Why is my Hardy Instrument performing erratically?

Power surges, power spikes, load cell line noise and/or static discharges can corrupt your Hardy Instrument's memory, causing drifting weight readings, loss of SET POINT and calibration data, and/or erratic performance. In some cases, rebooting the instrument will resolve the problem. In other cases the Random Access Memory (RAM) must be cleared and default parameters loaded back into memory to solve the problem. Erratic performance can be caused by any and all the following examples. Identifying which of these problems may be causing erratic performance on your Hardy Instrument will require close observation.

EMI/RFI (Static, Radio signal, Electromagnetic, AC Interference)

Shielding - Load cell cable shields must only be grounded at the controller or a single point. Verify, with an ohmmeter, the shield is only grounded at a single point. With all the shields properly connected, at the summing junction box or at any intermediary termination point, verify with an ohmmeter that there is less than one ohm resistance to earth ground. If this proves good, disconnect the shield at the controller (or single earth ground point) and check that now there is an open circuit between shield and ground at the summing junction box and all intermediary termination points. This verifies the shield is not connected to ground at the summing box, load cell or at any other point in the cable run. Cable shields are landed and only pass through the summing boxes and should not be connected to ground in the summing box.  There are summing junctions cards in the industry offering a grounded shield at the summing card.  Check to insure you are aware if your summing junction box is grounding the shield.

Moisture - Broken Load Cell seals and cable integrity can allow moisture to enter the Load Cell and cable. Moisture sets up stray capacitance charges in the cables and allow ground currents to exist. This could be a highly intermittent situation.

Cable Routing - Low voltage, as specified in the instrumentation installation code, is less than 50 V. Cable runs parallel to high voltage cables require a 3 inch minimum separation. Stay away from strong Electro-magnetic fields and keep a minimum clearance of 14 inches from SCRs, Motor controls and Relay banks.  High current cable runs for furnace operations, 4-6 feet may be required and specially shielded conduit in extreme cases.  Use a premium 8 conductor C2 certified load cell cable with heavy shielding and computer clean power. C2 certified cable is the only Hardy Instruments recommended cable.

Grounding - Use a good earth ground close to the equipment. Insure all equipment grounds are to that one common point. Insure all fill and discharge piping are grounded to earth ground to reduce static discharge of material during filling and discharging operations. Install ground straps to bypass the Load Cells so power surges do not contact the Load Cells themselves. Install isolation transformers to filter surges and power sags. Install active tracking filters to trap VFD power transients and AC noise.

A simple grounding test would be to apply a static charge to the vessel, or cabling and the reading should not vary. If the reading does change or if the equipment locks-up, the grounding is incorrect

Before you swap units, try to re-calibrate and re-install the configuration information on your Hardy Instrument. Clear memory to insure there isn't any memory corruption.  Saving to a nonvolatile memory location is automatic on 75% of the Hardy Instruments, you should have previously saved the configuration/calibration on your controller.  Restore the configuration from the Secure Memory Module (SMM) and you should be able to resume operation.

This memory restoration is normally executed when the unit is rebooted.  Some units will require