Flowmeters and 4-20mA outputs.

Archiver

I want to convert the 4-20mA signal which represents flow rate from a
natural gas flowmeter and transform it into total flow. This data
then needs to be converted into a serial bit stream which I would
like to access using the SERIN/SEROUT commands from my BS2. I have
thought of using a 12-bit A/D converter, a 250 ohm resistor, and some
intense software programing, but is there a better way to accomplish
this? I don't want to tie up my BS2 by constantly checking the flow
rate because I have it performing a lot of other tasks. Is there a
chip out there or some other device that can do this for me cheaply?
If that doesn't work, another option I have is to use the pulse
output from the meter. Any help would be greatly appreciated.

Archiver

A little confudsed here, if you want another chip to be tracking
total flow, then what would the BS2 be accessing? A chip to do what?

If you can get a pulse from the meter, how about using the count
command to count the pulses?

How many I/O are you using on the BS2? The pulses may be used to
drive a discreet counter, which you can quickly read as a parallel
data, though you may need to use several (8+) lines, but 2-8 bit
counters, a little multiplexing, and you could read it in as a high
and low byte. Once read every few seconds or so, you could reset the
counter for a fresh count, accumulating your readings for total.

Or, a slightly more expensive idea, use 2 BS2s, one simply collecting
data, and the other occasionally polling it for the serial totals.

Just some thoughts, reply back if any sound promising and you need
more help.

-Martin Hebel
SelmaWare Solutions
S-Plot:Graphical Data Acquisition and Control
http://www.selmaware.com/s-plot

Southern Illinois University Carbondale
Electronics Systems Technologies (soon to be...)
http://www.siu.edu/~imsasa/elm

--- In basicstamps@y..., prstava@e... wrote:
> I want to convert the 4-20mA signal which represents flow rate from
a
> natural gas flowmeter and transform it into total flow. This data
> then needs to be converted into a serial bit stream which I would
> like to access using the SERIN/SEROUT commands from my BS2. I have
> thought of using a 12-bit A/D converter, a 250 ohm resistor, and
some
> intense software programing, but is there a better way to
accomplish
> this? I don't want to tie up my BS2 by constantly checking the
flow
> rate because I have it performing a lot of other tasks. Is there a
> chip out there or some other device that can do this for me
cheaply?
> If that doesn't work, another option I have is to use the pulse
> output from the meter. Any help would be greatly appreciated.

Archiver

Has anyone used a sound card system to record
microphone input? What I'd like to do is to
get a sound wave into the Stamp and do some analysis
of the wave, but I can't digitize it fast enough.

Therefore, what I thought of doing was to grab
the bit stream of already-digitized data from the
sound card, and then I don't have to worry about
digitizing it myself.

By "sound card" I mean a common one found in
any PC. What I'm thinking of is something that
uses basically digitizes sound, and outputs a
bit stream.

Any ideas? Thanx....JP Harrison

Archiver

We have one BS2 right now constantly polling for a modem carrier
detect signal, and every fifteen minutes it SERIN/SEROUTS to five
seperate pieces of equipment to obtain two temperature readings and
three power readings. I don't think I would be able to use the same
BS2 to also constantly monitor a 4-20mA or pulse signal. Maybe your
idea of a counter would work, but we're trying to make this senior
design project compatible with most meters and not all gas flow
meters have a pulse output (a larger percentage have 4-20mA current
loops).

I'll look into the counter idea, it may work if it can count very
high numbers.


Thanks for your help,
Don Paulson


--- In basicstamps@y..., martin@s... wrote:
> A little confudsed here, if you want another chip to be tracking
> total flow, then what would the BS2 be accessing? A chip to do what?
>
> If you can get a pulse from the meter, how about using the count
> command to count the pulses?
>
> How many I/O are you using on the BS2? The pulses may be used to
> drive a discreet counter, which you can quickly read as a parallel
> data, though you may need to use several (8+) lines, but 2-8 bit
> counters, a little multiplexing, and you could read it in as a high
> and low byte. Once read every few seconds or so, you could reset
the
> counter for a fresh count, accumulating your readings for total.
>
> Or, a slightly more expensive idea, use 2 BS2s, one simply
collecting
> data, and the other occasionally polling it for the serial totals.
>
> Just some thoughts, reply back if any sound promising and you need
> more help.
>
> -Martin Hebel
> SelmaWare Solutions
> S-Plot:Graphical Data Acquisition and Control
> http://www.selmaware.com/s-plot
>
> Southern Illinois University Carbondale
> Electronics Systems Technologies (soon to be...)
> http://www.siu.edu/~imsasa/elm
>
> --- In basicstamps@y..., prstava@e... wrote:
> > I want to convert the 4-20mA signal which represents flow rate
from
> a
> > natural gas flowmeter and transform it into total flow. This
data
> > then needs to be converted into a serial bit stream which I would
> > like to access using the SERIN/SEROUT commands from my BS2. I
have
> > thought of using a 12-bit A/D converter, a 250 ohm resistor, and
> some
> > intense software programing, but is there a better way to
> accomplish
> > this? I don't want to tie up my BS2 by constantly checking the
> flow
> > rate because I have it performing a lot of other tasks. Is there
a
> > chip out there or some other device that can do this for me
> cheaply?
> > If that doesn't work, another option I have is to use the pulse
> > output from the meter. Any help would be greatly appreciated.