There are other A/D systems that interface to the PC serial port. I
have not developed code for any of these systems, but most come with software.
Using these with a Visual Basic application usually will be fairly easy.
Naturally, I have to suggest that you get a copy of my book, Visual
Basic Programmer's Guide to Serial Communications 4th Edition. Check the Books
link for information. Here are some serial A/D devices that I have
found. Note, costs may vary from what I mention here.
There are numerous manufacturers of Data Loggers. Data loggers feature
sample rates lower than most D/A systems (on the order of 10 samples/s or
less). They have lots of potential applications, but are simple enough to
use that they require limited software support. Most of these use serial
connections to the PC. I have decided to create a separate listing for
them. Click here for Data Loggers.
|
Name/Source |
Description |
| Serial Data Acquisition from
OnTrak control Systems. |
OnTrak
Control Systems serial data acquisition product boards range from the
ADR101/112: 2 8-bit or 12-bit, respectively inputs, with 8 DIO (RS-232)
through ADR1000: 8 8-bit inputs, with 32 DIO (RS-232, RS 422, and RS-485).
Next in line are the ADR2000/2020 boards with 8 12-bit inputs and 8 DIO
(RS-232) and the ADR2100: 4 10-bit inputs with 32 DIO (RS-232, RS-422,
RS-485). OnTrak also has a 16-bit board, ADR7700. |
| Serial Interfaces |
National Instruments serial interface information. |
| 4-Channel DAS modules from DGH
Corporation. |
DGH Corporation sells D5000 series four channel analog input
smart data acquisition modules. The D5000 series allow up to four sensors
to be interfaced to any computer, programmable controller or
processor-based equipment that contains a serial port. All data values are
communicated using ASCII command and response protocol via RS-232 or
RS-485 communications standards.
The D5000 series internal microprocessor automatically performs
internal zero and gain calibration. The modules also contain a user selectable
digital filter. All scaling, linearization and communications values are
stored in EEPROM, eliminating the need for internal potentiometers or
switches. Communications features include channel address, baud rate
(300-115.2K) and parity type.
Visual Basic example code may be downloaded from their web site. |
| DATAQ Instruments
manufactures a line of serial A/D modules. These start at the low
end with the DI-194RS starter kit. This starter kit's list price is
$25. See my article on a development that I did
using this A/D. |
The D1-151RS is a two-channel, 12-bit D/A with a maximum
sample rate of 240 s/s. The DI-194RS module is a four-channel 10-bit
module, with a maximum sample rate of 240 s/s. The DI-195 module add
signal conditioning. The DATAQ DI-1000TC is a multi-channel (4 or
eight in the basic configuration) thermocouple DAQ system that supports all
common thermocouple types. It is furnished with Windaq Lite software
and an ActiveX control that may be used for custom programming. The
serial interface is RS-422, so the box may be located at a significant
distances from the connected computer. See my
Windows CE Software page to see what I have done to work with this
hardware using a Pocket PC. |
| Omega Engineering
has a huge number of products for industrial automation. A number of
the data logging products that offer have serial interfaces. One of
their specialties is temperature monitoring devices. |
|
| CircuitSpecialists
has a line of DA boards with serial interfaces. Check their ADR
line. Prices range from $100 and up. Right are the
specifications for ADR101. |
The ADR101 serial data acquisition interface allows control
of 8 digital I/O lines and 2, 8-bit analog inputs ( 0 - 5VDC) via an RS232
link. This low-cost serial data acquisition interface is easy to use with
Visual Basic. |
| Pico
Technology Limited has a series of data acquisition products, both
software and hardware. |
Pico's PT100 provides 24-bit resolution for logging
temperature and humidity. Software is provided, including drivers and
examples for multiple languages, including Visual Basic. |
| StateLogic PALC is
a low-cost logger, controller. |
PALC Model 3
Programmable / Acquisition /
Controller / Logger
Data acquisition "toolbox." In addition to data
acquisition, control and alarm functions, DATA
LOGGING memory has been added to compliment the
stand-alone controller feature.
Major feature additions include
- Data logging with 65,000 sample non-volatile
EEPROM memory. Two memory modes - overwrite
previous data, or append data to allow starting
and stopping data logging while saving previous
data.
- Additional A/D channel for a total of 6
analog inputs.
- Quadrature Encoder Interface.
- 5.12 V, 100 mA reference output (twice the
50 mA of Model 2).
- User enabled conversion of individual
channels.
- Six independent controller set-points which
may be set to monitor any analog input and
activate any output (versus two set-points
pre-assigned to each channel in Model 2).
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