Digital Vernier is now suddenly a POS - Page 1
Forum section: electronics / general

author: T4P
author_rank: Super Contributor
timestamp: June 18, 2012, 03:15:42 pm
content: No, it's not as slidy as a used car salesman but it's as jumpy as a kangarooSometimes it works by Zero-ing out when it begins to jump but then it doesn't work sooner or later again ... (Ah well it's only 8.82 and it's served me well for 6 months, but i guess i broke it by dropping it)

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: June 18, 2012, 03:24:00 pm
content: Could be contamination on track - try taking it apart & cleaning it.

author: T4P
author_rank: Super Contributor
timestamp: June 18, 2012, 03:34:46 pm
content: Quote from: mikeselectricstuff on June 18, 2012, 03:24:00 pmAlcohol'dSame issue

author: SeanB
author_rank: Super Contributor
timestamp: June 18, 2012, 04:07:41 pm
content: Strip and clean, both the track and the battery terminals. Replace the batteries as well, and polish the new ones with a lint free cloth before inserting them.

author: T4P
author_rank: Super Contributor
timestamp: June 18, 2012, 04:18:42 pm
content: Quote from: SeanB on June 18, 2012, 04:07:41 pmI alco'd it one more time and now it's fine, the batteries alright, still the same value as a month ago

author: saturation
author_rank: Super Contributor
timestamp: June 18, 2012, 04:57:31 pm
content: I don't think the 4th significant digit on digital scales is practical for common use, on digital vernier calipers. Items one buys or fits often isn't specified to less than 0.1mm. My manual one is over 20 years old, works with no maintenance, good to 3 significant digits.A professional need or a production environment making many measurements daily could make errors with the manual scale and this maybe cost effective to offset the lack of robustness of digital scales.http://en.wikipedia.org/wiki/Caliper#ComparisonIf you're a stickler for absolute measures, you can go pretty high indeed, in which case a digital scale is the only way to go.http://www.amazon.com/dp/B002SG7QM4/ref=biss_dp_t_asn

author: T4P
author_rank: Super Contributor
timestamp: June 18, 2012, 05:36:04 pm
content: Quote from: saturation on June 18, 2012, 04:57:31 pmYou would be surprised ... the LSB is actually the 4th digit, it's every bit accurate

author: robrenz
author_rank: Super Contributor
timestamp: June 18, 2012, 05:40:29 pm
content: Quote from: saturation on June 18, 2012, 04:57:31 pmIt takes extremely good technique to use that .01mmresolutionof a good digital vernier in a repeatable manner.Also a high quality 50 division vernier (inch system) that reads directly to .001" is easily interpolated by a trained eye to .0005"

author: robrenz
author_rank: Super Contributor
timestamp: June 18, 2012, 05:46:44 pm
content: Quote from: DaveXRQ on June 18, 2012, 05:36:04 pmBe very carefull with that "accurate" word. Consistent or repeatable might be more appropriate in this case. Traceable accuracy is the same principle in mechanical measurement as in electronic.

author: SeanB
author_rank: Super Contributor
timestamp: June 18, 2012, 05:50:39 pm
content: Yes, but can it measure as big as my big one, 60cm. Bought at auction by my brother in law, who wanted the big wooden box it came in. Only goes to 0.05mm, but easy to read. Funny enough I do use it, but not often, but it is great when needed.

author: rr100
author_rank: Frequent Contributor
timestamp: June 18, 2012, 06:11:22 pm
content: I have precisely the same model as the one from the video (or at least so it looks). I don't use it often but each time I do the batteries are flat. I have plenty of AG13s (=LR44s or whatever it uses) at hand but still silly. It has space in the case for 2 batteries, I assumed they're for spares but it seems it might be a good idea to keep the batteries out of the device when not in use anyway. Didn't read the manual, maybe this is what they expect :-)

author: T4P
author_rank: Super Contributor
timestamp: June 18, 2012, 06:19:01 pm
content: Quote from: rr100 on June 18, 2012, 06:11:22 pmMine hasn't dropped much since it was out of the mailBut something strikes me that i only have space for a single battery and that if you look further back and open up the gate i can find a USB plugin on the board ( i assume )

author: rr100
author_rank: Frequent Contributor
timestamp: June 18, 2012, 06:24:32 pm
content: Sorry, mine is one battery also (really looks the same, color of the buttons, etc), I have PLACE for two spares in the foam in the box it came with.Battery-wise I'm talking (many) months in between...Now it's dead again, and I'm out of batteries in its box, time to get some more from the fridge :-)

author: T4P
author_rank: Super Contributor
timestamp: June 18, 2012, 06:43:20 pm
content: Quote from: rr100 on June 18, 2012, 06:24:32 pmYeah, it's really in "sleep" mode but that is a few nA'sNot too shabby this vernier caliper considering i really hate taking the time to read analog's ( I trust it, anyway )

author: saturation
author_rank: Super Contributor
timestamp: June 18, 2012, 06:54:33 pm
content: Glad you chimed in robrenz, given your experience and professional expertise. Yes, exactly part of my point. Given the additional resolution, one is left with the human component of the measurement, how much force on the jaws applied to surface being measured. So unless you're trained like a mechanical engineer to insure that resolution is repeatable and valid, extra resolution in untrained hands can be moot [ who knows if that last digit is really accurate?]As another mention and Wikipedia article mentions, many low cost calipers have high power-off current drain. Finally, given the quality of electronics in many Chinese made equipment, there is the added uncertainty of the longevity of device. So, a lot of things to worry about over just a simple and functional mechanical scale, is easy to check calibration, and will work for a lifetime until the caliper is damaged or lost.robrenz, I am almost certain you have calipers of various types, in your work are there brands that are held in high regard? Are there best ways to calibrate lengths and weights for the layman?I use US coins as they are widely available, make for simple checks of sizes and weights and since for everyday use at most 0.1g and 0.1mm resolution is several orders of magnitude less than the coins published specs.http://www.usmint.gov/about_the_mint/?action=coin_specificationsQuote from: robrenz on June 18, 2012, 05:40:29 pmQuote from: robrenz on June 18, 2012, 05:46:44 pm

author: SeanB
author_rank: Super Contributor
timestamp: June 18, 2012, 07:11:01 pm
content: Mass is easy, you get a set of masspieces in a box, and they come with an assize certificate. Then you have them verified by a metrology lab every few years, and handle them with care in between. I have a set of 20kg, 10kg, 5kg, 200g,100g, 50g,20g, 10g, 5g, 2g and 1g masspieces. They are certified down to 4 decimal places. I use them to verify massmeters, from precision analytical balances of 100g full scale to loadcells of 150kg full scale.Length is also easy by using precision blocks, where they are ground to a certain length and are certified to a certain degree of accuracy, though they are only really accurate at a specific temperature. Generally they come in a set with a precision micrometer as check units to ensure that the micrometer cage is not damaged.

author: rr100
author_rank: Frequent Contributor
timestamp: June 18, 2012, 07:34:42 pm
content: Quote from: saturation on June 18, 2012, 06:54:33 pmFunny thing I lost the first caliper I bought myself between cashier and car. That must be a record.

author: robrenz
author_rank: Super Contributor
timestamp: June 18, 2012, 07:39:54 pm
content: Quote from: saturation on June 18, 2012, 06:54:33 pmMitutoyo absolute digimatic calipers 500-159-20 are my favorite. They have 3.5 year battery life. They are truly absolute, you can remove the slide from the scale and it will not lose its zero (as long as it has battery power). Excellent update speed and they are much more accurate than the stated +/- .001"500-159-20I build a diamond wheel dressing unit for a major gear grinder manufacturer where I integrate the guts of these calipers inside my unit for 5 axes of measurement that don't need a zero routine except when changing a battery.Gage blocks are the general standard that you would use for calibration. It depends what level you are trying to calibrate to as to what grade of gage block would be sufficient. Grade 3 or B blocks would be sufficient to calibrate a digital caliper. Some of the chinese sets are not to bad. I have +/- 2u" chrome carbide blocks to check the chinese working blocks. Yes I have 0.1u" resolution electronic gage heads to do the comparison.

author: Monkeh
author_rank: Super Contributor
timestamp: June 18, 2012, 08:05:38 pm
content: Quote from: rr100 on June 18, 2012, 06:11:22 pmStop feeding it LR44s, then. It wants SR44s.

author: T4P
author_rank: Super Contributor
timestamp: June 18, 2012, 08:09:17 pm
content: Quote from: Monkeh on June 18, 2012, 08:05:38 pmYeah, LR44's have a short life that's allI believe the better ones have SR44's installed instead

author: rr100
author_rank: Frequent Contributor
timestamp: June 18, 2012, 10:00:25 pm
content: It says specifically LR44 in the manual, not that SR44 would hurt. Will pick some next time.I'm used with (small) clocks that will go for quite a while on LR44s. Measured now the consumption, it's 14 microamps, no matter if it's on or off!!!Probably with SR44 I'll get rid of the "dead again" symptom for the next few years but so will keeping the battery beside it in the box :-)

author: Psi
author_rank: Super Contributor
timestamp: June 18, 2012, 11:07:31 pm
content: My vernier is almost identical to yours and i've have issues of it jumping around beforeThe cause has always been the battery and/or battery contacts.Most of the time they just need a clean, if the voltage gets low it starts jumping around.

author: T4P
author_rank: Super Contributor
timestamp: June 19, 2012, 04:54:22 am
content: Quote from: rr100 on June 18, 2012, 10:00:25 pmI assume Sliver Oxide won't leak like Alkaline does. Anyway 14uA means the LCD .... never draws but the 8bit uC never sleeps !Quote from: Psi on June 18, 2012, 11:07:31 pmMine was the capacitive track (i think)

author: rr100
author_rank: Frequent Contributor
timestamp: June 19, 2012, 07:34:09 am
content: Quote from: DaveXRQ on June 19, 2012, 04:54:22 amYou mean leak as in leaking fluid or self discharge? Either way I'm rather pleased with the (random brand) cheapo LR44s (/AG13) and I'm using them for uh, probably "tens of years" would be correct (man I'm old). I have a small clock+thermometer, a portable clock/alarm/calculator and probably some more things and they just go on forever (well not like a simple CR2032 watch for 10+ years, but enough not to matter, like 1-3 years). I have some more random crap (scientific calculators and such) but nothing else that I regularly use. So probably self-discharge won't be a problem, but just parasitic drain would (for my calipers mentioned).Oh, wait funny thing: Idohave one more thing that eats 44's like there's no tomorrow: one of these kill-a-watt meters. It has two LR44s to keep settings (including clock) while it's unplugged but probably they got sloppy and left it with a high "off" current. Or they just designed it to rely on batteries when you unplug it and plug it in another socket, for just minutes at a time. In fact I need to check, maybe the design is so horrendous that it eats batteries even when it's plugged into mains. Well, not so bad in fact, I use the "autoreset when unplugged" as a function nowadays instead of fiddling with the buttons to reset it (and I ignore all the other functions like clock+night kWh prices, etc)

author: T4P
author_rank: Super Contributor
timestamp: June 19, 2012, 09:24:02 am
content: Quote from: rr100 on June 19, 2012, 07:34:09 amFluid dischargeI just read up that alkaline 44's discharge faster (lower capacity) but also because the voltage drops more then the sliver oxide equivalents(Alkaline's internal resistance rises very quickly)

author: saturation
author_rank: Super Contributor
timestamp: June 19, 2012, 02:27:17 pm
content: Thanks seanB and robrenz for those calibration tips. On checking the Mitutoyo and US Starett brand calipers, one can see the huge difference in cost for those requiring highest grade tools versus the common ones found in eBay or stores.FWIW due to interest in this thread, I found low cost Chinese vernier calipers down to 0.05mm resolution. There are many brands. Easier to read scale and no worries with batteries. Don't know inevitably how accurate they are, but for general purposes, them seem better made than the run-of-the-mill calipers in the hardware store, for the same money.http://www.ebay.com/itm/6-150MM-STAINLESS-STEEL-VERNIER-CALIPER-GAUGE-MEASURING-LAYOUT-EQUIPMENT-D52-/110884971962?pt=UK_Measuring_Tools_Levels&hash=item19d14265baCTC in Hong Kong specialize in measuring tools, and low cost. They are the only one's I know who provide super sized images of their wares, which suggest they know what people need to see when looking at venier scales.

author: icon
author_rank: Regular Contributor
timestamp: June 19, 2012, 02:42:26 pm
content: Quote from: robrenz on June 18, 2012, 07:39:54 pmI picked these sets up for virtually nothing. They enabled me to confirm that a 6" Mitutoyo caliper I had was wrong. It caught me out a couple of times, when things I'd made didn't fit - it didn't occur to me to doubt the caliper! Turned out it was reading just slightly wrong. Very annoying.John

author: robrenz
author_rank: Super Contributor
timestamp: June 19, 2012, 03:09:24 pm
content: That is where the terminology "Jo blocks" came from, C.E. Johansson.

author: SeanB
author_rank: Super Contributor
timestamp: June 19, 2012, 03:28:31 pm
content: Note also the very important spec with these, they are only accurate at a specific temperature. 20C in this case.If it is warmer then they will be slightly bigger, and the measurement will be out. The only times you really notice thermal effects, they are that precisely made.Pity they are imperial sizes though, I would have to keep a conversion table with them if I was using them, along with a metrology cert to be sure they have not worn over the years from use.

author: T4P
author_rank: Super Contributor
timestamp: August 29, 2012, 09:37:38 am
content: *Thread Revival!Well Dave got the same one with a smashed screen in his mailbag...Copper plate came out and in the process of placing it back i lost a grub screwBuying a metal housed version next, anyone used the metal housing version before?

author: TheWelly888
author_rank: Frequent Contributor
timestamp: August 30, 2012, 07:43:19 pm
content: I had a cheap digital caliper once, it failed so I got myself one of these dial calipers which I find much easier to read than vernier calipers. The resolution of mine is 0.02mm.

author: Rick Law
author_rank: Super Contributor
timestamp: February 11, 2013, 10:24:20 pm
content: Quote from: robrenz on June 18, 2012, 05:46:44 pmThis is where the words PRECISE or PRECISION is useful. Perhaps Dave means to say it is very PRECISE, but not necessarily very ACCURATE.I expect (based on reviews I have seen) the UT61E to be more ACCURATE than my very precise $10 radioshack DMM. With my RadioShack DMM, except for the last digit jitters, my 5% resistors is almost always reading the exactly the same value but >5% off the color code. Precise? Yes. Accurate? I don't know.This is bad, I am waiting for my UT61E still enroute to me. So, not being able to get my hands on it yet, I am loitering here to read about it. I should get back to doing something I need doing.

author: T4P
author_rank: Super Contributor
timestamp: February 11, 2013, 11:14:43 pm
content: Ahh, for that it's not accurate but inaccurately preciseand perhaps why did you did you revive a half year old topic?

author: Mechatrommer
author_rank: Super Contributor
timestamp: February 12, 2013, 12:36:57 am
content: semantics 101: precision tool must be "accurate and repeatable", if not then it is not precise

author: Rick Law
author_rank: Super Contributor
timestamp: February 12, 2013, 12:55:49 am
content: Quote from: T4P on February 11, 2013, 11:14:43 pmAs I said, I was expecting my UT61E which was touring San Francisco and taking its time in its eastward journey. Not being able to get my hands on the toy, I was loitering on a forum where I can read about the UT61e.And, as I said, I better get back to doing something I should do.

author: Rick Law
author_rank: Super Contributor
timestamp: February 13, 2013, 06:28:08 pm
content: Quote from: Mechatrommer on February 12, 2013, 12:36:57 amSilly, I know, but it interests me. From a movie character played by Peter O’Toole: “If you don’t know the word means, you cannot possibly mean what you’ve said.” Something like that.This is a forum and forum is for communication, words are therefore important. It is worth a flipping a few more bits to get some clarity here. Since this forum is rather international, I also like to highlight the issue that we are already aware of.In this case, we both could be right. Meaning of words may change across time, across geographic regions, and across culture. It could change even within the subculture of different disciplines.Gay: used to mean joy and happy and now it refers to sexual preferenceChemist: In Europe, I go to a Chemist to fill my medical prescription whereas I would go to a Pharmacist in the USA.CALORIES (all upper case for a reason): Ask a Physicist for a calorie of heat and you get enough heat to warm a *gram* of water by one degree Celsius. Ask a Nutritionist for a Calorie (typically upper case C) of heat and you can warm a whole *kilogram* of water by one degree C.Metal: Ask a Chemical scientist for a list of “metal” and ask an Astronomist for a list of “metal”, you will get a much longer list from an Astronomist.I know in this particular case it is not change of meaning “across time”. Searching for “precision” in Google and under “images for precision”, the “Arrow and Target” is still frequently used. In this explanation, the closeness between arrow impact points defines “precision” whereas the closeness of impact points to bulls-eye defines “accuracy.” So I know in this particular instance, out difference in interpretation it is likely not “across time” but “across disciplines” or “across geographic regions.”So I do have a serious question here – what do EE folks generally define as “precision”? Since this is the EEvBlog, I must therefore defer to the EE meaning of things while here.

author: T4P
author_rank: Super Contributor
timestamp: February 13, 2013, 07:32:00 pm
content: Precision? What's precision to me you ask.How precise a test instrument means basically how accurate it MIGHT beAccurate on the other hand is how close it is compared to a standard or another verified test instrument

author: robrenz
author_rank: Super Contributor
timestamp: February 13, 2013, 07:32:34 pm
content: IMO Repeatability coupled with resolution are the "precision" as in howsmallis the circle that all the arrows of a group fit in. Resolution comes into play in being able to define repeatability to a finer value. (higher resolution doesNOTimply higher repeatability) Accuracy is how close to being concentric with the bulls eye that circle is.

author: Mechatrommer
author_rank: Super Contributor
timestamp: February 14, 2013, 12:11:42 am
content: Quote from: Rick Law on February 13, 2013, 06:28:08 pmor means... happy time? we must come down to a "resolution" to avoid "repeatable" "confusion'ness".