[ontopofm]

can anyone tell me why it's at 1 instead of zero?

[O-cha]

Because its calibrated wrong, mechanical? You should get a good electrical gauge, they are much more accurate and reliable.

[ontopofm]

it's a mechanical
to mr. 5, you think you can exchange for a new one from where you bought this?

[scalbert]

Originally Posted by O-cha

Because its calibrated wrong, mechanical? You should get a good electrical gauge, they are much more accurate and reliable.

The sensors used in electrical kits are, at best, 1% FS (Full Scale); but can be 2% units. The pressure range being measured with the above gauge is 40 PSI but I suspect the overall range would be 50 PSI. 1% of 50 PSI is 0.5 PSI. Now add in the discrepancy from the drive mechanism and the inaccuracy could approach 1 PSI.

A mechanical gage can run in the 0.5% range which would mean they are about equal.

I have heard this often but it is unfounded in most cases. The cases where it is correct is when DAQ is used with at least 12 Bit A/D. In this case people will use a 0.1% sensor.

As an aside, we sell both pressure transducers as well as mechnical gages; about 100 times more of the former. We even calibrate about 30 units a day to 0.25% using a 0.01% NIST traceable system. I have some background in this arena.

[scalbert]

Originally Posted by ontopofm

can anyone tell me why it's at 1 instead of zero?

There may be an offset adjustment on the back of the gauge. It is most likely not zero'd correctly.

[O-cha]

Originally Posted by scalbert

The sensors used in electrical kits are, at best, 1% FS (Full Scale); but can be 2% units. The pressure range being measured with the above gauge is 40 PSI but I suspect the overall range would be 50 PSI. 1% of 50 PSI is 0.5 PSI. Now add in the discrepancy from the drive mechanism and the inaccuracy could approach 1 PSI.

A mechanical gage can run in the 0.5% range which would mean they are about equal.

I have heard this often but it is unfounded in most cases. The cases where it is correct is when DAQ is used with at least 12 Bit A/D. In this case people will use a 0.1% sensor.

As an aside, we sell both pressure transducers as well as mechnical gages; about 100 times more of the former. We even calibrate about 30 units a day to 0.25% using a 0.01% NIST traceable system. I have some background in this arena.

So basically your trying to say that an electrical gauge is not more reliable and accurate?

[scalbert]

Originally Posted by O-cha

So basically your trying to say that an electrical gauge is not more reliable and accurate?

I am saying that a pressure tranducer, when tied to a DAQ system will measure more accurately; the sum of linearity, repeatability and resolution.

An electrical gauge driven by a pressure sensor is not more accurate than a quality mechanical gauge. This is primarily due to the the resolution being the same for both.

The arguement can swing either way when depending on the gauge though. A quality electrical gauge can be much better than the $10 gauge purchased at the auto parts store. Conversly, there are some quality mechanical gauges out there as well.

[O-cha]

Originally Posted by scalbert

I am saying that a pressure tranducer, when tied to a DAQ system will measure more accurately; the sum of linearity, repeatability and resolution.

An electrical gauge driven by a pressure sensor is not more accurate than a quality mechanical gauge. This is primarily due to the the resolution being the same for both.

The arguement can swing either way when depending on the gauge though. A quality electrical gauge can be much better than the $10 gauge purchased at the auto parts store. Conversly, there are some quality mechanical gauges out there as well.

So your basing this off the resolution of mechanical and not so good electric gauges being the same? Are there quality fast acting mechanical gauges out there with a resolution of .1 PSI?

(I'm trying to be nice here, don't want people to peg me as even more of a bastard.)

[scalbert]

Originally Posted by O-cha

So your basing this off the resolution of mechanical and not so good electric gauges being the same? Are there quality fast acting mechanical gauges out there with a resolution of .1 PSI?

No, the mechanically driven (dial) electrical gauges have the same resolution as a pure mechanical gauge. In other words, the ability to read the dial is the most siginificant portion of determining resolution. But there is the ability to sense a change which is also the resolution. And yes, mechanical gauges generally have a greater measurement resolution as there is no A/D steps or sensor response resolution.

Electrical systems will normally have better linearity though.

We should seperate electrical dial gauges and digital displays though as there are differences with those. I was referring to the electrical dial gauges.

[scalbert]

Originally Posted by O-cha

(I'm trying to be nice here, don't want people to peg me as even more of a bastard.)

It is just a discussion.

[O-cha]

Originally Posted by scalbert

No, the mechanically driven (dial) electrical gauges have the same resolution as a pure mechanical gauge. In other words, the ability to read the dial is the most siginificant portion of determining resolution. But there is the ability to sense a change which is also the resolution. And yes, mechanical gauges generally have a greater measurement resolution as there is no A/D steps or sensor response resolution.

Electrical systems will normally have better linearity though.

We should seperate electrical dial gauges and digital displays though as there are differences with those. I was referring to the electrical dial gauges.

Basically you just said, no, there are no mechanical gauges with a resolution of .1 psi (Readable, doesn't really matter if it hypothetically has the same resolution if you cant read it.) Also I'm pretty sure a mechanical gauge is more prone to failure.

Based of that you could say that when you said this:

Originally Posted by scalbert

The sensors used in electrical kits are, at best, 1% FS (Full Scale); but can be 2% units. The pressure range being measured with the above gauge is 40 PSI but I suspect the overall range would be 50 PSI. 1% of 50 PSI is 0.5 PSI. Now add in the discrepancy from the drive mechanism and the inaccuracy could approach 1 PSI.

A mechanical gage can run in the 0.5% range which would mean they are about equal.

I have heard this often but it is unfounded in most cases. The cases where it is correct is when DAQ is used with at least 12 Bit A/D. In this case people will use a 0.1% sensor.

As an aside, we sell both pressure transducers as well as mechnical gages; about 100 times more of the former. We even calibrate about 30 units a day to 0.25% using a 0.01% NIST traceable system. I have some background in this arena.

You meant that crappy mechanical gauges and electrical gauges have the same resolution and therefore equal but that a good electrical gauge will have a higher resolution and therefore more accurate and reliable.

Originally Posted by O-cha

You should get a good electrical gauge, they are much more accurate and reliable.

A good electrical gauge:
http://www.veisystems.com/bhm-m.html (by the way it calibrates every power on)



You clearly have way more knowledge on the subject then me, I'm just defending my statement because I know my gauge is light years better than any mechanical gauge I've ever seen.



To the OP i suggest you ditch that gauge, I bet you can hardly tell the difference between 12-13-14 psi.

[scalbert]

Originally Posted by O-cha

Basically you just said, no, there are no mechanical gauges with a resolution of .1 psi (Readable, doesn't really matter if it hypothetically has the same resolution if you cant read it.) Also I'm pretty sure a mechanical gauge is more prone to failure.

You meant that crappy mechanical gauges and electrical gauges have the same resolution and therefore equal but that a good electrical gauge will have a higher resolution and therefore more accurate and reliable.

A good electrical gauge:
http://www.veisystems.com/bhm-m.html (by the way it calibrates every power on)

I know my gauge is light years better than any mechanical gauge I've ever seen.

Some mechanical gauges can have a fine resolution; much better than 0.1 PSI. It's resolution is based on the mechanical resistance which is minimal. The issue is to quickly see a 0.1 PSI change at a glance. But I beleive there is some confusion on what resolution is. The link provided shows an eletrical gauge with a digital display. They indicate a display resolution of 0.1 PSI. That is simply the display resolution and not the measurement resolution. The measurement resolution may only be 1 PSI (most likely much better than that), but they can digitally display to a tenth of that. On top of that, if they are using 8 Bit A/D, their measurement resolution is limited to 0.4% (1 / 256).

That is a caveat with digital metering system; pressure, temperature or even displacement; you have multiple resolutions to take into account. The sensors resolution and then the display resolution (actually three with digital systems; sensor, A/D and display). Only stating one does not help. This is not to say the unit in the link is not a fine unit; I can't say as I have never used one.

And then we haven't even gotten into repeatability and linearity which combine to give overall accuracy. But this is probably not the place for that.

I guess what is boils down to is that digital displays can be easier to read to some while I, and others, prefer dial gauges. Digital gauges can be harder to read when the process value changes quickly. Otherwise you have to slow the display update rate which slows the response.

And yes, you can easily discern about 0.25 PSI on a mechanical gauge fairly quickly; but that is about the extend of it.

What I do agree about is the general durability. Mechanical gauges tend to wear out quicker due to the nature of the measurement method.

[ontopofm]

Ocha: where did you order your Vei gauge? and how much

is this gauge any good?

http://prosportgauges.com/Digital-boost-1.aspx

[Mr. 5]

Originally Posted by ontopofm

it's a mechanical
to mr. 5, you think you can exchange for a new one from where you bought this?

I really doubt it.
I don't understand though. This gauge was at zero when I had it.
Did the gauge get dropped at all or did it bang against anything?

[ontopofm]

no, it read zero yesterday but the nylon tube was leak bcuz i over-tightened it. remember i told you about the hissing sound? i got a new compression fit and fixed it this afternoon and the needle moved to 1.

[Mr. 5]

Originally Posted by ontopofm

no, it read zero yesterday but the nylon tube was leak bcuz i over-tightened it. remember i told you about the hissing sound? i got a new compression fit and fixed it this afternoon and the needle moved to 1.

Maybe when you tightened it you rotated everything a bit inside.
I would re-check it to see.

[ontopofm]

hmm, maybe i should try to turn the bolt in the back to see if it fix the problem

[scalbert]

Check your compression fitting again. Have you driven the car since noticing this? I ask as I am curious if it is responsive.

Also, if you torqued on it pretty good you could have skewed the zero point. As entioned, undo the connection and see where it goes.

[ontopofm]

i tried to change to the fitting on the gauge so i loosened the nut on it. it's probably where i skewed the 0 point. then i realized i can't change it if it's not taking apart.
i changed the compression fitting and it should be good now (hand torqued). i've driven the car after i fixed the connection and i saw my boost go up to 15 psi. i knew something was wrong bcuz it can't be that high based on my data logging.
i know where to fix it. thanks guys