I am always looking for easier ways to do things and stumbled on this. I don’t know if it will work on all digital calipers, but it does work on mine. when I am ready to make a measurement, I turn on the calipers by pressing the on/off button, then I zero the device and then make my measurement. Next time you make a measurement, just slide the jaws of the calipers open without turning it on. Mine come on and are zeroed every time. I hope it will work with yours.
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Mine are at least 25 years old but were high quality, I’ll have to check that out. This one has a port for direct connection, is that pretty standard now?
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I am not sure about any port. Mine were not that expensive, only around $25. I liked the all metal construction instead of the plastic ones.
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I’ve got two digital calipers. One which works this way and one that is “absolute origin”. That one will give an accurate measurement even if you turn it on after you’ve moved the jaws.
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I will say the composite calipers are nice and light compared to Stainless.
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And non metal calipers are great for things easily scratched…
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The Horror Fright ones have this behavior - be advised, it implies that power is always being supplied to the circuit, even if the display is not on. I still only have to replace the batteries every year or so, which isn’t bad at all.
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I think mine do that. (Heck, I might have the same ones as you.) But I always find I need to 0 them every time to be on the safe side. Frankly, if my life depended on their accuracy, I’d probably be dead. 
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This is a case of “get what you pay for” really. the Harbor Freight ones and the like aren’t great, but you can get decent results by carefully zeroing every time.
As I get more confident with my lathe (the big reason I haven’t been either glowing or forging lately) I may set the cash down for a set of Mitutoyo calipers, but right now the metrology stuff I have is “good enough”
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Oh, absolutely. And I’m fine with that. I 0 them every time and it seems pretty okay.
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Yupyup! For woodworking, they’re overkill, even! And they’re fantastic in the glowforge context, for accurately getting material thickness.
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This is always the case because none of them have a proper on / off switch, just a button to wake them up. Possibly it takes a little more current to poll the sensor than it does to poll a button but probably not much. My expensive Mitutoyo ones don’t do it but my cheap plastic one does.
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Yep…that does work with mine. I just have to watch that they don’t turn on when I’m putting them away, or it will help the battery run down too fast.
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Due to the cheap ones not truly powering off I found that my battery was dead way too often. So I cut the power trace from the battery on the little PCB and soldered on wires and added a physical switch. I do have to zero every time I use them, but the battery should last a really long time now.
About a year after I did that little mod I bought an inexpensive analog caliper. They have both Inch and Metric on the dial and they have been great. I actually use them more then the digital ones now that I’ve become confident in reading them correctly.
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Well done. I hate that fact that nothing has proper switches on nowadays, whether it be battery or mains powered. Especially because batteries now corrode when they are flat.
Another way to do it is with a mercury tilt switch, so they turn off when placed face down. See http://hydraraptor.blogspot.co.uk/2017/06/mooshimeter-mod.html.
Or a normally closed reed switch so you place it near a magnet to turn it off. I got some from China but several had high contact resistance.
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I hold the world’s record I think. Bought mine like 30 years ago, and no switch so I took the battery out every time I used it which was very infrequent. Just replaced that battery when I started using the laser 6 months ago.
Nice mod there. 
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That’s real dedication. 
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