Is this a Zena diode?

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steve2004

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There is no marking on it. A diode usually is marked for polarity. It is crimped onto a connector that has 2 wires, a black and red wire (one end to the red the other black). The middle is very wide compared to a zena. It has 81Kilo-ohm resistance in either direction, and no voltage in either direction when checked as a diode. Thanks.
P.S. The resistance seem to go down each time I measure it. Last time I measured it it was 74.4 (Started as 81 Kilo-ohm, 78, 75,74 etc.)
 
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I'm assuming you mean a Zener diode, not a Zena. I have never heard of a "Zena diode" before.

That could be a zener, or it could also be a simple small-signal diode. You can test it with a multimeter (with a diode test function).
 
Thanks Derstrom8 for correcting the nomenclature. You are right about that there is no such thing as zena. Edison would have turned over in his grave. I don't think its a diode because it didn't check out with the diode test with a multimeter as I've mentioned earlier. Is it posible that its a thermistor? Thanks again.
 
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Hi Steve,


That doesnt look like a zena diode it looks more like her sister Xena

Seriously though, it could be a few different things. Here's some ideas how to go about testing this...

If you think it is a thermistor then connect the meter leads, wait about 1 minute then check the resistance. Then grab it between thumb and forefinger and see if the resistance goes down or up. If it goes down or up and keeps changing, it could be a thermistor.

If you have a resistor like 1k around and a battery like 9v you can bias it with that and check the voltage in each direction. That is, bias it one way and measure the voltage then turn the device around and measure that voltage across it too. If you see a limit like 6v then it is probably a zener. You can then check it with a different voltage (battery) or a different resistor (like 2k) and see if that voltage stays about the same.
However, zener voltages range from low volts to more than 200 volts so it may be hard to check if it is a higher voltage zener.
 
Zeners usually have a band on one end and measure high and low depending on the meters polarity on the leads. I was thinking it may possibly be a diac.
 
Hi,

Yeah unfortunately there are a number of things it could be so i guess he's going to have to throw a bunch of tests at it to be sure, and not blow it out during any of those tests.
 
My estimation goes toward a transient voltage suppression diode (bipolar)

Check out TRANSIL-Diodes such as NXP type 1,5KE.. (same type manufactured by FCI).

They are manufactured unipolar and bipolar.

They are designed to suppress transient voltage at very high speed taking up several A (up to 100)

The sample your photo shows might be an example of an unknown manufacturer.

Refer to the attached datasheet for more info.

Boncuk
 

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since i grew up in "Bahstin", i knew what he meant by "zena" diode.... ya use it wid a resista and a capacita ta get a voltage dat don't change.............
 
You guys are great and fun. The most likely winners are Mr. Al and Brevor. I put it on an Ohm meter. The resistance went down when I touched it with my fingers, and went back up when I removed my fingers. The only gizmo that has temperature dependnet resistance I know of is a thermistor.
Mr. Al and Brevor, I kowtow to you two.
Steve
 
You guys are great and fun. The most likely winners are Brevor and Mr. Al. I tested it with an ohm meter. If I hold on to it with my fingers the resistance goes down. When I let go of it the resistance goes back up. The only device I know of that has temperature dependent resistance is a thermistor.
 
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steve2004 said:
Mr. Al Xena would be shaped more like a figure 8 :>)
Click to expand...

Hi again,

Yeah that's true and i find that the hotter she gets the less she resists

I actually wasnt sure what kind of device this was because there are so many that come in similar packages, but as someone pointed out there was no polarity band so that was a good tip too. Most of the thermistors i have used in the past were either a little round flat pack like a ceramic capacitor or just a very very very small rectangular 'chip' which was surface mount. The chip type are really nice and small about 1/16 inch long so fit in hard to reach places but they are harder to work with. I got a bunch of them for about 17 cents each one time.

One quick tip which you probably already know anyway...
When testing with the finger, try to make sure that the finger does not bridge the two component leads or it might seem that the resistance goes down even when it really doesnt. The finger conducts so it could give a false reading. Touching only the body itself and not the leads works good however. I also find that bringing a hot soldering iron tip close to the device causes a big change in resistance (not too close with the hot iron of course).
 
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unclejed613 said:
since i grew up in "Bahstin", i knew what he meant by "zena" diode.... ya use it wid a resista and a capacita ta get a voltage dat don't change.............
Click to expand...

LOL unclejed613
True wat you sed tho

Cheers,
tvtech
 
unclejed613 said:
since i grew up in "Bahstin", i knew what he meant by "zena" diode.... ya use it wid a resista and a capacita ta get a voltage dat don't change.............
Click to expand...

I've lived in "Bahstin" long enough to understand the accent That's how I knew what he meant
 
i've seen 0.1% resistors packaged the same way and difficult to tell from a diode. some monolithic caps use a similar glass package as well. in both devices it looks like a solid rectangular bar in the center, white or brown for the caps, and metallic or black for the resistors. a thermistor would also be a black or metallic looking bar,
 
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