What are my upgrade options for a DAS-8 Series Board?

 

The DAS-8 Series offered 5 boards: DAS-8, DAS-8/LT, DAS-8PGA, DAS-8PGA/G2, DAS-8/AO.
Model
Input Range
Gains
Time Base
Channel Mode
Size

DAS-8

-5 to +5 VDC
fixed at 1

ISA Bus

Single Ended

half slot

DAS-8/LT

-5 to +5 VDC
fixed at 1

1MHz Crystal

Single Ended

half slot

DAS-8PGA

-10 to +10 VDC at gain of 0.5

0.5, 1, 10, 100, 500; Unipolar or Bipolar

1MHz Crystal

SE or Differential by Switch

full slot

DAS-8PGA/G2

-10 to +10 VDC at gain of 0.5

1, 2, 4, 8; Unipolar or Bipolar

1MHz Crystal

SE or Differential by Switch

full slot

DAS-8/AO

-10 to +10 VDC at gain of 0.5

0.5, 1, 10, 100, 500; Unipolar or Bipolar

1MHz Crystal

SE or Differential by Switch

full slot

*the A/D chip is a large, 28pin chip on the board with a gold in color metal square. On this metal square is the logo for Harris and a part number which will start with 574.

The A/D converter is 12-bit, successive-approximation with typical conversion times of 25 micro seconds (35 microseconds max) resulting in theoretical throughputs approaching 40KHz. However, this speed is both machine (interrupt processing) and software implementation dependent. Using the drivers from Keithley, throughputs of 4KHz are specified.

In addition to these analog input features described in the above table, the boards also have

  • 3 digital input lines
  • 4 digital output lines
  • 3 16bit counters (82C54)

Any upgrade or board replacement should be carefully planned. Often times software and cabling changes are required. Sufficient time should be allowed for complete understanding of the existing system as well as testing of the migrated system to fully discover any subtle differences. Study the documentation for your current system (or reverse engineer it from the wiring and source code) to determine which features of the DAS-8 Series board are actually in use by the application. Often, only a portion of the board's features are required, so board replacement purely on feature specifications can be misleading.

Upgrading to PCI cards: If the DriverLINX driver was used for code development for the DAS-8 Series board, then code migration to the KPCI multifunction boards will take only moments to complete.

If, however, the code for the DAS-8 Series was written with other methods (register level, mode calls for DOS, etc.), then a rewrite of the controlling software will be necessary. Keithley's PCI cards ship with Windows based DriverLINX support only.

PCI cards are typically memory mapped rather than I/O mapped. Controlling a PCI card from a DOS environment will require use of 32bit DOS extenders for access to the 32bit memory space of the board's registers. Your programming language needs to be able to access the 32bit registers of the card. Furthermore, PCI boards are Plug-and-Play devices so do not have base address switches to control what addresses they inhabit; your program needs to be able to enumerate the PCI bus to detect the card and to read out the assigned address configuration.

Register level control of PCI cards requires a significantly different skill and tool set than was required for ISA boards and often is done with third party tools like WinRT to gain real mode access into 32bit memory space.

Upgrading to Instrument Products: Especially if you have a strong motivation to stay in the DOS operating system, use of the Integra Series Data Acquisition Systems should be considered as an upgrade path. The 27xx mainframes of the Integra Series can be computer controlled via their bus interfaces (RS-232, GPIB or Ethernet) with simple string commands. So in addition to the Windows based IVI drivers and start up software, control from DOS based systems is also quite easy.

While reading rates of Instrument based products are typically slower than plug-in board products, the integrating A/D converters of instruments gives a much greater immunity to noise than plug-in board products. This greater noise immunity eliminates the need for signal averaging which is a common technique required when using plug-in board based systems. The effective sampling rates, especially for temperature monitoring applications, are quite comparable when considering that each single measurement from an instrument will be usable data.

Upgrading to other ISA cards: For minimal impact in terms of both software and cabling, one of the boards in the DAS-800 Series should be considered. The DAS-800 corresponds to the DAS-8 or DAS-8/LT, while the DAS-801 corresponds to the DAS-8PGA (high gain). The DAS-802 corresponds to the DAS-8PGA/G2 (low gain).

Software written for DAS-8 will operate with the corresponding DAS-800; software for the DAS-8PGA will operate with DAS-801/2 (register compatible).

Within the DAS-800 Series, there is no corresponding board for the Analog Output feature of the DAS-8/AO.