[Part 2] Arduino Data Logger

• For the external plug pack I selected the POWERTRAN MB8968B from Altronics.  Input is 100-240VAC @ 50-60Hz/0.8A, output is 24VDC @ 1A.
• To produce the 5VDC (from the 24VDC) for the Arduino I selected the Z6334 DC-DC Buck Module from Altronics.  Input is 3-40VDC, output 1.5-35VDC @ 3A maximum (adjusted to provide a 5VDC output).
• To maintain the date and time while the logger is powered off I selected the DS1302 based Real Time Clock Module from Altronics.  Reports online indicate that the DS1302 chip can be unreliable (as opposed to the DS1307) but I have had no issues with the one I purchased.
• The Arduino I selected was one I had already, the Freetronics EtherTen.  The on-board MicroSD slot was the main reason I decided to use this, I didn't require the Ethernet port.

[Part 1] Arduino Data Logger

This is the first post in a series in which I'll document the development of an Arduino-based data logger. The requirements for this data logger are:

• Data to be logged is a 4-20mA current loop signal (2-wire) from a sensor (using 4-20mA for analogue measurement is an industrial automation standard);
• Sensor requires a 24VDC supply (I'll be using a 240VAC-to-24VDC transformer plug pack to provide the 24VDC so there will be no mains supply work required);
• Whole system to be contained in a box that can be sealed up and made "weather-proof".