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

Magnus Danielson magnus at rubidium.dyndns.org
Fri Oct 7 14:04:19 EDT 2011

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?


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