Hardy HI 1756-FC - Manual (Page 48)

Erratic Weight or Rate Control
This section explains how to resolve problems relating to rate and Rate of Change (ROC)
calculation, Rate Exception Control (REC), motor speed control, and weight calibration.
Rate calculations
1. Rate calculations are no better than the scale’s calibration accuracy. Verify the
scale calibration using test weights.
2. Follow the weight troubleshooting flow charts and correct any equipment
binding, rubbing, and piping problems.
3. After an initial rate calibration on a new system, verify the calibration several
times to ensure consistency, and verify the calibration using the posted weight
loss over time.
4. If the rate displayed does not match your test samples:
 Re-calibrate the scale and then the rate.
 Review the troubleshooting tips for mechanical influences relating to the
feeder mechanism
 Look for leaks in the delivery system or refill gate.
5. If the system is slow to change rate (or weight) readings.
 Adjust the number of averages setting lower.
 Adjust the WAVERSAVER setting lower.
 See REC +/- settings below.
6. Look for a systematic and consistent weight loss. Determine what a stable rate
should be. If the rate displayed on the monitor continuously falls and rises and
you never get a stable rate or symmetrical weight loss pattern:
 The rate may be too slow for the load call capacity.
 The material may be bridging or liquefying and basically inconsistent.
 The feeder motor may be feeding too fast, mechanisms may be damaged, or
working conditions may not be right.
ROC calculation
The ROC reading does not necessarily indicate a smooth weight loss. The amount of
ROC control required depends on the material currently being fed.
1. Since ROC calculations are developed from the weight reading, the weight
reading must be correct.
2. The Loss In Weight (LIW) ratio is calculated from the total scale load cell
capacity. If an LIW rate error greatly exceeds the weighing error:
 Add decimal points up to 1 part in 50,000 to help determine the ROC.
 Balance the WAVERSAVER setting and averages.
Motor speed control output signal
If the motor speed control output signal indicates a problem, but the voltage and current
levels measured on the terminals is correct:
1. Adjust the OP% out in manual mode.
2. In the ON condition, verify that the output signal matches the percentage of full
range. For example: 50% of a 0-10V signal should read 5 VDC at the analog out
terminal.
3. Adjust the WAVERSAVER setting and averages.
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Chapter 6 ●
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