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ETH-2 functional block diagram
Thermo-hygrometer ETH-2 functional block diagram
Power supply
ETH-2 is designed to function both as a stand alone device, and to be connected to the AS2 control system via ELM-4 data bus. If operating standalone, ETH-2 can be powered by a standard low power 12V AC / DC adapter or a 12V car battery. It also contains internal Li-ION rechargeable battery, the capacity of which is sufficient for approximately 15 days of continual device operation; in that case the device is fully functional with the only difference being that it automatically enters “optically silent” mode in order to save the battery energy.
When connected to ELM-4 data bus, in addition to being powered internally or locally by AC / DC power adapter, ETH-2 can draw its power supply from the dedicated bus power supply lines. While it is expected for ELM-4 Central Controller to be able to continuously provide 15VDC / 300mA for all connected system components (taken together), all compatible equipment is designed so that data communication does not depend on that. Consequently, even when operating from its internal battery, ETH-2 is able to talk to the PC as usual.

Technical details
Operating temperature- and relative humidity range
  • device itself operates between -35°C and +70°C, and between 2% and 100%rH
  • temperature probes can withstand temperatures in -55°C to +120°C range
  • temperature is being measured in -35°C to +60°C range with precision and accuracy < 0.1°C
  • rH probes measure relative humidity in 5% to 100% range and -35°C to +80°C
    with precision and accuracy < 1% when calibrated, < 5% uncalibrated
Data communication
  • communication speed is 19.2 kbps (signals are compatible to RS-485 standard)
  • cable length can be > 100m
  • ELM-4 data bus is galvanically insulated from the central computer
  • all devices tied to the same ELM-4 databus are galvanically connected to one another
Power supply
designed by LP 2013