How we can make a counter with accurate nanosecond and picosecond steps measurement

Many of our members may be able to come up with ideas to assist you with this if you could elaborate on the nature of the measurement you are attempting to make.

For example, is the event something that you need to measure on a real-time basis or do you have the luxury of performing repeated measurements over a span of many seconds which can then be averaged to improve accuracy?

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Even creating an oscillator for that small a time base is tricky because you need such a high slew rate.

I am going to suggest a different tactic.

Set up a parallel rate of change event like a charging capacitor and turn the state of charge into a timecount.

Instead of reading a counter take sample and hold measurements and that level can be turned into a time count based on a constant rate of charge.

For extremely small time measurements like this that is the way to go.

For example if you are checking how long it takes a laser pulse to travel through a crystalline sample so you can determine the materials propagation rate, you would have a hard time finding a counter that will get into double digits. But Electrons move fast enough and you can convert the voltage increase in a low value capacitance into times accurate to the femtosecond.