Why do cheap digital calipers deplete batteries even when off? - Page 1
Forum section: electronics / general

author: Ducttape
author_rank: Regular Contributor
timestamp: August 09, 2018, 03:08:13 pm
content: Is it because of the 'soft' on-off button? Do higher end calipers use a mechanical on-off button?It's quite annoying to pick up calipers that have sat on the shelf for a year 'off' only to be greeted with a dim or blinking LCD display. How much do I need to pay to get a pair that actually turns off?

author: JimRemington
author_rank: Regular Contributor
timestamp: August 09, 2018, 03:18:56 pm
content: They are never really off. I take the battery out of mine when they are not in use.

author: tsman
author_rank: Frequent Contributor
timestamp: August 09, 2018, 03:21:58 pm
content: If you're leaving it on a shelf for a year then you should take the batteries out anyway to be safe.

author: mzzj
author_rank: Super Contributor
timestamp: August 09, 2018, 03:27:41 pm
content: Quote from: Ducttape on August 09, 2018, 03:08:13 pmBecause they are (badly)copied after Mitutoyo's AOS system that stays on "standby" all the time so that it doesn't lost the zero position.Older cheapo calipers don't eat batteries but they need to be zeroed every time you turn them off (or the damned auto-power-off)Don't know about cheapest but buy a real $150 Mitutoyo and your batteries should last 3-5 years.

author: Ducttape
author_rank: Regular Contributor
timestamp: August 09, 2018, 03:29:57 pm
content: Quote from: tsman on August 09, 2018, 03:21:58 pmWhile on its face that seems completely reasonable, the conundrum I face is that it is impossible to know when I am putting it on the shelf for a year. I can't count the number of times I've taken the battery out only to put it back in that same day. At some point, yes, I am setting it down not to be picked up again for a year. If only I could recognize that particular 'setting down' event there'd be no problem.

author: Ducttape
author_rank: Regular Contributor
timestamp: August 09, 2018, 03:33:39 pm
content: Quote from: mzzj on August 09, 2018, 03:27:41 pmPersonally, I have zero problem with re-zeroing them every time.

author: james_s
author_rank: Super Contributor
timestamp: August 09, 2018, 04:23:09 pm
content: Mine kills the batteries within a month or so if I leave it in. I've gotten in the habit of removing the battery every time I'm done using it, I wish it had a regular power switch instead.

author: rx8pilot
author_rank: Super Contributor
timestamp: August 09, 2018, 04:35:24 pm
content: My Mitutoyo calipers last a VERY long time. The entry level Fowlers seem to eat batteries like candy. The higher end Fowler devices are considerably better. My Fowler digital 1/10000 dial indicator goes many years.It does take some engineering effort to keep standby current extremely low. If the product is cheap, the engineering and premium parts are not in the budget.Short and misplld from my mobile......

author: Mechatrommer
author_rank: Super Contributor
timestamp: August 09, 2018, 04:49:48 pm
content: https://www.banggood.com/0-to-150mm-6-inch-Stainless-Steel-Vernier-Caliper-Gauge-Measuring-Tool-Set-p-1279615.html?gmcCountry=MY&currency=MYR&createTmp=1&utm_source=googleshopping&utm_medium=cpc_elc&utm_content=frank&utm_campaign=usc-elc2-my&gclid=Cj0KCQjwzK_bBRDDARIsAFQF7zPk1s2Cc4FFb0aconZWij4tBYCMxAmeK2bAwWS2CoW6HtGizfD7Ve8aAuazEALw_wcB&cur_warehouse=CN

author: Ducttape
author_rank: Regular Contributor
timestamp: August 09, 2018, 06:40:00 pm
content: Quote from: Mechatrommer on August 09, 2018, 04:49:48 pmIt's like I was Rickrolled. I feel so violated.

author: Tom45
author_rank: Frequent Contributor
timestamp: August 09, 2018, 06:55:31 pm
content: Some of the low cost digital calipers eat batteries because of the plastic case that comes with them. The foam in the lid presses on the on/off button and can turn the caliper on when you close the lid.I removed the foam in the lid in the area of the on/off button. That took care of the problem.

author: Gyro
author_rank: Super Contributor
timestamp: August 09, 2018, 07:06:03 pm
content: A lot of the cheap calipers come with alkaline LR44 batteries and can't use much of their steep discharge curve. If you put Silver oxide SR44s in them they last a lot longer (comparatively).The ones that use Lithium CR2032 cells last much longer, tend to be faster updating and have higher display contrast. The heads tend to be bulkier though.

author: james_s
author_rank: Super Contributor
timestamp: August 09, 2018, 07:18:27 pm
content: LR44's seem to last a long time in mine if I take them out when I'm done using it. If they wanted to be cheap, a simple hard power switch would have been preferable to battery hungry standby.

author: Ducttape
author_rank: Regular Contributor
timestamp: August 09, 2018, 07:37:35 pm
content: It just occurred to me that they could design it so a long press on the off button would fully turn it off. Software only change.

author: james_s
author_rank: Super Contributor
timestamp: August 09, 2018, 07:46:31 pm
content: Depends on how the hardware is designed. For a software change to allow full turn-off would require that some sort of switching element be designed into the circuit to enable the firmware to cut power.

author: Richard Crowley
author_rank: Super Contributor
timestamp: August 09, 2018, 08:17:02 pm
content: Quote from: Ducttape on August 09, 2018, 07:37:35 pmBut that would require that the microcontroller continue to be powered in order to recognize when you pressed the button again to turn it on!I don't believe I saw the answer to the original question: "Why do cheap digital calipers deplete batteries even when off?"It is because when you turn off the cheap gadgets, it only blanks the display.Presumably the higher-end products actually put the microcontroller into "sleep" mode.If they can make "solar powered" calculators, why can't the make "solar powered" digital calipers?

author: james_s
author_rank: Super Contributor
timestamp: August 09, 2018, 08:19:25 pm
content: Quote from: Richard Crowley on August 09, 2018, 08:17:02 pmNot necessarily. The power button could be wired such that it completes the circuit, supplying power to the micro when pressed. Then a transistor could latch the power on until the micro releases it, shutting itself off.

author: KL27x
author_rank: Super Contributor
timestamp: August 09, 2018, 10:30:29 pm
content: Even Mitt using the absolute reference scale draw some power while they are off. Making a latching power circuit is not worth the cost, because they last (per some forum members) up to 6-7 years on a single SR44.Some of the cheaper calipers draw more sleep current for an obvious reason; they automatically turn on when you move the calipers. They are either doing some ADC reads while off (and this doesn't mean they don't necessarily go to sleep between intermittent reads) or they are set to a comparator/ADC interrupt/wake up... which this also draws some current. The Mit absolute, you have to press the on/off button to turn them on. A digital input interrupt draws less power than a comparator or ADC interrupt. (ADC interrupt is an active thing, really, with sleep in between reads). Any analog input draws more quiescent current than digital. There's also potentially significant difference in sleep current between micros.That said, with my calipers, an alkaline LR44 will last something like 3 months before it goes on the fritz. Using SR44 silver oxide, same battery that the Mitts ship with, I have gotten over 3 years on a battery. There's no reason to take the battery out when you're not using it, if you don't cheap out on the battery. If you put an alkaline cell in a genuine Mitutoyo, I am sure it would be shitty, too.Apparently, the fake Mitutoyos which sell for up to $75.00 skimp out to save 10 cents on the battery. The battery package is printed SR44, but it's an alkaline button cell in the package. These are so much cheaper, they apparently include a second LR44 preinstalled in the calipers. The genuine Mitutoyos only come with the one battery. It seems stupid to skimp here, when the difference is so astounding. Nothing using digital logic should be running off a single alkaline; there are silver oxide cells and/or 3V li ion button cells. But if you get frustrated with your calipers 3 months after you bought them, that means you might buy MORE. This is smart. They just need the caliper to impress you long enough to get through a credit card chargeback window.The silver oxide discharge curve is so flat that silver oxide batteries are sometimes used as a 1.55V reference voltage. Alkalines start out at 1.6V+ and drop fairly linearly to below 0.8V when flat. Look at the minimum voltage requirement for microcontrollers and you see why a single alkaline cell doesn't last long. Even your TV remote takes 2 in series.

author: james_s
author_rank: Super Contributor
timestamp: August 09, 2018, 11:33:28 pm
content: Some day I'll buy a real Mitutoyo, for the time being the cheapie generic thing I got as a gift some time back does work fine, I just have to remove the battery when I put it away which is a pain.

author: BillyD
author_rank: Regular Contributor
timestamp: August 09, 2018, 11:38:29 pm
content: Co-incidentally I bought a new cheap digital calipers just today for that exact reason.I have a 'Workzone' digital caliper which I bought in Aldi a few years ago which I use on my bench. It drains its battery relatively quickly so I keep the battery disconnected.I also have a 'Powerfix' caliper in my shed which I bought in Lidl a few years ago and it's still on its original battery.So they're back in Lidl this week and I invested in another Powerfix caliper for 10 Euro to save all that hassle with batteries.

author: KL27x
author_rank: Super Contributor
timestamp: August 09, 2018, 11:57:17 pm
content: If you put an alkaline cell in a genuine Mitutoyo, I am sure it would be shitty, too.SR44 silver oxide battery might cost a few bucks for one, down to pennies per in bulk. For the $10.00 you spend on a caliper, you can buy 10-20 of these batteries, delivered. It's not 30% longer; not twice as long. It's closer to 10x difference. With that $140.00 you saved by cheaping out on your calipers, buy some decent batteries!I changed the batteries on my oldest calipers a couple months ago. That was the second or maybe 3rd time I changed the battery since first quarter of 2012. Same calipers lasted 3-4 months on an LR44. The constant low drain and minimum voltage requirement of a digital caliper doesn't match up well with an LR44. They work a ton better when you use the SR44, as would a watch.https://youtu.be/mBKZvAAp-tk?t=13Freeze frame and look in the bottom right corner of the Mitutoyo box.

author: Electro Detective
author_rank: Super Contributor
timestamp: August 10, 2018, 01:44:40 am
content: I got caught out a few times$$ by CDCDBS (Cheap digital calipers depleted battery syndrome)even when offand now just remove the battery every time. FWIW same battery still kicking 6 years later, and spare batt sitting pretty.I don't even bother to use the battery cover if I'm after a quick/close enough measurement, and just plonk it back into its custom fit cheap case.Also if the battery spills its guts, it won't be creeping into the CDC or real deal Mitutoyo etc

author: ignator
author_rank: Regular Contributor
timestamp: August 10, 2018, 03:06:32 am
content: Quote from: Richard Crowley onTodayat 03:17:02 pmMitutoyo has made one for years. Model 500-474. I have one, it sits in the tool box, as every time I use it on the lathe, it blanks out. There is a hold up capacitor, that take too long to fully charge. But even when charged, you get maybe 10 seconds of working time. My shop is lit up very well, but you need to have incident lights shining directly at the solar cells. Don't know if the newer models have made any improvements.

author: CJay
author_rank: Super Contributor
timestamp: August 10, 2018, 07:45:07 am
content: Quote from: mzzj on August 09, 2018, 03:27:41 pmThat's not what I find with my Mitutoyo calipers, they eat a battery every few months.They are old though so perhaps newer ones are better?

author: KL27x
author_rank: Super Contributor
timestamp: August 10, 2018, 09:09:14 am
content: If you put an alkaline cell in a genuine Mitutoyo, I am sure it would be shitty, too.

author: Jeroen3
author_rank: Super Contributor
timestamp: August 10, 2018, 09:14:32 am
content: The analog caliper has never let me down yet. I would only consider a digital one if I was to measure thingsa lot.Basically, when measuring is all you do for hours.What other advantages does the digital caliper offer that you must have a digital one?

author: glarsson
author_rank: Frequent Contributor
timestamp: August 10, 2018, 09:28:29 am
content: Quote from: Jeroen3 on August 10, 2018, 09:14:32 amYou can set your own 0. Either to measure relative distances or as a target (set 0 on some template or standard). On the traditional analog your 0 is always the closed position.

author: CJay
author_rank: Super Contributor
timestamp: August 10, 2018, 10:22:04 am
content: Quote from: glarsson on August 10, 2018, 09:28:29 amSerial capture as well which could be useful (though I've never used it)

author: KL27x
author_rank: Super Contributor
timestamp: August 10, 2018, 08:16:03 pm
content: Fewer moving parts? I feel like a digital caliper can be made pretty crappy and take a lot of abuse and still work fine. Dropping them on concrete, the glass doesn't stick out as much? Although I have cracked the glass on a digital. It's easy to do, if you use calipers in conjunction with power tools or whatnot that vibrate, and you get lost in the project. When the earplugs are in and you're doing w/e, things vibrate off the edge of the bench all the time. When you're done not cutting your finger off, you look over, and sometimes it was your caliper.QuoteIt doesn't matter the on/off button, specifically. If it pressed any of the buttons, this would greatly increase the drain due to the current through the pullup resistor.For me, the cases go in the trash. The tool is so much better when it's easy to access and is disposably cheap, anyway. For me, calipers are tools that are quite often used in conjunction with other tools; measuring things accurately is rarely the end goal. My garage shop calipers are stored in custom mounts right where they are used. Instead of carrying a pair of calipers back and forth, and having to retrieve them when they're "over there," I have one at both benches. My electronic bench calipers have no mount, but they also have first order accessibility. If I ever needed a proper case for say travel, I will buy another one for $10.00, and maybe keep the case. The existing calipers will stay where they are.

author: Electro Detective
author_rank: Super Contributor
timestamp: August 15, 2018, 11:47:42 pm
content: Quote from: Tom45 on August 09, 2018, 06:55:31 pmI tried that too, on two different branded ones purchased years aoart,removed only the plastic case foam section around the display and buttons = made no difference, cheap or expensive battery still goes flatEven when left out of the case, switched OFF and undisturbed, battery goes flatThere must be a standby/memory/zero function type constant drain somewhere... easily 'hacked' by removing the battery, lol

author: coppercone2
author_rank: Super Contributor
timestamp: August 26, 2018, 01:05:29 am
content: Quote from: rx8pilot on August 09, 2018, 04:35:24 pmI got old slyvacks and the battery is like 1 year

author: Bassman59
author_rank: Super Contributor
timestamp: August 27, 2018, 08:30:33 pm
content: Quote from: Tom45 on August 09, 2018, 06:55:31 pmHuh, I should try that. X-acto knife to the rescue. Also, I should cut some holes in the foam for spare batteries.

author: MacMeter
author_rank: Frequent Contributor
timestamp: August 27, 2018, 10:00:43 pm
content: If one had the time, make it really turn OFF:https://youtu.be/GcoUdIjZozY

author: Erwin Ried
author_rank: Regular Contributor
timestamp: August 30, 2018, 04:22:49 pm
content: I added a small switch (those on/off clicky switches)Already 1 year with the same LR44

author: JohanH
author_rank: Frequent Contributor
timestamp: May 11, 2023, 07:28:50 pm
content: Necrobump, but I also had enough with one of my old calipers that I never use, because battery is always drained.Added a small switch. Fast and no modification to the caliper itself.Details:https://baldpenguin.blogspot.com/2023/05/diy-caliper-on-off-switch.html

author: RoGeorge
author_rank: Super Contributor
timestamp: May 11, 2023, 07:39:31 pm
content: They usually don't deplete the battery. I have had one that depletes a new battery in a couple of months, while sitting unused. Bought from Bricostore, IIRC. Bad design, or bad lot of calipers, IDK.The one I have now (from LIDL) doesn't discharge much the battery. Has the same battery from 3+ years ago and still working OK (rarely used).

author: MacMeter
author_rank: Frequent Contributor
timestamp: May 11, 2023, 07:42:21 pm
content: I eventually bought a real Mitutoyo, problem solved.

author: shapirus
author_rank: Super Contributor
timestamp: May 11, 2023, 08:10:25 pm
content: I had no idea I needed a new digital calipers before I opened this thread.

author: RoGeorge
author_rank: Super Contributor
timestamp: May 11, 2023, 10:50:38 pm
content: I kept my first faulty one for a couple of years. After changing the battery a few times I've ended up removing the battery after each use, but it was used so rare that it doesn't bother me much.Maybe add a mechanical micro switch to disconnect the battery.

author: amyk
author_rank: Super Contributor
timestamp: May 11, 2023, 11:57:53 pm
content: Quote from: Richard Crowley on August 09, 2018, 08:17:02 pmAlmost 5 years later, but they do exist and there's even the cheap Chinese versions at the usual sites --- although I don't know if they're real orjust have a fake solar cell and a battery. Personally I prefer mechanical dial calipers.

author: Electro Fan
author_rank: Super Contributor
timestamp: May 12, 2023, 08:52:21 pm
content: Somewhat off topic but....iGaging IP54 Electronic Digital Caliper 0-6" Display Inch/Metric/Fractions Stainless Steel BodyClaimed Specs: Accuracy: 0.001" Repeatability: 0.0005" Resolution: 0.0005"/0.01mm/1/128"I leave the batteries installed until the batteries run low, use the tool occasionally (~monthly for several hours?), might need to change the batteries ~yearly or less often- Search on Amazon. $29.95- One of my most favorite tools (also makes a great gift). If you need a Mitutoyo you need a Mitutoyo, but the iGaging IP54 is plenty accurate for anything I've ever needed. I'm pretty sure I could buy batteries for the rest of my life and have saved $ vs a Mitutoyo.Edit: almost forgot the most relevant info for the OP - it has Auto Off

author: thm_w
author_rank: Super Contributor
timestamp: May 12, 2023, 09:45:24 pm
content: Quote from: Electro Fan on May 12, 2023, 08:52:21 pmYeah I recommend igaging in the related thread:https://www.eevblog.com/forum/mechanical-engineering/how-to-spot-fake-mitutoyo-calipers/CR2032 > SR44. CR2032 is everywhere and easy to get quality cells for a low price.

author: G7PSK
author_rank: Super Contributor
timestamp: May 14, 2023, 05:20:08 pm
content: Either get the ones which take lithium coin cells, which do not cost that much more than the ones taking LR4 cells. Or even better get proper Vernier callipers that require no batteries at all, I always use Vernier's with the lathe as suds always get into digital ones even the most expensive, not hard to learn how to use them.