Tuesday, January 28, 2014

The Way Things Work???

For the last few weeks I have been researching website analytics software packages.  These programs are able to look at the data, track who, what, where, when, and why visitors came to your site.  The programs take the data and generate graphs, paths, diagrams, and summaries suitable for consumption by your average third grader.
Grrrrr----or is it puppy love?

The program I used to use suddenly and inexplicably stopped working.  As is often the case, the software company no longer supports that version.   

Most of the programs I've evaluated are great for large corporations with a big marketing budget and marketing department.  While many of their products sound great, what's changed are the pricing structures and platforms.  Log files are no longer used.  (These are records in a spreadsheet encoded with all kinds of information - time of day, IP address, duration of visit, which pages were visited per session, etc.)  Instead, javascript tags are used, which requires placing a tag on each and every page you wish to track.  When your website is over 500 pages, it's no small task, but totally do-able.

The real kicker though, is the pricing model.  Besides not really being able to get a clear-cut cost, prices are quoted in terms of transactions or band-width.  Most of the plans are overkill for our purposes.  Unfortunately, so is pricing on the on-demand, subscription based plans.

From my point of view, the software companies are up-scaling themselves right out of the market.  They seem to be going after the low hanging fruit.  Let's hope they get over it soon and start addressing the needs of small and medium size B2B businesses.   

I hope this isn't a harbinger of things to come on the Internet.  Lots of fancy-smancy bells and whistles that add a lot to the cost; that make the product unaffordable for small to medium size companies.  The prices I've been quoted so far are so far out of the ballpark, I won't even entertain the idea of presenting them to my boss.  Sadly, the ROI is just not there.

So it looks like we'll be sticking with Google Analytics for a while to come.  

(Pssst...do you know of any reasonably priced web analytics programs?  Let me know!)

Photo credit;  http://uberhumor.com/grrrr

Tuesday, January 21, 2014

XRF Power Supply - High Voltage, Low Ripple


XRF Type Power Supplies 

XRF Tube Power Supply
Designed specifically to power negative voltage tubes for portable, hand-held applications, VMI's XRF power supplies have many standard features.  

The high output voltages and currents are programmable and monitorable.  Low output ripple and extreme stability provide a significant performance improvement over other technologies, and are standard feature.  Remote control, remote programming, output monitoring, output status and self-protective circuitry are typical design features.

XRS Series
  • Input range:  7-12V DC
  • Output voltage options - -40kV, 100uA
                                              -50kV, 200uA

  • Output Ripple Voltage:  < 1% peak-to-peak

    Custom features include unique packaging, miniaturization, high reliability, assembly integration and high performance

All aspects of design and manufacture are carried out in-house at VMI to maintain control and repeatability of each process.  No out-sourcing here!  Modern, cost-effective SMT manufacturing methods means improved reliability in the smallest footprint possible.  Computer controlled automatic testing and 100% burn in are standard procedures to insure that customer specifications are met.

VMI is dedicated to helping customers find innovative, cost effective solutions to their high voltage problems.  Put VMI's proven design team to work for you.

Contact us to request a quote for the XRF type power supplies, or get started on your own, custom designed high voltage power supply.

Thursday, January 16, 2014

Where Can I Find a 5kV, Glass Passivated, 30ns High Voltage Diode?

The answer to that question is, "VMI, of course!" 

In fact, VMI doesn't offer just one 5kV, 30ns diode.  There are at least ten to choose from!  Of course, not all of them are axial-leaded glass-body diodes.  Some are epoxy J-leaded devices, and some are formed-lead glass-body types.

Current ratings range from 40mA (M50FF3)  to 500mA (1N6837LL).  All are 5kV, 30ns diodes.

There are more than a few high voltage diode manufacturers out there, all of them good.  But when it comes to high voltage, super-ultra-fast Trr, glass passivated devices, VMI offers the biggest selection available.

J-Lead Devices

J-Lead Devices
High Voltage Diode - J-lead Terminations
J-leaded devices (SMF50FF3 and SXF50FF3) have the advantage of being surface mount.  They were specially designed to be used in pick-and-place machines.  The package is extremely repeatable, which makes it easy for automatic assembly equipment to pick-and-place them on to a printed circuit board (pcb).  They are available on tape-and-reel.

Formed Lead Devices

Formed lead devices (1N6837LL) start out with the standard diode, but use a thicker silver lead that is formed and trim.  The leads provide stability, and keep the diode body away from the pcb or substrate.  In air-cooled systems, this provides a way to keep the diode cooler than if it was placed close to the mounting service where air flow may be restricted and improves voltage isolation from other board components. 

Formed lead diodes generally have a higher current rating than their axial-leaded or J-leaded cousins. 
Formed Lead High Voltage Diode
Formed Lead High Voltage Glass-body Diode

 Super-ultra-fast recovery time diodes are very useful at the higher frequencies that switching power supplies often use.  Fast Trr helps minimize reverse voltage power losses, and in soft recovery diodes, like VMI's, noise is reduced too. 

High Voltage Diode - Glass Body
Axial-leaded, Glass Body, High Voltage Diode
Different 5kV diodes work better for different applications.  The diodes feature different body styles, terminations, physical dimensions, and ratings.  Don't let decision paralysis stop you.  If you're not sure which diode would be best for your app, contact us

VMI diodes are RoHS compliant, and VMI is ISO9001:2008 registered.

Wednesday, January 8, 2014

What Does This Optocoupler Look Like to You?

OC250 High Voltage Optocoupler

The OC250 is a 25kV optocoupler featuring high isolation voltage and high gain.  It has the highest reverse voltage of all VMI’s optocouplers and features an isolation voltage of 40kV minimum.   

Isolation Voltage

Isolation voltage in this case is the minimum voltage isolation between the LED light source and the 25kV optodiode – in other words, the minimum isolation between coupled ‘systems’.


Internally, the photodiode junctions are exposed to LED generated light.  LED generated light is controlled via the forward current through them.  The light-leakage current provides a link between two isolated systems, and a way to control one through the other.   
The entire assembly is encapsulated in an optically clear material that provides electrical isolation mechanical strength. 
The OC25 has integrated mounting holes, making them a cinch to mount.

Electrical Specification

Electrical specifications include .068% DC current transfer ratio, and a generous, linear leakage current range of 250nA to 100uA, and maximum power dissipation of 1W. 


Terminations and Dimensions

Connections to the optodiode are made via isolated solder terminals.

Connections to the LEDs are made via insulated copper lead wire. 

Overall dimensions, including mounting flanges, are .140”w x 2.10”l x 1.0”h (35.6mm x 43.2mm x 25.4mm).

VMI is ISO9001:2008 certified.

Our devices are 100% made in the USA and 100% tested.

Contact VMI for more information.

Not exactly what you're looking for?  Check out more optocouplers data sheets   

(BTW, I am reminded of a cute little frog when I look at the OC250.  But that's just me). 

2014 Trade Show Schedule

Every year VMI attends several U.S. and international trade shows.

Trade shows provide a great venue for meeting and greeting customers, sales reps, and friends.

Below is VMI's trade show schedule.  Drop by for a visit if you're in the area, or call us to set up a meeting!  

VMI Trade Show Schedule for 2014

Photonics West      
Feb 4-6
Moscone/ San Francisco      
Mar  3-6
Mar 17-19
Fort Worth Convention Ctr
May 20-22
Jun 15-19
Baltimore, MD
Nov 11-14

Friday, January 3, 2014

Answers to Questions You Were Afraid to Ask - High Voltage Optocouplers

Optocoupler Links and Applications Notes

     High voltage optocouplers (2kV and higher) differ from lower voltage optocouplers in a number of ways, most notably, the type of applications or environments each one is used in. They are similar in that both can provide electrical isolation within a system in otherwise noisy environments.

In the case of high voltage optocouplers, their use can prevent ground loops between high and low voltage subsystems, or otherwise provide a means for monitoring and controlling independent systems.

Below are several reference links to things such as FAQs, and Application Notes. Topics range from optocoupler gain, to how to configure them as a high voltage op-amp.

Scroll down even further and you’ll find links to the optocoupler data sheets. Their voltage ratings range from 2.5kV to 25kV, and they come in different package styles and gains.  


Optocoupler FAQs


High voltage optocouplers operate at 2.5kV or higher. The photo diode generates leakage current when it's reversed bias. The leakage current is proportional to the exposure to light from LEDs. Light from LEDs is proportional to the forward current through them.

If the forward current through the LEDs varies, so will the leakage current in the photo diode.

Monitoring and controlling either one (If or Ir) provides a clean way to interact and get feedback from two isolated systems. It is just one of the ways high voltage optocouplers can be used.

Other topics include - 

           · Long term Gain Degradation
           · Turn-On/Off Time
           · Thermal Resistance
           · Sensitivity to Incident Light
           · RoHS Compliance
           · Parallel Connections
           · Series Connections
           · Current & Power Gains
           · Package size 
           · Custom configurations  

And more….

Optocoupler Application Notes

Application notes vary from how to use an optocoupler in an op amp application, to pockels cells, to high voltage relays.

Optocoupler Data Sheets 

Lastly, VMI offers several voltage ratings in different package styles and gains. Generally speaking, the higher the gain, the lower the long-term gain stability.
In this case, Vrwm refers to the reverse voltage across the photo diode.





If you have any questions about VMI high voltage optocouplers, give us a call at 559.651.1402.