Where can you find the most accurate digital-to-analogue converter (DAC) in the world, and the fastest oscilloscope on the planet?
Middlesex is the answer, at the National Physical Laboratory - home of UK precision measurement, and keeper of its physical standards.
There are only two other metrology labs in its class: the US National Institute of Standards and Technology (NIST), and Physikalisch-Technische Bundesanstalt (PTB) in Germany, and all three have a close working relationship.
When Electronics Weekly visited NPL, scientists were putting the finishing touches to the DAC.
Built to calibrate the most accurate ac voltmeters, it takes advantage of Josephson junctions - quantum devices used to define the Volt internationally.
4,096 of the junctions have been formed on one chip - made in Germany - and immersed in liquid helium they will be switched in and out to construct the calibrated waveform.
The oscilloscope, or what is effectively an oscilloscope, has been built to assess commercial sampling scopes and the signal generators that are used to calibrate them.
"The big thing now is full waveform calibration, it used to be rise time only," Dr Matthew Harper told Electronics Weekly. "Sampling oscilloscopes run up to 100GHz at the top end. The one we made here is 6-800GHz."
It fills a table tennis table-sized anti-vibration bench.
The generator is centred around a femtosecond laser producing 150fs pulses of 850nm light at 80MHz.
Sampling in the scope section is through directing a 1ps pulse from the same laser at a gap between two conductors on a GaAs substrate.
Both NIST and PTB have similar set-ups.
"NIST's system only has a commercial photodetector, not a gap in GaAs, and PTB's is more or less a copy of ours. The advantage at NPL is high frequency resolution," said Harper.
Both the DAC and the sampling scope are examples of NPL mission to support UK industry.
It is essentially a government-funded research university, tasked with doing what ever it takes to provide ways to link industries measurement requirements to recognised international standards.
Like a university, it licences technology and spins off companies.
Its measurement activities are backed up by training services, as well as more general help for industry.
The move to Pb-free solder, for example, has meant far greater uses of high-tin solders, and with them the threat of tin whiskers - needle-like crystals that grow out of tin coatings, and even bulk tin, sometimes shorting out signal lines in the process.
"We are studying how whiskers move - in electric fields for example, how they touch, and what they do when they touch," said Dr Chris Hunt.
The team is also looking at the properties of solder under vibration, extracting parameters that it hopes will lead to mathematical models.
For manufacturers attempting to develop anti-whisker coatings and treatments, NPL has developed a surface that whiskers in a predictable way.
Samples with the surface in its pre-whiskers state can simply be posted to coating companies.
The same department is investigating forests of carbon nanotubes as a thermally conductive interface to extract heat from semiconductor chips.
To support the development of organic electronics, NPL is working on nanoscale probing techniques.
One frequently feature of organic electronics, solar cells for example, is a distributed p-n junction formed as a thick layer of mixed n and p-type semiconductor whose concentrations vary through the thickness.
NPL is using scanning probe microscope to measure energy levels on the surface, and secondary ion mass spectrometry to measure composition at various depths.
This kind of spectrometry involves hitting the surface with an ion, then analysing the secondary ions that are blasted out of the surface.
Heavy ions are better at knocking off surface atoms in a controllable way, so the lab is using C60 Bucky balls and looking to use clusters of argon atoms.
200nm X-Y resolution is achievable, plus 5nm depth resolution as the ions etch down through the structure.
A particular problem for organic electronics on plastic substrates is keeping out water which will cause rapid deterioration if it gets inside.
The answer may be barrier layers of various kinds.
But how is one barrier technology to be compared with others when only tiny amounts of water diffuse through?
"They don't know what they need, and they don't know how to measure it," said Dr Craig Murphy. "To date, there is not a traceable method to measure water permeation through barrier layers."
So the lab has started a project, working with HP Labs in Bristol.
"We can measure parts per billion of water in gasses for inorganic semiconductors, and think we can modify that for organic permeation," said Murphy.
Moving from the very small to the very large, NPL is also playing a part in maintaining waveform quality on the UK power grid.
Once fed by a few huge generators, it now has hundreds of wind turbines and solar installations attached.
"In the last five years, we have been working on analysing the harmonic content of fluctuating harmonics," said researcher Paul Clarkson.
Supporting the compliance testing industry, the lab investigated commercial power quality meters.
"When we started, a number of analysers worked fine for steady-state, then did very badly with fluctuating harmonics," said Clarkson. "Most analysis could not cope with a fluctuating waveform."
One of the reasons turned out to be the use of fast Fourier transforms, he said: "FFT blurs. We needed another way to decompose waveforms."
By turning to wavelet transforms and other signal processing techniques, NPL now has the ability to analyse arbitrary power waveforms.
It also develops power grid interface components that make analysis possible.
"We were involved in an EU joint project to develop transformers, Rogowski coils and dividers," said Clarkson.
The lab is attempting to reduce the output noise of existing dividers, and has produced a six channel digitiser with noise down at 10ppm on voltage measurements, and is working on wireless sensors.
It will soon be taking its techniques into the field, looking at high voltage grids for renewable and other generation.
For antennas, NPL has a world-class anechoic chamber with -40dB reflectivity from 400MHz to 110GHz where it calibrates probes, measures antennas, calibrates standard antennas (where it is arguably the world leader), and does one-off tests.
Sensing techniques include using electro-optic converters at the antenna to allow signals to be lead out of the chamber on fibre-optic cable.
By eliminating common-mode currents "there is a 20dB difference using RF to optical transducers," said Dr Tian Loh.
Imaging using THz radiation is another NPL speciality - so much so that one of its licensing activities is selling a copy of its 100GHz to 4THz time domain spectrometer.
Dr Richard Dudley dispelled one of the myths that was popular a few years ago: Scanning people with THz radiation at airports would be a useful security technique.
"Body scanning with microwaves between 50 and 100GHz is best," he said. "THz is better for passive sensing."
Passive scanning, which works by viewing the 6THz radiation emitted naturally by warm objects, may be of use in diagnosing skin diseases.
The lab has a wide range of THz techniques at its disposal, including firing a femtosecond laser into GaAs to generate precisely-timed pulses.
"Quantum cascade lasers can make THz radiation directly," added Dudley.
It also works on imaging and detection techniques including thermal bolometers and electro-optic sampling.
As well as scanning skin, THz radiation can be used for non-destructive testing of coatings, like those on pills, where time-domain spectrometry allows the depth of this analysis to be controlled.
"NPL is supporting UK THz companies," said Dudley. "Three or four of them are the best in the world."
How accurate would you like your Amp sir?
Standards people love quantum effects because, as far as anyone can tell, some of them are invariant.
And they especially love atomic clocks because these rely on quantum effects and can already be made to produce frequency with extraordinary accuracy and stability.
So the mission is to relate everything to quantum standards, preferably including frequency.
The Volt has been done.
At NPL, precision voltage is made using an ac Josephson junction - two superconductors separated by a narrow gap exposed to electromagnetic radiation.
The potential between them takes on discrete values described by the Josephson constant which is 483.597,9THz/V.
Using these, voltage can be generated to within 0.000,000,01V/V.
As yet, the Amp has not succumbed to the frequency treatment, but it may not be long.
The idea is to develop an electron pump that will dispense single electrons in time with a clock.
Two of the possibilities are: persuading them to ride waves in an electric field, or to ride microwaves in single file along a nanowire.