High-Precision Timer: Solving a 500ps Accuracy Challenge

• Scott Nelson
In summary, Bob is designing a board-level circuit to measure pulse width, and he is looking for a high-precision timer that uses a clock frequency of 2GHz. He is considering using a frequency divider (prescaler) to knock down the frequency of his signal.
Scott Nelson
Hi,

I am designing a board-level circuit to measure pulse width, in which I need a high-precision timer. I want to use a high-speed counter to implement the timer. Since the timer requires an accuracy of 500ps, this implies that the clock to the counter has to run at a frequency of 2GHz. Since I am not designing chip-level circuit, I would like to purchase such an external timer/counter which achieves such precision. Does Anyone have an idea what to buy? If such high precision timer is not easily available in the market, is there anyway I can solve the problem through other means?

Thanks!

You can use a frequency divider (prescaler) to knock down the frequency of your signal to more manageable levels.

Here is simple divide by 128 or 256 chip:

http://cgi.ebay.com/MB506-FUJITSU-8-Pin-DIP-MB-506-FREQUENCY-PRESCALER-/370284928318?pt=LH_DefaultDomain_0&hash=item5636b39d3e

What is the range of pulse widths you need to measure, and do you require 500 ps resolution, or 500 ps accuracy? I have used simple transistor circuits to convert a pulse width to an analog voltage on a capacitor, which can be digitized by an ADC. The analog output voltage signal can be calibrated using pulse width standards.

Bob S

Thanks for the input! But What I need to measure is the width of arbitrary signal. Moreover, I also need to measure the signal transition time. How can a frequecy divider be useful in this scenario?

waht said:
You can use a frequency divider (prescaler) to knock down the frequency of your signal to more manageable levels.

Here is simple divide by 128 or 256 chip:

http://cgi.ebay.com/MB506-FUJITSU-8-Pin-DIP-MB-506-FREQUENCY-PRESCALER-/370284928318?pt=LH_DefaultDomain_0&hash=item5636b39d3e

Thanks! the spec requires that the resolution to be 500ps, but does not specify the range of pulse widths. Moreover, I also need to measure the transition time of a digital signal (not pulse). I plan to input the signal to two comparators with pre-set start and stop thresholds to trigger and stop the counter. BTW, for the case of pulse, the shape is arbitary, which might mean converting pulse width to volatge not working.

Bob S said:
What is the range of pulse widths you need to measure, and do you require 500 ps resolution, or 500 ps accuracy? I have used simple transistor circuits to convert a pulse width to an analog voltage on a capacitor, which can be digitized by an ADC. The analog output voltage signal can be calibrated using pulse width standards.

Bob S

I still don't fully understand your application; e.g., resolution vs. accuracy requirement, etc.

This TAC (Time-to-Amplitude Converter, see Fig. 1) provides the general concept of storing pulse width information as a charge on a capacitor (C101, 330 pF). This circuit can provide resolution much better than 500 ps. Even though I have specific reservations about the design, the concept is correct.

http://www.ko4bb.com/~bruce/TAC.html

Bob S

What is a high-precision timer and why is it important?

A high-precision timer is a device used to accurately measure time intervals down to nanoseconds or even picoseconds. It is important in scientific research, industrial applications, and other fields where precise timing is necessary for accurate data collection and analysis.

What is the 500ps accuracy challenge?

The 500ps accuracy challenge refers to the need for a timer to accurately measure time intervals with a margin of error of 500 picoseconds (ps) or less. This level of precision is necessary for many advanced applications such as quantum computing, high-speed data transmission, and ultrafast spectroscopy.

How does a high-precision timer work?

A high-precision timer typically uses a crystal oscillator or atomic clock as a reference to generate a stable and precise frequency. This frequency is then divided down into smaller intervals, which are counted by the timer to measure the desired time interval.

What are the challenges in achieving 500ps accuracy?

Achieving 500ps accuracy requires overcoming several challenges, including minimizing signal noise, reducing thermal drift, and compensating for any delays in the electronic circuitry. Additionally, the timer must be calibrated and tested regularly to maintain its accuracy over time.

What are the applications of a high-precision timer?

A high-precision timer has a wide range of applications in scientific research, telecommunications, computer networking, and other industries. It is used for measuring the speed of light, synchronizing data transmission, and conducting experiments in fields such as quantum physics, astronomy, and chemistry.

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