MERRICK MC3 35.00.EX, Operation And Maintenance Manual, Page: 9 / 69

(page 49) or Electronic Calibration (page 50). You can also set it
manually. See Scale Factor on page 28.
Sample Time
How often the controller re-calculates all internal variables. See
Sample Rate on page 29. Normally, two different sample times are
used, one while feeding or filling, and a longer time while idling.
Rate Calculation
This is where the feedrate through the feeding device, R[251], is calculated, by taking the
difference between two samples of the Weight.
Loss Slots
How many samples the two weight values are separated to calculate
the Rate. Set to 10 by default. See Loss Slots on page 30.
Setpoint Signal Conditioning
The Batch Setpoint is taken from the Network, an Analog Input or locally on the controller
screen. If an analog input is used, the Setpoint has to be calculated in a similar way as
the Weight. The analog Setpoint signal taken as input passes through an A/D converter
and produces a Batch Setpoint as an output. All parameters can be set in the Analog
Setpoint menu. See page 31. There is also an automatic calibration procedure for setting
the counts, Analog Input Procedure (page 52). Parameters are:
SP Lo Cnts
A value in counts from the A/D converter representing a Minimum
setpoint.
SP Hi Cnts
A value in counts from the A/D converter representing a Maximum
setpoint.
SP Min Value
This is the minimum setpoint value, normally zero.
SP Max Value
This is the maximum setpoint value, normally the same as the Max
Batch Weight for the feeder.
Setpoint filter
A fluctuating setpoint is undesirable. To avoid fluctuations due to noise on analog signals
or in networked follower implementations, this averaging filter can be used to produce a
smoother value. It takes the Batch Setpoint as input and produces the Average Setpoint,
R[245], as output, by calculating the arithmetic average of a settable number of samples.
There is only one parameter:
Setpoint Slots
How many setpoint samples used to form the Average Setpoint. Set
in Setpoint Slots, page 30.
Stability Calculation
The controller uses two live weight values, one immediate, R[193], characterized by fast
update, and one high quality, R[184], updated only when the weight value in the hopper
is stable. When precision batching, the stable weight is acquired before and after the fast
and fine feed. The immediate weight is used during feeding and re-fill. Parameters are
set in the Stability Settings menu. See page 27.
Stable Time
How log the controller will wait for stability.
Stable Span
Max allowed weight difference between the Stable Samples.
Stable Samples
The immediate weight has to stay within Stable Span for this number
of samples.
Hopper Parameters
The Hopper Parameters deal with the material in the hopper, filling, emptying etc. They
are all set in the Hopper Parameters menu. See page 26.
Fill Weight
The hopper weight at which the fill gate closes when the weigh
hopper is re-filling.
35.00.EX O&M Manual 5