> Noise spectra down into the 1/f region (< 10 Hz) would be nice.
Usually that stuff scales with the master clock frequency.
There are a couple of shorted-input graphs on page 11. They go down to 1 Hz.
Figure 15 on the next page goes down to 0.2 Hz.
For EFC type uses, I'd expect the drift o
On 06/29/2010 01:45 AM, Hal Murray wrote:
The one I'm building up is a ADS1278
http://focus.ti.com/lit/ds/symlink/ads1278.pdf
There are others in the series with fewer inputs. As with a lot of
converters, there isn't a whole lot of data on them.
What are you looking for?
There is a section o
Hi
Noise spectra down into the 1/f region (< 10 Hz) would be nice.
Bob
On Jun 28, 2010, at 7:45 PM, Hal Murray wrote:
>
>> The one I'm building up is a ADS1278
>> http://focus.ti.com/lit/ds/symlink/ads1278.pdf
>> There are others in the series with fewer inputs. As with a lot of
>> converters
> The one I'm building up is a ADS1278
> http://focus.ti.com/lit/ds/symlink/ads1278.pdf
> There are others in the series with fewer inputs. As with a lot of
> converters, there isn't a whole lot of data on them.
What are you looking for?
There is a section of DC parameters on page 3.
No missin
;
> -Original Message-
> From: Bob Camp
> Sender: time-nuts-boun...@febo.com
> Date: Mon, 28 Jun 2010 13:18:32
> To: Discussion of precise time and frequency measurement
> Reply-To: Discussion of precise time and frequency measurement
>
> Subject: Re: [time-
-boun...@febo.com
Date: Mon, 28 Jun 2010 13:18:32
To: Discussion of precise time and frequency measurement
Reply-To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] EFC tracking
Hi
TI has a line of ADC's that drop a chopper stabilization loop around a fairly
Hi
TI has a line of ADC's that drop a chopper stabilization loop around a fairly
normal 24 bit "audio ADC" part. Their claimed benefit is that they take down
the level of flicker noise and DC drift present in audio only parts.
Since most of the "interesting" stuff on an EFC is long time span,
ge-
> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
> Behalf Of Poul-Henning Kamp
> Sent: 26 June 2010 21:06
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] EFC tracking
>
> In message <4c265bb1.8090...@earthlink.
In message , "John Miles" writes:
>> That is actually a very debatable proposition, a lot of them are
>> tracking types that conveniently cover up any lack of linearity
>> on the analog side of the fence.
>
>Can you elaborate on that? Linearity is linearity - wouldn't it ultimately
>show up in th
Didier Juges wrote:
I am not sure how to translate the IMD specs into integral or
differential non-linearity, but from what I have seen, IMD specs are
not significantly better for 24 bit sound cards than for the older
high-end 16 bit models, when high-end 16 bit models were available.
Noise specs
Didier Juges wrote:
I can only guess at what a sound card with linearity specs
approaching those of the AD kit would cost, and it's still AC
coupled, and as Poul pointed out, has no long term stability spec.
This *is* an issue.. the audio ADCs have great performance in the "sub 1
second" sort
Date: Sat, 26 Jun 2010 15:25:28
To: Discussion of precise time and frequency measurement
Reply-To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] EFC tracking
> >sound card ADCs, the high end 24 bit ones, are pretty darn linear [...]
>
&
Hi Steve,
Let me build on the VFC idea for a minute. If I am understanding your interest
properly, you are wanting to monitor and track the EFC changes then process that
information as a form of studying the stability to some degree. Is that
correct ?
Well, it occurred to me, admittedly after
> >sound card ADCs, the high end 24 bit ones, are pretty darn linear [...]
>
> That is actually a very debatable proposition, a lot of them are
> tracking types that conveniently cover up any lack of linearity
> on the analog side of the fence.
Can you elaborate on that? Linearity is linearity -
o.com
Date: Sat, 26 Jun 2010 12:57:37
To: Discussion of precise time and frequency measurement
Reply-To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] EFC tracking
Didier Juges wrote:
> Steve,
>
> You may want to check the "Analog Devices Min
Here we go again
C
-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Poul-Henning Kamp
Sent: 26 June 2010 21:06
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] EFC tracking
In message <4c265bb1.8
In message <4c265bb1.8090...@earthlink.net>, jimlux writes:
>sound card ADCs, the high end 24 bit ones, are pretty darn linear [...]
That is actually a very debatable proposition, a lot of them are
tracking types that conveniently cover up any lack of linearity
on the analog side of the fence.
T
Didier Juges wrote:
Steve,
You may want to check the "Analog Devices MiniKit for ADuC702x-series".
http://www.google.com/search?q=Analog+Devices+MiniKit+for+ADuC702x-series
This kit includes a 24 bit ADC and integrated ARM processor in a small PWB with
all the tools and sample code to do what
At 01:43 +1200 27-06-2010, Steve Rooke wrote:
> I don't know if it qualifies as simple/cheap, but Analog Devices and others
have single chip low-rate sigma/delta converters with good to excellent
> properties; these were meant for strain gauges but should be able to track
> slow-moving cont
At 06:40 -0700 26-06-2010, jimlux wrote:
J.D. Bakker wrote:
Charge injection is a bit on the high side on a
4066; a more expensive (A)DG4xx-series chip may improve on that.
Or the traditional chopper approach of a mercury wetted reed relay?
Good luck with that in this day an
[voltage-to-frequency converter]
> I just had one of those duh! moments :) It does make the sampling a little
> more complicated as I'd have to take a number of samples and do something
> like a FFT to get the frequency, I think. My idea seemed just a simple way
> to just make a single, or limited
Original Message-
> > From: time-nuts-boun...@febo.com
> > [mailto:time-nuts-boun...@febo.com] On Behalf Of Steve Rooke
> > Sent: Saturday, June 26, 2010 7:13 AM
> > To: Discussion of precise time and frequency measurement
> > Subject: [time-nuts] EFC tracking
>
> To: Discussion of precise time and frequency measurement
> Subject: [time-nuts] EFC tracking
>
> I would like to track the EFC voltage in hardware using
> something cheap and ready to hand. I was thinking of using a
> sound card as it has good resolution but it's obviously on
Steve,
Do a simulation and see how your card behaves. I've had some unexpected
results in similar attempts years ago.
Nothing like an add on card suitable for the job. These cards are not cheap.
>I would like to track the EFC voltage in hardware using something
>cheap and ready to hand. I was
Steve,
Large amplitude signals on the input ports tend to leak into the inputs on
sound cards. Isolation testing required!
>> Soundcards have inputs and outputs. You can feed the output with a
>> series of samples that represent your control waveform. The PC becomes
>> the oscillator and you kn
Steve Rooke wrote:
The eval board for the part may have a computer interface built into it.
So I need to locate this if possible, any pointer please?
Go to Analog Devices website (http://www.analog.com/) and find your
ADC.. typically there's an eval board with a USB interface available.
Fo
Oz-in-DFW wrote:
Chopping is used to cancel DC offsets in imperfect amplifiers, it adds
no gain. If there is a DC component and you filter with a cutoff
frequency below the chop rate, the offsets of the amplifier can be
effectively canceled.
Chopping isn't quite that magical. You chop the D
Oz,
On 27 June 2010 01:49, Oz-in-DFW wrote:
> Soundcards have inputs and outputs. You can feed the output with a
> series of samples that represent your control waveform. The PC becomes
> the oscillator and you know it's frequency and relative phase track.
Brilliant!
> Chopping is used to ca
On 27 June 2010 01:40, jimlux wrote:
> J.D. Bakker wrote:
>>>
>>> I wonder if anyone has done something like this before and could share
>>> their experiences.
>>
>> The general principle should work. However, as you're interested in slow
>> changes, there are some error sources that might be unac
On 6/26/2010 8:36 AM, Steve Rooke wrote:
> Oz,
>
> On 27 June 2010 01:09, Oz-in-DFW wrote:
>
> On 6/26/2010 7:12 AM, Steve Rooke wrote:
>
>>>
>>>
>>>
>> I've done similar stuff in work projects, but never written code. I've
>> thought about this some as well. I'd consider a few thin
Bill,
On 27 June 2010 01:21, WB6BNQ wrote:
> Steve,
>
> I think using a voltage-to-frequency converter would solve that problem. They
> are not too expensive and there are several flavors from Amalog devices and
> some
> others.
I just had one of those duh! moments :) It does make the sampling
JDB,
On 27 June 2010 01:19, J.D. Bakker wrote:
>> I wonder if anyone has done something like this before and could share
>> their experiences.
>
> The general principle should work. However, as you're interested in slow
> changes, there are some error sources that might be unacceptable, including
J.D. Bakker wrote:
I wonder if anyone has done something like this before and could share
their experiences.
The general principle should work. However, as you're interested in slow
changes, there are some error sources that might be unacceptable,
including the drift of (differential) channel
Oz,
On 27 June 2010 01:09, Oz-in-DFW wrote:
>
>
> On 6/26/2010 7:12 AM, Steve Rooke wrote:
>>
>> I next thought about turning the DC into AC by chopping it, IE.
>> inverting 50% of the voltage via an oscillator. This way I could pass
>> the square wave directly into an unmodified sound card, tak
Steve,
I think using a voltage-to-frequency converter would solve that problem. They
are not too expensive and there are several flavors from Amalog devices and some
others.
Just set it for a 1KHz start point or maybe 10KHz.
BillWB6BNQ
Steve Rooke wrote:
> I would like to track the EFC v
I wonder if anyone has done something like this before and could share
their experiences.
The general principle should work. However, as you're interested in
slow changes, there are some error sources that might be
unacceptable, including the drift of (differential) channel
resistances for th
On 6/26/2010 7:12 AM, Steve Rooke wrote:
>
> I next thought about turning the DC into AC by chopping it, IE.
> inverting 50% of the voltage via an oscillator. This way I could pass
> the square wave directly into an unmodified sound card, take
> measurements and then do an RMS calculation on th
I would like to track the EFC voltage in hardware using something
cheap and ready to hand. I was thinking of using a sound card as it
has good resolution but it's obviously only AC coupled so it would not
measure the DC of the EFC. I thought about modifying a sound card to
make it DC coupled but mo
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