Streaming serial input

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:

A streaming serial device (or serial stream, if you prefer) sends a periodically updated stream of text-format data consisting of numeric variables (delimited by commas), with each batch of data concluded with a carriage return character.   There may be one or more non-numeric text variables as well.   Selecting this option opens the window shown below,in which you can select which of the variables in a 'stream' to use.   Variables are shown in the 'value' column.   Text blocks that do not convert into numbers (i.e., they contain characters other than " + - . 0 1 2 3 4 5 6 7 8 9 ") are shown as blank ('--').

The program knows the parameters of a number of streaming serial-capable instruments (mainly those from Sable Systems), such as the Sable RH-100 relative humidity sensor in the example at right.  For a 'known' instrument, appropriate variable labels are automatically inserted.   If your instrument is not being read correctly, try clicking the Reload data button.

  • Troubleshooting:   Serial connections are simple in principle but can be tricky in practice.   If you have problems, start by making sure the baud rate is correct (the default is 9600 baud).

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