HF-10 Serial Port / USB Four-Channel Voltage Logger

The HF-10 is a 4 channel voltage monitor for logging to a Host PC or similar using the serial COM port or a USB interface. For more details see the USER MANUAL
Here's a better copy of the Circuit Diagram than the one in the manual

Click for larger image

Uses could include :

Voltage monitoring, and drift
Battery health and charge discharge characteristics
Signal strength from a receiver S-Meter
Remote monitoring, beacons, repeaters, remote stations
Antenna measurements, pattern plotting
Temperature monitoring and plotting
Logging light levels
Ground resistance changes
Long term power consumption

If you want to play with the code or make your own from scratch, PIC firmware is to be found here
Hex Code and Assembler Code