Portable, multi-channeled voltage sensor

Hello,

I'm looking for a portable device (possibly a microprocessor, on the
scale of an inch or two but I'll take what I can get) which can sense
multiple analog voltages on the order of millivolts. Preferably this
device would have many channels (over 10). I'm looking to couple this
kind of sensor to several piezoelectric cables, which would allow me to
gather pressure data on the cables without the immediate need for a PC
(data would be recorded (transmitted) by this device and then uploaded
to (received by) a PC to be analyzed). Also it would be good to have a
sampling rate of around 1KHz or higher (I would be happy with 1KHz).
Anybody have any ideas?

Thanks,
Hayden

 

[Jamie]

diogenes500@gmail.com wrote:

Hello,

I'm looking for a portable device (possibly a microprocessor, on the
scale of an inch or two but I'll take what I can get) which can sense
multiple analog voltages on the order of millivolts. Preferably this
device would have many channels (over 10). I'm looking to couple this
kind of sensor to several piezoelectric cables, which would allow me to
gather pressure data on the cables without the immediate need for a PC
(data would be recorded (transmitted) by this device and then uploaded
to (received by) a PC to be analyzed). Also it would be good to have a
sampling rate of around 1KHz or higher (I would be happy with 1KHz).
Anybody have any ideas?

Thanks,
Hayden

microchip has several PIC's that come with Analog inputs

i even think from Maxx you can get an io expander that
would allow you to multiplex lines.


--
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

 

[Roger Hamlett]

"Jamie" <jamie_5_not_valid_after_5_Please@charter.net> wrote in message
news:tpxbf.9939$7s1.4559@fe04.lga...

diogenes500@gmail.com wrote:

Hello,

I'm looking for a portable device (possibly a microprocessor, on the
scale of an inch or two but I'll take what I can get) which can sense
multiple analog voltages on the order of millivolts. Preferably this
device would have many channels (over 10). I'm looking to couple this
kind of sensor to several piezoelectric cables, which would allow me to
gather pressure data on the cables without the immediate need for a PC
(data would be recorded (transmitted) by this device and then uploaded
to (received by) a PC to be analyzed). Also it would be good to have a
sampling rate of around 1KHz or higher (I would be happy with 1KHz).
Anybody have any ideas?

Thanks,
Hayden

microchip has several PIC's that come with Analog inputs
i even think from Maxx you can get an io expander that
would allow you to multiplex lines.
The problem here is the 'millivolt' part of the requirement. The ADC on

the normal PICs is 10bit, and loses linearity below a Vref of about 2V. So
the smallest 'step' resolution, is around 2mV. I cannot think of any
micro, that has an ADC able to give good resolution to this sort of level,
but the obvious answer is an analog multiplexer, followed by a gain stage.
There are a few PICs offering higher accuracy ADC's (the 16C77x, with
12bit, and the old 14000), but even with these amplification will be
needed for any reasonably resolution, and (assuming the source has a
relatively high impedance), to meet the drive requirements of the ADC
itself....
The sample rate is not a problem. Even the standard PIC ADC, can sample in
the order of 30000S/sec, but if using a multiplexer (either external, or
the one inside the chip), the time needed to select the new channel,
acquire this, and then read this, needs to be included. The simplest
solution, would probably be to use a buffer amplifier on each input,
bringing the signal range up to about 2.5v peak. Then a 2.5v bandgap
reference, and a chip like the PIC18F4515 (which already has a 13way ADC
multiplexer), and about 3K of RAM, to hold readings. If more storage than
this is needed, add an FRAM.

Best Wishes

 

[Markus Baertschi]

diogenes500@gmail.com wrote:

Hello,

I'm looking for a portable device (possibly a microprocessor, on the
scale of an inch or two but I'll take what I can get) which can sense
multiple analog voltages on the order of millivolts. Preferably this
device would have many channels (over 10). I'm looking to couple this
kind of sensor to several piezoelectric cables, which would allow me to
gather pressure data on the cables without the immediate need for a PC
(data would be recorded (transmitted) by this device and then uploaded
to (received by) a PC to be analyzed). Also it would be good to have a
sampling rate of around 1KHz or higher (I would be happy with 1KHz).
Anybody have any ideas?

Thanks,
Hayden

Such a device is called data logger. All sizes and prices are available.

http://www.google.ch/search?q=data+logger+voltage

will list more than you care for .

Markus

 

[Mark Zenier]

In article <1131304956.304276.219110@g43g2000cwa.googlegroups.com>,
<diogenes500@gmail.com> wrote:

Hello,

I'm looking for a portable device (possibly a microprocessor, on the
scale of an inch or two but I'll take what I can get) which can sense
multiple analog voltages on the order of millivolts. Preferably this
device would have many channels (over 10). I'm looking to couple this
kind of sensor to several piezoelectric cables, which would allow me to
gather pressure data on the cables without the immediate need for a PC
(data would be recorded (transmitted) by this device and then uploaded
to (received by) a PC to be analyzed). Also it would be good to have a
sampling rate of around 1KHz or higher (I would be happy with 1KHz).
Anybody have any ideas?

The buzzword is Datalogger (or variations on that theme).
A battery powered microcomputer with input circuitry for
measurements and enough memory to save the information until
offloaded. One name that comes to mind, for miniatures, was
Onset(?). For regular sized equipment, Fluke.

Mark Zenier mzenier@eskimo.com
Googleproofaddress(account:mzenier provider:eskimo domain:com)