[time-nuts] the care and feeding of LPRO's

Eric Garner garnere at gmail.com
Fri Oct 7 18:16:59 UTC 2011

fortunately, everything in the "lab"(basement) is on UPSs so in theory
the input voltages to the equipment should be pretty constant and I
was already planning on using a linear supply.

as far as magnetic disturbances go, what is a reasonable precaution
short of making a muMetal box?

On Fri, Oct 7, 2011 at 11:04 AM, Magnus Danielson
<magnus at rubidium.dyndns.org> wrote:
> On 07/10/11 19:01, Chuck Harris wrote:
>> There are lots of ways you can unintentionally affect a device
>> like an LPRO. For instance, suppose the internal power supply
>> dissipates a different amount of heat depending on the input
>> supply voltage. This could cause the oven to momentarily shift
>> its internal temperature a small amount... which may show up
>> as a frequency shift. Or suppose the current change due to
>> changing input voltage causes a magnetic disturbance that shifts
>> frequency?
>> We're time-nuts. We are trying to get more from these devices
>> than the manufacturer ever intended.
> So you let in normal mains into you lab? >:-)
> If you have linear supplies, you want to
> 1) Steer voltage to be within a tight spec. This will remove variation in
> burned power in the linear supplies.
> 2) Run at higher frequency, say 400 Hz, to create smaller ripple after caps,
> 3) With 400 Hz the lower ripple will increase the effective voltage after
> rectification and caps, so the "mains" voltage can now be reduced resulting
> in even less power dissapation from the power-supply.
> No, I haven't done this, but I realized this after fiddling around with
> supplies and verified the ideas with a friend of mine designing supplies all
> the time. He also pointed out that many switch supplies tend to run better
> when the supply voltage is on the low side of things.
> So, there is things to do if you really want to control your environment.
> Now, how many labs log their mains voltage and correlate frequency
> deviations to that?
> Cheers,
> Magnus
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Eric Garner

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