problem with digital vernier

[P.G. BHANDARYParticipant @p-g-bhandary50582]

[P.G. BHANDARYParticipant @p-g-bhandary50582]

The DISPLAY on the AEROSPACE make DIGITAL VERNIER WORKS ONLY AFTER WARM-UP.i.e. after exposing it to sun light heat. It works for a couple of minutes and again the display goes BLANK.What could be the reason.Can anybody suggest a SOLUTION?

P,G,BHANDARY

[P.G. BHANDARYParticipant @p-g-bhandary50582]

Thank U.Awaiting for approval.

[Neil WyattModerator @neilwyatt]

Hello P.G., welcome to the forum.

I'm afraid that sounds like a tired battery. Although most digital verniers switch off the display after about five minutes, it should 'wake up' on the first press of the on/off button.

Neil

[MM57Participant @mm57]

If it's the cheap generic caliper like :

http://www.ebay.in/itm/Aerospace-Brand-Digital-Vernier-Caliper-150mm-6-inch-Caliper-Micrometer-Guage-/281316102477

(although that looks like it's an expensive price to what we can get them on UK Ebay)

…then either a fresh battery is needed or it is faulty. These types switch off the display, but are still "powered on" under the covers, meaning short battery life. I have two of these, both are now faulty, failing in the first few weeks of use – they are now used as rough and ready mechanical calipers, reading the scale by eye.

My (genuine) Mitotoyu digital calipers are perfect….huge battery life even when left switched on, perfect zero-ing every time even after being switched of and on irregularly etc

Edited By Martin Millener on 19/12/2014 17:06:41

[the artfull-codgerParticipant @theartfull-codger]

I find that they don't like the cold,they work better when warm, my mitutoyo fares much better & doesn't seem to mind the cold, as martin says above it's a digital caliper , digital verniers don't exist ,even some of the sellers[box movers] call them digital verniers, I also regularly use a mitutoyo vernier with a scale reading 0-50 & is really easy to read [just to keep my hand in!!]

Graham.

[Jesse Hancock 1Participant @jessehancock1]

As far as being cold goes there's not a battery in the world that I know of that isn't affected, lithium, alcaline, nicad,lead-acid you name it. You only have to listen to cars starting up on a good frosty morning to realise what effect the cold has.

If it's possible (with out undue wear and tear on the battery cover) pop the battery out when not in use, and before replacing it in your vernier warm it up in your hand you should be able to extend battery life. This also stops corrosion often found in torches and the like.

Some verniers and other measuring devices have a solar array which helps as long as they are in a strong light source. In which case keep it under a light sourse as long and often as possible (without it being on). Occasionally Model engineer magazine give away a digital vernier but you do have to take out subscription for a year and ofcourse it is a one and only one time offer.

When replacing batteries try to obtain them from someone who has a large turnover in batteries, ensuring they are fairly new. Don't buy lots of batteries at once only enough for your needs. (refer previous note on supplier) Together these little tips may help keep your verniers going.

The best compromise I have found is a digital readout (numbers) which has mechanical movement like an odometer but that is only on a micrometer of mine. As backup I have a set of normal verniers but I also need my bifocals on to read them accurately these days.

Jesse.

[FMESParticipant @fmes]

Having spent most of a morning explaining use of PME including micrometers and vernier calipers to our apprentices and giving them some practice using them, we then go on to show them the digital calipers, which of course they all like as they are much easier to read.

At least one of them will ask if there is such a thing as a digital vernier, which I assume to be a combination of a vernier scale and digital readout.

What should I tell them, are they made?

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Lofty76 on 13/01/2015 21:29:42:

… At least one of them will ask if there is such a thing as a digital vernier, which I assume to be a combination of a vernier scale and digital readout.

What should I tell them, are they made?

.

Lofty,

That raises an interesting 'philosophical' point [you clearly already appreciate that 'digital vernier' is commonly used incorrectly to describe a caliper with digital display]

I have been toying with the idea of making a true 'Digital Vernier' … wherein the traditional alignment of lines 'by eye' is replaced by optoelectronic sensors and LED indicator lamps [with an optional numeric read-out].

Although the Vernier is mechanically analogue, there is a reasonable case for interpreting the overall system [i.e. including the human who is reading the scale] as digital … because we always accept that one pair of marks is aligned.

MichaelG.

.

Sorry that doesn't really answer your question, but it might get a few people thinking.

[LimpetParticipant @limpet]

Posted by Jesse Hancock 1 on 13/01/2015

and before replacing it in your vernier warm it up in your hand you should be able to extend battery life.

This is not advised as the moisture in the skin can flatten the coin cell type battery if both sides are touched at the same time

Lionel

[MuzzerParticipant @muzzer]

Make sure you have a silver oxide battery fitted (SR44), NOT a lithium one like the LR44 etc. They both fit but the silver ones have a life that is 10-20 times longer and are what is recommended for these devices.

Murray

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by Muzzer on 14/01/2015 08:43:05:

Make sure you have a silver oxide battery fitted (SR44), NOT a lithium one like the LR44 etc. They both fit but the silver ones have a life that is 10-20 times longer and are what is recommended for these devices.

Murray

LR44 batteries are alkaline not lithium. You definitely need a silver oxide battery for these things unfortunately a lot of batteries sold as "equivalent to" SR44 are in fact LR44s.

Russell.

[Jesse Hancock 1Participant @jessehancock1]

Really Lionel? Care to explain how you get your batteries out of the pack and into said venier and only touching one side of the battery? Addmittedly batteries don't like short circuiting their posts but practicality has to be the order of the day so if you are worried make sure your hands are thoroughly dry before proceeding.

Good tip on the Murray I'll look out for that.

Jesse

[Neil WyattModerator @neilwyatt]

> Care to explain how you get your batteries out of the pack and into said venier and only touching one side of the battery

I pop them out of the packaging onto a hard surface. It's then fairly easy to handle them by touching the sides only, especially as they go into place with the small terminal down.

Neil

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by Limpet on 14/01/2015 06:17:04:

This is not advised as the moisture in the skin can flatten the coin cell type battery if both sides are touched at the same time

The resistance between my fingers when gripping something like this is about 10 MOhm. If I lick my fingers first I can get it down to 0.5 MOhm. Even at that the current drain is only 3 microAmps, hardly enough to flatten the battery even if you hold it all day. With 130 mAh capacity you would need to hold it continuously for 1,800 days to flatten it!

Russell.

[LimpetParticipant @limpet]

The resistance in the skin can vary depending on humidity, temperature etc. And depending how the battery is held it may only have a mm of distance. If you don't feel it's a concern for you Russell then ignore it. I handle coin batteries with thin cotton gloves

Lionel i

[MuzzerParticipant @muzzer]

Well spotted Russell – senior moment etc!

Looking at typical voltages for alkaline and silver oxide batteries, the silver oxide seems to be typically around 1.6V (SR44) and the alkaline about 1.2V (LR44). Although they are physically the same size, the LR44 probably struggles to operate the circuit in the calipers unless it's almost new. And the smaller capacity of the LR44 gives a very short life (in my experience) relative to the specified SR44. Together, the experience is not satisfying.

Murray

[FMESParticipant @fmes]

Posted by Muzzer on 14/01/2015 18:35:16:

Well spotted Russell – senior moment etc!

Looking at typical voltages for alkaline and silver oxide batteries, the silver oxide seems to be typically around 1.6V (SR44) and the alkaline about 1.2V (LR44).

Hi Muzzer, I just bought some LR44 Alkaline today (Duracell) and the pack says 1.5v, these seem ok in my mics for about six months, must try the SR44's tho.

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by Limpet on 14/01/2015 17:09:36:

The resistance in the skin can vary depending on humidity, temperature etc. And depending how the battery is held it may only have a mm of distance. If you don't feel it's a concern for you Russell then ignore it. I handle coin batteries with thin cotton gloves

O.K. look at it another way. You said, "This is not advised as the moisture in the skin can flatten the coin cell type battery if both sides are touched at the same time".

Now it should take less than a minute holding the battery when inserting it. To fully discharge a 130 mAh battery in one minute requires a current of nearly 8 A. This is impossible given that the internal resistance of said battery is about 100 ohm. Yes, the skin resistance does vary with many factors but even with wet hands it is very unlikely to fall below 1,000 ohm and the time to flatten the battery would then be three days.

If you have dirty or sweaty hands, yes wearing gloves is a good idea to reduce the risk of the battery contacts becoming corroded.

Russell

[Michael GilliganParticipant @michaelgilligan61133]

This graph should illustrate why SR44 is preferable to LR44

MichaelG.

[michael howarth 1Participant @michaelhowarth1]

In my experience SR44 batteries only last for a marginally longer period than an LR44 when used in cheapo callipers. I have now ditched all of my cheapos except for the silver coloured "Workzone" ones from Aldi which work fine(ish) on LR44s. I have also recently had gifted to me (Xmas) a Mitutoyo digital calliper which has worked wonders for my blood pressure. Talk about chalk and cheese! If anyone is wondering whether to lash out on one I would unhesitatingly recommend it.

Mick

[FMESParticipant @fmes]

I'd love to see a 'Digivern' one day, anyone got one?

Oh, and BTW the Bronze 'spring' appears to be a gib held in place with two grub screws, one of which locates into a hole in one end to stop it sliding out and the other takes out any slop in the slider. (M&W 6" Vernier Caliper, Mitutoyo 6" digital caliper)

The apprentices have just taken the M&W apart to see how it works!!

[Michael GilliganParticipant @michaelgilligan61133]

Useful reference:

This NPL document [updated September 2014]

MichaelG.

.

P.S. for Bogstandard2

Fig.24 may be of interest [constant force contraption]

Edited By Michael Gilligan on 15/01/2015 13:22:41

[LimpetParticipant @limpet]

Russell I see where you're coming from my original comment was in response to 'hold it in your hands to warm it up' I agree normal battery changing should not degrade the battery noticeable. I wear gloves when handling coin cell out habit from my job

Lionel

[FMESParticipant @fmes]

Posted by Bogstandard2 on 15/01/2015 16:16:12:

Thanks for that Michael, I didn't know such devices existed, but none of us know everything, and it does prove my point that there is a problem with digiverns (or just for Lofty, digital verniers) and differing operating pressures. The way to show it is to hold both blades tight against the part to give yourself a good reading, and with the other hand, press on the top of the main plastic block at either end and you should see deflections of the reading, this is caused by the bronze tensioning spring compressing.

BTW, I love 'contraptions'

John

Edited By Bogstandard2 on 15/01/2015 16:16:57

Thank you kindly for your interpretation Bogs, I'm sure you will realise what you have said, one day.

[Author]

Posts