Thursday, September 30, 2010

Two Big Product Announcements in GPETE

Two big GPETE related product releases this week that I need to cover. First, the #3 volume scope provider LeCroy takes the scope bandwidth lead with the Wavemaster 8Zi-A which offers 45 GHz of bandwidth on one channel, 30 GHz on two channels, and 20 GHz on four channels. Back on June 14th in my post entitled "The World's Fastest Real-Time Scope!" I talked about how Agilent's Infiniium 90000 X-Series oscilloscope family took the bandwidth lead on scopes at 32 GHz of true analog bandwidth over Tek. It looks like Agilent only held that lead for 4 months with LeCroy's announcement today. LeCroy achieves the 45 GHz bandwidth by interleaving three sampling channels together into a single 120 GSample/s channel. Follow the link for more info: Wavemaster 8Zi-A Oscilloscopes 

The second product release announcement is Tektronix has just released a family of counters (they refer to them as Timer/Counter/Analyzers). These counters have impressive specs including 12 digits of resolution, 50 ps (FCA3100 Series) or 100 ps (FCA3000 Series) Single-shot Time Resolution, and up to 250 KReadings/s of time stamped measurement data to memory. They can do gapless sampling up to 250 KReadkings/s giving them some modulation domain analysis (MDA) capability. The large display on these counters provide the capability to do histograms and trend charts. I am 99% sure that these new Tektronix counters are OEM'd from Pendulum's CNT-91 and CNT-91R counter family simply because the specs, front panel features, and form factor are pretty much the same. Follow the link for more information on the new Tek counters: FCA3100 and FCA3000 Series

Wednesday, September 29, 2010

Danaher Buys Keithley!

Big acquisition news for test and measurement and GPETE, Danaher buys Keithley Instruments for 341 million! For those of you who do not know who Danaher Corporation is, they have a $26.5 billion market cap and they provide a wide breath of products in the following industries: Professional Instrumentation, Medical Technologies, Industrial Technologies and Tools & Components. The last few years Danaher has been an acquisition machine in the test and measurement world gobbling up well known names such as Tektronix and Fluke. For more information on Danaher click here.

Keithley is a well known name in both test and measurement and GPETE. Some of Keithley's product lines include DMMs, current sources, high speed power supplies, and switch products. For more information on Keithley click here. Danaher has reported that they plan to add Keithley to their Tektronix business. It will be interesting to see what Danaher does with Keithley product lines that overlap with their current product lines, such as 6 1/2 digit bench top DMMs. If I were to speculate I would say in the coming years we will see one of three things happen to Keithley product lines:

  1. Product lines that Keithley is well known for such as SMUs and Parametric test equipment will live on with the Keithley name.
  2. Switching and GPETE product lines that Danaher does not have will probably take on the Tektronix name since it seems Danaher is really trying to extend the Tek name beyond scopes and arbs.
  3. Product lines that Danaher already has and that Keithley OEMs will go away.
Of course all that is pure speculation on my part. Feel free to comment with your thoughts. Below is a link to an LA Times article on the acquisition.

Saturday, September 25, 2010

Innovative Way to Interface a Measurement Instrument with a Computer

In this post I am taking a turn from the usual. Typically when I praise a new product it is an Agilent product. Here I am going to lay some praise on an innovative new NI product, USB-TC01 Thermocouple Measurement Device. The innovation in this device is not the measurement technology but the way it interfaces with a computer allowing you to easily retrieve data. Typically interfacing a measurement instrument with a computer and retrieving measurement data from it involves either installing software (that you may have to pay for) or installing drivers and creating your own software. The clever USB_TC01 requires no drivers and no software! The way it works is by connecting to your computer via USB. To Windows the TC01 appears as a mounted disk drive (so no driver). By navigating to the now mounted TC01 “drive” you can launch software that is stored on the TC01. The software allows you to display readings, log readings, and download readings. It also has extras that make it easy to interface with LabView. Pretty cool functionality for a mere $129 price tag.
The technology is similar to the LXI instrument connection standard (to learn more about LXI click here). An LXI compliant instrument acts like a web server so you can connect it to a computer via LAN. The difference between LXI and the TC01 is LXI does require software (web browser which everyone already has), you need to know the instrument’s IP address or host name, and the LXI standard only requires instrument manufacturers to put network setting control in the web interface and not instrument control. Although most LXI instrument manufacturers, like Agilent, allow you to control and retrieve data from the instrument via the web interface.

Monday, September 20, 2010

Sequencing Multiple Power Supply Outputs

Today’s high performance power supplies continue to add more and more capabilities to make the test engineer’s job easier. The capability that I am going to talk about here is sequencing on or off multiple power outputs. This capability allows you to set the order and timing that each power supply output powers on or off. This is useful for designing and testing embedded system designs. Embedded systems can be made up of any combination of microcontrollers, FPGAs, ASICs and memory chips. These individual integrated circuits often have multiple power input requirements that must be properly sequenced on and off to prevent latch-up. Latch-up may cause a wasteful initial surge of current at turn on, or it may be severe enough to inflict permanent damage to the semiconductor device. Ultimately these devices will have a power distribution system with regulators that will ensure the proper sequencing and timing for each power supply turn on and turn off, but during initial design and testing the power distribution system is often not in place yet so test and measurement equipment is used in its place to simulate the proper turn on and off conditions of the design.
In the past power sequencing was typically done in one of two ways: using programmable power supplies with software or using supplies with custom switches. The first way uses programmable supplies and then in software the supplies are properly sequenced on or off. The drawback to this method was unless you were running a real time operating system (windows is not a real time operating system) there was no way to accurately guarantee the timing from one supply output to the next with better than 30 ms of precision. The other method required additional hardware in the form of switch cards and control circuits. A hardware timed control circuit would provide the precision timing that a computer operating system could not. The control circuit would then control the sequencing of the supply output on or off using switches. If you wanted to avoid switch bounce you had to use solid state or mercury switches versus traditional mechanical switches. The problem with this method is complexity it adds to the testing process.
With the capability built into the supply you avoid the complexity of dealing with multiple pieces of hardware and since the timing is done inside the hardware of the supply it is highly accurate. Agilent’s N6700B series of supplies and the N6705B DC Power Analyzer are examples of supplies with built-in power output on / off sequencing. Each one has up to four power supply outputs per mainframe that can be sequenced on or off. Sequencing from one mainframe to another is also possible for applications that require sequencing of more than four power supply outputs. The figure shows a picture of the N6705B DC Power Analyzer being used to test an embedded design that requires turn on power sequencing.

Monday, September 13, 2010

Largest Modular Instrument Introduction Ever

Today at Autotestcon Agilent is launching the largest modular instrument introduction in test and measurement history! Agilent is introducing 47 products in both PXI and AXIe (more on AXIe form factor click here), with the bulk being in PXI. The products range from RF switches to pulse pattern generators to DMMs. If we rewind back a couple decades, Agilent was the pioneer in modular instrumentation with their extensive VXI portfolio. While still staying in the modular instrumentation arena, over the last decade they focused more on high accuracy ‘box’ instruments. With this introduction it is clear that Agilent plans on playing a bigger role in the modular instrumentation industry. You can see a list of Agilent’s modular instrument introductions in the top figure (click on it to enlarge).
Since this is a GPETE blog I wanted to fill you in on the details on Agilent’s new PXI DMM family. The family consists of the M9182A (shown in lower figure) and the M9183A. Both are 6.5 digit DMMs, the M9183A provides higher speed performance and added features. Here is a quick rundown on specs and features:

  •      6.5 digit resolution
  •      4.5 digits at 4,500 rdg/s (82) and 20,000 rdg/s (83)
  •     Measurement capability: dcV/I, acV/I, 2/4-wire Ω, Freq, °C/F, and capacitance (83 only)
  •     DCV basic 1 year accuracy: 30 ppm
  •     Compatibility: cPCI, PXI-H, PXI-1
Surprisingly there are not really many PXI DMMs out there. National Instruments is by far the leader in this space with about 90% of the PXI DMM market so Agilent has an uphill battle. If you’re a consumer of PXI DMMS this is good news! Fierce competition means lower prices, more promotions, and more innovation for you as the end user. For more info on Agilent’s new PXI DMMs see the links below.

Tuesday, September 7, 2010

Understanding Ground Loop Error in Voltage Measurements

A true ground potential is something that only exists on paper or in simulations. In the real world there is no such thing as a true ground which in test and measurement leads to ground loop errors. Ground loops present problems when measuring low level signals such as thermocouple measurements. When measuring voltages in circuits where the DMM and the device-under-test are both referenced to a common earth ground, a ground loop is formed. As shown in the figure, any voltage difference between the two ground reference points (Vground) causes a current to flow through the LO measurement lead. This causes an error voltage (VL) which leads to inaccuracies in the DMM’s measurement.
When considering ground loops just in terms of DC, as long as Ri is a large value (meaning air between the two potentials) the error will be fairly insignificant when measuring mV and up. Agilent DMMs such as the 34401A, the 34410A, and the 34411A have a Ri of 10 Gohm at 80% humidity. 80% humidity is high for a lab environment so in most settings the actual Ri is much greater than 10 Gohms. Error caused by DC ground loops can be further reduced by keeping the ground path of low level signals as short as possible.
The bigger source of noise and error from ground loops is the AC component. The DMMs impedance to ground is lower with AC because of the capacitive component, Ci, in parallel with Ri. The capacitive component results from the windings in the transformer inside the DMM. Referring to the Z calculation at the bottom of the figure, as the frequency increases the Z isolation of the DMM to ground begins to decrease. Now in most low frequency settings the ground loop noise is from the power line so it is 60 or 50 Hz. The effect of AC power line ground loop noise can be reduced by setting the DMM’s measurement integration time to 1 or more power line cycles (for 60 Hz that is 16.67 ms). If your testing environment consists of high frequency signals, high speed digital signals, or noisy components like relays or motor it is best to put any sensitive voltage measurements on a separate ground potential if possible.

For the ground loop Wikipedia page click here

Wednesday, September 1, 2010

Some More on Waveform Summing Using the 33521A and 33522A

On the Aug 6th post (click here to go to Aug 6th post) I promised to follow-up with some more information on Agilent’s new 33521A and 33522A 30 MHz FG/AWGs waveform summing capability. The function can be accessed through 3352xA’s modulation menu. The sum feature allows you to mathematically add one waveform to another to easily create more complex waveforms. For instance you could do a ARB + sine wave or gaussian noise + square wave. The summing feature allows you to define the frequency and amplitude ratio (up to 100%) of the summing waveform. As an example, the scope screen shot shows a 10 KHz square wave with a 100 KHz triangle wave summed at 10% amplitude (kind of looks like Bart Simpson’s head). A great example application for the summing functionality is testing a circuit's noise immunity. For instance you could simulate a clock signal and add noise to it to see how it affects signals derived from the clock. Or you could add a 60 Hz sine wave to a custom arb waveform to simulate power line noise.
I recently got a question from a 33521A customer asking how the waveform specs, such as jitter or harmonic distortion, change when using waveform summing. I think this customer was assuming that we use some type of analog method to do the summing. The answer is the waveform specs don’t change at all. The reason is because the summing is performed mathematically in the chip that creates the waveform points so you can think of the summing feature as an easy way to create an arb.