General Cautions for Solid State Devices

General Cautions and Recommendations from FW Murphy for solid-state devices such as the following models:

Pressure Devices (PXT-K), Temperature Devices (MDTM, TDX6, TDXM, RTDT(X)), Automation Systems (S400, S500, S510), Engine Controls (EMS447, EMS448, EMS467, EMS547) and Compressor Panel Components (LCDT, MARK III, MARK IV, TTDJ, S1501, COM Series C267, C277,C287, Millennium MC Series, Centurion M-VIEW, TTD, VRU Pro,
WellPro II)

Connect to battery for your direct DC power.

FW Murphy recommends that the power source (+ and -) connection points of any panel containing any solid-state device, such as those listed above, be made directly to the terminals of the battery (+ and -). This will allow the battery to act as a filter and absorb any voltage spikes or noise generated by the alternator or other devices located on the equipment being controlled by the solid-state device. The preferred method is to tie the negative battery terminal to proper earth ground (e.g. earth ground rod) and tie any needed frame/chassis grounds to that same point as well. Connection of power and DC common at any other point will cause increased noise susceptibility in the system. Depending on the actual configuration of the end application, this can cause various control problems, such as erratic operation, inaccurate sender/transducer readings, remote communication problems, etc.

Use reverse biased diode with inductive loads.

FW Murphy recommends that any inductive load tied to a solid-state output (relays, solenoids, valves, actuators, rack pullers, etc.) has a reverse-biased diode across the coil to snub the inductive kickback. This prevents the field collapse of the coil from damaging the solid-state output devices and keeps the DC power clean from spikes.

Welding Precautions

FW Murphy recommends that no welding take place directly on the equipment or on the equipment that is physically connected to equipment where solid-state electronics are used. If welding must be performed on this equipment, FW Murphy recommends that the following precautions are taken to reduce the chance of the solid-state electronics being permanently damaged or damaged enough to fail at some later time. FW Murphy will not warrant any device that has been subjected to damage caused by welding. These precautions will lessen the chance that a high electrical potential will pass through or across the control panel and/or its components.

  1. Open the control panel and any associated subpanels or swing panels.
  2. Disconnect power and ground connections and all ribbon and other cable types leading to or from any solid-state device (i.e. those listed above). Note: Most cables should have a keyed connector for ease of reconnecting or have removable terminal.