Craig Sawyers

Happy birthday Jacob - good to see you back.

Happy birthday!

Oh bloody hell. Mother and daughter in a few days. RIP Debbie Reynolds. I went through an on-line photo album of those that we have lost in 2016, because of the sheer number who have gone you lose track - and it is a roll-call of the great and the good. Quite a depressing year in that regard.

Regarding battery, our daughter had precisely the same problem in her Ford Fiesta. Fine for a week or two, then totally dead until started on cables. Fine for a week or two - repeat as necessary. Turned out to be the battery. Apparently modern batteries can do this, caused by an intermittent short (or open) circuit inside. The dead one was the original battery, fitted when the car was new.

Jeeze - Carrie Fisher. Same age as me - and oh boy is that a sobering thought. RIP Carrie

My son just now said "What the fuck - George Michael just died aged 53. This damned year just decided to pack a few more in". Suspected heart failure. RIP George Michael

It just seems to keep on coming this year. RIP Ric Parfitt, again far too young at 68.

Happy birthday! You're in illustrious company - 25th December was Isaac Newton's birthday too

But, but - they are upside down! The bases will come out with the wrong phase

Aged 66. Too damned young. RIP Frank Murray.

Have a great one!

I completely agree that a chip, or hybrid solution would be best. In fact the concept of using a laser trimmed metal foil R2R network, where the foil network was layed down by photolith ought to be superb, hermetically sealed and dry nitrogen filled. Cheap it would not be...

Unless my use of Google is in meltdown, the PCM1704 is obsolete. Is this wrong? For discrete R2R, assuming that matching is done correctly, the whole resistor chain needs to be kept isothermal. There is little evidence that this is the case, but could be arranged to be the case.

There is absolutely nothing to prevent laser trimming, or selection to any tolerance you like provided that temperature and voltage coefficients are low enough. 0.01% tolerance is 10ppm or 1 ohm error in 10k. Temperature coefficient is around 3ppm/C so to match tolerances at a 10ppm level the measurement temperature has to be constant to 1C or thereabout. Foil resistors are superb, but are punishingly expensive. And any SM component has to be soldered using precisely the soldering profile in the datasheet for the parts - because component stress and thermal shock will shift the resistance too. However you look at it, it isn't trivial, is all I am saying.

It is all down to how the tolerance is statistically distributed. You can get two different scenarios. (i) All resistors in any production batch are clustered in value or (ii) resistance values in a batch are randomly distributed. This could only be established by measurement. However, if (i) holds then the batch will have a constant error and if (ii) holds then the values will be normally distributed. Typically the nominal tolerance will be 3-sigma, which would mean that less than 0.27% of resistors were out of tolerance. So the majority of resistors will be significantly better than nominal tolerance. The difficulty in getting accuracy is that you need to test a large number of resistors. If 100 resistors are tested the nominal error is 10%. To get 1% confidence you would need to test 10,000 resistors - er, no thanks at that level!

You always crack me up

I see your fat German and up you a skinny geriatric Brit - the impeccable Ginger Baker, superbly recorded in 2005 in an 8 minute solo:

Now up to at least 31 dead RIP, with many survivors with up to 90% burns. Agree with Dusty - the youtube coverage is horrendous.

No - I've never been an academic. I did my first degree in electronics and then a doctorate in laser physics. But my career was first in professional consultancies and then in industry (including 7 years at Oxford Instruments - which is why we live here). And for the last 20 years as a self employed technology and business/management consultant. In fairness in my mid 20's I applied for a "new blood" lectureship at St Andrews University in Scotland. That was the strangest interview I have ever had, and decided academia was not a good fit for me (from my perspective didn't pay nearly enough, no prospects etc), and we parted company. Plus the clowns approached the CEO of the tiny 20 person company I worked for, for a reference without asking me first. So had I not left anyway to join PA Technology my career there would have been blighted. I did have a five year foray back into an academic environment in recent years, but as a self-employed large project manager. What particularly surprised and dismayed me is what a political and backbiting environment it is, particularly at a senior professorial level. Everyone watches their backs pretty much continuously, jockeying for position. I'd have hated that aspect of university life.

Erdogan and Putin have issued similar statements to the effect that the murder of the Russian ambassador is "nothing but a provocation". So, although essentially dictators in their own countries, they are allies and are talking and agreeing a form of words. So there will be no Russian reaction.

And that is absolutely correct. After 20 years I'd forgotten how a darned dilution fridge worked. I said " The hotter atoms of helium 4 diffuse upwards into the helium 3 (no viscosity, remember), and a truly impressive pump attached to the mixing chamber sucks these hotter helium 4 atoms out. That shifts the equilibrium point, and the next hottest helium 4 diffuses upwards, etc etc " Which is the wrong way round. Of course, the He3 sets up a concentration in the He4, and you pump the on the He4 side to reduce the equilibrium 6% of He3. The He3 moves very easily through the He4 because of its superfluidity. The downward evaporation of more thermally excited He3 into He4 is the cooling mechanism. The guy in the video describes it very well - thanks for posting it.

Have you got any test gear - DVM (preferably more than one), oscilloscope etc? The T2 is such a complex beast I wouldn't like to trouble shoot without test gear. Offhand it could be anything from a fault in the left hand power umbilical to breakdown in a passive component to an active component going noisy, or a bad connection to a tube pin (I have that with one of my input tubes; wobbling it stops the problem. Note to self: must fix more permanently), or something else entirely.

RIP the victims of the Berlin truck attack on shoppers. 9 confirmed dead so far. RIP The Russian ambassador to Turkey, gunned down by an off duty police officer. WTF just happened in the last few hours?

Makes you feel like the front of your face is about to explode off your head. Get better soon Dusty!

She certainly lived a full life in the fast lane! Quite a character. RIP Zsa Zsa.