Peak voltage measurement

[[email protected]]

I'm looking for a cheap way to test a system I have, The system works
by starting at 0V. When it is triggered it will produce a peak voltage
with a magnitude of less then 100V, the system then produces a voltage
of the same or lower magnitude but with the opposite sign, and then go
back to 0V. All of this will occur over about 1/2 a second. I'd like to
come up with a way of measuring the voltage of the peaks without using
an oscilloscope.

My first thought was looking for a cheap voltage meter that could
measure peak voltage, but as far as I can tell such a device doesn't
exist. If someone knows of such a device, or another solution that
would work for this I would be extreamly grateful.

 

[chuck]

I'm looking for a cheap way to test a system I have, The system works
by starting at 0V. When it is triggered it will produce a peak voltage
with a magnitude of less then 100V, the system then produces a voltage
of the same or lower magnitude but with the opposite sign, and then go
back to 0V. All of this will occur over about 1/2 a second. I'd like to
come up with a way of measuring the voltage of the peaks without using
an oscilloscope.

My first thought was looking for a cheap voltage meter that could
measure peak voltage, but as far as I can tell such a device doesn't
exist. If someone knows of such a device, or another solution that
would work for this I would be extreamly grateful.

Because your transient voltage changes so slowly (~1/2 second) you have
several options available.

You can construct an op-amp peak hold circuit for a couple of dollars
and read peak voltages with your DMM. Do a google search on "peak hold
op-amp" and you'll find several simple solutions.

If the system you are testing has a reasonably low internal impedance,
you can also charge a capacitor to the peak voltage and then measure
that voltage with a high internal resistance DMM. 10 Megohms is typical
for DMMs. If the capacitor is low-leakage, you can connect the DMM to
the capacitor after charging and read the peak voltage. A diode in
series with the capacitor will ensure that only the positive (or
negative, if you prefer) peak will charge the capacitor. Without knowing
how much loading your system can withstand, and the risetime of the
voltage peak, it is really impossible to suggest values for components.



Chuck