Dwell time for HP4195A and HP8563E - Hewlett Packard

This is a discussion on Dwell time for HP4195A and HP8563E - Hewlett Packard ; I am trying to determine what the dwell time is for these instruments. By dwell time I mean the amount of time it samples the signal for each data point. This does not appear to be a configurable value, nor ...

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Thread: Dwell time for HP4195A and HP8563E

  1. Dwell time for HP4195A and HP8563E

    I am trying to determine what the dwell time is for these instruments.
    By dwell time I mean the amount of time it samples the signal for each
    data point. This does not appear to be a configurable value, nor does
    there seem to be a way to query this value.

    For these instruments, is this parameter fixed or variable? If it is
    fixed how
    do I find out what it is? If it is variable, is it calcualted by simply
    dividing the
    sweep time by the number of data points?

    TIA,
    -larry


  2. Re: Dwell time for HP4195A and HP8563E

    On 1 Dec 2005 14:07:16 -0800, "Larry Martell"
    wrote:

    >I am trying to determine what the dwell time is for these instruments.
    >By dwell time I mean the amount of time it samples the signal for each
    >data point. This does not appear to be a configurable value, nor does
    >there seem to be a way to query this value.
    >
    >For these instruments, is this parameter fixed or variable? If it is
    >fixed how
    >do I find out what it is? If it is variable, is it calcualted by simply
    >dividing the
    >sweep time by the number of data points?
    >
    >TIA,
    >-larry


    It is indirectly adjustable, at least on the 4195.
    The measurement time depends on your resolution bandwidth (Res BW
    button) setting. Lower bandwidth setting will take longer to make a
    measurement. You can divide the total time by number of points to come
    up with an estimate if you use the same bandwidth for all points
    (non-auto mode). If you use the Auto Res BW, the resolution bandwidth
    will be different for different frequency bands which can speed up the
    total measurement time (slow at low freqs, faster at the higher
    freqs). If you use the video filter, this will add more time to the
    measurement process. On the 4195, you can manually change the
    bandwidth in the middle of the sweep if you need to hurry things up or
    reduce noise in critical areas.

    ---
    Mark

  3. Re: Dwell time for HP4195A and HP8563E

    Larry
    I'm not certain about the 856X series but I suspect it is the same as
    for the newer analyzers. If so, the way the detector works depends on a
    number of factors:
    o how fast one is sweeping.
    0 detection mode (peak,sample, neg. peak)
    0 resolution bandwidth

    As the analyzer's LO traverses the spectrum between measurement bins
    (each bin of width = span/#measurment points), depending on how the
    detector is selected, the A/D takes 1-to-many measurements. Maximum
    sweep rate is limited by the need to let the detected signal settle (the
    group delay of the RBW filter) and the ability of the LO itself to move
    quickly and accurately. For the ESA series, multiple measurements may
    be made within each bin. Peak Detect modes just save the max or min
    value for the bin. Sample Detect (probably) measures the value at the
    center(or end, I 'm not sure) of the bin and throws away any other
    measurment. For some analyzers there is a non-sweeping mode wherein the
    A/D runs as fast as it can. I think that is a 50 ns measurement time for
    ESA.

    While there may be no dwell time selection, you may be able to influence
    the time spent by judicious selection of span, RBW and sweep time. But
    then, the question arises "why do you want to do that?". The SA should
    already manage things to avoid over-sweeping, trying to take data faster
    than the if filters can handle, and the detection mode selection should
    allow you some fleximbility as to whether you're looking at a peak or
    sampled mode.

    Glenn

    > I am trying to determine what the dwell time is for these instruments.
    > By dwell time I mean the amount of time it samples the signal for each
    > data point. This does not appear to be a configurable value, nor does
    > there seem to be a way to query this value.
    >
    > For these instruments, is this parameter fixed or variable? If it is
    > fixed how
    > do I find out what it is? If it is variable, is it calcualted by simply
    > dividing the
    > sweep time by the number of data points?
    >
    > TIA,
    > -larry
    >


  4. Re: Dwell time for HP4195A and HP8563E


    qrk wrote:
    > On 1 Dec 2005 14:07:16 -0800, "Larry Martell"
    > wrote:
    >
    > >I am trying to determine what the dwell time is for these instruments.
    > >By dwell time I mean the amount of time it samples the signal for each
    > >data point. This does not appear to be a configurable value, nor does
    > >there seem to be a way to query this value.
    > >
    > >For these instruments, is this parameter fixed or variable? If it is
    > >fixed how
    > >do I find out what it is? If it is variable, is it calcualted by simply
    > >dividing the
    > >sweep time by the number of data points?
    > >
    > >TIA,
    > >-larry

    >
    > It is indirectly adjustable, at least on the 4195.
    > The measurement time depends on your resolution bandwidth (Res BW
    > button) setting. Lower bandwidth setting will take longer to make a
    > measurement. You can divide the total time by number of points to come
    > up with an estimate if you use the same bandwidth for all points
    > (non-auto mode). If you use the Auto Res BW, the resolution bandwidth
    > will be different for different frequency bands which can speed up the
    > total measurement time (slow at low freqs, faster at the higher
    > freqs). If you use the video filter, this will add more time to the
    > measurement process. On the 4195, you can manually change the
    > bandwidth in the middle of the sweep if you need to hurry things up or
    > reduce noise in critical areas.


    Thanks much for the reply Mark. This is very helpful.

    -larry


  5. Re: Dwell time for HP4195A and HP8563E


    Glenn wrote:
    > Larry
    > I'm not certain about the 856X series but I suspect it is the same as
    > for the newer analyzers. If so, the way the detector works depends on a
    > number of factors:
    > o how fast one is sweeping.
    > 0 detection mode (peak,sample, neg. peak)
    > 0 resolution bandwidth
    >
    > As the analyzer's LO traverses the spectrum between measurement bins
    > (each bin of width = span/#measurment points), depending on how the
    > detector is selected, the A/D takes 1-to-many measurements. Maximum
    > sweep rate is limited by the need to let the detected signal settle (the
    > group delay of the RBW filter) and the ability of the LO itself to move
    > quickly and accurately. For the ESA series, multiple measurements may
    > be made within each bin. Peak Detect modes just save the max or min
    > value for the bin. Sample Detect (probably) measures the value at the
    > center(or end, I 'm not sure) of the bin and throws away any other
    > measurment. For some analyzers there is a non-sweeping mode wherein the
    > A/D runs as fast as it can. I think that is a 50 ns measurement time for
    > ESA.


    Thanks very much for the info Glenn, it is very hlepful.

    > While there may be no dwell time selection, you may be able to influence
    > the time spent by judicious selection of span, RBW and sweep time. But
    > then, the question arises "why do you want to do that?".


    I have to perform some EMI emissions tests that have specific dwell
    time requirments
    (>= 0.15 sec), and I will need to prove to my customer that I am
    meeting these.

    Thanks!
    -larry

    > The SA should
    > already manage things to avoid over-sweeping, trying to take data faster
    > than the if filters can handle, and the detection mode selection should
    > allow you some fleximbility as to whether you're looking at a peak or
    > sampled mode.
    >
    > Glenn
    >
    > > I am trying to determine what the dwell time is for these instruments.
    > > By dwell time I mean the amount of time it samples the signal for each
    > > data point. This does not appear to be a configurable value, nor does
    > > there seem to be a way to query this value.
    > >
    > > For these instruments, is this parameter fixed or variable? If it is
    > > fixed how
    > > do I find out what it is? If it is variable, is it calcualted by simply
    > > dividing the
    > > sweep time by the number of data points?
    > >
    > > TIA,
    > > -larry
    > >



  6. Re: Dwell time for HP4195A and HP8563E

    Larry


    >
    >>While there may be no dwell time selection, you may be able to influence
    >>the time spent by judicious selection of span, RBW and sweep time. But
    >>then, the question arises "why do you want to do that?".

    >
    >
    > I have to perform some EMI emissions tests that have specific dwell
    > time requirments
    > (>= 0.15 sec), and I will need to prove to my customer that I am
    > meeting these.
    >

    OK, that helps. In that case you'll want to use the peak detect mode
    (max) and slow the sweep time down to (.15sec/bin * #bins/sweep). That
    should get you to .15 seconds within each bin and a measured level
    corresponding to the peak within that time. To be thorough, you'll
    probably want to make sure that the RBW is set to be at least as wide as
    a bin.

    Glenn

  7. Re: Dwell time for HP4195A and HP8563E


    Glenn wrote:
    > Larry
    >
    >
    > >
    > >>While there may be no dwell time selection, you may be able to influence
    > >>the time spent by judicious selection of span, RBW and sweep time. But
    > >>then, the question arises "why do you want to do that?".

    > >
    > >
    > > I have to perform some EMI emissions tests that have specific dwell
    > > time requirments
    > > (>= 0.15 sec), and I will need to prove to my customer that I am
    > > meeting these.
    > >

    > OK, that helps. In that case you'll want to use the peak detect mode
    > (max) and slow the sweep time down to (.15sec/bin * #bins/sweep). That
    > should get you to .15 seconds within each bin and a measured level
    > corresponding to the peak within that time. To be thorough, you'll
    > probably want to make sure that the RBW is set to be at least as wide as
    > a bin.


    Glenn, thanks very much for the info!

    -larry


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