PDA

View Full Version : Digital caliper current draw, offshore vs. Mitutoyo



superUnknown
01-26-2015, 11:41 AM
I checked the current draw on a couple of calipers. Interesting results; the difference between on and off is about 2 microamps. That's what the LCD is drawing, otherwise the calipers stay "ON". The current draw on the cheapos is insanely high! Here's the vid:


http://youtu.be/E8oopG2GpF0

digiex_chris
01-26-2015, 11:59 AM
fantastic! very cool. real numbers beats conjecture every time. Now I know for sure what's going on when I was suspecting about my cheap calipers vs my good ones, with the measurements going crazy at some unexplainable point.

One other thing I seem to have noticed varies but never fully tested with a proper method is temperature compensation. My cheap ones will be a couple thousandths off between a hot and a cold day compared to the Mitutoyo's. That whole effect where resistance and capacitance change with temperature needs to be compensated for in many types of digital measuring tools, like scales. I know of one shady jewler that's used a cheap temperature-vulnerable scale to make a few bucks buying gold.

Old Hat
01-26-2015, 12:17 PM
Think, BMW, to get to work.
Think Mitutoyo, once there and get'n down to Bizness.

PixMan
01-26-2015, 12:51 PM
I really appreciate the confirmation of why my Mitutoyo calipers use so few batteries.

If you ever get the chance to check a Starrett, I'd bet they're right up there with the Chinese no-name ones in terms of power consumption, or worse. They use a relatively huge battery and it doesn't last but 1/5th or less of the time a little SR44 does in my Mitutoyo.

superUnknown
01-26-2015, 01:37 PM
One other thing I seem to have noticed varies but never fully tested with a proper method is temperature compensation.

That is a great question! I'll look into it.

dp
01-26-2015, 04:16 PM
This was written up some years ago - either here or at PM, or perhaps even both. I learned of it by example since the second time I went to use any digital instrument I was always met with a dead battery. I finally decided I prefer non-electric instruments and I especially like my dial calipers though it would be nice to easily convert between imperial and metric :)

lakeside53
01-26-2015, 05:15 PM
My Mitutoyo and B&S calipers and mics last years.. so many I can't remember ever changing batteries. I had a set of "SPI" (import) mics.. maybe 6 months.... sold those.

Rich Carlstedt
01-26-2015, 05:59 PM
That's an awesome review of a common issue with Digital Calipers.
Thank You Superunknown....

I would say that both my Mitutoyo and Fowler (both Japanese ) have great battery life !
My old Starrett 722 is a fantastic Digital but also used lots of power when sleeping.
Having a 200+ dollar inspection tool that reads in tenths ( yes, .0001) was worth having so I modified it
and will post the pics here , when Photobucket gets back on line.
I am not sure if the solution will work with current imports, but it is a simple technique to dramatically reduce battery changes.
Rich

PStechPaul
01-26-2015, 06:48 PM
I did the same test on my older (better) HF calipers some years ago, and I think the current readings about matched those in the video. The LR44 (http://en.wikipedia.org/wiki/LR44_battery) battery has about 150 mAh and the SR44 about 200 mAh. So 20 uA should result in about 10,000 hours or 1.14 years. I have recently found on-line sources for these batteries for about 25 cents each so I don't mind changing them. My older calipers blink the display for a low battery condition, and turning them off just blanks the display and drops current by about 20%, but holds zero. My newer cheapo from HF has auto-shutoff and you must re-zero. I haven't tested my newest HF calipers which also have fractional reading, but they do hold zero when turned off.

oldtiffie
01-26-2015, 07:00 PM
I accept that my batteries in my digital stuff - micrometers and calipers - regardless of whether they are "Starrett" or "Off-shore" - will use up battery power albeit at varying rates.

I just accept it as part of the cost of having them and so as changing a battery is only a minute or two of time I replace the battery if/as required and get on with what ever I want to do.

Battery cost is of no concern here - probably dearer than in the USA - and provided they don't leak I am OK and up and running again in next to no time at all.

oldtiffie
01-26-2015, 07:04 PM
It could be that variation of accuracy with temperature could be due to the effects of temperature co-efficient of expansion (or contraction).

It can easily be countered by using the caliper to measure a know-size object (at room temperature) and noting the difference and allowing for it.

Doc Nickel
01-26-2015, 07:58 PM
I have a Mitutoyo quill readout on my vertical mill. After looking at some photos of some millwork from a while ago, I realized I'd had that readout on the mill for over ten years... And I think I've replaced the battery in it once. Maybe.

I also have a set of the usual cheap import calipers- $24 at O'Reillys' auto parts years ago- and those things have a blinking display (low battery) pretty much every time I pick them up, it seems.

Just proof again you pay for quality. :)

Doc.

oldtiffie
01-26-2015, 08:18 PM
Well, if it were me and knowing that I'd have to change the battery I'd make it part of my start-up procedure - only a couple of minutes and less that 1$ per time.

Its all to easy to be "too aware" of the "time" you save without considering the time and consumables costs without going over-board into "penny wise and pound (UK) foolish" territory.

A cost-benefits analysis might render a few surprises - but put a realistic value on your time ($60US per hour = $1US per minute?).

For me, batteries are "consumables" and just part of the every day cost of running a shop - same as electricity and welding rods and gasses etc..

Doc Nickel
01-26-2015, 08:42 PM
I was going to say it's also 'pound foolish' to buy the cheap batteries, but in this case, it's probably one of the highest and best uses for cheap no-name cells. For the Mitutoyos, though, I buy the good stuff- yeah, they may be $4 retail from the grocery store, but I think $4 every ten years on the quill readout, and another $4 over the past 5 years or so I've had the calipers, is a small price to pay.

Doc.

Black_Moons
01-26-2015, 08:49 PM
I buy 4 packs of LR44's at the local dollar store for $1
So I really don't care anymore how long my caliper batteries last.

macona
01-26-2015, 09:35 PM
One problem with the video, it really takes a special meter to measure down that low, you have an issue with burden footage across the sense circuit that screws up low current readings. I have one of these little guys at work to measure down to the nA range, I had to design a temperature transmitter that would run off two AA batteries for two years:

http://www.eevblog.com/projects/ucurrent/

superUnknown
01-26-2015, 10:06 PM
agreed, but I don't have a Ucurrent, so as a comparison I think it pretty telling.

PStechPaul
01-26-2015, 11:09 PM
The current sense resistors are usually for 199.9 mV full scale, so the 20 uA reading on the 200 uA range (1kohm) probably dropped 20 mV. Not really very significant for a rough comparative reading with a 1.5 V source.

My Ortmaster reads current as low as 50.00 A FS on a 1000A 100mV shunt, which is 5 mV FS and 500 microvolts for a 5.00A reading, about as low as needed for that application. It uses an AD620 instrumentation amplifier front end which can be programmed for a gain of as much as 1000 using a single resistor. I'm reading AC, which is more difficult than DC to filter noise. It uses a computed true RMS so it reads the same for 5.0 AAC as it does for 5.0 ADC. It's designed for 60 Hz line frequency, and samples at 2400 samples/sec, so I have RC filters with a knee at about 300 Hz.

CCWKen
01-27-2015, 12:31 AM
I take the batteries out of my HF Cen-Tech calipers when they're not in use. Both have lasted well over five years on SR44s. Only takes a couple of seconds to put the battery in or take it out. But, HF no longer sells the Cen-Tech branded calipers. They have an even cheaper made unit at twice the price. :confused:

The way I look at it is I can go for about 3,000 years on batteries before breaking even on a Mitutoyo for no better performance.

Frank Ford
01-27-2015, 01:51 AM
In case you hadn't seen it before, here's a link to an interesting article about digital caliper current draw:


http://www.fliptronics.com/tip0006.html

mf205i
01-27-2015, 04:11 AM
Battery life is not an issue. I get ten LR44 button cells for a buck at the .99 cent store. On average the cells last 7 months in the HF calipers. To pass up a tool that is accurate, reliable and inexpensive because you need to spend 20 cents a year is absurd.
I was a committed dial caliper guy but I was curious about the digitals. About 6 years ago HF had 6-inch digital calipers on sale for 10 bucks. So to satisfying my curiosity I asked the wife to pick up 10 of them. She came home with 9 calipers. I set down for the evening with my standards and each one was checked at 12 different sizes for accuracy, fit and finish. All but one was within plus or minus .001 inch over their entire range of 6 inches and a couple were much better. The worst one was smoother and more accurate than the last Mitutoyo dial caliper that I purchased, NO BS. I gave most of them away, kept several for myself and put one into service. For about 6 years now it would have been a rare day that it wouldn’t have been used at least once. It has been dropped on concrete 4 times, it has had the points reground 3 times, the slide tension has been adjusted twice and I am still on the original caliper. It is still in tolerance of plus or minus .001 inch over 6 inches. I don’t feel bad about using it to scribe layout lines and the first time I knocked it off of my old Monarch, it wasn’t nearly the event that it would have been had it been the Mitutoyos.
They won’t impress your customers or your friends but they certainly are accurate, reliable and an incredible value. So, get one, learn to check zero every time you pick it up, change the battery twice a year, don’t pretend it’s a micrometer and I think you will find that you won’t be in a hurry to “upgrade”.
Mike

Old Hat
01-27-2015, 09:43 AM
I bet one could construct some kind of a story problem
that could be part of pre-employment screening.

This way, if the applicant can somehow find a way to convince him/her self,
that a HF caliper is "right up there" with a Mitutoyo..............
well, you can shake his/her hand and say, "Thanks for your time".

loose nut
01-27-2015, 10:51 AM
I haven't found a cheap caliper HF or other that is anywhere near as nice as my Mityutoyo Digimatic. There are many difference besides battery life.

I do have a cheap digital scale on the quill of my bench mill, not the most accurate thing. I don't know what is wrong with it, it is 20+ years old, I frequently forget to turn it off and I have only changed the battery twice. Can I fix this by using cheap no name LR44 batteries???

superUnknown
01-27-2015, 11:08 AM
"The worst one was smoother and more accurate than the last Mitutoyo dial caliper that I purchased, NO BS."

Apples vs. Oranges OR is them's fightin' words? :p

superUnknown
01-27-2015, 11:15 AM
Should anyone be interested:
Previous to the current draw vid I tore down the $10 caliper. Not for the faint of heart!!! (caveats: apples vs. oranges, ymmv, $10, etc etc)


http://youtu.be/WvszAb0Y0Ec

mrriggs
01-27-2015, 11:23 AM
I take the batteries out of my HF Cen-Tech calipers when they're not in use. Both have lasted well over five years on SR44s. Only takes a couple of seconds to put the battery in or take it out. But, HF no longer sells the Cen-Tech branded calipers. They have an even cheaper made unit at twice the price. :confused:

The way I look at it is I can go for about 3,000 years on batteries before breaking even on a Mitutoyo for no better performance.

Same here, put the battery in when you start working and take it out when you are done, battery lasts for years.

Other than the battery "issue", the Cen-Tech calipers are as good as any. Sure, it doesn't have micrometer precision but that is because it is not a micrometer. Calipers are very convenient for quick, rough measurements. It doesn't matter if one brand is slightly more accurate than another. When size really matters, NO caliper is the right tool for the job.

superUnknown
01-27-2015, 11:47 AM
The current sense resistors are usually for 199.9 mV full scale, so the 20 uA reading on the 200 uA range (1kohm) probably dropped 20 mV. Not really very significant for a rough comparative reading with a 1.5 V source.

My Ortmaster reads current as low as 50.00 A FS on a 1000A 100mV shunt, which is 5 mV FS and 500 microvolts for a 5.00A reading, about as low as needed for that application. It uses an AD620 instrumentation amplifier front end which can be programmed for a gain of as much as 1000 using a single resistor. I'm reading AC, which is more difficult than DC to filter noise. It uses a computed true RMS so it reads the same for 5.0 AAC as it does for 5.0 ADC. It's designed for 60 Hz line frequency, and samples at 2400 samples/sec, so I have RC filters with a knee at about 300 Hz.


Excellent info and explanation Paul! Thank you!

superUnknown
01-27-2015, 11:57 AM
maybe I'm looking at this the wrong way, but I'd rather have a well designed, well built tool than fiddle with a work-around every time I want to use it.
Fiddling with the battery? Ugg.

lakeside53
01-27-2015, 12:38 PM
Same here, put the battery in when you start working and take it out when you are done, battery lasts for years.



lol.. sorry, life is too short to take the battery in and out every day (yes, I use my caliper daily) :)

Rosco-P
01-27-2015, 12:51 PM
maybe I'm looking at this the wrong way, but I'd rather have a well designed, well built tool than fiddle with a work-around every time I want to use it.
Fiddling with the battery? Ugg.

Agreed.
Somehow I just knew the thread would take this turn.

lakeside53
01-27-2015, 01:23 PM
yep - those that have the el-cheapo and the premium brands defend their choices just like oil threads, ford/chevy. lol. Whatever floats your boat. If you only use your calipers/mics a few times year, no big deal, but...

Oh .. for those that like to take their batteries out - remember to wash your hands first, don't break the compartment door, and don't put finger prints on the batteries! ;)

PStechPaul
01-27-2015, 01:55 PM
What, you don't wear white gloves when you service your calipers in your environmentally controlled clean room? For shame! :rolleyes:

I couldn't (or didn't want to) watch the entire video of the guy bad-mouthing the Chinese calipers. Yes, there are quality problems, especially with the newer Pittsburgh as compared to the older Cen-Tech versions with the same stock number, but they are certainly usable as guessing sticks or measuring wrenches. In our shop class, we were told that calipers are only to be used for fairly rough measurements where +/- 0.005" is acceptable, and thus for part tolerance of 0.01" or 0.02" or greater. I think we are "spoiled" by finding that digital calipers usually are accurate to 0.001", and that also applies to most dial calipers as well.

Much depends on attitude and preconception, and perhaps an "anality" when it comes to tools and saving/spending money. I admit to being on the cheap side of the fence, and I have dealt with some quite bad tools, but in many cases I have been able to fix or modify them to be acceptable, which has been a challenge and learning experience. My latest $10 HF calipers were bought with the intention of hacking them to use as a Z-axis DRO on my mill, but I was pleasantly surprised by their fairly good performance. This may remain an unwinnable argument for those on both sides of the fence, and I doubt that anyone will jump over that fence into the opposite camp due to any of the rhetoric expounded by those who firmly hold to their viewpoints and prejudices.

For things like the shorter battery life, (and other attributes), it's a case of "mind over matter". If you don't "mind", it doesn't "matter". :p

Puckdropper
01-27-2015, 08:42 PM
maybe I'm looking at this the wrong way, but I'd rather have a well designed, well built tool than fiddle with a work-around every time I want to use it.
Fiddling with the battery? Ugg.

I have three digital calipers. The one that eats batteries is around here somewhere, the two that don't are on workbenches. I'd like another caliper, but am not willing to mess with fiddling with the battery.

Some folks complain about the caliper losing zero when it shuts off, but to me that's no big thing. Close them, zero, and open them back up.

lakeside53
01-27-2015, 08:52 PM
Current draw can't be that hard a problem. I guess the cheap brands just don't care. I have a 1984 "CENTRAL" (when it was Japanese, not a Chinese brand name) 6" caliper. it get 2-3 years out of and SR44 battery and doesn't even turn itself off. Of course, in 1984 it cost a week's wages!

My Digimatic and B&S don't loose zero or any other setting, Nice...

R.Bolte.Jr
01-27-2015, 10:13 PM
I must have the best luck in the world.
I bought a Starrett 797B, 7 years ago.
It has been used at least a couple times a week since, rarely turn it off, just let it time itself out.
It has the original battery in it.

Must be like all of those urban legends back in the 70s about the secret, 200mpg carburetor that was confiscated from "a friend of my cousins neighbor"

Rich Carlstedt
01-27-2015, 10:34 PM
Like I said in Post #8, I like my Starrett 722 and modified the case to save the battery life
Since it's a super precision Caliper, it is only used at certain times and does not lay around on the bench.
I have other cheaper calipers for that.
Photo is self explanatory and the fix is a piece of cake
Rich

http://i273.photobucket.com/albums/jj220/StationarySteam/Shop%20Tools/P5270008-1.jpg (http://s273.photobucket.com/user/StationarySteam/media/Shop%20Tools/P5270008-1.jpg.html)

http://i273.photobucket.com/albums/jj220/StationarySteam/Shop%20Tools/P5270004.jpg (http://s273.photobucket.com/user/StationarySteam/media/Shop%20Tools/P5270004.jpg.html)

http://i273.photobucket.com/albums/jj220/StationarySteam/Shop%20Tools/P5270007.jpg (http://s273.photobucket.com/user/StationarySteam/media/Shop%20Tools/P5270007.jpg.html)

flylo
01-28-2015, 12:14 AM
Battery life is not an issue. I get ten LR44 button cells for a buck at the .99 cent store. On average the cells last 7 months in the HF calipers. To pass up a tool that is accurate, reliable and inexpensive because you need to spend 20 cents a year is absurd.
I was a committed dial caliper guy but I was curious about the digitals. About 6 years ago HF had 6-inch digital calipers on sale for 10 bucks. So to satisfying my curiosity I asked the wife to pick up 10 of them. She came home with 9 calipers. I set down for the evening with my standards and each one was checked at 12 different sizes for accuracy, fit and finish. All but one was within plus or minus .001 inch over their entire range of 6 inches and a couple were much better. The worst one was smoother and more accurate than the last Mitutoyo dial caliper that I purchased, NO BS. I gave most of them away, kept several for myself and put one into service. For about 6 years now it would have been a rare day that it wouldn’t have been used at least once. It has been dropped on concrete 4 times, it has had the points reground 3 times, the slide tension has been adjusted twice and I am still on the original caliper. It is still in tolerance of plus or minus .001 inch over 6 inches. I don’t feel bad about using it to scribe layout lines and the first time I knocked it off of my old Monarch, it wasn’t nearly the event that it would have been had it been the Mitutoyos.
They won’t impress your customers or your friends but they certainly are accurate, reliable and an incredible value. So, get one, learn to check zero every time you pick it up, change the battery twice a year, don’t pretend it’s a micrometer and I think you will find that you won’t be in a hurry to “upgrade”.
Mike

I must have bought the same ones & I bet I have 6 or better & they've done well. 2 or 3 in the shop, 1 in each truck, 1 in the house, etc. Great advice!

vpt
01-28-2015, 08:13 AM
After hundreds of years my mitutoyo has gone funky. I am still using it but the reading isn't trustworthy. I finally just put in a bid on a new mitutoyo. Maybe I'll take better care of this one so it lasts a few hundred years instead of a couple hundred.

mrriggs
01-28-2015, 11:20 AM
maybe I'm looking at this the wrong way, but I'd rather have a well designed, well built tool than fiddle with a work-around every time I want to use it.
Fiddling with the battery? Ugg.

On that we can agree. I too would rather have top of the line tools, but as long as I'm working 60 hours a week to put food in the kid's mouths, spending $100+ on a Guess-O-Meter is not going to happen. It wasn't a choice of buying the cheap one over the expensive one. If I didn't have the Cen-Tech digital caliper then I would have no digital caliper. So the convenience of having a decent digital caliper far outweighs the minor inconvenience of having to take the battery out of it.

Mike Nash
01-28-2015, 01:16 PM
Psst, unless you live in Japan, Mitutoyo IS ALSO an offshore manufactured item.

lakeside53
01-28-2015, 03:32 PM
Probably offshore to Japan also now ;)

oldtiffie
01-28-2015, 09:02 PM
I could not give a big rat's ar$e about where a machine tool or object is made so long as is warranted to the end-buyer to meet the buyer's requirements.

I would be very surprised if all Mitutoyo products are made in Japan and that some are out-sourced to other countries.

"Vertex" and "Ali Baba" have got this down to a very high level of skill and consistency.

In short, if the Mitutoyo or other "off-shore" product meets my needs I will buy it - and on that basis the dearest/most expensive product does not "win" for me and by the same token/criteria the cheapest does no always win it either.

The trick is knowing what your real needs are.

There is no way that there is any "bragging rights" stuff in my shop - just stuff that does the job to my requirements with reliable consistency at a reasonable cost.

loose nut
01-29-2015, 10:05 AM
What ever works for you Tiffie but on the flip side of the coin, I have had several cheap calipers and only one of them was any good. It quit on me after a few months. The cost of several cheapies I bought would have gone a long way to pay for my Mityutoyo.

michigan doug
01-29-2015, 11:42 AM
They both have their uses. I have both. Hey, but did you make something today???

Here's a perfect application for the ten buck HF digital caliper. I was working on making some baffles for my new suppressor. I wanted the wall thickness of the cone to be 0.060". There was no way to get a caliper in there through the 1/4" hole, or any other convenient and fast/direct/reliable method.

So, I took my fancy schmancy (proven and reliable and accurate) ten dollar cheapy, and ground the top blade thin and narrow so it would sneak into that hole and measure the wall thickness directly.

Worked like a champ. I how have a pair of "duck billed" calipers for narrow and inconvenient spots.


Wouldn't you feel bad mangling up your nice expensive mitutoyo like that???


doug

loose nut
01-29-2015, 07:20 PM
Wouldn't you feel bad mangling up your nice expensive mitutoyo like that???


If I was drunk enough to do that to a MIT then I would probably feel a lot worse the next morning.

oldtiffie
01-29-2015, 09:16 PM
What ever works for you Tiffie but on the flip side of the coin, I have had several cheap calipers and only one of them was any good. It quit on me after a few months. The cost of several cheapies I bought would have gone a long way to pay for my Mityutoyo.

Let us compare oranges with oranges.

I said that I only bought lesser cost calipers and items that suited my need as regards cost, performance, reliability and longevity.

All of my ("cheap" and "off-shore") calipers (amongst others) meet those objectives.