Difference between Fluke 709H and Fluke 754

From memory, the 709H used only HART common and universal practice commands, it could not interpret a DD file (no way to load a DD into it).

The 754 can handle DD files, but I don't know whether you can add/delete or whether you're stuck with the factory installed DD's.

I'm sure there are other differences, but I'm not professional shopper, you'll have to read the spec sheets or manuals.

To add to Shockiscan's excellent reply on HART connection problems - I doubt the 754 will connect to any device the 709 would not connect to under identical circumstances. If the 709 won't connect; the 754 won't either.

In addition to the lack of adequate loop resistance, the other reasons HART connections fail are

- attempting HART connections across the power supply

- no DC loop power to the transmitter (communicator does not power the transmitter)

-attempting to make a change via HART to a write-protected HART device

- noisy power supply (excessive ripple) faults HART comm

- someone put the communicator's target address at something other than zero

- attempting to talk HART to a transmitter that is equipped for Profibus, Foundation Fieldbus, Honeywell DE, Modbus or some other protocol

- attempting to talk HART to a HART device on which HART has been disabled (typically for security reasons).

- bad electrical connection due to corrosion or mechanical problem with the communicator/calibrator's spring clips.

- attempting to talk HART to a HART device at connection point where a non-HART device, like a loop powered indicator, strips out the HART signal.

None of the issues above will be resolved by getting a more sophisticated HART communicator/calibrator.