Application Notes

EAP-031023

Zero Point Compensation for Strain Gauge Transmitter

In general, load cells are used to measure powder and grain flow in a system utilizing a hopper and CFW (Constant-Fed Ware). Since powder tends to stick to the hopper and CFW, following zero-point compensation for strain gauge transmitter output is required to compensate a batch for power remaining in the hopper from the previous batch: 1) The weight of residual in the hopper before powder loading (as measured by the load cell) should be subtracted from the weight measured after loading powder into the hopper. 2) It's also necessary to compensate for zero offset caused by powder sticking to load sensing rollers in the CFW.
Figure 1
By combining a Math Function Module M2SBS with a Track/Hold M2AMS, its possible to compensate the zero point of the Strain Gauge Transmitter M2LCS output (refer to Figure 2). To provide an absolute zero-point offset, turn the Hold command switch on. For example, if the zero is offset by 5% (high), X1 is held at 5% so that when the actual measurement value is X2, corresponding output of the Match Function Module is X0 =X2 — 5.
Figure 2