Simple Test of TVS Protection Diode

Well that's cool and easy! Quick question; you mentioned DC power supply.....does it matter...DC vs AC for testing?

You can test with AC or DC.  However, to test with AC, you really need a 'scope, so that's not a simple and easy test.  With DC, all you need is a DC supply that can exceed the voltage breakdown of the TVS in question.  The current limiting can be accomplished using a resistor, but since I had a current controlled power supply, I didn't need the resistor.

I could have taken my two 30VDC supplies and wired them in series to get to the required voltage, but I happen to have an HP 0-50VDC power supply, so I just used that.

Exactly how I would do it.  Thanks John for putting it in words and pictures for present and future reference.

Mike

@gunrunnerjohn posted:

You can test with AC or DC.  However, to test with AC, you really need a 'scope, so that's not a simple and easy test.  With DC, all you need is a DC supply that can exceed the voltage breakdown of the TVS in question.  The current limiting can be accomplished using a resistor, but since I had a current controlled power supply, I didn't need the resistor.

I could have taken my two 30VDC supplies and wired them in series to get to the required voltage, but I happen to have an HP 0-50VDC power supply, so I just used that.

Thanks GRJ....simpler is always better. Besides, I wouldn't know what to do with a 'scope....except maybe in a submarine! 😁

@Junior posted:

Thanks GRJ....simpler is always better. Besides, I wouldn't know what to do with a 'scope....except maybe in a submarine! 😁

Hence my selection of DC to illustrate the test!   I spent my time on an aircraft carrier, no stinkin' subs for me!

@gunrunnerjohn posted:

Hence my selection of DC to illustrate the test!   I spent my time on an aircraft carrier, no stinkin' subs for me!

Hey hey…..watch those subby comments……..lmao.

The closest to a sub I got, besides taking the tour at Pearl Harbor, was medevacing a crew member from the sail of one, I was very surprised at how unstable a platform on the surface they are. Landing athwartships on an old LST was simpler than maintaining the hover over the sail until he was onboard.

The submarine USS Growler is parked along side of the USS Intrepid in NYC, I took a stroll through that one, made me sure I never wanted to serve on one!   The USS Intrepid is the same class of aircraft carrier that I was on, the USS Shangri-La.  It was kinda' fun to see it after all these years.

@gunrunnerjohn posted:

As discussed frequently here, the TVS diode is a handy way to protect against damaging voltage transients that are usually generated based on collapsing magnet fields in coils/motors.  The topic of testing frequently comes up.  Obviously, testing for a shorted TVS is easy, an ohmmeter.  If it's shorted, it's really shorted, and will read as a short.

Testing for an open is a bit trickier.  I reached in my parts box and produced a  1500W 36V TVS at Digikey, the Littlefuse 1.5KE36CA.  I connected it to a 0-50V DC power supply, set the current limit at around 25ma, and did a voltage sweep from 0V to 50V.  In the video below, you can see right at 35V, the voltage stops increasing as we are in current limiting due to the TVS diode conducting.  This shows that the TVS diode is conducting and not allowing the voltage to go any higher.  If we look at the specifications of this TVS, we'll see that the minimum breakdown voltage is 34.2 volts, so right above that we should go into current limiting, and we do.

This test has indicated the TVS is not open and is correctly functioning.  Note that for a bi-directional TVS such as this one, it's necessary to repeat the test with the diode connected in reverse polarity to insure that both polarities are clamped properly.

This simple test that can be performed on the bench to test a TVS protection diode.

John, I have to comment on that analog power supply. I can't make out the first number of the product number, but I'm almost 100% sure it's a Hewlett Packard 6200B. Are you the original owner? Has it ever been repaired? LoL That unit was probably manufactured around 1967, and it looks brand new! Tough little bugger! As a retired HP employee I always like to see old stuff like that PS still in use today.

@WesternPacific2217 posted:

John, I have to comment on that analog power supply. I can't make out the first number of the product number, but I'm almost 100% sure it's a Hewlett Packard 6200B. Are you the original owner? Has it ever been repaired? LoL That unit was probably manufactured around 1967, and it looks brand new! Tough little bugger! As a retired HP employee I always like to see old stuff like that PS still in use today.

It is indeed the 6200B.  I got it in the 1980's when Univac was closing some locations, they had a pile of stuff that we could have our pick.  I got a Tek 'scope and this P/S, the 'scope is long gone, but I still have the P/S.  Still works, and it's one of the few that can get to 50VDC, so I keep it around.