home made test gauges

[fordtech2005]

I am a diesel and heavy equiptment tech. I want to build my own test gauges for hydraulic pressures fuel pressures engine pressures and so on. Looking for any input. Will take all suggestions.

 

[richs]

Hi-

You are asking for a wide range of sensor inputs here.
Anywhere from a few psi for fuel input to several hundred
for cylinder pressure.

For some of the lower pressure requirements, you might
want to look at the Freescale (ex Motorola) line of
sensors. They unfortunately require around 10V of
driving current and are unamplified (but temp compensated)
sensors. There are some new 5V only, 0-5V in some of
the lowest pressure sensor ranges from them and I believe
one of the Japanese companies.

As a starting point you might want to look at the Digikey
catalog on line for some information on parts. Then
drill into the site for the datasheets associated with
them.

http://dkc3.digikey.com/PDF/T071/P2004.pdf

I am not affiliated with Digikey, but I buy stuff from
them.

Some of the amplified might be easier to use as they
have most of the circuitry needed to pass into a
microcontroller that has an A/D attached to it.

Hope this helps get you started.

Cheers,

Rich S.

 

[itsmoked]

Wow!! Why, why, WHY? Would you want to waste your time reinventing a very nasty 'wheel' over and over? Baffling! You must have better things to do then spend weeks creating something you can buy for $20 - $100?

There are countless reasons why you should NOT do this.

Perhaps your question is broken or.... Maybe you need more of a description of what you are trying to do.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[richs]

Hi Keith-

OP said:
"I want to build my own test gauges for hydraulic pressures fuel pressures"

I made an assumption that he wanted electronic pressure
fuel gauges. That was an assumption on my part. He might
be wanting "reference pressure guages", all mechanical.
Don't know and it was my bad. However:

I'm going through the same process. Not to just build them
but to LEARN! He can certianly find state of the art
processes, and dig into the "black box" of the sensor
and I beileve (and I'm sticking to my story) that he will
have a better understanding of the operations and
particularly the pitfalls of the associated devices.

Even if he never puts a homegrown sensor in one of his
designs, he is (I hope) going to understand the operation
far better.

I, as mentioned, am looking at the Freescale (Motorola)
sensors. Yep. I'm looking at them too. My design
has a 3 op amp differential input instrumentation amp
followed by an active low pass filter. This all feeds
a 12F675 PIC microcontroller. The op amps? LM358s.
Yep. Those good old workhorses. Sure I can use the
quads, but they are at hand and specs are pretty well
known. Several hours of fun having the micro do auto
offset and scaling.

This is a back burner project that I work on in the
evenings when I get the urge and tired of the current
project de jour (project of the day). It's taken me
weeks to continue populating the PC board. I prototyped
it with the push in and push in wire prototyping, laid
out the PC board and fabbed it. I originally had both
sockets for either a 12F675 and a 10F222 PICs on it,
but the layout was easier with just one.

So, am I wasting time, maybe. But I personally am chalking
it up as a learning experience. BTW, the "application"
is a bubbler for a water tank level. Not a rush issue
but still something to have experience with and if there
IS a requirement for it in the future, then its there and,
more importantly, a lot of "hard earned" experience.

So, to fordtech2005, I say "go for it"!. Even time lost
might not be time wasted.

In fact, you might want to do both! Build your own, and
buy. Put them in parallel and see the strengths and
weaknesses of both.

Cheers,

Rich S.

 

[itsmoked]

Hi Richs. I understand your position and commend it.

But.. He said hydraulic pressure. Making your own 5,000PSI gauge is just um.. nuts. And trying to get the materials happy for fuel..

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[Comcokid]

There is another forum "Automotive Engineering other Topics" forum108 which might be better suited for your question.

 

[richs]

Hi Keith-

Yep. No problem. Just giving the OP for wanting to
explore!

Cheers,

Rich S.

 

[randi]

A pressure gauge that cannot be tested or was not tested is useless. It's another thing that you may want a low accuracy and inexpensive throw away gauges.

Like most others have said do not try to re-invent the wheel.
Building testing gauges is one thing and building your own test station is another.

Hope you are heading in the right direction.

You may want to check what you want on

http://www.omega.com

and check prices. If you really want to build your own then get the applicable ANSI std. which would cost you a few bucks and then get the applicable design guidelines too.