Starting new project in AD

I not to big on analog and I'm starting a new projest with 2 vacuum transdusers (1V to 5V output) and 9 inputs (switches). What is going to happen, when one of the inputs are set I need to load the difference between the two vacuum transdusers into vmen. This is the small picture, the big picture is harder to explain. I'm in the thinking phase now and on the first step.

1. I'll have to set my analog card for 2 inputs
2. Need 24V and 5v DC
3. Set program to read 2 analog inputs
4. subtract 1 input from other input
5. load difference to vmen
6.
7
ect
ect
100. Setup touchscreen and Excell

MMMMMMMM that is a start
Don't mine me just thinking outloud

Rich, my first thought is:

What kind of vacuum transducers?
Are these typical absolute pressure transducers suitable for low pressure measurements in the 10-760 torr range?

Or are these high vacuum transducers like convectron, piranni or ionization gages suitable for vacuum in the 10^-3 or 10^-6 torr range?

Because the former is going to give you a linear output, but only suitable for rough vacuum. The latter will give you an output that is not only non-linear but also logarithmic, which is going to present real problems if you just want so subtract one from the other and have it mean anything unless you first perform some advanced scaling.

Rich,

I have used the Druck pressure sensors (-15 PSI to 30 PSI) with the DL205 PLC with H2-WinPLC and Entivity Live! flowcharts and it's neatly like "falling off of a log."

The Entivity Live! simplifies reading the analog values GREATLY and will also simplify the overall programming!

oldNovice

Rich1955 said:

1. I'll have to set my analog card for 2 inputs
2. Need 24V and 5v DC
3. Set program to read 2 analog inputs
4. subtract 1 input from other input
5. load difference to vmen
6.
7
ect
ect
100. Setup touchscreen and Excell

Click to expand...

I am not sure why you would need a 5 volt power supply. Most transducers will take the 24 volts and supply the 1-5 volts from it.

I am not sure why you would need a 5 volt power supply. Most transducers will take the 24 volts and supply the 1-5 volts from it.
The one I'm looking at is 1 to 5 Volts to match my analog cart.

Or are these high vacuum transducers like convectron, piranni or ionization gages suitable for vacuum in the 10^-3 or 10^-6 torr range?
I was talking to the engineer today and we pull down to 500Mil tor, Might have to do some rethinking.

We are trying to build a prototype cheap to test our theary to prove to the bosses that it works so then they will fork out the money for the good stuff.

More to come, wife is pushing my out the door, wants to go shopping.

Rich1955 said:

More to come, wife is pushing my out the door, wants to go shopping.

Click to expand...

There you go. The wife is always getting in the way of good engineering time!

lol

Yes, but most 1-5 volt transducers use either 12 volts (not so common) or 24 volts (more common) to power them and the 1-5 volts is produced by the supply voltage.

Honestly i have never seen a transducer for 1-5 volts that is fed from a 5 volt supply. Even loop powered equipment.

I'm not disputing it, just never have seen it. (lots in the world that I haven't seen yet, but instrumentation is something I have done a bit of.)

woops forgot I changed the one I was going to use

SPECIFICATIONS

Excitation: 10 to 30 Vdc unregulated

Output: 1 to 5 Vdc (3-wire)

Supply Current: <3.0 mA

Insulation Resistance: 100 MΩ @ 50 V

Accuracy: ±0.4% BFSL

Hysteresis: ±0.2% FS

Repeatability: ±0.05% FS

Stability: ±1.0%/year

Durability: 100 million cycles

Response Time: 5 ms

This is the one I went with today (could change tomarrow)


[font=Verdana, Arial, Helvetica, sans-serif]PX603-30VAC5V [/font][font=Verdana, Arial, Helvetica, sans-serif]

[/font][font=Verdana, Arial, Helvetica, sans-serif]$300.00 [/font][font=Verdana, Arial, Helvetica, sans-serif]0-30 inch of Mercury vacuum transducer with 3 foot cable and 1-5 Vdc output [/font]

Still doing my homework. Gee been out of school for 30 Years and still got homework.

I can vouch that the Omega sensors work well. I was very satisfied with their PX105 transducers... :nodi:

The ones I used DIDN'T accept a 24VDC supply. I had to use a separate 12VDC supply, but I needed 12VDC for an LVDT sensor on the machine anyway, so it wasn't a problem.



-Eric