Series Zener Instability
Series Zener Instability
(OP)
My regards circuit jockeys,
I have a sensor device that is lowered into a well. Its power cable also serves as its data transmission line. The voltage supplied to the circuit is regulated by two zeners in series. This creates two voltage rails, one to power the sensor, the other lower voltage to power a multivibrator that shapes the output of the sensor into square pulses coupled to the line. I want to increase the voltage of the second zener, to raise the voltage of the pulses, but when I do the signal gets obfuscated in noise.
I have this gut feeling that the series zeners are the cause of this problem, but I can't think of why this is happening. The word leverage comes to mind, I read over zeners in my old textbook, but it didn't give me any new ideas. Can anybody explain this to me?
I have a sensor device that is lowered into a well. Its power cable also serves as its data transmission line. The voltage supplied to the circuit is regulated by two zeners in series. This creates two voltage rails, one to power the sensor, the other lower voltage to power a multivibrator that shapes the output of the sensor into square pulses coupled to the line. I want to increase the voltage of the second zener, to raise the voltage of the pulses, but when I do the signal gets obfuscated in noise.
I have this gut feeling that the series zeners are the cause of this problem, but I can't think of why this is happening. The word leverage comes to mind, I read over zeners in my old textbook, but it didn't give me any new ideas. Can anybody explain this to me?





RE: Series Zener Instability
Dan - Owner

http://www.Hi-TecDesigns.com
RE: Series Zener Instability
RE: Series Zener Instability
120V DC line
32V total to the sensor with 5.6V to the multiV, works fine
24V total with 12 to the multiV, still working
24V total with 18 volts to the multiV, choppy distored signal.
RE: Series Zener Instability
If you are trying to drive a long cable, you need lots of current, which is anathema to a zener circuit.
As suggested by Operahouse, the LM341: http:/
TTFN
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RE: Series Zener Instability
RE: Series Zener Instability
Keith Cress
kcress - http://www.flaminsystems.com
RE: Series Zener Instability
RE: Series Zener Instability
RE: Series Zener Instability
TTFN
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RE: Series Zener Instability
Time for a look at the circuit - you can upload it to engineering.com as part of your reply.
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If we learn from our mistakes I'm getting a great education!
RE: Series Zener Instability
An analogy: If I need, for example, a shaft with bearings for a measuring wheel, I go to a shop to get it done. I do not start my old lathe and produce a substandard shaft.
And, I agree that putting two zeners in series and not even know if you are into avalanche region all the time sounds like a very bad idea. There are standard solutions to most telemetry situations.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Series Zener Instability
Circuit is posted for those that want a look at it.
RE: Series Zener Instability
The point about the current is NOT the zener power capacity, but about your circuit stealing bias current from the zener. If your zener is only barely biased into breakdown, then ANY current reduction will cause a drastic voltage change.
TTFN
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RE: Series Zener Instability