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Click Here to Learn More!Your communications type or polling frequency will not cause a lockup of the controller. Normally communication loss is due to outside environmental conditions such as fluctuating input power, improper grounding, and/or static discharges through the load cells.
Review the following steps to help eliminate system reset and communication lock-up problems:
1. Check that the shields are grounded to a single point earth ground. The Shield terminal on the back plate is a good ground. Verify there is single point grounding with an ohmmeter. If there are two grounding systems (plant and instrument), verify the potential between them is less than 1 ohm.
2. If you are unsure if you have a proper System Ground, consult a local or plant electrician for testing and ground grid diagnostics.
3. Install grounds to the incoming power supply, vessel, and exit piping. This is to provide a path for static discharge to ground and not through the load cells or cables.
4. Load cell cables inductively pickup voltage/current when run in the same conduit with high voltage cables. As a test, isolate cable runs outside the conduit and verify operation. Re-installing the original cable runs one at a time, and testing, can help indicate which cable runs are causing problems. The best choice is to run high voltage cables (anything over 50 volts is considered high voltage in instrumentation) in separate conduit from low level cables such as load cell cables.
5. Cable installations with data cable trays need only separate the sensor cables slightly. Loose cable association, 2-3 inches, rather than all the cables being bundled tightly together. A cable that is run in a serpentine fashion will reduce the length of parallel cable run and reduce inductions. Locating cables to minimize exposure from EMI/RFI noise sources is the main thrust of concern to reduce system noise.
6. If you are using a Remote Function connection, the cable run to the contacts can be an antenna for noise. Keep the switching cable run less than 48 inches. Use twisted pair shielded cable and route away from high voltages to reduce noise. If the Remote Function cable run is over 48 inches use a relay (installed close to the baseboard) for control.
7. Power isolation, swapping displays, cards, and power converters can help isolate a problem, but usually without improvement. The problems usually stay with the cabling and not the instrument or power.
8. Verify voltage between neutral and ground is less than one VAC. Verify the proper voltage from hot to ground is the same as hot to neutral to ensure the ground cable is connected.
