Help me find a simple unit conversion tool for industrial use?

May 9, 2009 12:59 PM

A friend is working in an industrial plant and needs to frequently convert convert lbs to kgs. They currently use a calculator and divide by 2.2046, but find constantly punching in "xxxxx / 2.2046 =" tedious and error-prone. They'd like a reasonably-priced device (a calculator or PDA application) with reasonably sized buttons or a touch screen that would simplify this process. They'd like to have the answer displayed as digits were input (without needing to hit = or enter), as well as being able to clear the input amount without resetting the units to be converted.

LB->KG is the only conversion that they currently need to do.

The process cannot be changed. They have access to a computer, but it is not convenient to use.

Something like an iPod Touch is probably too expensive (and at risk of theft) but if there is a specific conversion application for the iPod/iPhone that works well, that would be an interesting data point.

I've tried Googling for variations of "unit conversion calculator", but only web applications are returned.

posted by theclaw to technology (28 comments total)

This seems like a job for a programmable calculator. I would write little programs like this all the time on my HP calculator, so you would just enter a number and then hit run to get the converted result.
posted by pombe at 1:01 PM on May 9

Slide rule?
posted by hattifattener at 1:06 PM on May 9 [2 favorites]

Yeah, any TI calculator from OfficeMax would do this for $50 or so, and it would still be overkill.

Example that you could easily extend to pick a source unit and go either way with:

http://www.ticalc.org/pub/81/basic/math/lboz2kg.81
posted by kcm at 1:10 PM on May 9

What about an old Palm Pilot?
posted by odinsdream at 1:15 PM on May 9

Most of the Sharp Engineering Calculators have a series of built-in conversion tables. They aren't exactly friendly to access, but if you were doing the same conversion all day you would easily remember to hit the 3-button sequence to execute the conversion.
posted by odinsdream at 1:17 PM on May 9

An alternative to a programmable calculator would be an Excel file (or any other spreadsheet program). If the computer is in a convenient location, they could set up an excel file which would automatically perform the division operation on any number that's put into one cell and display the result in the next cell. That would be automatic, resettable, and wouldn't require too many button pushes.

To do this, open an Excel file. Put a random number in cell A1. In cell A2, type "=(A1/2.2046)" and hit enter. Now whenever you type a new number into cell A1, that number divided by 2.2046 will be displayed in cell A2.
posted by asras at 1:27 PM on May 9

2nding the TI suggestion - this would be simple to program on a TI-83 or similar.
posted by Salvor Hardin at 1:29 PM on May 9

I use NeoCal on my Palm. Type in the number, press the "lb" button to indicate pounds, then press the "kg" button to indicate that you want to convert to kilograms. Easy as pie, although not quite as perfect as what you are envisioning.
posted by grouse at 1:31 PM on May 9

Couldn't one just put 2.2046 onto the Memory button of the calculator?
posted by lucidium at 1:40 PM on May 9

I'm dredging this up from my childhood memory, but I just tested it on one calculator and it seems to work. As I remember it, on most basic calculators, if you do the first calculation, e.g.

3 ÷ 2.2046 =

and then without clearing the display or doing anything else, just type another number and hit equals:

5 =

the calculator will repeat the calculation, without having to re-enter 2.2046.
posted by chrismear at 1:46 PM on May 9 [1 favorite]

Go to Amazon and look for "conversion calculator" or "metric calculator"

Sharp
posted by b1tr0t at 2:01 PM on May 9

There's quite a lot of programmable calculators that could easily do this.

But if this is all they need to do, maybe they can look at some of the older models, which will probably be cheaper.
posted by movicont at 2:19 PM on May 9

Since you're asking for a cheap solution, this probably won't help, but if his personal cell is an iPhone, there is a cheap, <$5 app called "units" that will do this conversion just fine, and instantly.
posted by Jason Land at 2:46 PM on May 9

Man, you can totally get a generic calculator for about $7 that will make this work I'm pretty sure. Look for one with M+, MRC, and MC buttons.

M+ adds to memory. MRC recalls, and MC clears. Read the destruction manual. Fairly sure your operation should be something like 2.2046, M+. Then number, /, MRC. Enter. I had one in the past that would actually recall the function too, so it would just be Number, MRC.

I'd probably over engineer it with an old TI-81 or 82 or 83 or 85 or 90 or whatever, and make a little app that just gave you a prompt with "enter pounds", and then would spit out the number. Bonus points because the device actually has other applications.
posted by TomMelee at 3:17 PM on May 9

TI does make at least one model of scientific calculator with metric -> US conversions built in here is one of them.

casio makes them as well

The way it typically works is you enter in the number, then hit a button (maybe something like {2nd} then {lb to kg})
posted by ArgentCorvid at 4:33 PM on May 9

If you go the cheap Palm route, there is a freeware app called "Converter" that does exactly what you want - you select lbs to kgs, and then it automatically displays the conversion as you input the number to be converted. No "enter" key needs to be pressed.
posted by birdsquared at 5:09 PM on May 9 [1 favorite]

Graphcalc is a Windows download graphing calculator, and it has a CONV button with a series of menus to convert almost any unit imaginable. It's free and fits on a floppy. I highly recommend it for anyone regardless of graph use, because if you're not graphing, it keeps a long list of your previous calculations in the empty space to refer to at anytime, like an adding machine.
posted by Brian B. at 5:45 PM on May 9

If you wanted to make a little hobby of this (and be very job-specific) you could hook an Arduino up to a keypad and an LCD. Build the program to do live conversion while you type, provide a reset button to clear out. Pop it all in a wall-mount box.
posted by odinsdream at 6:13 PM on May 9

There's also this. A free download that converts only metric.
posted by Brian B. at 6:25 PM on May 9

One of the dedicated conversion calcs is probably what the poster wants. Note that they specifically don't want a computer based calculator.
posted by b1tr0t at 6:56 PM on May 9

You can get currency calculator. Just the same style as a normal pocket calculator with an extra couple of buttons. Instead of the exchange rate between currencies, you can just use the value you've already said. That would require pressing a button after you've input the amount though - but I can't see a way around that - how would the calculator know if you meant 1 or 10 or 100 etc?
posted by kg at 4:14 AM on May 10

Are the range of masses infinitely variable, or are there just a few likely inputs? If the latter, a simple table stuck to the wall would be quicker, cheaper, and likely less accident-prone.

Are the numbers being read from a scale? Dual metric/imperial scales are available.

If it's an industrial plant, there may be safety/commercial liability issues in relying on punching stuff into a calculator. Maybe something to bring up with supervisor?
posted by scruss at 5:50 AM on May 10

This looks like just the thing... A calculator for doing conversions to/from metric units. Looks like you can keep the current conversion stored in memory and then just press the value to convert and then the "to metric ->" key.
posted by Morbuto at 9:40 AM on May 10

Almost all scientific calculators these days have units conversion. Do they really need the measurements to 5 digits? I usually just use 2.2.
posted by chairface at 1:54 PM on May 11

b1tr0t has what I was looking for; I just didn't know the name or how to find it. It's not perfect, but it's about as simple as it can get with a one-line display. I had an old Sharp engineering calculator that had the conversion tables built in (I had forgotten that it had the ability to do that), and I've gone over using the memory function with them in the interim.

Developing an graphing calculator or Arudino application is kind of overkill for the application. I haven't touched my HP 48G in over five years and I've never owned a TI, so it'd take me a while to develop something for them. They don't like using the stylus on the old Palms.

Most of the scales (and all of the documentation) has been converted to metric, but there is some older equipment that hasn't been updated yet. The range of values is large enough that a table isn't feasible, and 2.2 isn't enough precision.

Thanks, everyone!
posted by theclaw at 3:39 PM on May 11

Quite a lot of even very crappy two-dollar four-function calculators have an operate-on-constant function built in, as chrismear mentions. If the ones you're already using don't work the way he suggests, then a fairly common variant is to type in the number you want, then hit the appropriate operator key twice, after which you can just keep typing numbers followed by = to apply the stored number and operator. So in your case, you'd type

2.2046 ÷ ÷

to set the thing up, then

192 =

should immediately display 87.096, and

22046 =

should immediately display 10000, and so on.

Another common design is similar but doesn't swap the order of the operands for division and subtraction as the above example assumes it will. If you've got one of those, then the key sequences above would get you 0.01148 (i.e. 2.2046 ÷ 192), 0.0001 (i.e. 2.2046 ÷ 22046) and so on which is not what you want. So your initial setup would need to be

1 ÷ 2.2046 = × ×

after which you could just enter a series of pound amounts followed by = as before.

On most calculators I've used, using the CE button to clear a mis-keyed number won't break the operate-on-constant calculation setup.

If you do in fact find an appliance that does conversion on-the-fly, digit by digit, without requiring some kind of terminating keypress to convert the entered number, then you're getting no way to check that your input digits have been accepted correctly. That strikes me as risky design. Needing to press = after completing entry of the weight in pounds seems much safer.
posted by flabdablet at 9:39 PM on May 12 [2 favorites]

flabdablet: You just taught me something new about calculators. I find that amazing. Thanks!
posted by odinsdream at 3:17 PM on May 18

Comes of being old enough to have actually bought a four function calculator that came with an instruction manual :-)
posted by flabdablet at 4:10 PM on May 18