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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.



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

  1. 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.
  2. Additional A/D channel for a total of 6 analog inputs.
  3. Quadrature Encoder Interface.
  4. 5.12 V, 100 mA reference output (twice the 50 mA of Model 2).
  5. User enabled conversion of individual channels.
  6. 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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Last modified: 11/25/09
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