Why do cheap digital calipers deplete batteries even when off?

[Ducttape]

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?

[JimRemington]

They are never really off. I take the battery out of mine when they are not in use.

[tsman]

If you're leaving it on a shelf for a year then you should take the batteries out anyway to be safe.

[mzzj]

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?

Because 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.

[Ducttape]

If you're leaving it on a shelf for a year then you should take the batteries out anyway to be safe.

While 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.

[Ducttape]

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?

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).

Personally, I have zero problem with re-zeroing them every time.

[james_s]

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.

[rx8pilot]

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......

[Mechatrommer]

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

[Ducttape]

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

It's like I was Rickrolled.  I feel so violated.

[Tom45]

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.

[Gyro]

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.

[james_s]

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.

[Ducttape]

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.

[james_s]

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.

[Richard Crowley]

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.

But 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?

[james_s]

But that would require that the microcontroller continue to be powered in order to recognize when you pressed the button again to turn it on!

Not 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.

[KL27x]

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.

[james_s]

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.

[BillyD]

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.

[KL27x]

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=13
Freeze frame and look in the bottom right corner of the Mitutoyo box.

[Electro Detective]

I got caught out a few times$$ by CDCDBS (Cheap digital calipers depleted battery syndrome) even when off   

and 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 

[ignator]

Quote from: Richard Crowley on Today at 03:17:02 pm

If they can make "solar powered" calculators, why can't the make "solar powered" digital calipers?

Mitutoyo 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.

[CJay]

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?

Because 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.

That'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?

[KL27x]

If you put an alkaline cell in a genuine Mitutoyo, I am sure it would be shitty, too.