Technical Specifications

ValVue Digital Communications Software Ver. 2.80
448
GE Oil & Gas
HART Compliance
The VECTOR requires a HART compliant communications loop. The HART protocol specifies the
noise level, impedance requirements, and configuration of the loop. Conventional
communications loops consisting of the following components meet requirements for HART
compliance.
 Quality current source having low noise and high impedance
 Minimum loop impedance of 250 Ohms
 Twisted pair cable suitable for 4 to 20 mA current loops
When a safe barrier separates the communicating devices, a HART compliant barrier must be
used.
Communicate Failure
If the PC (using a modem) fails to communicate with the HART or ValVue the message No
Devices Found appears in the Overview screen. If the device communications fails during the
session, the message HART I/O Failed appears. Communication failure prevents the PC from
establishing a link. Possible causes of communications failure related to installation include:
 Insufficient Loop Current and Voltage
 Poor wiring contacts
 Improper connection of the HART modem to the computer
 Incorrect serial port
 Using the VECTOR with another HART master terminal in service
 Insufficient loop impedance (a minimum of 250 Ohms is required)
 Field device has a nonzero polling address (Set the VECTOR to multidrop)
If HART compliance problems are suspect prepare a detailed description of the loop, including
all devices on the loop, type of wiring used, loop length, and presence of any possible
interference sources before contacting the factory for assistance.
Some Distributed Control System output circuits are incompatible with the
HART protocol. Connecting a HART modem to such a circuit can cause a
process upset. Use a HART filter. Consult the DCS manufacturer to verity
that the DCS is compatible with HART, before connecting a HART modem
and using the ValVue VECTOR.