A Message from VMI President, Dennis Kemp

Ken Haag, Vice President of Sales and Marketing

Co-Founder of Voltage Multipliers Inc.

Ken passed from this life on Sunday, July 10th, 2022. Ken was a great friend and mentor for more than 40 years.

Ken was responsible for creating and building VMI’s sales and sales rep system. I recall many occasions where customers were upset by a problem sometimes real—sometimes perceived. When I was reacting in a panic, Ken would respond rather enthusiastically with something like “great—we have an opportunity to impress the customer with our response.” I eventually saw that he was right, even though I still try to avoid those types of “opportunities”.

In the early days of VMI, Ken and I reviewed our plan every day, and he was always optimistic and encouraging, even when the outlook was dim. Ken had an exceptional ability to see customer application opportunities, when it was not obvious. He repeatedly used the phrase that he did not try to “sell” products—he tried to “educate” the customer and provide a solution to their problem.

I recall a specific situation, in the first year of business, when a prospective customer visited our meager manufacturing operation. After a brief tour, we took the customer on an afternoon drive into the nearby Sierra Nevada mountains. Unfortunately, my car broke down and I was devastated as we were stranded in a remote area. As we waited for assistance, Ken walked the visitors to a large granite rock, sat down, and convinced them to give us a large purchase order—on the rock. They remain a large customer of VMI to this day.

Ken traveled many thousands of miles visiting customers and sales reps. On one occasion, he drove his motor home on a lengthy tour across the entire USA and back, making customer visits and meeting with sales reps.

I have had the great honor to partner with Ken , he was not only an exceptional business partner, but also a good friend.

I will never forget the trust and commitment that we had.
Without Ken, VMI would not have achieved the level of success that we enjoy today.

Rest in peace, my friend.
Dennis Kemp

Retirement Celebrations!


On February 18, 2022, VMI celebrated these amazing employees for their dedication and hard work. Their commitment and contribution to our shared goals has been a vital part to the success of VMI.

We appreciate you and wish you all a Happy Retirement!

Thank you!

Ignacio Franco – 40 years 

Beverly Franco – 39 years

Tess Ramos – 37 years      

Randy Bethel – 31 years

Eleanor Flores – 24 years

Katy Moya – 24 years

High Voltage Optocoupler App Note

Every once in a while Voltage Multipliers Inc. receives an inquiry about parts being sensitive to ambient light.

One question recently was about one of the high voltage optocouplers – the OC150 family.  The OC150 family uses two LED to illuminate light-sensitive silicon junctions in high voltage diode (the photo diode).

Glass encapsulated diodes can be sensitive to ambient light.  Just how sensitive depends on many factors – the wavelength of the light, temperature, orientation of the diode junctions, distance from the light source, thickness of the glass, and so on.

Normally it’s not an issue, but when you’re dealing with very low levels of leakage current, light sensitivity can be a problem.

For that reason, many VMI customers take steps to protect their optocouplers from ambient light by over potting them with an optically opaque material.  Another strategy is to coat the optocoupler with a non-conductive coating, making sure that you’re not creating a leakage path that might allow the optocoupler to arc.

How to Test Vf and Polarity in High Voltage Diodes

High Voltage Diode Vf Testing

Here at VMI, by virtue of working in the niche high voltage area, we get all manner of customer questions about issues that are somewhat more complicated by virtue of our unique devices.

Recently, a customer asked how they could confirm:
1)  The working ability of a high voltage diode
2)  Double-check the polarity of the device.

High voltage diodes have a higher VF than the ‘ideal’ model of 0.7V, so that many of the traditional ways of checking to make sure a diode is not failed shorted, or to verify the polarity of the device, will not work with high voltage diodes.

Using a Fluke handheld multi-meter that has a diode check function, for instance, probably won’t be able to overcome the forward voltage of a diode, even at low currents. A multi-meter is providing perhaps 2.4V and some of our diodes have a rated VF of over 30V!

VMI Vf and Polarity Test Methods
VMI measures the VF of our diodes using precision, current controlled power supplies capable of providing 50V or more. Though not necessarily readily available to all users, the easiest way to test the polarity and functionality of a high voltage diode is a similar method.

Current Limiting
​Current limiting a power supply to a low level of perhaps 100µA – 1mA and connecting it up to the diode will do the trick without much effort. You need a power supply that can provide more voltage than the rating of the diode, but make sure the power supply is limited so that it cannot provide more voltage than the breakdown level of the diode.

See the simplified block diagram for an idea on how to connect the power supply up to the diode. Depending on your power supply, you might need to use a current limiting resistor and an external current meter.

How To Tell the High Voltage Diode is Good
Once you have your setup, the diode should conduct your current (100µA – 1mA, depending on how you limited the supply) in the anode-cathode direction.  Reversing the current flow by flipping the diode to cathode-anode should block the current down to the leakage levels of the diode (less than 1µA). If the diode conducts in both directions, then you have a failed (shorted) diode. If current does not flow in either direction, you have a failed (open) diode.

Questions?  We would be happy to help, so give us a call – 559.651.1402.

Running Diodes in Oil­ — New App Note

Recently concluded testing indicates that running high voltage diodes in oil may allow for operating beyond the forward current ratings (Io).

All cautions apply — we do not recommend exceeding the current rating of any diode without extensive testing in your application, and basically the trick is to keep the diode junctions cool.  In other words, strive to get the heat out.

Here’s the App Note – AN0400 -1N6519 Power Dissipation in Oil

Give us a call if you have any questions: 559.651.1402, or visit the website for more app notes and FAQs.