# Trouble with first part of Experiment 11 (Make: Electronics) when using multimeter

Here is my circuit. It works well, as described in a book, but I want to understand it better, so I want to check voltage on capacitor. But when I do it, LED doesn't blink and voltage goes up to 4V. When I turn off multimeter - it works again. Мultimeter is connected to capacitor directly. What did I do wrong?

• Is this an analog multimeter or a digital one? – Brian Drummond Nov 29 '14 at 21:03
• If it goes up to 4V, input impedance of the multimeter is 1 MOhm, it is a digital one. You should try with another multimeter, a better one. – Roger C. Nov 29 '14 at 21:10
• 1Mohm is a bit low for a DMM. – Ignacio Vazquez-Abrams Nov 29 '14 at 21:11
• Try using a scope. – Leon Heller Nov 29 '14 at 21:13
• To understand simple circuits I always recommend using a simulator; it rarely suffers from similar issues. – PlasmaHH Nov 29 '14 at 21:25

With the high resistor value of $470 K\Omega$ even an internal resistance as high as $1 M\Omega$ has a remarkable impact on your circuit.
When you have the parts at hand, you could change your circuit to use $47 K\Omega$ and $22 \mu F$. The time from flash to flash shouldn't change. However the flash duration would be 10 times longer.