What is Acceptable Percentage of Error for a Guage
- Thread starter Impact701
- Start date
Did they say +/-10% of span or +/-10% of indicated?
If this is an ASME Commercial Class D gauge, then it is supposed to be accurate to +/-5% of span over its entire range. Which for a gauge with a span of 0 to 300 bar would be +/-15 bar (+/-217.557 psig). User parallax and needle width on a gauge face with no mirror overlay could add another +/-5%. As such a reading could be +/-10% of range or +/-30 bar or +/- 435.113 psig.
In the nuke submarine navy we had a saying for anything "Nuclear Grade", including our instrumentation, for why it cost so, so, so much more - Measure to 4 atom thicknesses, mark it with chalk, cut it with a chainsaw.
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Prior to retirement I worked with gauges a lot. Your basic off the shelf gauge is accurate to + - 10% of the full scale. Yes that is a little scary and the vast bulk of them or more like 2-3 % however the folks that made the gauge 10% + - is acceptable.
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My rule of thumb for any measuring device is 5% or less error. Most of the time it’s probably not a problem but the one time it becomes a problem once too often. When you’re looking at air pressure it can be catastrophic and not just in terms of damaged equipment but personal injury. 10% is acceptable? I’m calling bulls&*t on that.
Rick H.
Rick H.
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20 bar high, all the time? i.e. when empty at ocean level it reads 21 bar?
If it's always off by 20 bar, you could just rotate the backing screen for the gauge. But that would require opening it up.
If it's always off by 20 bar, you could just rotate the backing screen for the gauge. But that would require opening it up.
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Is the gauge at least consistent in its 20 bar too high reading at whatever pressure? A little sharpie editing of the scale/face might be easier than returning it. And note to all that the brand isn't accurate, thanks.
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My DRS fills to 230 bar, 230 bar reads 250 bar so that is what I have been using. It seams to consistently read 20 bar high.
The gauge that FX put on my DRS is completely unreliable, it never reads the same when its filled to 230 bar.
Must be a Swedish gauge thing ???
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1. If the gauge is analogue - the next time you have degassed the gun, thump the side of the gauge housing using your thumb and forefinger. If the needle jumps, then the connection between the bourdan tube and the indicator movement is bad.
2. If the gauge is digital - slowly degass the gun and check that the indicated pressure decreases linearly and doesn't fluctuate up and down. Do the same when you slowly pressurize the gun.
If it does fluctuate -
1. Check that the battery has not leaked.
2. Change the battery, ensuring the connections are clean.
3. Retest
4. If the indication still fluctuates, then the circuit card or piezo-resistor is bad, and you need a new gauge.
2. If the gauge is digital - slowly degass the gun and check that the indicated pressure decreases linearly and doesn't fluctuate up and down. Do the same when you slowly pressurize the gun.
If it does fluctuate -
1. Check that the battery has not leaked.
2. Change the battery, ensuring the connections are clean.
3. Retest
4. If the indication still fluctuates, then the circuit card or piezo-resistor is bad, and you need a new gauge.
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Also note that the air temperature will impact the pressure, both gauges and air should be at the same temperature for a valid comparison.
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