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.
Advantech ADAM-4019 The ADAM-4019 is a low-cost and versatile device with high accuracy, but also a couple of limitations. It has 8 channels of 16-bit analog-to-digital conversion 
that can be used to read voltages or several types of thermocouples. Importantly, thermocouples can be attached directly, without amplification or ice-point references. The ADAM-4019 can communicate at speeds of up to 38.4 Kbaud, but it's stated maximum sampling rate is 10/sec (all channels combined). However, in tests using LabHelper, rates of up to 30/sec (one channel) have been achieved. LabHelper uses 9600 baud, which is the ADAM default. Also, the 4019 lacks any digital or analog outputs (digital outputs can be added via the inexpensive ADAM-4050, but their use requires building a simple extra circuit).
You can add a second ADAM A-D module (either another 4019 or the volts-only 4017) to obtain a total of 16 input channels.
The ADAM series uses the RS-485 communications protocol and you will need an RS-232 to RS-485 converter to use it with the TrippLite USA-19HS. I have tested the RS232-RS485 converter shown at right and it works fine without the need for auxilliary power -- at least with a short cable length. This was purchased from Amazon.com for about $10 and -- judging by shape -- the same device seems to be sold under a bewildering variety of brand names.
The ADAM-4019 has adjustable input voltage ranges (go to the A-D menu to see how this is done). Most instruments have output voltage ranges of 0-5 volts to 0-1 volts, so select the unit's voltage range accordingly. For devices with higher outputs, you can use voltage dividers to reduce your instruments' recorder output voltage to an acceptable range.
The ADAM 4019 comes with screw terminals to which you can directly attach
instrument recorder cables or thermocouples. However, you may want to build your own
junction box with connectors that are easier to use.
Note: Because of its low sampling rate, the ADAM-4019 has only limited usefulness in oscilloscope mode.
