Frequency counter on Rigol DS1102E

[Beowulf]

I'm having a hard time using my oscilloscope to check the clock signals. This oscilloscope has a built in frequency counter but the readings I'm getting are not what they should be.
For a 14Mhz signal, for example, I get 2mhz and other oscillating readings allover the place.
So if anybody has one of these, can you point out if there are any settings or something I need to do.

Regards,

[tom66]

Re: Frequency counter on Rigol DS1102E

Depends what counter/freq measure you are using.
If you use Measure ... Freq... I'd expect that with noise sources
Therefore, I'd recommend using Utility... Counter which works better.

If that is still giving problems you need to set up your trigger better as it bases that off the number of trigger pulses per second. Try selecting a LPF or HPF for the trigger, or increasing the noise rejection parameter in the trigger menu.

[Beowulf]

Re: Frequency counter on Rigol DS1102E

Hey Tom Thanks a lot for the info. I'll try it and see how it goes buddy.

[Beowulf]

Re: Frequency counter on Rigol DS1102E

Alright will continue messing with it tomorrow. Couldn't get it to give me the right readings. Think will need to read more.
A question. For this reading does it matter if one uses the ground clip and connect it to the board's ground?
I'm practicing reading the crystal from a computer motherboard. It's a 14mhz one.

[Kiriakos GR]

Re: Frequency counter on Rigol DS1102E

You should use a metal spring on the probe as ground, so to eliminate any inference by other near by signals on the same PCB.

The signal straight in oscillators is very low, it is best to test your scope with a function generator at 14Mhz so to test the sensitivity of the frequency counter VS Low mV.

[Beowulf]

Re: Frequency counter on Rigol DS1102E

Alright, thanks kiriakos.

[tom66]

Re: Frequency counter on Rigol DS1102E

The signal straight in oscillators is very low, it is best to test your scope with a function generator at 14Mhz so to test the sensitivity of the frequency counter VS Low mV.

Most oscillators I have found easily give a 1Vp-p output, if not more.

[Beowulf]

Re: Frequency counter on Rigol DS1102E

Hey guys found my problem after a response from rigol support department. Turns out that I had to try on channel 2. Dont know why and the user's manual say nothing about it but as soon as I took the reading on channel 2 it gave me the right reading without even pressing on the auto button.

Thanks.

[Kiriakos GR]

Re: Frequency counter on Rigol DS1102E

Just run some tests in my GDS-2102A regarding input sensitivity at 14MHz, proper triggering starts from 80mv p-p & both channels are equally sensible.

[tom66]

Re: Frequency counter on Rigol DS1102E

My old HP 54501A would do as low as 10mVp-p at 10MHz, and <1mVp-p at below 1kHz.

[Kiriakos GR]

Re: Frequency counter on Rigol DS1102E

sensible.

= sensitive

Frequency counter is an additional circuit and the exact sensitivity VS frequency range usually is always undocumented.

What it is documented from the serious manufactures is the minimum input voltage so one scope to archive it highest specified accuracy in volts measurements.

The old scopes are much less capable in the sector of accuracy, and so it makes more sense to compare apples with apples.

[tom66]

Re: Frequency counter on Rigol DS1102E

Frequency counter on every scope I have used just uses the trigger out signal, which is also available on the rear of many scopes. Because of that, it means it has exactly the same specs as the trigger circuit (sensitivity, etc.)

[Kiriakos GR]

Re: Frequency counter on Rigol DS1102E

The only public presentation (in Video) about the functionality of trigger output that I have see is the one made By GW INSTEK for the count of Wfms/s or waveform update rate in their GDS-2000A.
By having as reference 1MHz sine wave at 1V P-P, and the output was the 80,000 Wfms/s in an actual signal of 80,000KHz.

By having this in mind I do not see any 1 to 1 relationship with the input signal.
Either way I am not insisting in anything, I am currently doing my homework about scopes, and I have make a very significant progress for an electrician.

Tektronix got interested to offer me a THS3000 for a product review and to discover further it functionality, we are currently in negotiations.
I have allot to discover regarding functionality and features of the latest scopes, and I am just in the beginning.

[tom66]

Re: Frequency counter on Rigol DS1102E

The scope may update the display 80,000 times a second, but can receive a (simple) trigger all the way up to its maximum triggering frequency, which is typically a little higher than its bandwidth. For example, my Rigol DS1102E scope will count frequency at least up to 100MHz (+/- a few Hz), I have tested it on a 100MHz oscillator. It only has 200 to 1,000 wfms/s. What I'm not certain is if the trigger frequency counter works for complex triggers, like ramp and risetime triggers.