Current Vs Voltage Piezzo diesel injector
Current Vs Voltage Piezzo diesel injector
(OP)
Hello
I connected my scope to the two wires of a Siemens piezzo diesel injector. One chanel reading voltage and the other reading current with a current clamp.
I get voltage growing around to 50v, stepping up and then falling to zero (This is normal).
In exactly the same time, current starts going up from zero to around 10 Amps and then falls to zero for a while but (here is were i don't understand...) it goes negative the same amount it has been positive before and goes back to zero.
I have a picture that is more explicit but I don't know how to post it here.
In a book that I have, Bosch has the same pattern for the same kind of injector (so, its a normall pattern) but does not explain how it works.
Question: How can I have, at the same time, in the same circuit, voltage in one sense and current that reverses?
Best regards
Carlos Reis
Lisbon, Portugal
I connected my scope to the two wires of a Siemens piezzo diesel injector. One chanel reading voltage and the other reading current with a current clamp.
I get voltage growing around to 50v, stepping up and then falling to zero (This is normal).
In exactly the same time, current starts going up from zero to around 10 Amps and then falls to zero for a while but (here is were i don't understand...) it goes negative the same amount it has been positive before and goes back to zero.
I have a picture that is more explicit but I don't know how to post it here.
In a book that I have, Bosch has the same pattern for the same kind of injector (so, its a normall pattern) but does not explain how it works.
Question: How can I have, at the same time, in the same circuit, voltage in one sense and current that reverses?
Best regards
Carlos Reis
Lisbon, Portugal





RE: Current Vs Voltage Piezzo diesel injector
You might take a look here:
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RE: Current Vs Voltage Piezzo diesel injector
The Piezo elements that are being driven have a very large capacitance. In order to change their shape, you apply voltage. This voltage has to "charge" their capacitance, which you see as "positive pulse" current. In order to return them to their original shape, that capacitance has to be "drained" away. Hence, the "reverse pulse" current.
-Tony Staples
www.tscombustion.com
RE: Current Vs Voltage Piezzo diesel injector
As far as I have understand, the piezo works like a capacitor and the feed circuit "discharge" it at the end of each cycle in order to close the injector.
Did I got it?
Thanks
Carlos Reis
RE: Current Vs Voltage Piezzo diesel injector
RE: Current Vs Voltage Piezzo diesel injector
You've got it! Good luck!
-Tony Staples
www.tscombustion.com