Propagation Delay measurement using counters in DAQ

[alekhya11]

Hi All,

We are testing timing parameters for a buffer device with DAQmx. We have timing measurements in the order of ns. As i see the spec of DAQ counter, it says the resolution is 32 bits and the maximum external frequency is 100Mhz. I need a clarification if i can measure in order of ns with Counter,

Please help me in finding this.

[Henrik_Volkers]

A 100MHz clocked timer has 10ns resolution ...  20ns uncertainty

analog or digital buffer?

There are tricks to measure phase in higher resolution .. I remember my HF professor told something about mixing ...

Groupdelay of an analog buffer can be measured with sine excitation and sine aproximation (or simpler using tone detection.vi) with lower samplerates in fractions of the samplerate.  I found less than 50ps resolution (about 0.01° standard dev.)  while sampling 20ms (line periode;)) of a 100kHz sine with 10MHz 🙂 (NI 5922)  (always measured twice with swapped channels to compensate interchannel delay differences) 

And with sine approximation you can coarsly say that the resolution depends on the number of samples ...

(provided a stable generator)

For a digital buffer ... mh. How fast are modern XOR gates?  followed by an integrator (RC) give an analog voltage propotional to delay...    put a small adjustable delay (R_pot with small C) in both inputs and adjust to zero while feeding with same square wave?