Calibrating a pressure gauge

[cheb]

My question actually came from testing a tyre's pressure with three different gauges, a stick, a cheap and nasty one that might have come from a Christmas cracker and a cosseted genuine PCL forecourt jobbie. There was a about 10psi difference between them. I like to set my tyres to an accuracy of plus or minus 0.1psi of the correct pressure, obviously this has to be done with due attention to the current and forecast outside temperature and atmospheric pressure.. They are filled with a bespoke mixture of nitrogen, oxygen and some trace gases.

I'll leave you to guess which one I might trust.

 

[brightspark]

My question actually came from testing a tyre's pressure with three different gauges, a stick, a cheap and nasty one that might have come from a Christmas cracker and a cosseted genuine PCL forecourt jobbie. There was a about 10psi difference between them. I like to set my tyres to an accuracy of plus or minus 0.1psi of the correct pressure, obviously this has to be done with due attention to the current and forecast outside temperature and atmospheric pressure.. They are filled with a bespoke mixture of nitrogen, oxygen and some trace gases.

I'll leave you to guess which one I might trust.

race formula one do you

 

[8ob]

You could always send off a half decent gauge for calibration and use that for back to back testing.

Bob

 

[brightspark]

You could always send off a half decent gauge for calibration and use that for back to back testing.

Bob

but if it just sits there in different temperatures and humidity doing nothing who is to say it still acts accurately

 

[8ob]

but if it just sits there in different temperatures and humidity doing nothing who is to say it still acts accurately

BS you could say the same about an engineers square if you insist on using it as a hammer, if its looked after and calibrated it should do the job.

Bob

 

[optima21]

My question actually came from testing a tyre's pressure with three different gauges, a stick, a cheap and nasty one that might have come from a Christmas cracker and a cosseted genuine PCL forecourt jobbie. There was a about 10psi difference between them. I like to set my tyres to an accuracy of plus or minus 0.1psi of the correct pressure, obviously this has to be done with due attention to the current and forecast outside temperature and atmospheric pressure.. They are filled with a bespoke mixture of nitrogen, oxygen and some trace gases.

I'll leave you to guess which one I might trust.

ah you just need to be a tyre kicker...... that should be accurate enough

 

[Maker]

Instruments need recalibrating regularly, it's usually every 12 months. You might think it's still accurate because you've kept it somewhere safe, and you're probably right, but anyone that needs a proper traceable calibration won't accept it, it has to be within date. If you're just inflating tyres to an overly anal resolution, an out of date calibration is almost certainly fine.

You must be using a digital gauge if you're reading 0.1 PSI, and I'd really want 0.01 resolution to reliably measure to 0.1, especially if it's well out of calibration (Do you trust the last noisy digit on your multimeter?), so that means want something like a Fluke 2700G, only fourteen hundred quid.

 

[500e]

If you can tell the difference in 0.1psi crack ok

 

[Guzrik]

I615SPC-13G-4025 | Druck DPI 615 0bar to 20bar Pressure Calibrator | RS

nl.rs-online.com

We have something like this at work.
20 years since last calibration, have a quote to calibrate, cost more than a new one.

 

[mike os]

the only way to calibrate anything it to have a certified standard to work with... anything else is just guesswork

if you require a calibrated/certified gauge, then just buy one, if you need several and need to check calibration frequently then but a calibrator.... and have that certified at least annually, more frequently if used often or its really critical.

very few diy operations will require any kind of real accuracy, ie a standard gauge will already be accurate enough.

 

[minimutly]

I615SPC-13G-4025 | Druck DPI 615 0bar to 20bar Pressure Calibrator | RS

nl.rs-online.com

We have something like this at work.
20 years since last calibration, have a quote to calibrate, cost more than a new one.

I have one exactly like that (used to be an instrument tech). Dead weight tester is better, but heavy to move around.

 

[voipio]

Simply connecting a pressure gauge to a car tyre valve will lower the tyre pressure by an amount, dependent on the volume of the measuring system, and the leakage past the seal made between tester and valve.

The findings of a comparison made using a Topeak Smart Gauge and an oldish Halfrauds tyre inflator with digital readout (both give readings having a resolution of 0.5psi) were that the readings of both gauges were the same pretty much all of the time.

Taking repeated measurements using both gauges, with the Halfrauds, used only as a pressure gauge, saw the readings gradually fall over repeated measures, with measurements using the Halfrauds falling faster than the Topeak, owing to the larger measurement volume of the Halfrauds. Something like a 1psi fall over 30 repeated measurements on a standard profile tyre on 15" rim.

 

[zzr1200]

My question actually came from testing a tyre's pressure with three different gauges, a stick, a cheap and nasty one that might have come from a Christmas cracker and a cosseted genuine PCL forecourt jobbie. There was a about 10psi difference between them. I like to set my tyres to an accuracy of plus or minus 0.1psi of the correct pressure, obviously this has to be done with due attention to the current and forecast outside temperature and atmospheric pressure.. They are filled with a bespoke mixture of nitrogen, oxygen and some trace gases.

I'll leave you to guess which one I might trust.

Will you also need a accurate thermometer, so you can test the tyre pressure at exactly the same temperature as the master control gauge???..........










I have a calibrated (about 3 years ago, cost about £9.00) PCL tyre pressure inflator/gauge that I use for my tyres.

But my initial tyre pressure control is first my eyes, then the second part of the control system test, is my right foot bonce test......

Then the tyre gauge.....

Tyre pressure changes so much depending on tyre temp/air temp that anyting within a +/- 2psi is ok.

 

[voipio]

2psi can make a noticeable difference to handling, especially on corners.

Looks like the Draper digital gauge display resolution is 0.1psi, accuracy +/-1psi:

https://www.amazon.co.uk/Draper-1071-Digital-Pressure-Reader/dp/B079NCJQTT

 

[zzr1200]

2psi can make a noticeable difference to handling, especially on corners.

Looks like the Draper digital gauge display resolution is 0.1psi, accuracy +/-1psi:

https://www.amazon.co.uk/Draper-1071-Digital-Pressure-Reader/dp/B079NCJQTT

Depends if your cornering on three or all four wheels really......

 

[mike os]

if you want that kind of accuracy there is only 1 way to get it... a temperature controlled filling booth with atmospheric pressure compensation and a very accurate gauge... expect to spend several hundred, and replace after it gets dropped

 

[Neilj]

I'd say for that application you'd want something that's repeatable rather than incredibly accurate. Play around with your tyre pressures until you find the best setting and take a reading with whatever gauge you've got. Then set your pressure to the same figure, using the same gauge, at the same temperature / atmospheric conditions every time and you should have a repeatable tyre pressure. Whether that is 30 psi, 30.2 psi or 29.8 psi is largely irrelevant if you check it with the same gauge every time.

 

[Robotstar5]

2psi can make a noticeable difference to handling, especially on corners.

Looks like the Draper digital gauge display resolution is 0.1psi, accuracy +/-1psi:

https://www.amazon.co.uk/Draper-1071-Digital-Pressure-Reader/dp/B079NCJQTT

Mrs Robo can tell that, she will ask me to check her pressures and I will find a couple of psi difference.

 

[zzr1200]

Mrs Robo can tell that, she will ask me to check her pressures and I will find a couple of psi difference.

Can you ask Mrs Robo if she does training classes, please.

My other half has trouble with 15psi difference..............women.......

 

[Ross365]

The 10psi variance you report is totally unacceptable. I am generally happy to measure tyre pressures to within 1 psig. I have two of the old Dunlop pencil gauges and I use those as my definitive gauges (I don't think I have ever compared them with my "Master Gauge" which I mentioned earlier - must find time to do that.

Re "Bespoke" gas mixtures; how often do you inflate and deflate them? Most polymers are surprisingly permeable to gases, so there will be exchange of gas with the atmosphere. I wonder how long it takes to be able to measure changes in composition after the tyres have been inflated?