Technical Specifications
ValVue Digital Communications Software Ver. 2.80
20
GE Oil & Gas
HART Compliance
The positioner 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 - 20 mA current loops
When a safe barrier separates the communicating devices, a HART compliant barrier must be
used.
NOTE You cannot connect or use ValVue and another HART master
terminal device (at the same time), for example a handheld device.
CAUTION 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. A HART filter can be used.
Consult the DCS manufacturer to verity that the DCS is compatible
with HART, before connecting a HART modem and using ValVue.
Failure to Communicate
If the PC (using a modem) fails to communicate with the HART positioner the message No
Devices Found appears in the Connected Devices page. The message HART I/O Failed appears
if the device communications fails during the session. 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 ValVue with another HART master terminal in service
Insufficient loop impedance (a minimum of 250 Ohms is required
Field device has a non-zero polling address (Set ValVue to multidrop)
If HART compliance problems are suspected 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.