标签: meter

In the recent months, I've been working with Max Maxfield on the analog meter problems and design challenges pertaining to his Inamorata Prognostication Engine , Ultra-Macho Prognostication Engine , and Vetinari Clock projects.   As you may have read in his columns, Max and I have been in almost constant daily communication, by either email or phone. During our conversations, we have had a blast talking about various aspects of these meters, such as the fact that some meter movements deflect 100 degrees, while others deflect only 90 degrees. This point took Max by surprise after he incorrectly had his graphics guru Denis create the Vetinari Clock's "Hours" faceplate assuming a 100-degree movement when the meter was designed to operate over a 90-degree swing. Fortunately, we managed to make the meter's movement match the faceplate.   As part of this, I've been telling Max about some of the meters we make and repair here at Instrument Meter Specialties (IMS). Take the small Triplett .5E edgewise meter that goes in an older aircraft. These meters read "GOOD" in a green area in the middle, with red areas on either side. They would cost hundreds of dollars when the aircraft were created, but they now sell for thousands. The thing is that the planes were certified with these meters, which are FAA approved, so no substitutions are allowed.   Another job I was telling Max about involved an upgrade on some meters that go in a nuclear power plant. These meters were stockpiled when the plant was commissioned. As they started to reach their end of life, replacements were brought online, but they were failing their 0.6% calibration tolerance, and we had to work our magic on them. (I'll describe how we achieved the required accuracy in my next column.)   We do a lot of work on the older Hickok tube tester meters. We've also experienced an analog meter resurgence in the recording industry. In fact, we make several different meters for old audio compressors from companies/products such as Fairchild, Gates Sta-Level, and Federal TV. Being a custom meter shop with the ability to make complicated artworks means we can satisfy just about any meter-related requirement, so long as the parts are available.   Based on his projects, the topic Max and I have spent the most time discussing by far has been the creation of artworks (faceplates) for the meters. A lot of work goes into analog meter movements and artworks. This tends to be why new meters can cost a lot of money. The parts can be as small as those in Swiss watches, and it takes skilled hands to make a really good meter movement. This is why we always have our trusty microscope at the ready. Even meters with a "linear scale" only have movements rated to be within 1-2% of the full scale input at any given point of the scale. The trick to this "linearity" is accurately placing the coil within the magnetic field and making sure that nothing affects the spring constant, like friction caused by two spring turns rubbing against each other or deformations such as creases in the spring. That said, as important as the meter's quality is to accuracy, equally important -- especially for high accuracy -- is the meter's artwork.   The highest-accuracy analog meters actually have the divisions on their artworks printed to address nonlinearities in the meter movement's, um... movement across the dial (faceplate). This is interesting, because it allows lower-quality meter movements to compete with higher-quality ones, especially if the nonlinearity is somewhat repeatable during production. That said, making nonlinear artworks is challenging. It can require a great deal of time, knowledge of interpolation that few have, and/or the use of custom software. All of this greatly complicates the creation of meter artworks, and this was especially true earlier in the history of analog meters.   The process of printing of analog meter artworks has undergone several changes over the last century. Originally, everyone was using the same methods -- offset printing press and hand-drawn. Hand-operated offset presses were typically used for printing more than a single dial, while hand-drawn dials were created for prototypes and single-piece custom orders. The offset presses used were a bit different from letter presses, as they were meant to print on to metal and not paper.   The Grauel model R-1 printing press as used by many meter shops and manufacturers. The ratchet mechanism made a distinctive hollow clanking sound like a sad bell.   Aside from that, the process was similar. There are five main components on an offset press: the ink disk, ink rollers, vacuum table for the positive plate, rolling printing pad, and printing table where the dial blank goes. The ink was taken from the inking disk to the positive plate by the ink rollers. Next, the rolling printing pad took the ink off the positive plate and rolled it on to the dial plate. Single-color artworks were typically the norm, because cost was prohibitive for more colors. Requesting another color meant a great deal of headache for the meter manufacturer, since each added color required a separate artwork.   Before printing could begin, a hand-drawn artwork would be created using India ink on a substrate that allowed the easy and accurate removal of the dried ink. Fonts could be penned using a KE Leroy set or large Letraset sheets.   I have never actually seen one of these Leroy sets in operation, but it was fun having my grandfather show me how they worked.   All this work would be done at about 4X scale to increase accuracy. The artworks were then sent out to be photo-reduced to actual size, and a matching film transparency would be created. From that point, the transparencies would be used to burn an offset press plate.   Here's an example of a zinc offset press plate and the corresponding faceplate. I have actually seen these used.   The transparencies were retained in case a new plate was ever needed. This occurred quite often after the material used to form the plates changed from zinc to a plastic, which suffered from warping and cracking.   A zinc offset press plate and its plastic equivalent. As you can see, the plastic positive plates did not fare well over time.   Once the plates were received back in house, the actual printing could begin. During the printing of each artwork, faceplates were often scrapped due to alignment issues. Remember that each color required its own artwork. Due to problems with alignment, a three-color artwork might require 20-30 attempts to obtain five "good enough" faceplates. Observe the photograph of the Hickok faceplate below, and note how the red line is not quite in the right place.   Known for their vacuum tube testers, most Hickok artworks had at least two colors. It is impressive how many of them were actually better than this one.   The tolerances for alignment were very tight -- within about 0.015" for single-color artworks and 0.005" from the first layer for each additional color. Making things more difficult, the faceplate's screw/mounting holes were the registration marks, and they were only about one inch apart. Much of the success came down to the skill of the individual press operator to align the registration marks of each plate in relation to the dial. This is not as easy as it sounds, and there was a long tradition of rude phrases moving ballads during operation. As they do to this day, customers would call in the hope of expediting their orders. This pressure didn't help the printers who were waiting for the ink to dry in their industrial ovens. Each printing would take a day to dry before the next could be performed.   Not surprisingly, there was an extra cost added for each color on the faceplate. Additionally, for each color there would be an increase to the cost of each finished meter due to the difficult task of aligning the artworks with one another. Back in the 1960s to 1980s, for example, artworks would have started at $75 for one color with $25 for each additional color. Converting 1960s dollars to today's value, that comes to about $600 and $200, respectively. Jewell Instruments currently charges $150 for a one-color custom scale. Each additional color costs $75. It would seem the company still uses offset printing, but it probably works with computer-generated transparencies these days. Compare that to $0 to $75 for artworks generated here at Instrument Meter Specialties using a direct-to-dial process and our own PHP script. (Again, I'll describe this in more detail in my next column.) Back then, however, these services were seen as a loss leader. The goal of the manufacturer was to minimize loss and hopefully generate a big order.   Perhaps those big orders were more of a common thing back in the heyday of analog panel meters. I found the following picture of an Apollo control room at NASA with more than 100 analog panel meters in view.   I counted more than 100 analog meters that I could identify in this picture (which is presented here with the permission of Shaun O'Boyle), but there may be quite a few more.   Installations involving such quantities ensured that any loss associated with creating the faceplates was recovered in the cost of each meter. That said, low-quantity custom orders required an entirely different printing method. Faceplate blanks with division markings would be stocked, and numbers would added by hand using Letraset dry transfer characters.   I have used Letraset pages before. I was trained to use a pencil and to push hard, so I could see where I had rubbed and perhaps take advantage of the graphite as a lubricant. I remember using these sheets with mixed success.   Even though these faceplates were created by hand, new artworks were still charged at $75 for single colors. This covered the time required for a certain skilled someone to sit down and -- using dry transfer sheets -- carefully place each character on the faceplate with the proper spacing. Many times, this was good enough for customers who wanted multiple colors, especially since colored regions could be added on to the division set with a permanent marker or using some other DIY method. Prior to the 1960s and rub-on lettering, a KE Leroy pen set could be used to ink a custom dial (an image of this was shown earlier). This was more difficult than the rub-on lettering, and it was abandoned after rub-on letters became available.   From about 1995 to 2005, the meter industry experimented with, and tried implementing, various printing techniques. Many still retained the offset press method, if only for current artworks. One popular method was lovingly referred to as "using paper dials." This meant that the faceplate image was printed on a waterproof surface that would absorb the ink, and then this "paper" would be adhered to the blank dial. This technique employed mid-level and high-range consumer inkjet printers for color matching purposes. This became more popular in the late 1990s with the availability of inkjet bumper-sticker sheets. Even though this approach saved much time over the offset press method, it was still a fairly time-consuming process. Laser etching was attempted in the late 1990s, but the low number of custom built machines, the high cost of those machines, and the lack of duo-toned or multi-toned substrate that would work in different brands of meters meant that adoption was low.   Eventually, the "Holy Grail" of faceplate printing was found in small format, inkjet, flatbed presses. But this still leaves the task of creating the artwork in the first place. In my next column, I will describe an innovative technique we developed here at Instrument Meter Specialties that made Max say, "Wow, I am very impressed." Until then, I welcome any comments and questions.   Jason Dueck Product Designer Instrument Meter Specialties

Recently, quite a few people have been inquiring about the state of play with regard to my Vetinari Clock project, so I thought this would be a good time to bring everyone up to date.   I did run into a slight problem when I discovered that one of my prize analogue meters intended for use in my Ultra-Macho Prognostication Engine had shrugged off this mortal coil. For a time, I feared that I was going to have to repurpose the main meter from the collection I'd earmarked for the Vetinari Clock. Happily, my chum Rick Curl and one of his colleagues resurrected the meter in question, thereby saving the day.   Another aspect to all of this is the fact that I'm going to need new faceplates for my meters reflecting the data they are intended to represent. In the case of the Vetinari Clock, for example, I intend to have a large meter displaying the hours from 1 to 12, two medium-sized meters displaying the minutes and seconds from 1 to 60, and a small meter oscillating back and forth like a miniature metronome keeping time with the tick-tock sounds we will be generating.     I've been pondering a variety of ways to create new faceplates. The image below is of an AC meter that cannot be used for any of my projects. I discovered that I can capture an accurately-sized representation of the faceplate on my scanner, and then convert this to a vector representation.     I received an email from EETimes community member John Strupat in Canada. John is the president of an engineering company that specializes in creating prototypes and one-off custom projects for its customers. One of the services it offers is the restoration of older equipment. The main points as far as we're concerned are (a) John has access to all sorts of useful equipment and (b) after reading my blogs, he's become interested in creating a Vetinari Clock of his very own.   In his email to me, John said: I have an idea I'd like to try out if you have a spare meter faceplate and a graphics file to send me. The graphics file should show the mounting screw holes to locate everything correctly. The process I have in mind involves matt polyester film, as the inks used here cannot be printed directly onto aluminum or other metals. I'm confident that the film can be trimmed easily to align with the complex shapes of those old meter faces and to give an impressive result. All color combinations of background and text/graphics are available, including the vintage light yellow/brown aged paint look.   Well, I already had a scan of the faceplate from my AC meter as shown below.     I immediately sucked this image into Visio, generated a vector version of the outline and mounting holes, and threw a test face together that displays things in terms of "Grokles" (whatever they may be). I also added some color, just to see what would happen.     I emailed this graphic up to John. I also dropped the faceplate in the post to him. Sad to relate, the faceplate disappeared into the nether regions of the postal service. Eventually, after more than ten days had gone by, John grew tired of waiting, and simply fabricated a couple of dummy faceplates out of thin aluminum sheet. Yesterday as I pen these words, John emailed me the following image.     According to John: One part has a powder-coated gloss-white background, while the other has a "yellowed" background using the laminate process. These parts are fabricated by printing on either film laminated to a substrate or directly onto a powder-coated substrate. The printer inks penetrate into the material giving a high-contrast durable result. A more rugged result with UV resistance can be accomplished with a clear spray overcoat or with a protective polycarbonate film.   John went on to say: In the case of an analogue meter scale, we can work with the original faceplate or create a new part from the outline from a hi-res scan. In either case we need the graphic file to print the new image. There are no restrictions on colors for graphical elements or for the background. We are now testing laminated assemblies printed on transparent substrate for backlit meter scales, windowed areas, and even capacitive touch panels.   John also tells me that his company is now considering offering this capability as a service to other makers. The idea is that folks could email in their desired graphics for the new faceplate. If they also send in existing faceplates, John's company could print on those. Alternatively, it could fabricate a new faceplate from the ground up. John is interested in knowing your thoughts about this -- is this a service you think the maker community would welcome?   As an aside, while I was chatting to John on the phone a few minutes ago, I asked how far away he was from Ohio. He immediately replied, "Six hours to Dayton, Ohio." So I asked if he'd heard of Hamvention, and he responded that he goes every year, so we're planning on meeting up there. (It really is a small world when you come to think about it.)   But we digress … My chum Denis is a Web guru and a graphics expert. Denis's company, CroDesign , specializes in creating mobile-ready responsive websites and apps. When last we spoke, Denis said he will create the graphics for the new faceplates, but that first he needs to know more about the way in which the meters are going to be presented -- not just their relative positioning, as shown below, but also the materials used to create the enclosure.     Well, another one of my friends is a master carpenter called Bob. (I tell you, the old saying "It's not what you know, it's who you know," is so true!) A few weeks ago, I was waffling on to Bob about my Vetinari Clock, and he told me that he wants to make the box for it. At that time, Bob mentioned that he had some wood veneer that looked like brushed aluminum with a wood grain. Apparently he had used this some time ago on a dashboard for a sports car for one of his clients, and he still has a bit left over.   To be honest, at that time I wasn’t so sure, but I was passing by Bob's shop yesterday, so I stuck my nose in to say "Hi," and he rooted out a sample of this veneer. OMG -- it looks incredible, as you can see in the image below.     Now, this will just be on the front panel -- the rest of the box will be some other color (maybe dark cherry or something). I'm thinking the clock will look amazing with an Art Deco look and feel.   I just sent a bunch of images of this veneer over to Denis in Hawaii. I'll be scanning the faceplates for the meters over the weekend and will get those to him as soon as possible. I cannot wait to see what he comes up with. When he has created his masterpieces, I will share these graphics with you in a future column. Until then, we'll all just have to wait on Denis in dread anticipation. In the meantime, what do you think about the way things are going with regard to this project, such as the choice of veneer?

A few weeks ago, the Mighty Hamster (a.k.a. Mike Field) graced my humble office with a visit. While he was here, Hamster noticed some of the antique analogue meters scattered around my office, and he shared an idea with me -- to build a clock using this sort of meter as the display. Hamster kindly said that I was free to run with this idea myself, so I added it to my list of hobby projects.   Most of the meters in my possession were already committed to other projects. Fortunately, at the time of Hamster's visit, the annual Huntsville Hamfest was fast approaching. It opened at 9:00 a.m., but I got there at 8:15 a.m., because I wanted to be at the front of the queue.     All I can say is that I made off like a bandit on the antique meter front. When I attended last year's event, I arrived empty handed and ended up staggering around with loads of carrier bags. I soon noticed that the more experienced attendees were sporting backpacks to stash their acquisitions. This year, I wore a backpack, but I wish I'd taken a rolling trolley, because I had to make numerous trips back and forth to my truck. The image below shows the meters I picked up, along with a few other items I couldn't resist.     Yes, I know this is a lot of meters. What can I say? I am a weak man when it comes to antique stuff in general and analogue meters in particular. All I know is that, when you can pick up meters like this for only $2 apiece, you grab them while the grabbing is good. Quite apart from anything else, I promised to pick up some meters for the Mighty Hamster. As soon as I post this column, I'll email him to ask which ones he wants.   I decided to use a large meter to display the hours and two medium-sized meters to display the minutes and seconds. I also plan on using a small meter to flip back and forth like a metronome in time with the "tick-tock" sound I intend to generate.   The image below shows a Visio drawing of my first-pass layout. The great thing about doing this sort of thing in Visio is that you can easily move the elements around to try different scenarios. I don't want to have all the meters in a straight line, because that would be boring. Once I was in Visio, I quickly gravitated to having the big meter on the left, the two medium meters on the upper right, and the small meter between and below the medium meters.     Originally, I'd vaguely thought about arranging things so that the distance from the top of the big meter to top of the two medium meters was the same as the distance from the bottom of the big meter to the bottom of the small meter, if you see what I mean. However, I quite like the arrangement shown above, in which the bottom of the two medium meters and the top of the small meter line up with the horizontal centerline of the big meter. Good grief, it's hard to explain this in words, but I'm sure my Visio drawing will help clear things up.   I have to admit that I'm fighting my natural inclination to overengineer everything. I keep on thinking about adding meters to display things like the seasons and moon phases, but if I did that, I might end up with something huge and ungainly that looks like the cockpit of a Victorian spaceship, so I'm resolved to stick with the four meters as discussed above.   In fact, I've already picked out the meters I intend to use, as shown below. (This explains why the previous image includes actual measurements.) Of course, I'll have to change the graphics and legends on the meter's faceplates, but we can discuss this in a future column.     As fate would have it, I visited my chum Bob the carpenter a few weeks ago. Bob has a workshop in downtown Huntsville, Ala., where he specializes in restoring and recreating antique furniture. I took my four meters down to show him and ask his advice. We decided that a dark walnut case would look rather tasty. I had been thinking of a dark front panel also, but Bob says he has some wood with a very interesting grain and an almost silvery hue. He says he used some of it to replace the dashboard in a sports car, and the result looked almost like aluminum with a wood grain. He says that we can give my clock a real Art Deco look and feel. Ooh, shiny.   As I mentioned earlier, my clock is definitely going to feature a robust "tick-tock" sound. I'll include a small loudspeaker and stream real-world audio recordings. As part of this, I'm also planning on including an optional Vetinari Mode based on Lord Havelock Vetinari from Terry Pratchett's Discworld book series.   Lord Vetinari, the scary dictator of the city-state of Ankh-Morpork, has a strange clock in his waiting room. It does keep completely accurate time overall, but it sometimes ticks and tocks out of sync: "tick, tock, tick, tock… tick-tock-tick… tock…" In fact, it occasionally misses a tick or tock altogether. For anyone sitting in Vetinari's waiting room, the result is somewhat discombobulating. By the time you come to your audience, your nerves are already frazzled. Hey, if it's good enough for a Patrician of Ankh-Morpork, it's certainly good enough for yours truly.   What say you? Do you like the sound of this project (no "tick-tock" pun intended)? Are there any other special modes you would include? And, if this version is successful and I eventually decide to construct a more fulsome model, what other factors -- number of days to the next full moon, for example -- could/should I present?

Today's fiber-optic connectors have the amazing mechanical precision that allows low-loss mated pairs, especially considering that single-mode fiber has an optical core of about 9 microns in diameter. Two of these cores, from opposing fibers, must be aligned with almost-perfect mechanical precision to affect the least amount of optical loss.   Positive contact and angled polish keep losses and reflections to a minimum. Of course, this small core size means that the slightest speck of dust on the single-mode core can introduce disastrously high levels of loss, so absolute cleanliness (cleaning the end faces of the connector ferrules) is a must every time a connection is made.     It was not always this good. Quite a few years ago, optical fiber networking was becoming mainstream in the LAN arena. At that time, 50/125, 100/140, and later, 62.5/125 (core and cladding diameter in microns), multimode optical fiber sizes were the short-distance LAN choices. The large diameter core allowed optical launch using LEDs, rather than more costly and finicky lasers.   The 906 SMA optical connector was one of the first popular optical connectors, but it had a few annoyances. For example, a "Delrin sleeve" (hollow plastic cylinder) was required to mechanically align the ferrules of a mated pair, precisely enough that the loss should remain under 3 dB. Being detachable, these Delrin sleeves had a habit of falling on the floor and rolling under anything that prevented someone from ever finding them again.   Compared to today's connectors, with losses of a fraction of a dB, this 3dB loss spec was atrocious. But it was a fact of life, and we had to live with it.   One day, our lab technician was setting up the optical portion of our corporate network and ran into difficulty. He came to me for help because he was getting unexplained bit errors over all the optical links. We had just started manufacturing an Ethernet 10Base-T and FOIRL (Fiber Optic Inter Repeater Link) hub, but he was trying to use Cabletron optical transceivers at the desktop ends. Plus, he had set up an optical patch panel that added an extra mated pair per patch cord.   I had designed the optical cards for our own product. In spite of much complaining from production, I insisted on tweaks to ensure that the green "Link Good" indicator LED would not turn on unless the incoming optical signal level was sufficient to ensure a bit error rate of better than 10 -9 . This was a requirement of the FOIRL Specification.   The Cabletron folks did not want expensive tweaks, so they designed their gear with a "Link Good" indicator LED that turned on with the slightest optical input -- never mind that it was so weak that the bit error rate made the link unusable -- thus, their gear was not FOIRL compliant.   Our lab technician was fooled by the Cabletron desktop transceivers "Link Good" LEDs. I showed him, with my optical power meter, that the link was not good, and that the Cabletron LEDs were lying to him. Then I told him the only solution was to rearrange his patch panel to eliminate one of the two optical couplings -- use cord and splice bushing only, rather than splice bushing to patch cords to another splice bushing. This eliminated 2 dB to 3 dB of loss and the links worked.   Note: 3 dB of optical loss is equivalent to 6 dB of electrical loss.   Glen Chenier Engineer

One of the many astonishing aspects of today's fiber-optic connectors is the mechanical precision that allows low-loss mated pairs, especially considering that single-mode fiber has an optical core of about 9 microns in diameter. Two of these cores, from opposing fibers, must be aligned with almost-perfect mechanical precision to affect the least amount of optical loss.   Positive contact and angled polish keep losses and reflections to a minimum. Of course, this small core size means that the slightest speck of dust on the single-mode core can introduce disastrously high levels of loss, so absolute cleanliness (cleaning the end faces of the connector ferrules) is a must every time a connection is made.     It was not always this good. Quite a few years ago, optical fiber networking was becoming mainstream in the LAN arena. At that time, 50/125, 100/140, and later, 62.5/125 (core and cladding diameter in microns), multimode optical fiber sizes were the short-distance LAN choices. The large diameter core allowed optical launch using LEDs, rather than more costly and finicky lasers.   The 906 SMA optical connector was one of the first popular optical connectors, but it had a few annoyances. For example, a "Delrin sleeve" (hollow plastic cylinder) was required to mechanically align the ferrules of a mated pair, precisely enough that the loss should remain under 3 dB. Being detachable, these Delrin sleeves had a habit of falling on the floor and rolling under anything that prevented someone from ever finding them again.   Compared to today's connectors, with losses of a fraction of a dB, this 3dB loss spec was atrocious. But it was a fact of life, and we had to live with it.   One day, our lab technician was setting up the optical portion of our corporate network and ran into difficulty. He came to me for help because he was getting unexplained bit errors over all the optical links. We had just started manufacturing an Ethernet 10Base-T and FOIRL (Fiber Optic Inter Repeater Link) hub, but he was trying to use Cabletron optical transceivers at the desktop ends. Plus, he had set up an optical patch panel that added an extra mated pair per patch cord.   I had designed the optical cards for our own product. In spite of much complaining from production, I insisted on tweaks to ensure that the green "Link Good" indicator LED would not turn on unless the incoming optical signal level was sufficient to ensure a bit error rate of better than 10 -9 . This was a requirement of the FOIRL Specification.   The Cabletron folks did not want expensive tweaks, so they designed their gear with a "Link Good" indicator LED that turned on with the slightest optical input -- never mind that it was so weak that the bit error rate made the link unusable -- thus, their gear was not FOIRL compliant.   Our lab technician was fooled by the Cabletron desktop transceivers "Link Good" LEDs. I showed him, with my optical power meter, that the link was not good, and that the Cabletron LEDs were lying to him. Then I told him the only solution was to rearrange his patch panel to eliminate one of the two optical couplings -- use cord and splice bushing only, rather than splice bushing to patch cords to another splice bushing. This eliminated 2 dB to 3 dB of loss and the links worked.   Note: 3 dB of optical loss is equivalent to 6 dB of electrical loss.   Glen Chenier Engineer