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Inexpensive DA, control modules use plug-and-play USB

Posted: 02 Mar 2005 ?? ?Print Version ?Bookmark and Share

Keywords:data translation? module? usb? econseries? usb 2.0?

Data Translation has been supplying data acquisition/control products for years, and it's clearly still on the forefront of plug-and-play instrumentation product development. Witness this series of four modules that leverage the hot-swappable plug-and-play features of USB.

In its ECONseries product roll-out, Data Translation relies on serial USB 2.0's so-called full-speed mode, operating at 12Mbps. With that speed, you can use a Windows-based PC equipped with a USB 2.0 or USB 1.1 port (Data Translation saves USB 2.0's high-speed 480Mbps capacity for wider bandwidth products; not covered here).

The ECONseries modulesof which there are fouroperate at conversion speeds from 25kHz to 50kHz, which is just what you might need in embedded controller applications or sensor stimulation and conditioning applications, for example.

Of course, looking like USB peripherals, they're self enumerating. They're the epitome of plug-and-play.

MUXd modules
Let's take a closer look at the new modules. A DT9812-10V ECON module offers eight single-ended multiplexed analog inputs and two analog output channels. It will handle input signals in the range of 10V, converting with 12bit resolution at a 40kHz throughput rate. It also confers eight digital I/O lines and one counter/timer line.

A DT9812-2.5V module is similar; as the part number suggests, it only handles 2.5V signals. The DT9812-2.5V and DT9812-10V modules also provide programmable gains of unity, 2, 4 and 8.

A lower cost A/D and DAC DT9810 ECON module handles signals in the range of 0 to 2.44V, but with 10bit conversion resolution and 25kHz throughput.

All of these high input-Z modules are shielded, which ensures more noise immunity when making low-level measurements.

Lastly, Data Translation's DT9817 is for digital I/O expansion. It provides 28 I/O lines and one counter/timer line.

Plug-and-play measurements
In use, you connect one of these ECONseries modules to your PC's USB port, and then route I/O signals to and from its screw terminals.

There's no need to power-up the module separately either; they derive their operating power from the host PC's USB port, usually pulling less than 100mA per module (the higher input-range module uses less than the 500mA high power device permitted under the USB spec; it typically operates drawing less than 250mA from your PC, which means you can even use it with a battery-powered laptop).

Beyond that, each ECON module uses a transformer to provide power isolation, and opto-couplers in its data path. As such, ECOM modules provide a hefty 500V of isolation between your data-acq app and the controller PC. That's just the ticket for many industrial and lab applications where signals may be riding on higher voltages, or where common-mode voltages are present. The modules also thwart ESD as high as 8kV.

Once you fire up the GO! Application Windows software, you then choose a combo of digital and analog I/O channels that your application needs. Windows lets you set the resolution and signal range you expect (although you can subsequently zoom on a display).

Multiple simultaneous operations
Significantly, you can actually run multiple ECON subsystem operationssimultaneously. You can sync the analog input operations of multiple DT9812-2.5V or DT9812-10V modules, for example, by connecting the output of a module's counter/timer from one module to the clock input of the next.

As such, you can run a mix of oscilloscope, recorder, voltmeter, waveform generator, digital I/O, counter/timer, and rate generator functions, as well as operate the software's file viewer. Simultaneous operation of all sub-systems also lets your analog and digital I/O channels be used at the same time, which is just the ticket for many control-loop applications.

By the way, the file viewer function lets you load a previously stored Excel file, and it also supports the system's scrolling and zooming, as well as letting you print.

DMM operation
If you choose to let the ECON module operate as a voltmeter, it will let you measure data from up to eight analog inputs, displaying the level just as a 5-digit DMM would. The display can also indicate a maximum voltage, or an RMS value.

For its part, the ECON's scope function lets you display, stream, plot, and analyze data from up to eight analog inputs. The software lets you set the trigger type (internal or external), level and channel. Likewise, the GO! Application lets you run the system's chart recorder. It will support recording of up to 32,000 data points from up to eight analog input channels, logging data to an Excel spreadsheet file.

Generating outputs
Need to generate a waveform? The system's DAC waveform generation function can create DC levels as well as sine, rectangle, and triangle waveforms, on two output channels. In use, you use the GO! software to set the desired frequency and amplitude, as well as any possible offset and duty cycle desired.

You can actually generate a waveform at the same time that you're acquiring a signal, thus supporting stimulus-response test-and-measurement. Very nifty.

To simultaneously work in the digital domain, the ECON's digital I/O control lets you monitor the status of up to 28 digital inputs using LEDs. You can also control the state of up to 28 digital output lines using switches.

For external event counting, the system lets you count pulses from the counter/timer for 1-, 2- or 5s, or for an unlimited time. You can view counts on a 9-digit on-screen display. Likewise, the built-in rate generator lets you control the frequency of a continuous pulse output signal (from the system's counter/timer).

So, there you have it. From unpacking the box to plugging in the modules and running the CD-ROM software, Data Translation promises no more than five minutes will elapse! Don't you just love USB?

As DT says, its ECONseries modules represent a new class of instruments: so-called mini-instruments that can be handheld, and are low cost (usually less than $200). They can be carried from the lab to the office or home (you do take work home, don't you?), or out into the field.

Anyone with a notebook PC can view analog and digital signals with a just a point-and-click. The software detects which module is in use, configures it, and provides instrument-like display panels that you already know and love. And, optionally, you can order a special mounting kit that will make any of these ECON modules DIN-rail mountable for non-bench industrial-type applications.

- Alex Mendelsohn

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