I think I am finally going to take the plunge and get a DS1054Z oscilliscope. To help push me over the edge, I have questions about how I could use the scope. I have longed to be able to test and measure capacitors and inductors in circuit. Especially to find bad electrolytic caps that have elevated Equivalent Series Resistance. There appears to be a way to use an oscilliscope and a waveform generator to do this. By using a sinusoidal or triangular waveform you can compare the shift between the current and voltage signals to measure capacitors and inductors. And if the peak voltage of the waveform is small enough, you can keep from turning on semiconductors.
So my question is, does the base Rigol DS1054Z oscilliscope on the adafruit page, without any add on modules, have a waveform generator on board that would let me do this kind of testing?
DS1054Z usage
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adafruit_support_mike
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Re: DS1054Z usage
Nope, the DS1054Z is only an oscilloscope ('only' a 4-channel scope for less than $1200, which is pretty amazing).
If you want to test reactive components like inductors and caps, you can get a lot of mileage out of a simple Arduino.
One of the basic principles in signal processing is that you can learn everything you need to know about a frequency-dependent circuit by seeing how it responds to an impulse (a very fast high/low burst) or a unit step. Impulses are hard to generate, but the rising and falling edges of square waves are good approximations of a unit step. Set an Arduino to send its GPIO pins high and low at various frequencies and you get a range of unit-step approximations that you can use for testing.
Start by connecting one of the pins to your scope and zoom in on the rising and falling edges. You'll probably see some minor overshoot and ringing due to the parasitic inductance and capacitance of the wire. Then connect a known-good 1uF capacitor and see what effect that has.
What you'll see are rising and falling exponential decay curves that replace the nice, sharp edges from before. The time it takes for the curve to rise to full value depends on the value of the capacitor and the impedance of the Arduino's pin. The time it takes for the output to cross 2/3 of the gap between high and low is the RC time constant for the system, which is also the product of R and C.
To find the 2/3 point, use the scope's cursors under manual control.. that lets you move the cursors left and right or up and down, and the scope will give you information about where those lines intersect the input curve.
If you know any two values of R, C, and RC, you can find the third. A 1k resistor between the Arduino and the capacitor will dominate the value of R, and you can use that with the time constant to calculate the exact value of C.
That last bit is the basic procedure for testing caps with a scope: apply an input square wave through a known resistance, find the RC time constant, and use that to find the value for the cap. If the value you get from the calculation is a long way from the number on the cap, it's a sign that the cap is dead.
One tip: Testing capacitors in a circuit can be tricky because the input signal may be strong enough to power any ICs nearby. To avoid that, limit the amplitude of your input square wave to 350mV. That's far enough below the turn-on threshold for any silicon diode or transistor to keep them from interfering. The step response should still be easy to see on the 100mV/div or 200mV/div settings though.
If you want to test reactive components like inductors and caps, you can get a lot of mileage out of a simple Arduino.
One of the basic principles in signal processing is that you can learn everything you need to know about a frequency-dependent circuit by seeing how it responds to an impulse (a very fast high/low burst) or a unit step. Impulses are hard to generate, but the rising and falling edges of square waves are good approximations of a unit step. Set an Arduino to send its GPIO pins high and low at various frequencies and you get a range of unit-step approximations that you can use for testing.
Start by connecting one of the pins to your scope and zoom in on the rising and falling edges. You'll probably see some minor overshoot and ringing due to the parasitic inductance and capacitance of the wire. Then connect a known-good 1uF capacitor and see what effect that has.
What you'll see are rising and falling exponential decay curves that replace the nice, sharp edges from before. The time it takes for the curve to rise to full value depends on the value of the capacitor and the impedance of the Arduino's pin. The time it takes for the output to cross 2/3 of the gap between high and low is the RC time constant for the system, which is also the product of R and C.
To find the 2/3 point, use the scope's cursors under manual control.. that lets you move the cursors left and right or up and down, and the scope will give you information about where those lines intersect the input curve.
If you know any two values of R, C, and RC, you can find the third. A 1k resistor between the Arduino and the capacitor will dominate the value of R, and you can use that with the time constant to calculate the exact value of C.
That last bit is the basic procedure for testing caps with a scope: apply an input square wave through a known resistance, find the RC time constant, and use that to find the value for the cap. If the value you get from the calculation is a long way from the number on the cap, it's a sign that the cap is dead.
One tip: Testing capacitors in a circuit can be tricky because the input signal may be strong enough to power any ICs nearby. To avoid that, limit the amplitude of your input square wave to 350mV. That's far enough below the turn-on threshold for any silicon diode or transistor to keep them from interfering. The step response should still be easy to see on the 100mV/div or 200mV/div settings though.
Please be positive and constructive with your questions and comments.