Is it possible to create a meter that would indicate the voltage of a Zener diode? I find myself with countless amounts of un-labled zeners and I can't use them, because I don't know the voltage of them.<p>Thanks,
~Kyle
Voltage measurement of Zener Diodes???
Re: Voltage measurement of Zener Diodes???
Very simply, connect them in a small test circuit. A la power supply--reseistor--zeener--ground. Measure the votage accross the zeener and it will be its zeener value. Make sure the zeener is at full conduction by measuring the zeener voltage while increasing the power supply voltage. The zeener voltage will reach its voltage limit and thats it. Like any regulator, the input voltage has to be more than the regulated output. i.e. a 7805 5v regulator requires about 8 volts to supply 5 volts.<p>This can be done on a breadboard.<p>Greg<p>[ February 07, 2003: Message edited by: Greg ]</p>
Re: Voltage measurement of Zener Diodes???
Alright, thanks for the prompt response, I'll wire it up today when I have the chance.<p>~Kyle
Re: Voltage measurement of Zener Diodes???
Use sufficient current limiting to prevent damage to your diodes. Less than 1mA is usually safe. You can probably go much higher with most diodes but don't get carried away.
Re: Voltage measurement of Zener Diodes???
Yes of course, high resistance value. Wouldn't want to blow up the diodes that I'm trying to measure the voltage of!! :p <p>~Kyle
Re: Voltage measurement of Zener Diodes???
That is why i mentioned a resistor, for current limiting. Value....not important, better higher than lower. 10K-470K
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Re: Voltage measurement of Zener Diodes???
And your supply voltage has to exceed the zener voltage. Hang one meter on your power supply output and another across the zener (or switch your one meter back and forth between those two points). Anytime your supply voltage equals the zener voltage, you have to increase the supply voltage. If you increase the supply voltage with little change in zener voltage, then you're OK. If you can never get the supply voltage to be greater than the zener voltage (the two are always equal), either you have a very high-voltage zener (they do exist into the hundreds of volts but aren't common devices) or you have an open zener (but they usually short since they're silicon devices).<p>Dean
Dean Huster, Electronics Curmudgeon
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Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines).
R.I.P.
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Re: Voltage measurement of Zener Diodes???
Also, you can test the zener by using a constant current supply. If you set one up at 1mA and have the max voltage set at soem high value (25 could handle most of these), the zener would be automoatically regulated at the zener knee voltage. If you have a supply with a volt readout, it would indicate the zener voltage right on the display. If you don't have a regulated supply, you can build one with a high DC voltage supply and a linear regulator. Set the linear regulator with a resistor which holds the output to the wanted current, then tie the resistor from the output terminal to the ground terminal. Do not ground the ground terminal, this becomes your output for your zener diode. This would keep your current constant no matter what the zener voltage is. This is a handy circuit to have on the bench and it's cheap.
Rick Capps
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Re: Voltage measurement of Zener Diodes???
Chessman:<p>One of several hairbrained ideas I have is for a multimeter adapter for just that. It would use a constsnt current source just like Rick suggests. It would of course need something to convert 9V to around 150V at maybe 2mA. I haven't gotten around to that just yet, but I do have some tiny PCBs for the CCSs. Would you like a couple of them?
Re: Voltage measurement of Zener Diodes???
Yeah if you have a couple of them extra that'd be awesome. Oh yeah, I got the PCBs from Advanced Circuits today.
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