600 seconds to a TDMS data file. Estimated file size = (8 x 8 x 2560 x 600) = 98,304,000 bytes or 96,000 KB (98,304,000 bytes/1024 bytes / KB).

For more information about iTestSystem or file sizes, contact Chase Petzinger @ (844) 837-8797 x704.

Vibration and Strain Gauge Level Report Automation with iTestSystem

Our test engineers are often called upon to deploy unattended or “black box” data acquisition systems in the field.  These systems are deployed on machinery, vehicles, and industrial processes to constantly record strain and vibration data at sample rates between 100 and 100,000 Hz. That adds up to a lot of data to sift through.

In situations where we are trying to identify system operation outliers or damaging events, we utilize the Automated Analytics application in iTestSystem to limit the amount of data searches required. The Automated Analytics application allows users to analyze, build, and send sensor level reports only when specific vibration and strain limits are exceeded.  Instead of searching through data files, engineers can easily review the report and download relevant data files from deployed systems for further analysis.

This video demonstrates how to build and send vibration and strain reports using Automated Analytics and other iTestSystem tools and applications.

For more information about our iTestSystem or ITM’s testing services, contact Ryan Welker @ (844) 837-8797 x702.

Related Links

Data Acquisition Equipment Rentals

Do you need software and National Instruments (NI) C-Series hardware to fulfill your testing requirements? During this uncertain time, Integrated Test & Measurement (ITM) is here to support you. We offer various C-Series voltage, strain, vibration, and temperature modules for rent that can be easily configured in our iTestSystem software for you to record and collect data. The rental hardware can be packaged in a ruggedized case for harsh environments. Also, the rental hardware can be set up for unattended testing applications.

For more information about eligibility, equipment availability or to request a quote contact josh.fishback@itestsystem.com

Click Here for more information about equipment rental.

Click Here for more information about our iTestSystem software.

Creating XLS files from TDMS Files

Precision testing generates precision data. Acquiring, accessing, and analyzing these data files allows engineers and scientists to lower product costs, engineer time-saving solutions, and even save lives. National Instruments (NI) created the Technical Data Management Streaming (TDMS) file format for high performance data streaming and retrieval. This binary file is structured for easier sorting and access of the complex data within the file.

What we offer

Are you looking for expert assistance understanding and manipulating TDMS data files? ITM has greatly simplified things with iTestSystem, its free custom engineering software platform that enables you to organize, acquire, view and analyze data. 

 Allow our experts to walk you through TDMS files or point you to our free solutions.

Before NI standardized on the TDMS data file engineers and scientists had to create their own high-performance file types. The TDMS file format is supported not only by iTestSystem, but also across all NI software.

WHAT HAPPENS WHEN YOU WANT TO SHARE THESE FILES WITH COLLEAGUES WHEN THEY DO NOT HAVE ITESTSYSTEM INSTALLED ON THEIR COMPUTERS?

In these instances, it is often easiest to export a TDMS file to a more commonly used file type like Microsoft Excel (XLSX).

NI provides a free program / plug-in that allows users to open TDMS files in Microsoft Excel. This means anyone can convert a TDMS file into an XLSX file and open it in Excel, and once there the file can be easily saved just like any other spreadsheet. Once saved as an Excel file, you can share, open, view and edit it just like any other XLSX file.

HOW DO I GET THE TDMS IMPORTER PROGRAM / PLUG-IN FOR MICROSOFT EXCEL?

If you have installed iTestSystem, the TDMS Importer program / plug-in for Microsoft Excel is already installed. If not, then you can download the software here: https://www.ni.com/example/27944/en/

Once you have downloaded the NITDMExcel program by following the link and using the built-in installation wizard, you can save TDMS files as XLSX Excel files. To open a TDMS file in Excel, you can simply double-click the TDMS file. If that doesn’t work, you will need to right-click, navigate to “Open With”, and find the NITDMExcel program wherever you installed it on your computer.

Figure1: Right click on a TDMS file to import into Excel.

Each time you open a TDMS file in Excel, it will create a new workbook. Each workbook will have multiple sheets, one for the file properties such as the name of the test, date the data was taken, and more. The other sheet(s) will contain the data points plotted as part of the test, which would normally be used to create graphs in TestView Plus.

Now you can save the Excel and share it just like any other XLS file!

Related Links

Auto-Zero Utility Update
Wireless Strain Measurements with iTestSystem
Strain Gauge Installation for Field Testing

For more information about sharing data, iTestSystem, or test equipment rental, contact Ryan Welker @ (844) 837-8797 x702.

Accelerometers for Rotating Machinery Vibration Measurements

Choosing an accelerometer for rotating machinery vibration measurements can be a daunting task since there are so many options available. This blog outlines the characteristics you should consider when choosing a piezoelectric single axis accelerometer for general purpose vibration measurements and presents some accelerometers to consider.

Characteristics of a General Purpose Accelerometer

When measuring vibration on rotating equipment such as motors, pumps, and generators, the most common measurement location(s) are on the shaft bearing housing(s) at the shaft centerline. At this location, typical vibration levels perpendicular to the shaft are < 100 g and the frequency range of interest is < 5000 Hz.  A general purpose single axis piezoelectric accelerometer with either a 10 mV/g or 100 mV/g sensitivity fits this criteria.

Other characteristics to consider are size, mounting options, cable connections, grounding, and cost. Several mounting options are available. They include magnetic bases, adhesive bases and stud mounts. The mounting option you choose affects the frequency range of your accelerometer measurements. The table below shows typical frequency limits for accelerometer mounting methods.

Mount Type Typical Frequency Limit
Magnet 2,000 Hz
Adhesive 5,000 Hz
Stud 6,000 Hz

5 General Purpose Accelerometers

The table below shows some examples of stud mounted general purpose piezoelectric accelerometers. These accelerometers all have a female 10-32 coaxial / microdot connector.  It is important to note that this is not a complete list of accelerometers and there are many options available from each manufacturer. I would encourage you to go to the websites linked in the table and see what’s available.

 
Manufacturer PCB Dytran BRÜEL & KJÆR Endevco Kistler
Model # 353B03 3055D1 4533-B 256HX -10 8702B500-M1
Sensitivity 10 mV/g 10 mV/g 9.8 mV/g 10 mV/g 10 mV/g
Frequency Range (±5%) 1 to 7000 Hz (±5%) 1 to 5000 Hz (±10%) 0.2 – 12800 Hz (±10%) 1 to 10000 Hz (±5%) 1-10000 Hz
Temperature Range -65 to +250 °F -67 to +250 °F –67 to +257 °F -67˚F to +257˚F -67˚F to +257˚F
Height 0.88 in 0.64 in 0.54 in 0.55 in 0.67 in
Weight 0.38 oz 0.35 oz 0.3 oz 0.14 oz 0.32 oz
Housing Material Titanium Titanium Titanium Titanium Titanium
Electrical Connector 10-32 Coaxial (side) 10-32 Coaxial (side) 10–32 Coaxial (side) 10–32 Coaxial (top) 10–32 Coaxial (side)
Mounting Thread 10-32 Female 10-32 Female 10-32 Female 10-32 Female 10-32 Female

For more information about collecting vibration data, accelerometers, iTestSystem, or test equipment rental, contact Mark Yeager @ (844) 837-8797 x701.

How Do I Collect Vibration Data with iTestSystem and a cDAQ?

Our test engineers collect vibration data on rotating machinery using four basic tools.  We use a Laptop computer with iTestSystem software to stream accelerometer and rotational/speed pulse sensor data from a National Instruments cDAQ equipped with vibration and voltage input modules.  The video above shows how to collect vibration data using iTestSystem and a cDAQ.

Vibration Test Equipment

Vibration measurements are usually derived by analyzing data collected from IEPE accelerometers mounted to the rotating machinery structures and components of interest with magnetic bases or epoxy and a rotational/speed pulse sensor.  Typical rotational/speed pulse sensors are magnetic pickups excited by gear teeth and keyways or optical sensors triggered by reflective tape adhered to the rotating machinery.

The most important part of the data collection process is choosing a sample rate.  If  you choose a sample rate that is too low, the data you have collected is useless.  According to the Nyquist Theorem data must be sampled at a rate that is at least 2X the highest frequency you wish to record.  2X the highest frequency is a minimum number.  Most test engineers like to sample from 2.5x to 10x higher than the highest frequency they wish to collect.

Typical general vibration measurements are sampled at 2kHz.  However, vibration data collected from accelerometers and gear teeth pulses which is used for phase and speed measurements, and bearing fault detection, and torsional vibration determination must be collected at much higher sample rates like 50kHz.

Related Links

For more information about collecting vibration data, iTestSystem, data logging or test equipment rental, contact Ryan Welker @ (844) 837-8797 x702.

Wireless Strain Measurements with iTestSystem, LabVIEW, and Arduino

On a recent project, one of our engineers needed to measure structural strain at several locations on mobile lifting equipment while in operation. Since the strain measurements were distributed and mobile, a wireless internet of things (IOT) solution was required. This blog describes the steps and tools we used to integrate our solution into iTestSystem and LabVIEW™.

What we offer

Are you looking for expert assistance with strain gauging, a wireless IOT solution or free custom engineering software platform that enables you to organize, acquire, view, and analyze data?  

One of the wireless devices that we evaluated to monitor strain was a SparkFun Thing Plus (ESP32 WROOM) with a Load Cell Amplifier (HX711). The SparkFun Thing Plus uses the Espressif ESP32 Wi-Fi and Bluetooth MCU. It accepts a variety of digital interfaces including high-speed SPI, UART, I2S, and I2C. The HX711 load cell amplifier accepts four-wire Wheatstone bridges and outputs 24-bit data at either 10 Hz or 80 Hz. The digital signal from the HX711 was connected to a GPIO pin and clock pin on the SparkFun Thing Plus.   We used a Lithium Ion 2Ah battery to power both devices.

Figure 1: Wireless Strain Prototype Connected to a 4-Wire Bending Bridge

After making the connections and installing the device in a 3D printed case for mobility testing, our development engineer programmed this device using the Arduino IDE. Our wireless strain prototype was programmed to auto connect to a Wi-Fi network and output device ID, tag names, and data values via UDP or Webservice. We chose UDP because we only needed the latest strain/load values. Bundling the device ID with the strain data would allow iTestSystem to collect data from multiple devices. To test the wireless strain prototype and develop the UDP interface for iTestSystem, we modified the Simple UDP LabVIEW example vi.

Figure 2: Arduino IDE with Example Program

Next, we integrated the wireless strain prototype into iTestSystem by adding a new communication class into the existing iTestSystem IOT Communication utility. This new class allowed the utility to read the specific UDP data type associated with our prototype and output data to a shared variable. Shared variables can be logged to disk and analyzed with iTestSystem alongside other machine data.

Figure 3: Simple UDP LabVIEW™ Code

For more information about this application, iTestSystem, or our strain gauging services, contact Mark Yeager via email at mark.yeager@iTestSystem.com or phone @ 1.844.837.8797 x701.

ITM Winter 2020 Yeti Cooler Giveaway

Our engineering services department is sponsoring a Yeti Cooler Giveaway.  This giveaway runs from January 6th, 2020 to February 28th, 2020.  To register for this giveaway and view the official rules click the Register Now button below.

Contact Ryan Welker via email:ryan.welker@iTestSystem.com or phone: 1.844.TestSys x 702 for help with any structural testing, strain gauging, and industrial monitoring applications.

iTestSystem Tip: Strain Gauge Rosette Analysis

When troubleshooting structural failures or validating FEA models through testing, strain gauge rosettes are used to find the full state of strain at areas of concern around the structure.  iTestSystem’s Rosette Analysis tool is used to calculate the principal strain, principal strain angle, shear strain, principal stress, and other values from strain gauge rosette data. This video shows how to use the Rosette analysis tool.

For questions about using the Rosette Analysis tool or other iTestSystem analysis tools contact Chase Petzinger.

Download your free version of iTestSystem today.

Another Successful Condition Monitoring System Installation

Last week our team successfully and safely installed another Boiler Monitoring System (BMS).  This system, a Sootblower Fouling Detection (SFD) system, monitors structural and vibration sensors that quantify the boiler’s response to sootblower operations. The SFD system analyzes the boiler response data and outputs Key Performance Indicators (KPIs) such as fouling level, sootblower efficiency, and sootblower health to automated boiler cleaning systems.

This boiler uses over 50 sootblowers located at different elevations to clean soot build-up from boiler steam tubes.  Since the vibration measurement locations are relatively far apart, the SFD system requires a distributed monitoring system consisting of several junction  boxes that monitor and process data for groups of sensors.  One team of engineers mounted the vibration sensors to the sootblowers and confirmed communication back to a local junction box containing the National Instruments condition monitoring hardware.  The other team installed the junction box panels and terminated the sensor cables.

After all the sensor installations and terminations were completed, each sensor’s location and calibration were verified.  While the sensor verification was being completed, one engineer worked with the mill IT department and the controls engineer to establish remote connection to the system and confirm communication with the mill’s automated cleaning system.

After commissioning the system and returning to our home base, our engineers are now monitoring the system through a VPN connection and assisting boiler operators with optimizing their cleaning process.

For more information about our boiler condition monitoring systems, contact Ryan Welker via email at ryan.welker@iTestSystem.com or phone @ 1.844.837.8797 x702

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