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Halfords Digital Tyre Pressure Gauge

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I have a Halfords digital tyre pressure gauge that I have been using for a couple of years.  On the packaging it states the accuracy is: +/- (1% + 1LSD).  Does anyone know what this means and can translate it into PSI figures.

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Well, a Google search revealed the following:

Lysergic acid diethylamide (LSD), also known colloquially as acid, is a psychedelic drug. So, accuracy must be within +/- 1% of a gram of acid.


On a more serious note, LSD probably stands for Land Surface Datum, or the pressure at the particular altitude. Therefore if the pressure at 100m is 1 bar, the gauge will be within 1% of that measurement.

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This is the degree of it's accuracy and you don't convert this figure into PSI figures. Just use it and it'll show you the PSI.

It means that it is reasonably accurate, certainly should be ok to use on your car 👍


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In a digital display, LSD will be Least Significant Digit being the one furthest to the right, The further right you go the more accurate eg. good electronic test equipment is between 6-10 digits

say it reads 34.5 psi it will be within +/- 1 Least Significant Digit (.1) +/- 1% (0.001)- depending on the device and its primary calculation you may lose or add due to the conversion between parameters due to rounding and the LSD used


Many moons ago i build an Arduino boost gauge based on a Bosch MAP sensor with a second for barometric pressure, that was calculated with Kpa then to Psi with a Bar option also allowing automatic barometric adjustment or ASL




simply put it, reads a number and the gauge goes Pshhh after removal

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