AS a recent recruit to the Hart protocal I want to check a couple of things with people.
The HART protocal when used with transmitters can be used in 2 different ways,
1, Use the 4-20mA signal for primary data transmission and then superimpose the HART digital signal on to this for control purposes.
2, Use the transmitter in a pure digital manner on the equivilent of a 4mA BUS. This method has the advantage of enableing the connection of up to 16 units on one loop.
This is how I undeerstand that the system can be used.
My question is what sort of collision detection does the HART system, master or slave / both, employ to detect collision of data?
does it matter, can the master detect more than one signal simultaniously?
with a number of devices on a HART loop what level signalling is possible, ie number of transmissions per second per transmitter?