#Jonesy-Makes #video of restoring a Victorian-era ruling engine for #machining rulers on brass or possibly steel. #manufacturing #history #metrology
on 02026-08-25Says that type K #thermocouples (#sensors #hardware for use with #electronics), the common kind of thermocouples, work from a couple degrees above absolute zero up to 1260°C, with ±2.2°C or ±0.75% error, whichever is greater. Gives a data table for their output voltages, running from -6.458mV at -270° to 0 at 0° (by convention) to 29.129mV at 700° to 54.886mV at 1372°, which presumably is where they melt, which is about 40μV/°C, with predictable variations from linearity on the order of 3%. #metrology
on 02026-08-19#Witchcraft-and-Alchemy #video about #bootstrapping thinner aluminum #foil material for a ribbon microphone, noting that the usual stuff is about 10μm, testing with a micrometer, while ribbon-microphone #sensors are ideally 1.5–3μm. He reduces the thickness of household foil by etching the foil with NaOH #materials, 4g dissolved in 200mℓ of water (½ molar, he says), which evidently thins the foil fairly evenly. He glued foil to some plastic roundrects to hold it in place during the process. There’s a point where the foil becomes a very fine mesh, some time before being ripped apart by the hydrogen bubbles after about half an hour. He did a 4-liter test to try to hold temperature more constant. I suspect you could get smoother dissolution with the proper regime of #electrolysis, reducing asperities, but he didn’t try that. For thickness measurement, he did the same repeated-folding-in-half thing that I did, but with a micrometer instead of calipers or a ruler to measure the result. He says some of the foil had “the structural integrity of a wet paper towel,” making the process more difficult. The thinnest acts like gold leaf, sticking to his tweezers. The data shows a linear decline in thickness from 10μm at 5 minutes to 0 at 40 minutes, with a 35-minute sample being 2.2μm thick.
So he made some more samples; he tried to etch them for 32 minutes (before a citric-acid stop bath and water rinse) but they fell apart at 25 minutes.
In order to compensate for unknown temperature and agitation variations, he decided to measure the foil’s resistance during the etch process with a constant current. For #metrology, he amplifies the voltage drop across the foil with a differential-to-single-ended converter based on a LM833 dual op-amp #electronics, with an LM317 set up as a 100mA constant-current source, and a couple of relays set up to reverse the current direction through the foil to eliminate any offset errors, including from any unintended galvanic cells. Also he used an angle grinder to cut some blank PCB into a four-wire Kelvin probe so he’s only measuring the resistance of the foil itself, not the resistance of the copper leading down to the foil. The copper is painted black, presumably to protect it from the NaOH. And he’s using something like a Black Pill to record the data.
The 10μm foil is about 70mΩ (=7mV) at first, decreasing roughly linearly with less than 10nm of noise, enabling thinning the foil down to under a micron before it broke.
If you were doing this electrolytically, you could presumably stop the etch directly from the microcontroller with a transistor or even directly from a GPIO.
Then he repeats the etching with a large sample in the same bath with the thin foil strip whose resistance he’s measuring. And then he corrugates his foil ribbon microphone ribbons before etching them to thin them, which answers a burning question I had, and then he recorded the video with the resulting microphone!
An amusing editing trick is that he recorded himself erasing a whiteboard drawing line by line with his finger, then played the video backwards with a voiceover to make it look like he’s drawing with his finger.
on 02026-08-11#ebook containing Anders Celsius’s paper from 01742 proposing to put water’s freezing point at 100° and the boiling point at 0° (backwards from today’s convention) so that thermometers in Paris and Uppsala give the same reading. #history #metrology
on 02026-08-04another #metrology #paper #PDF about the #Tellurometer, explaining how it works using signals of 10 MHz, 9.99MHz, 9.9MHz, and 9MHz, modulated onto a 3GHz carrier wave. It explains the whole algorithm.
on 02026-07-27#ebook of Rolt’s #metrology book Gauges and Fine Measurements, recommended by Gelbart, with tables where people measured the sizes of pieces of metal over 100 years.
on 02026-07-27“On top of these signals an RTK receiver takes in an RTCM correction stream and then calculates your location with 1cm accuracy in real time”!!! #GPS #metrology
on 02026-05-26apparently a 77-minute #Gelbart #lecture #video: “Summary of Sensors, Limits of Accuracy, and Unusual Sensors, by fizzym” about how digital calipers were originally inductive, switched to capacitive (bad in a machine shop, and also using incremental encoders), and some have now switched back to inductive. Also talks about #Tellurometers, and material stability with time (he says steel and regular invar shift by 1 or 2 ppm in a year) and recommending Rolt’s #metrology book Gauges and Fine Measurements. And how laser microphones bounced off windows work. And how the Russians bugged the US embassy. And nonlinear junction detectors for finding bugs, using a second-harmonic narrowband filter to detect parts per billion of nonlinearity in the reflected signal. And how you detect eyes looking at you by scanning the scene around you with a 10mW 830nm laser and looking for retroreflections a million times weaker (10 nanowatts, a “huge signal” in #optics).
on 02026-05-17VSMOW used to be used in the definition of the kelvin. #metrology #history
on 02026-04-27#PDF of #Epson real-time clock #electronics module RX8804CE #datasheet. 3.4ppm and 5.0ppm precision grades, with a “digitally temperature compensated crystal oscillator” (#DTCXO). #metrology #hardware. I²C. They’re like US$8 on Digi-Key.
on 02026-04-16new LCR #metrology #hardware with Kelvin clips for measuring parasitics on components for US$48: “FNIRSI® LCR-ST2 100K LCR ESR Meter 2-in-1 Digital Tweezers Bridge” #electronics
on 02026-04-13#video listing books on #machining, mostly high #precision stuff, including Precision Hole Location from the Moore Tool Company, as well as their other books; ASME’s Handbook of Industrial Metrology (#metrology); Frank D. Graham’s Audels Machinists and Tool Makers Handy Book [sic sic sic!] from 01941; Franklin D. Jones’s “Old-Fashioned Toolmaking”; Henry Ford Trade School’s Shop Theory from 01934; The Starrett Book for Student Machinists; Goodrich and Stanley’s 01923 Tool and Gage Work; Miller and Russel’s Toolmakers Handy Book; Calvin & Stanley’s Gear Cutting Practice, reprinted by Lindsay Publications; Henriksen’s Jig and Fixture Design Manual; Moore, Davis, & Coplan’s Building Scientific Apparatus; Shigley’s Mechanical Engineering Design (by Budynas and Nisbett); US Steel’s The Making, Shaping, and Treating of Steel; Frank Curtis’s High Frequency Induction Heating; the ASM’s Metallurgy for the Non-Metallurgist, edited by Reardon; Dossett and Boyer’s Practical Heat Treating; the ASM’s Heat Treater’s Guide; and Edward F. Connelly’s Machine Tool Reconditioning.
on 02025-12-09#Marco-Reps #metrology #precision #toread #electronics video on an 0.1-ppb-resolution Guildline Model 9930 direct-current resistance comparator from the 01960s, specifically November 24, 01969, according to the light-beam galvanometer inspection card. At 2'21" there’s a very alarming CERN slide, “The availability of magnetic materials has been declining over the years.
As of 2024 the assembly can be produced, but there is no replacement yet for the obsolete radial shield material (Nanophylm).” #collapse
The key here is that numbers of transformer windings “don’t have temperature coefficients or long-term drifts”, so they’re accurately ratiometric in a way that’s stable until and unless you bend the wire.
Guildline gave him the service manual, SM9930-H-00.
Internally it has an ovenized Weston cell in a test tube, which is used with a second light-beam galvanometer for feedback control of a 50mA current through a critical precision resistor, which is wire wound around a several-kilogram cylinder of brass; the soldered connections to the manganin (?) wires are stuck into a hole deep inside the brass to reduce possible thermal EMFs.
The nanovolt amplifier is a pair of antiparallel photocells powered by a lightbulb whose light is deflected by a third mirror galvanometer, this one 3.6kΩ.
on 02025-09-28“Self-Calibration: Reversal, Redundancy, Error Separation, and “Absolute Testing”” abstract on #precision reversal methods etc. “Over the years many techniques have been developed for accurate measurement of part features without reference to an externally calibrated artefact. This #paper presents a partial survey of such methods for dimensional #metrology, their ranges of application, and their limits. Finally, the paper attempts to distil the common features of the various methods in the hope that this may provide the basis, or inspiration, for development of ‘new’ methods. (...) The methods described in this paper seem to be reasonably well known to the staff at the national measurement institutions and universities but are generally less familiar on the factory floor.”
on 02025-09-02“What’s all this Teflon stuff, anyhow?” Bob #Pease’s war story from 01991 about picoamp bias current testing of #opamps back in the 70s. #electronics #history #precision #metrology
on 02025-09-02#metrology #paper #toread about taut wire measurement of straightness
on 02025-08-26#video #toread #metrology #precision “Measuring the flatness of a surface with a laser and a webcam to microns over large surfaces” by removing the lens from the webcam.
on 02025-08-12#Marco-Reps #video #toread on #precision #metrology power supplies #electronics #hardware
on 02024-11-12#Marco-Reps #video on #precision #metrology for evaluating his open-source ADR1000 voltage standards. He ends up #3D-printing #flexures out of ASA for its low creep to preload copper-on-copper rotary-switch contacts to try to keep oxidation down. His stator contacts are bare copper on an aluminum PCB. #electronics #hardware
on 02024-11-12#video demo of picoamp #metrology: at 10V they measured 98.8GΩ on their nominally 100GΩ resistor, but 99.1GΩ with a guard plane turned on. This suggests 300pA leakage through the Teflon standoffs, representing a 33TΩ resistance.
on 02024-11-11#video #toread about #precision time #metrology with TCXOs, OCXOs, GPSDOs, and a rubidium atomic clock, using #ngscopeclient to visualize the phase shifts, by #azonenberg
on 02024-09-231002 km quantum key distribution record in 02023 using ultra-low-loss fiber and ultra-low-noise superconducting quantum detectors. I guess that means erbium-doped-fiber amplifiers don’t preserve quantum superpositions of polarization. #quantum-cryptography #security #metrology
on 02024-09-14CERN’s 8.5-digit DIY open-source voltmeter, now in the Open Hardware Repository. #electronics #hardware #precision #metrology
on 02024-05-21Hantek LCR meter #hardware #metrology #video
on 02024-04-05reinventing calipers with tiny sculpted brass hands and human foot and a micrometer thread with a half-nut, a quick-release micrometer #video #machining #metrology
on 02024-04-03Doug Hoyte’s slide deck about how to measure small-value capacitances by loading a JFET Hartley resonator. #electronics #metrology #hardware
on 02023-12-29notes on the #history of #metrology, specifically with regard to thermometers: Santorio perhaps invented the thermometer because he liked to invent measuring instruments like the pulsilogium and hygrometers. #thermodynamics
on 02022-11-06#avalanche transistor pulse generator #hardware for speed-of-light #metrology
on 02021-11-11#caliper #hardware #metrology #protocols with oscilloscope photos.
on 02021-11-06#hardware by thamart63@gmail: “Data are transmitted in a continuous data stream when the #caliper is switched on; Each complete dataset consists of a series of 24 bits; The caliper uses a 1.5V logic level, which means that we need to amplify the signal to make it compatible with #Arduino’s 5V logic; Data are transmitted by means of a data line and a clock line; The logic level of the data line needs to be read on the transition of the clock line from HIGH to LOW; Between each series of 24 bits there is a longer period during which CLK remains HIGH; The first bit is always high and does not have any proper meaning; The next bits codify the value of the caliper reading, starting with the least significant bit (LSB); In mm–mode the resulting value corresponds to the caliper measurement multiplied by 100. E.g. 1,5mm will produce the readout 150; Bit 21 is the sign bit: if bit 21 is HIGH, the value is negative.” He used a divider three 10kΩ resistors across the Arduino’s 5V supply to run the 1.5V caliper between 1.66V and 3.33V above Arduino’s ground, eliminating the need for level shifters. #metrology #protocols
on 02021-11-06#paper on the state of weighing #metrology in 02018. #CC PD but not open access
on 02021-02-17#metrology #paper from 01947 about a quartz ±0.1ppm weighing scale for submilligram quantities
on 02021-02-17#PDF #metrology #paper on weighing things: “The Uncertainty of Weighing Data Obtained with Electronic Analytical Balances”
on 02021-02-17#PDF #metrology #paper on #hardware for weighing things or otherwise measuring things with strain gauges
on 02021-02-17apparently some #caliper #hardware, even US$5 plastic calipers, has SPI data streams in it that tell you what it's measuring. #metrology
on 02020-11-18Darius Bacon wrote a Python implementation of the units(1) definitions file format #metrology
on 02020-11-12Hugh Hunt, Keeper of the Clock, explains how the Trinity College tower clock works and reaches 0.1 ppm precision, how gravity escapements work, and how John Harrison’s gridiron pendulum corrects for temperature by causing its #TCE to vanish through differential cancellation. cc-by-nd. #metrology #horology #hardware
on 02018-11-21atomic clock #metrology #hardware in a US$1000 35-gram chip
on 02017-06-07A chapter from Livio Catullo Stecchini’s #ebook “A History of Measures”, based on his doctoral dissertation (sometime in the mid-20th-century?), about ancient #metrology and the #archaeology of Mesopotamia. The images are lost, but the chapter claims that the Sumerian cubit was close to twice 249.7 mm and was divided into 30 “fingers” or, I suppose, šusi, and that earlier Sumerologists who believed in a 16-finger #Sumerian “foot” were misinterpreting a single statue from a temple dedicated by Sumerian regent Gudea. Also he derives pre-metric European units of measure from Mesopotamian and Babylonian-Egyptian units.
on 02016-09-11The Encyclopedia Britannica 1911 article on weights and measures; its section II, “historical”, seems to be the source for Adrian Mariano’s Assyrian cubit and other measures, including the susi. #metrology
on 02016-09-11#ebook archives of the NIST’s (previously NBS’s or just Bureau of Standards’s) Journal of Research, largely about #metrology. 6949 etexts in all, from 1928 to 2010.
on 02015-09-28