USB Data-Acquisition Module Does the Job
Product Tryout
Martin Rowe, Senor Technical Editor -- Test & Measurement World, 9/23/2005 7:13:00 AM
iUSBDAQ Model U120816. Hytek Automation, www.hytekautomation.com. Price: $79.
| Read Martin Rowe's impressions of three low-cost USB data-acquisition modules in "USB reaches mainstream status," T&MW, June 2005. Read more commentary from Martin Rowe. |
The iUSBDAQ provides eight 12-bit analog inputs, 16 digital I/O lines, two programmable pulse-width output channels, and one 16-bit counter channel. Analog sampling rate is 32 ksamples/s on a single channel, which divides among the number of channels you use.
The first thing you'll notice is that the iUSBDAQ comes with a screwdriver so that you can connect signals to its terminal strip-connectors. Without it, I'd have to buy a screwdriver. Only one of the three $150 models I evaluated came with that. The other manufacturers chose not to provide one citing their modules' low cost.
Hytek Automation makes its software application and iUSBDAQ driver available online so you can always get the latest version. The full software install will add the LabView runtime engine to your computer because the software application is written in that language. You also get LabView VIs that provide programming examples if you need to write your own application. The software includes a driver DLL and the user guide provides you with programming information.
When you run the iUSBDAQ full software install, you get iTest&Log, an application that lets you operate all the module's functions. A set of tabs lets you choose the type of function you wish to control. The analog-input tab lets you set up each of the eight channels. Buttons let you operate the device with single or streamed measurements. If you use streamed measurements, you'll see your waveforms on the chart-recorder screen, which displays each channel in a different color and you can change each color as desired by right-clicking on it. The software also lets you save data to disk in csv format, which is compatible with Excel.
After you save your data, you can analyze it using the Analysis Graph tab. Here, you can import saved data and plot it. You can choose from several types of graphs including line, bar, and dot plots. Because the graphs are built with LabView, you can change their scales simply by typing new high or low values. Cursors with coordinate displays let you measure time and amplitude differences.
As part of my tests, I checked the iUSBDAQ's accuracy against an Agilent 34401A DMM. I used a 3.538 VDC test voltage. With the iUSBDAQ, I made 1000 measurements at 200 samples/s and calculated the average to eliminate any noise on the test signal. The average of the iUSBDAQ's measurements came within 3 mV of those made with the DMM. Thus, I conclude that you'll get accurate measurements with the iUSBDAQ.
When you use the streaming-data feature, watch out because you must set the scan rate no lower than 128 Hz. Values below 128 will produce an error message. But, the iTest&Log's default scan rate is 1 Hz. That's confusing and should be changed. If you need to measure at scan rates below 128 Hz, you must oversample and calculate an average.
I also tested the iUSBDAQ's pulse-width frequency output. At 50% duty cycle, I checked the frequency of pulse trains at frequencies ranging from 5 kHz to 250 kHz. The frequencies were somewhat low, with errors ranging from 2% to nearly 10%.
All in all, you get a useful instrument for little money. It's not perfect, but the iUSBDAQ comes close.
