New HIDS Drum Scales!
Click Here to Learn More!Why do I divide the value for minimum control level per minute by 120 to get minimum change per second? (Seems like I should divide by 60)
The question is about an article written for fine tuning an HI 2160RC rate controller. The question on the 120 calculation follows below. 60 seconds is for a standard system to determine the calculated minimum rate. Fine tuning the rate controller parameters, that calculated low rate level can be cut in half. That is why we show the 120 second number in the calculations. If your rate is below this last calculation the rate controller will not be able fine tune enough to control the rate properly.
Establishing the minimum control flow rate of the scale system.
Divide the total load cell capacity by 250 for 3 mv/V load cells and 175 for 2mvV load cells. This will give you the engineering units (EU) per minute minimum control level of your scale.
Divide this number by 120 to get the minimum change per second. (Minimum scale resolution).
Calculate the amount of weight change for your smallest target weight to determine the amount of material to be fed in one second.
EXAMPLE: 15,000 EU of load cell capacity/250 = 60 EU/m, 60/120= .5 EU/sec (This is your recommended control minimum)
The target rate is 15 EU/minute divided by 60 = .25 EU/ sec or 2 seconds to feed .5 EU.
This number equals the minimum amount of material that must be fed in 1/20th of the time base. There are 20 divisions in a time base and you must to see an equal change in weight for each division.
20 times the 2 seconds calculated, it takes to determine a weight loss, equals the minimum time base setting.
With the new Feeder and rate controllers (HI 4060, HI 1756-FC and HI 1769-FC):
