A Mass of 100 kg Is Not a Feed Rate of 100 kg/h
Separate hopper mass in kg from feed rate in kg/h, and understand why a simple weight-difference calculation cannot be used unchanged during refill.
Mass Is Not Feed Rate
One video combines Korean narration with Korean and English on-screen subtitles. The article keeps the assumptions and calculations explicit.
The amount remaining in a hopper is a mass, measured in kilograms. The amount discharged per hour is a mass flow rate, measured in kg/h. A 4–20 mA signal format does not, by itself, identify the engineering unit. This example assumes that the transmitter reports hopper mass.
Coperion's loss-in-weight explanation describes controlling feed rate from the rate of weight loss, with different handling during refill.
A half-kilogram drop over thirty seconds
Assume there is no refill and all mass loss within the weighing boundary is caused by discharge. If the mass falls from 100 to 99.5 kg in 30 seconds:
A single reading of 100 kg cannot reveal this rate. We need two mass readings and the elapsed time. The result is an average over a thirty-second window, not a guarantee of instantaneous flow or control accuracy.
Why refill changes the calculation
Suppose 10 kg is added while 0.5 kg is discharged in the same thirty seconds. The final mass is 109.5 kg. Ignoring the incoming material produces a naive estimate of −1140 kg/h. That does not mean the actual discharge rate is negative; it means the no-inflow assumption is invalid.
BLOCKED_REFILL and does not use the simple finite difference as discharge-rate feedback. It does not blindly clip the estimate to zero or speed up the feeder because the estimate turns negative.The correct refill-control behavior depends on the equipment and the manufacturer's control specification. This article is not ready-to-run PLC software or a safety-function design.
Document the value and its unit together
| Value | Example unit | Meaning |
|---|---|---|
| Raw | counts | Value converted by the input module |
| Hopper mass | kg or 0.1 kg/count | Mass remaining in the hopper |
| Feed-rate estimate | kg/h | Estimated discharge over a time window |
| Feed-rate setpoint | kg/h | Desired delivery rate |
| Drive reference | Hz, %, V, etc. | Speed-command unit defined by the drive interface |
This is a conceptual distinction, not a finalized PLC address map or module specification. Scaling raw counts into kilograms and estimating kg/h from changes in mass are separate steps.
Related guides
Why Raw 800 becomes 100 kg · Continuous Dosing training lab case
Source and reproducibility
Coperion — How to Troubleshoot Your Feeder for Optimal Performance / Gravimetric Feeders
The numerical values are original teaching assumptions. The test code and results are provided for reproducibility. No real-machine performance claim is made.