Hello jpb.
I post a picture from my counter with the three LEDs. There you can see the "trigger a " LED. I don't know if the LCD backlight shines through from behind. This is independent of what I set on the device.
The behavior of the LCD is bad to describe. Everything looks right from the front. From the lateral angle it looks restless. A little as if horizontal, from bottom to top, strips of light go through.
Jörg
backlight way to powerful maybe you could dim it a little mod the circuit ??
Hello jpb.
I post a picture from my counter with the three LEDs. There you can see the "trigger a " LED. I don't know if the LCD backlight shines through from behind. This is independent of what I set on the device.
The behavior of the LCD is bad to describe. Everything looks right from the front. From the lateral angle it looks restless. A little as if horizontal, from bottom to top, strips of light go through.
JörgI've not noticed this before, and it doesn't worry me but when I disconnect so the trigger is off then there is a little light bleed so that the trigger looks faintly green as in the attached photo (similar to yours).
I'm not sure why your gate light is on with no connection - we must have different settings - I've set mine to measure frequency back-to-back.
Hello jpb. If you are not an engineer you must read first much on continuous time stamping with linear regression.
For optimal working with this counter, you must acquire much background knowledge. I am not an expert in this field and i wonder about different measurements, depending on equipment setup.
We're talking about very high resolution frequency measurements, which can be adversely affected by many sources of error.
Depending on the type of error, the one or the other measuring methods can deliver better results.
I am still on the search for information, to better understanding this technique.
That between start-stop counting or continuous timestamping counting with linear regression, different results of the StdDev and AllanDev are, I understand quite well.
But that the MEAN result is always different averaged over the set of samples, I still do not understand.
backlight way to powerful maybe you could dim it a little mod the circuit ??Yes, it is rather bright - I poked around the menus to see if it was adjustable and couldn't find any options.
I'm a bit reluctant to poke around inside. The brightness doesn't bother me - it is not dazzling - the only concern would be the light burning out prematurely but presumably if there was such a problem with the design it would have emerged by now, it is not a particularly new counter and even in the Tek form it has been around for quite a few years.
backlight way to powerful maybe you could dim it a little mod the circuit ??Yes, it is rather bright - I poked around the menus to see if it was adjustable and couldn't find any options.
I'm a bit reluctant to poke around inside. The brightness doesn't bother me - it is not dazzling - the only concern would be the light burning out prematurely but presumably if there was such a problem with the design it would have emerged by now, it is not a particularly new counter and even in the Tek form it has been around for quite a few years.I've now done the unthinkable and actually looked at the manual!
The LCD screen contrast can be adjusted using the up and down arrows when there is no input expected. It is not the same as brightness but it does allow some adjustment.
Interestingly the screen inverts at one extreme and then I noticed that the screen inverts anyway (white on black) when viewed from an angle (polarisation I suppose).
Hi All
I've just bought a Pendulum CNT-90 but I can't seem to get it to work as expected. I'm inputting a 10MHz square wave @280mv pp from CH1 on my Siglent SDG1025 which is clocked by my BG7TBL gpsdo into the 10Mhz Ext Ref input. The display shows EXT ref to show it has accepted the signal.
The I connected CH2 of my sig Gen to Input A on the CNT-90 and supplied a 10MHz sine wave at 5v.
The issue is that whatever gate speed/resolution I choose, the last couple of digits on the CNT-90 dance around by about 20 counts. I had assumed that if the extref is essentially the same clock, the display should be crack on and the display would be. for example, 10.000 000 000 000 but even on faster gate times like 100mS, the last couple if digits dance around, effectively showing more error for faster gate times.
I've played around with different voltage levels for ext ref and sine/square and while these do make a small difference, the display doesn't zero.
Am I missing something here?
Thanks
Steve
Hello jpb. If you are not an engineer you must read first much on continuous time stamping with linear regression.
For optimal working with this counter, you must acquire much background knowledge. I am not an expert in this field and i wonder about different measurements, depending on equipment setup.
We're talking about very high resolution frequency measurements, which can be adversely affected by many sources of error.
Depending on the type of error, the one or the other measuring methods can deliver better results.
I am still on the search for information, to better understanding this technique.
That between start-stop counting or continuous timestamping counting with linear regression, different results of the StdDev and AllanDev are, I understand quite well.
But that the MEAN result is always different averaged over the set of samples, I still do not understand.I am an engineer by background, though I now work in software, and have done quite a lot of work in the past on curve fitting to measured data.
I think the difference is nothing to do with the source of noise but simply in the way the data is handled. If you have n points going from t1 to tn say, then the standard counter mode will treat this as (n-1) cycles in (tn-t1) seconds or a frequency of (n-1)/(tn-t1). In the linear regression mode the counter fits a least-squares (I'd guess) straight line to the data which may not exactly go through any of the points. The frequency is then the slope of the fitted line.
If you're looking for the best average frequency and assume that the points are all equally noisy then the slope is probably better - the variance in the slope is less than that of the difference in end points. For analysing the data further with ADEV I would guess that you probably want the actual phase measurements since different time periods are used when working on the same data - also some points may be glitches (outliers) and it is probably better to simply remove them rather than allow them to affect the measurements.
I think it is similar to the arguments that photographers have about jpeg and RAW camera data. The jpegs look good straight out of the camera but serious photographers want to work on the RAW data rather than lose information.
I would recommend Bob Riley's web site and in particular his book (available as a free pdf report) and his software Stable 32 which is now also free.
http://www.wriley.com/
http://www.stable32.com/Handbook.pdf
Hello jpb.
How did you import the data from your TEK FCA 3100 in the Stable32 software.
Thanks Jörg
Hello jpb. Thank you for your help. Please note, BtB is not possible with the FCA3000.
Please disable this function when your FCA 3100 for the comparison of the measured values.
I was also able to determine the influence of the trigger mode.
With the trigger mode "Auto " the count error is slightly lower, but the short-term stability is slightly worse.
If you then set the trigger to "manual" mode, the count error is slightly higher and the short-term stability at ADev is slightly better.
Thanks Jörg.