Eratic Reading in Weigh Bridge

Well, there will always be a voltage between neutral and earth as it expresses the current flowing in the neutral conductor, which isn't a perfect conductor in itself and is there to carry the imbalance current presented by a range of single-phase loads connected to a 3-phase supply, and the earth loop impedance, so that's nothing to worry about. The earth conductor is a safety provision and its job is to carry the fault current until the circuit protective device(s) operate(s) to disconnect it from the supply.

There should be a very-high-to-sort-of-infinite resistance between the earth conductor and both the live and neutral conductors with the device's cable disconnected from the supply. If there isn't, then it needs correcting; call a qualified local Electrician.

More likely to be the cause of the problem is a piece of the raw material jamming up the mechanism in some way so as to give a deflection that suggests 1-2ton at the read-out. Another possibility is a loose connection onto the primary measuring device. Another possibility is water ingress to the primary measuring device or some part of its cabling. These are the things that need to be checked out first, if necessary in the company of the equipment supplier's local Service Technician; make the phone call and get 'em in.

I suggest you verify and ensure that the shielding and static drains on all the instrument wiring from the weight sensor (load cell?) and all other sensitive devices are intact and properly terminated to earth ground with <1 ohm impedance.

These electrical noise "drains" should only be attached on one end so that a circulating induced voltage loop is not created.

If the shielding and drains are ok, and you still have the issue:

Procure/obtain a dual channel oscilliscope and following the scope operation OEM directions for safe operation:

1. Set one of the channels of the scope up on AC coupling and connect the probe between the signal conductor and earth or circuit reference.

2. Set the other channel to DC coupling and connect it in parallel with the AC coupled channel.

3. Operate/activate the scale and observe the scale signal circuit waveform to determine the type and magnitude of signal variation.

4. Move the scope probes throughout the signal testpoints and identify the source of the issue.

5. Repair or replace the component that is causing the issue.