Rice Lake JB1010 Signal/Excitation Trim - Manual (Page 9)

6
6.0 Transient Protection System
The tran sient pro tec tion net work uses gas tubes selected for low leak age to ground in a network that has been
prov en ef fec tive with load cells. Con nect the ground stud on the junction-box enclosure to a suitable low im-
ped ance ground. If a local ground is used, make sure that it is a single ground rod and not a “net work”. The
best place to ground is to the ground lug on the side of the tran sient suppressor which protects the source of the
ex ci ta tion voltage. This keeps the system on a single point ground.
If the gas tubes are hit by lightning or transients related to lightning, they may begin to leak to ground. This
problem usually shows up as in sta bil i ty, drift, or an overload or underload con di tion on the in di ca tor. If this
occurs, remove the ground wire and see if the problem persists. If it goes away, then the board may be bad or
load cells may be damaged. Use a quality volt me ter with a nano-sieman conductivity range to fi nd the leakage
to ground and cor rect it. Gas tubes that fail while pro tect ing against transients are intentionally sacrifi cial and
not a war ran ty item. They are simply performing their function in the system.
If you think the board may be damaged, record the current DIP switch settings, then reset the DIP switches to
disable all trim ming as shown in Figure 4-1. Disconnect the ground wire from the JB1010. This ef fec tive ly
hooks all cells in parallel, dis ables all trim and isolation, and removes any leakage source to ground. If the
sys tem problems still persist, check the load cell cable and load cells for dam age.
Return the switches to their previous positions you have marked down once the problem has been re paired. If
new cells have been added, they must be trimmed as part of re-calibration.