[time-nuts] Low noise power supply recommendations

[Will Matney]

Paul,

Remember the HP 412? It used incandescent bulbs, a spinning disc, and a
syncronous motor. I actually still use two of these, and the bulbs are the
only fault.

Getting back on topic, somewhat, has anyone ever checked the noise on the
rails feeding the OCXO's in this GPS equipment? Especially the ones ruiing
off 12 volt car lead-acid batteries?

The reason for the question is, I was always taught that batteries were the
best souce, when noise or cleaness of supply voltage was needed. It was
never stated which battery to use, etc. From the article, it said that
alkaline batteries had a cleaner supply than others, but then again, their
not rechargable. Does anyone remember anything about the mercury batteries?

Best,

Will

*********** REPLY SEPARATOR  ***********

On 6/14/2011 at 10:21 PM paul swed wrote:

>Though its a bit off topic
>Ran into this chopper issue also on a HP410. I replaced the thing with a
>modern chopper amp. I think an LTC. This was quite a few years ago (10
plus
>easily) and it works very well. Still does actually. It did take a bit of
>rework to get things back in balance correctly.
>
>On Tue, Jun 14, 2011 at 10:14 PM, J. Forster <jfor at quik.com> wrote:
>
>> The reason I asked is that most microvolt bridges use choppers and have
BP
>> filters at the chopper frequency, so noise is largely uncorrelated.
>>
>> On the neon photochoppers, it has been discussed at length several times
>> on the HP-Agilent Yahyoo Group. A similar thing is used in the 410C.
There
>> are apparently issues with the CdS cells.
>>
>> Best,
>>
>> -John
>>
>> ===============
>>
>>
>> > John,
>> >
>> > No, it's DC. I'm trying to meet the original specs of the batteries in
>> not
>> > only voltage/current, but cleanliness of the current.
>> >
>> > Now inside the Fluke 844, it has a chopper, and it uses an AC power
>> supply
>> > internally to feed its circuitry. The Vishays bridge uses the
batteries
>> > voltage, and one small AC power supply to run the digital portion of
the
>> > bridge for the PPM readout. The bridge itself is half analog and half
>> > digital. The analog for the measurement, and the digital for the PPM
>> > difference.
>> >
>> > By the way, has anyone ever converted a neon NE-3 driven chopper to
using
>> > LED's? The bulbs have a sqaure wave coming into them of around 100-200
Hz
>> > if I recall.
>> >
>> > Thanks,
>> >
>> > Will
>> >
>> > *********** REPLY SEPARATOR  ***********
>> >
>> > On 6/14/2011 at 6:50 PM J. Forster wrote:
>> >
>> >>Is the bridge excitation AC or DC. If it's AC, you may not even need
>> >>low-noise power supplies.
>> >>
>> >>-John
>> >>
>> >>==============
>> >>
>> >>
>> >>
>> >>> Hi Will,
>> >>>
>> >>> You could consider building your own power supply system for the
>> >>> replacement of
>> >>> the batteries.  Use a separate power transformer which, I suspect,
>> >>> would
>> >>> be small
>> >>> as the current requirements would be low for driving a bridge
circuit.
>> >>>
>> >>> The main company to look toward for high quality, low noise
regulators
>> > is
>> >>> Linear
>> >>> Technology.  Here is a candidate part to look at :
>> >>> http://www.linear.com/product/LT3082
>> >>>
>> >>> This is the lowest noise (33uv/10Hz to 100KHz) low dropout regulator
>> > that
>> >>> can
>> >>> handle regulating 24 volts and is adjustable, meaning use can use
this
>> >>> part for
>> >>> all three voltages (i.e., three regulators).  You will have to
decide
>> >>> if
>> >>> it noise
>> >>> specs are suitable for your needs.  Keep in mind that battery noise
is
>> >>> typically
>> >>> random whereas the noise out of a regulated system tends to be
>> >>> constant.
>> >>>
>> >>> If you really think you need lower noise then you could consider an
>> > LT1000
>> >>> shunt
>> >>> reference.  Typically the circuit designs for LT1000 type devices
are
>> >>> as
>> >>> references and lack current capability above about 10 milliamps.
>> >>> Adding
>> >>> additional current circuitry would add more noise.  See:
>> >>>
>> >>> http://www.linear.com/product/LTZ1000
>> >>>
>> >>>
>> >>> Bill....WB6BNQ
>> >>>
>> >>>
>> >>> Will Matney wrote:
>> >>>
>> >>>> Hello,
>> >>>>
>> >>>> I am in need of a very clean 24 Vdc power source, to replace some
old
>> >>>> mercury cell batteries with. What would a good low noise, clean,
power
>> >>>> supply be in your recommendations? I thought of using two 12 Vdc
>> >>>> lead-acid
>> >>>> batteries in series, and making a charging circuit with regulators,
>> >>>> but
>> >>>> I
>> >>>> am hoping to purchase a good used supply off ebay, etc. The old
>> >>>> circuit
>> >>>> used two 12 Vdc snap terminal mercury batteries in series, for 24
Vdc,
>> >>>> along with a 7 Vdc mercury cell, and two plain AA carbon 1.5 Vdc
>> >>>> batteries
>> >>>> in series for 3 volts. Any help and or ideas would be appreciated.
>> >>>>
>> >>>> Thanks
>> >>>>
>> >>>> Will
>> >>>>
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>> >>
>> >>
>> >>
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