A-D converters:    Sable UI2

Note for all A-D converters:   Modern Macs lack built-in serial ports, so you'll need a USB to serial converter and driver software.    The units made by Keyspan (now, TrippLite), specifically the USA-19HS, function reliably with LabHelper.   Other brands have not worked well, or at all.
Other A-D converters:


Sable Systems Universal Interface 'UI2'    This is the default, preferred A-D converter for LabHelper and is a good compromise between speed, versatility, and cost.    Although serial-based A-D converters are intrinsically slower than most internal A-D cards, the Sable UI2 is quite capable.   It communicates at up to 115.2 Kbaud and can sample a single channel at up to 200 samples/sec on a modest computer -- somewhat faster on up-to-date machines.

UI2's have eight channels of high-resolution analog-to-digital conversion (± 5   or ± 5.12 volts depending on model), 4 channels of temperature conversion (thermistors) that can also be used to measure positive voltages or resistances, a counter, two analog output channels (0-5 volts), a serial input channel, and eight digital I/O lines that can be directly connected to digitally-controlled external devices such as gas flow multiplexers.

Some users find the UI2's BNC connectors to be a bit of a pain, because many non-Sable instruments have other kinds of voltage output connectors.   But since there are only two conductors involved, a little splicing and soldering are all that's necessary to make an appropriate hybrid cable.

A standard 'straight-through' male-to-female DB9 cable should be used to connect the UI2 to the computer (more specifically, to the USB --> serial converter; see above).   Since the communication speed is fairly high, do not use a cable longer than a couple of meters.


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