passive recording from an analog data line..
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I have a rather specific need for a voltage recording setup. I have
multiple lines transmitting analog data from one device to another
device. I want to 'tap into' these lines with my PC, to be able to
passively record the changing voltage levels on these lines (without
effecting the signals being transmitted on the lines).
As far as I see it, I could passively record voltage levels on each
line by connecting one voltmeter probe to a line, and the other
voltmeter probe to ground. This would not effect the signals being
transmitted on the lines because the voltmeter has a very high
resistance, and very little current travels through it.
However, I need to passively record from many lines at once, and I
need the recordings to be saved on a computer hard drive. I've seen
examples of using PIC micros to record voltage levels, but these
examples use the PIC's ADC, and simply convert an analog input
signal into digital. As far as I understand it, this method could
not passively record from my lines without effecting the signals on
the lines.
It seems like this should be a very easy thing to do (to
passively record from a line which is transmitting data), but I
guess I don't understand some fundamentals of electronics well
enough. Thank you for any input!!
multiple lines transmitting analog data from one device to another
device. I want to 'tap into' these lines with my PC, to be able to
passively record the changing voltage levels on these lines (without
effecting the signals being transmitted on the lines).
As far as I see it, I could passively record voltage levels on each
line by connecting one voltmeter probe to a line, and the other
voltmeter probe to ground. This would not effect the signals being
transmitted on the lines because the voltmeter has a very high
resistance, and very little current travels through it.
However, I need to passively record from many lines at once, and I
need the recordings to be saved on a computer hard drive. I've seen
examples of using PIC micros to record voltage levels, but these
examples use the PIC's ADC, and simply convert an analog input
signal into digital. As far as I understand it, this method could
not passively record from my lines without effecting the signals on
the lines.
It seems like this should be a very easy thing to do (to
passively record from a line which is transmitting data), but I
guess I don't understand some fundamentals of electronics well
enough. Thank you for any input!!
Comments
5 volts, you can record it with the Stamp.
The single-tasked nature of the Stamp means
monitoring many lines can take some time.
You might want to look at the PIC 16F876,
or PIC 16F877, which have 5 pins of ADC
native to the chip.
Or, you can look at using an external ADC
chip, and interfacing to the Stamp with
an 'SPI' bus (SHIFTIN/SHIFTOUT) interface.
Parallax has an excellent example for the
ADC0831 chip. Note most ADC chips have
very high input impedance, so will affect
the circuit as little as a voltmeter.
--- In basicstamps@yahoogroups.com, "Sam" <hard-on@t...> wrote:
> I have a rather specific need for a voltage recording setup. I have
> multiple lines transmitting analog data from one device to another
> device. I want to 'tap into' these lines with my PC, to be able to
> passively record the changing voltage levels on these lines
(without
> effecting the signals being transmitted on the lines).
> As far as I see it, I could passively record voltage levels on each
> line by connecting one voltmeter probe to a line, and the other
> voltmeter probe to ground. This would not effect the signals being
> transmitted on the lines because the voltmeter has a very high
> resistance, and very little current travels through it.
> However, I need to passively record from many lines at once, and I
> need the recordings to be saved on a computer hard drive. I've seen
> examples of using PIC micros to record voltage levels, but these
> examples use the PIC's ADC, and simply convert an analog input
> signal into digital. As far as I understand it, this method could
> not passively record from my lines without effecting the signals on
> the lines.
> It seems like this should be a very easy thing to do (to
> passively record from a line which is transmitting data), but I
> guess I don't understand some fundamentals of electronics well
> enough. Thank you for any input!!