More to do with the button cells than the callipers I think.
I guess that callipers are so evidently simple to use that few of us bother to refer to the instructions, which clearly state that you must use
1.55V silver Oxide cells – not 1.5V
Alkaline cells. The discharge characteristics of each cell are quite different. Silver Oxide maintain their voltage to a point at which they fail. Alkaline – which are already below the stated 1.55V voltage needed by the callipers, taper off and soon fall below the voltage at which the callipers will operate.
People often say “you can buy a sheet of calliper button cells for a quid at Pound Shops” but in fact you can't - not if you're buying the correct type of LR44 cell as per the instructions. Not all cells are created equal! The ones that the likes of Poundland et al sell are 1.5V
Alkaline. I don't know what the initial Voltage or the capacity of a new pound shop alkaline SR44 cell is, but if it falls below 1.45V in use, (which I dare say won't take long), the callipers will malfunction. Furthermore, silver oxide cells not only have a higher Voltage – they have a higher capacity and a very different discharge curve..
Short battery life and malfunction of digital callipers (apart from dirt in the sensor head), is far more likely caused by using the wrong LR44 cells. (Using cheap alkaline cells instead of silver oxide). I've got three digital callipers of various makes - all of them budget types. (The oldest is 22 years old). They all work fine using the correct 1.55V solver oxide cell and the readings compare very closely.
I've only got one set of instructions now (for a Clarke/Machine Mart instrument) and here's what they state:
Quote:
8-<
Power Source: One silver oxide 1.55V LR44, capacity 180 mAh. Current <20uA
'Troubleshooting': Digits flash randomly or all five digits flash simultaneously: Battery Voltage below 1.45V.
Unquote.
8-<
I never remove the cells on any of my callipers and they last at least a year.
When I bought the callipers, in all three sets, the LR44 silver oxide cell was stored in the little round hole in the foam till fitted. I keep a spare one in the hole in each one for when needed. The only problems I've had with one of the callipers is that I use it when I'm woodturning and through allowing fine dust to get on it, which gets drawn into the slide so I have to remove the slide assembly and clean it with a sable artists brush. To remove the assembly, there are two tiny grub screws, one either side of the locking screw on the top side of the slide.
Of my three callipers only the Clarke one has an on/off switch - the other two auto switch off when left alone for a few seconds, so I suspect that they go into 'sleep mode' and draw a minute current till next operated, because they 'wake up' the second that the slider is moved. (It would take a long time to reduce the battery Voltage of a 180mAh silver oxide cell from 1.55V to 1.45V at only <20µA).
It's easy to make a mistake when buying them, even though it does usually state either alkaline 1.5V or Silver Oxide 1.55V on the package.
EG, these are both Energizer brand, both LR44, and both packages look almost identical except for the small print:
1.5V Alkaline:
https://www.amazon.co.uk/Energizer-L...GXNDMMD3ETRRJ1
1.55V Silver Oxide:
https://www.amazon.co.uk/Energizer-S.../dp/B000IX2GXI
I don't want to infer that there can't be other things that can cause callipers to malfunction, just that it's worth trying a correct cell, which might just be at the root of the problem.
Take a look at the discharge graphs on the datasheets:
Silver Oxide:
https://www.murata.com/products/productdata/8809693806622/SR44R-DATASHEET.pdf?1615298419000
Alkaline:
https://www.celltech.fi/fileadmin/user_upload/Celltech/Prod.sheets/11186.pdf
Hope that’s of interest.
David.
