Can I connect one HI 4000 series unit to another HI 4000 series unit?

Can I connect a HI 4000 series unit to another HI 4000 series unit and get them communicating with each other? If so, how would I do this? Is there any sample logic available?

The HI 4000 series units are individual, stand alone units.  They do not communicate directly with each other.  If you need to pass data between multiple units, you would need to set up communications to another device, like a PLC, for each HI 4000 to communicate with.  This other device (like a PLC) would then collect and distribute data to/from each unit as programmed.

If you truely needed peer to peer communications, you should consider the HI 3000 series units.  These units have peer to peer communications over Ethernet TCP/IP.