I have experience with higher end tire pressure gauges we make for NASCAR, Indy teams and the airlines. They are a bit bulky for motorcycle trips and pricey for most people. Thing I have learned, much of which is from our customers:
You get what you pay for. There is a lot of junk out there:
http://blog.tirerack.com/blog/tire-...ressure-pressure-gauge-vs-ambient-temperature
If you drop a mechanical gauge it
will affect its calibration. All gauges eventually get dropped.
Mechanical gauges lose accuracy as their mechanical parts wear or get corroded.
If you drop a digital gauge and didn't break anything, its accuracy is not affected (no moving parts).
Liquid-filled gauges become very inaccurate as you get above or below normal ambient temperatures.
Most inexpensive digital gauges are more accurate than mechanical gauges.
Mechanical gauges are most accurate near the middle of their range. Digital gauges are most accurate in the upper part of their range. Consider this when selecting a pressure range.
You need to replace the rubber washer at the tire chuck when it gets old. It will eventually leak and affect your readings.
Check tires first thing in the morning or after they have cooled for at least 3 hours. Never let air out of a hot tire. Tire pressure will be too low when the tire cools. Do what you want on your own car though, this is an FAA rule.
Use the gauge within its rated pressure range. For example, putting a 60 psi gauge on a 150 psi compressed air line will usually ruin it. Pulling a vacuum on a gauge not meant for it may ruin it.
A "temperature compensated" digital gauge means that the pressure sensor has a built-in thermistor used to correct for temperature induced errors. This is seldom perfect (except in very expensive calibration gauges), but it greatly reduces a major source of error.
The inexpensive digital gauges should never be used for liquids. They use sensors designed for dry gases only.
If no accuracy specs are stated, be very afraid. Most accuracy specs only apply at normal ambient temperatures.
Racing and aircraft tires are usually measured with ±0.25% full scale accuracy gauges because that is what is recommended by tire manufacturers. These get a little pricey, but ±0.5% should be good enough for passenger cars.
No affiliation with Accutire nor have I ever used one, but reports on the web seem positive.
I found a few links where people have tested gauges:
http://townhall-talk.edmunds.com/direct/view/.ef017dc/0
http://www.animalnetwork.com/mcn/technical/200511gauges.pdf
