Counters Gate Time and hold off delay

[PrescottDan]

Using a Counter to measure time duration

How does a tech know what is the best Gate time setting for a counter?

If you set the Gate time to short it will chop off and display a false reading

When do you use the Delay Holdoff on a counter?

Using a counter to measure time duration's is better then using an Oscope? it's more accurate then an Oscope when measuring time durations? very short time durations and very long time durations

 

[Venkadesh_M]

Counter Gate clock frequency is depend on accuracy in timing, number of bits of counter and maximum time duration.

What do you mean delay holdoff ?

using oscilloscope or counter is depend on situation and availability.

 

[chuckey]

Counters used as timers are very accurate for long time durations. This is because the input signal opens a gate to let 1µ Sec pulses through which the counter counts, so if the signal is 1 pulse per second, it can count up to 1,000,000 with an accuracy of 1 part in 10^8 or better. If the input signal is at a 1KHZ rate, the counter can only count up to 1,000, so its accuracy is 1 part in 10 ^3.
As counter use the longest gate period possible, i.e. 10 Seconds, this way the indicated frequency is +- .1 HZ, if you use 100µS, the accuracy will be +- 10 KHZ
Frank

 

[PrescottDan]

What do you mean delay holdoff ?

HP5315B Universal Counter manual says Gate time/delay hold off depending on which mode you're in

I'm having a problem with Frequency counters when the voltage input to them is in millivolts, the frequency counters have a hard time to stabilize the frequency why is that and how can I fix this problem?

I'm using a HP5334B Universal Counter

Also another problem is that the HP5315B Universal Counter has a 1meg ohm input and the HP5334B Universal Counter has a 50ohm input

It seems like the HP5334B with the 50ohm input is used for only with an RF generator because the output of an RF generator is at 50hms

If I use a Function generator there output is 75ohms or 1K ohms at a max peak beyond 5 volts peak AC RMS

The AC RMS peak max voltage is different for each frequency counter, and you have to watch what your function generators output is so you don't damage the input to the counter

Plus when setting the function generators output to millivolts , the frequency counter has a hard time to stablize the frequency

I was using red and black banana cables which causing the frequency counter to not stablize well also, but using Coax cables has help some

Any reasons why?

 

[Venkadesh_M]

If you want to completely rid of all problem kind of problems like amplitude, input resistance then why not you construct your own schmitt trigger in the input.

 

[chuckey]

"
I'm having a problem with Frequency counters when the voltage input to them is in millivolts, the frequency counters have a hard time to stabilize the frequency why is that and how can I fix this problem? "
You are trying to use the counters outside of their specifications. Build your self a amplifier.
Frank

 

[D.A.(Tony)Stewart]

"
I'm having a problem with Frequency counters when the voltage input to them is in millivolts, the frequency counters have a hard time to stabilize the frequency why is that and how can I fix this problem? "
You are trying to use the counters outside of their specifications. Build your self a amplifier.
Frank

When in doubt RTFM , Read The Fine Manual, You may find the spec sensitivity is only 50mVrms

Use an external amplifier and coax for best SNR either high or low impedance. even use an old analog scope for gain and external,video out to counter works.

HP5315B is very sophisticated and accurate. When signal has random noise source e.g. VCO, RF , averaging by gate time reduces jitter by root N of number of cycles counted in gate time.

Since all,gate triggers have small hysteresis , the signal must exceed this hysteresis when trigger level,is centred.

VaRiable holdoff is another option to prevent false triggering. delayed trigger allows time for a signal,to grow before being counted by external gate control.