| A-D converters: DataTakers |
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.
Data Electronics DataTakers are expensive, rugged, and highly capable (although not particularly fast). Several models are available; all use the same (or very similar) basic instruction set and all are impressively versatile. They have only 5-12 numbered hardware inputs, but several different instrument outputs can be connected simultaneously to each input, greatly increasing the number of sensors that can be monitored. An analog input on a DataTaker 800, 80, or 85-series has 4 connectors labeled #, +, - , and *. On a DataTaker 500 and related models, R is used instead of #.
• DT50, 500, 600 series The DT50 has 5 channels of high-resolution analog-to-digital conversion; the others in this series have 10 A-D channels; the 600 series have an LCD display and simple keypad but are otherwise the same as the DT500 (note that early DT500s had a black case as shown in the picture below; this was changed in later models to a rather garish purple, as seen in the picture of a DT600 at left).
As described above, each A-D channel can be set up to read voltages, resistances, or thermocouples, or can be used as a digital counter. Four digital I/O lines are available (for controlling external devices).
Note: I have not tested all of the many versions of the DT50/500/600 series with LabHelper, but they should function similarly. I have used the DT500 fairly extensively and users report no problems with the DT50.The cable joining these DataTakers to the computer (more specifically, to the USB --> serial converter) needs to have the correct connections. The wiring diagram in the DataTaker manual for IBM-compatible 9-pin (DB9) connectors works well.
Note: Because of their low sampling and communication rates, these DataTakers cannot be used in oscilloscope mode.
DT800 series The DataTaker 800 series are more modern, higher-speed versions of this sophisticated A-D converter. The basic DT800 has 12 channels of high-resolution analog-to-digital conversion; each channel can be set up to read voltages, resistances, or thermocouples, or can be used as a digital counter. Eight digital output lines are available (for controlling external devices).
The cable joining the DT800 to the USB --> serial converter needs to have the correct connections. The wiring diagram in the DataTaker 800 manual for IBM-compatible 9-pin (DB9) connectors works well. In brief, it requires two female DB9 connectors and 5 conductors:
• join pins 5 on both DB9s
• join pin 3 on one DB9 to pin 2 on the other, and vice versa
• join pin 7 on one DB9 to pin 8 on the other, and vice versa
Since the communication speed is fairly high, do not make the cable longer than a couple of meters.
Note: The DataTaker 800 can be used in oscilloscope mode, but maximum sampling rates are fairly low. The main constraint is the speed of the serial connection. Using the DT800 in oscilloscope mode is described in more detail here.
DT80 and 85 series The DT80 and DT85 are medium-speed DataTakers (up to about 25 samples/second) that differ in the number of analog inputs: 5 on the DT80 and 16 on the DT85. There have been several within-model upgrades over the years, and there are multiple versions of each (with and without cell phone modems, etc.).
The cable joining the DT80 or DT85 to the USB --> serial converter needs to have the correct connections, but these are simple: only three conductors are needed (as shown clearly in the operator's manual).
Note: The DataTaker 80 and 85 can be used in oscilloscope mode, but maximum sampling rates are pretty low.