[time-nuts] Anyone (ideally in the UK) got a spare rotary knob for the 5370B TI counter?

Tom Miller tmiller11147 at verizon.net
Sat Dec 31 14:57:04 EST 2016

----- Original Message ----- 
From: "Dr. David Kirkby (Kirkby Microwave Ltd)" 
<drkirkby at kirkbymicrowave.co.uk>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
Sent: Saturday, December 31, 2016 11:01 AM
Subject: Re: [time-nuts] Anyone (ideally in the UK) got a spare rotary knob 
for the 5370B TI counter?

> On 31 December 2016 at 13:03, EB4APL <eb4apl at gmail.com> wrote:
>> Hi,
>> I'm not totally sure about the limits, but I have read several times that
>> in the UK the nominal supply voltage is 230 V +10%/−6% to accommodate the
>> fact that most supplies are in fact still 240 V. The context was that a 
>> lot
>> of test equipment failed when operated at around 250 V and many input
>> capacitors (particularly the ones inside a know brand IEC socket - 
>> filter)
>> caught fire.
>> Wikipedia says that several areas in UK still have 250 V because this
>> value is withing the current limits.
>> I think that the governing document is British Standard BS 7697: Nominal
>> voltages for low voltage public electricity supply systems —
>> (Implementation of HD 472 S1).
>> Regards,
>> Ignacio, EB4APL
> Hi,
> I have just been on to the phone of a friend of mine who spent much of his
> like working in the electricity generating industry. Working at both
> Darlington (coal) and Bradwell (nuclear) power stations in the UK. Among
> many other things he said
> * He did not know the current specifications limits for certain, but he
> said easy to check. (What you say - 230 -6%/+10% does seem to be quoted in
> many places, but I guess I should check it out.)
> * Supply voltage is likely to be highest about at 2-3 am in Summer
> * Supply voltage is likely to be lowest on a cold Winter's afternoon.
> * Voltages in use around the county include at the least 11, 22, 33, 66,
> 132, 275 and 400 kV.
> * There's not much standardization of generator voltage - Bradwell nuclear
> power station was 11.1 kV.
> * There are taps on the 275 kV transformers to keep the 132 kV close to 
> 132
> kV
> * There are 6 taps on the 11 kV transformers feeding my house to adjust 
> the
> voltage. Those can only be adjusted with the 11 kV off - they can't be 
> done
> with it online. Essentially this means to change the taps, an area would
> need to be powered off.
> * If voltage is out of spec, it should be possible to get something done
> about it.
> * The electricity board can install monitor equipment.
> * Since I am right by the 11 kV transformer, and other places further 
> away,
> dropping the voltage at my place might put other places too low.
> I think short-term I will put the auto transformer in line. I will monitor
> the mains, and report it in the summer, when I'm told it is likely to go
> higher.
> It hit 250.04 V in the last hour or so, but I have not seen the magic
> figure of 253 V.
> I'll get my 3457A calibrated by Keysight, then look to measure this and if
> appropriate make a formal request to have the voltage checked, and
> hopefully the problems would occur during the time it was monitored.
> Dave
> _______________________________________________

There are some devices that benefit from the higher voltage. Motors usually 
run cooler and last longer due to the lower I2R losses.
Maybe just use a buck transformer in your lab for the (older) test 

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