Valmet SMART-PULP Operating And Installation Instructions page 26

SMART-PULP
2. Two-point calibration
In this calibration the selected curve (which converts
the sensor's shear force to consistency signal) is
moved in the direction of consistency so as to effect
a zero offset and to change the slope of the curve.
The curve is adjusted to pass via two consistency
points. SMART-PULP calculates new values for P1
and P2.
IMPORTANT: The difference between the
consistency points in two-point calibration must be at
least 25%, calculated from the lower point. This is to
prevent possible sampling and consistency analysis
errors from having a noticeable effect on the slope
of the curve. SMART-PULP will issue a warning
against calibrating at less than 25% consistency
difference by blinking USE BOTH text (0.8 < Cs2/
Cs1 <1.25).
Two-point calibration is recommended when you
want accurate measurement over a wide measuring
range and/or when you are calibrating a pulp mix or
pulp type that does not have a predefined calibration
curve in the menu, or pulp that has a large unknown
filler content. Considerable differences may also
occur between different recycled fiber pulps in
relation to the basic slope of the calibration curve.
CALCULATION:
P 1 = (LAB2 - LAB1)/(SAMPLE2 - SAMPLE1)
P2 = LAB1 - P1 x SAMPLE1
Before starting, check from the MEASURE menu
that the recipe to be calibrated is active.
1 START
Press ENTER to start sample taking.
END SAM
The display blinks until you press ENTER again to
tell SMART-PULP that sample taking has been
completed.
The average consistency reading for the sampling
period is saved in memory.
If you use a sampling valve equipped with a switch
that gives an "open/closed" binary signal (in SMART-
PULP's binary input 4: 24V = valve closed, 0V =
valve open), the sampling period will exactly match
the consistency measurement period. This is
indicated by a small square at the bottom of the
display; the square is open at the moment of
sampling, and closed when the valve is closed.
Unconnected input 4 equals 0 V, i.e. valve is open.
1. CS X.XX%
Average consistency for the sampling period. Press
an arrow key to proceed.
1. Sd X.XX%
Standard deviation. Blinking Sd display indicates
that standard deviation for the sampling period was
more than 5% of the sample average. It is then
advisable to wait for the process to become steady
Smart Consistency Transmitter
and take a new sample. Press an arrow key to
proceed.
1. F XXXXG
Shear force corresponding to the displayed
consistency. Press an arrow key to proceed.
Taking a second sample is not compulsory in single-
point calibration.
2 START
Start taking a second sample. The same as 1
START. 2.CSX.XX%, 2.SdX.XX% and 2.FXXXXG
are the same as above.
If required, repeat the procedure for one or both
samples.
Finally press ESC to return to the main menu.
2.3.3 The LABORATO menu
When laboratory results are available, activate the
LABORATO submenu from the Calibration menu:
RECIPE n
Select the number of the recipe you want to
calibrate.
ASH X.XX%
The filler percentage defined in the NEW RECI
menu. You do not change this unless a more specific
value is obtained from laboratory.
Entering the filler content is optional if the
transmitter is recalibrated each time the filler content
changes.
1 CS X.XX%
The average of SMART-PULP's consistency reading
at sampling time. Change this in accordance with
the total consistency indicated by the laboratory
results.
2 CS X.XX%
See above.
CHNG CAL
Select the calibration method.
USE FRST
Accept single-point calibration with first sample, or
press arrow key to go to the next option.
USE SCND
Accept single-point calibration with second sample,
or press arrow key to go to the next or previous
option.
USE BOTH
Accept two-point calibration with both samples, or
26
BCs160VA
Nov. 15, 1997