Trying to find an accurate tyre pressure gauge

[twas_brillig]

From https://winters.com/engineering/gauge-accuracy/
"Accuracy can be expressed as percent of span or percent of indicated reading. Percent of span is the most common method with percent of indicated reading being generally limited to precision test gauges or high resolution digital gauges. Accuracy as a percent of span means that a 100 psi gauge with a 2% accuracy is accurate to within 2 psi whether the gauge is reading 1 psi or 100 psi. Accuracy as a percent of indicated reading means that a gauge with 0.1 % accuracy displaying 100 psi is accurate to 0.1 psi while the same gauge displaying 50 psi is accurate to 0.05 psi—twice as accurate."
My working career was pretty much oil & gas, primarily pipelines, so I'm guessing that the gauges I ran into were probably percent of indicated reading - which is not applicable outside of some pretty narrow bounds. Doug

 

[twas_brillig]

Further down the above web-page:

 

[twas_brillig]

From https://www.instrumart.com/pages/539/pressure-gauge-accuracy-grades
"Accuracy can be expressed as percent of span or percent of indicated reading. Percent of span is the most common method with percent of indicated reading being generally limited to precision test gauges or high resolution digital gauges. Accuracy as a percent of span means that a 100 psi gauge with a 2% accuracy is accurate to within 2 psi whether the gauge is reading 1 psi or 100 psi. Accuracy as a percent of indicated reading means that a gauge with 0.1 % accuracy displaying 100 psi is accurate to 0.1 psi while the same gauge displaying 50 psi is accurate to 0.05 psi—twice as accurate."
I worked mostly in the oil and gas industry, so may have been exposed to the 'percent of indicated reading', which sure doesn't apply to tyre gauges!

 

[twas_brillig]

(Sorry guys - I seem to have managed to duplicate several posts. Dang)

If I have a 60 psi dial tyre gauge built to ASME B40.1, accuracy 'B (commercial gauges)', then I have 2% of the span (1.2 psi) over the 15 to 45 psi range. Unless the packaging specifies the accuracy range, then I've got a pretty good chance that it is 'D (commercial gauges)' and has a +/-5% accuracy (+/-3 psi) over the entire range; 6 psi, in other words.

 

[twas_brillig]

I've just skimmed through the Amazon/Rhino site and - hooray!!! - all questions are answered.
"Q: Your product states ASME B40.1 accurate. What grade accuracy has this been certified to B, A, 4A, 3A, 2A, 1A?"
"A: Hi Sabrina, sorry about the delayed response we have been very busy with Black Friday and Cyber Monday promotions. Our Gorilla Gauges are certified to A Grade which is +-1%. "
This is an industrial standard, and provides 1% accuracy from 25 to 45 psi on a 60 psi gauge. Doug