this channel. In Section 8, above, you ensured that Channel No. x is within
the current system SCAN RANGE, as it
must be if it is to be calibrated.
b. You should first arrange for a “live” display of Channel No. x. If this chan-
nel does not appear on any of your system’s initial data-display pages,
you will have to compose a new video page for its display, following the
guidelines given in Section 5, above.
c. At this point, you should determine whether your display’s current refresh
rate is satisfactory. Every mainframe is normally preset to update
dis-
played
data approximately 10 times a second. You may increase or
reduce this rate, if you wish, by enabling the EEPROM Write Protect func-
tion and commanding
REF = n [CR]
For the “refresh constant” (n), you should enter an integer from 1 through
60. This number is related to the actual screen “refresh rate” (R, in Hertz)
by this equation: 60/n = R (Hz). The range of possible refresh rates is
therefore 1 through 60 Hz.* For example, if you enter a refresh constant of
“5,” data appearing on your screen will be updated approximately 12
times a second, while a value of 30 for “n” will yield a rate of only 2 times a
second.
d. Establish a
zero input for Channel No. x by removing all load from the
source transducer.
e. Make sure the EEPROM Write Protect function is enabled, and enter from
the keyboard a command of
ZRO x [CR]
The displayed value for Channel No. x should now be zero. If it is not,
recheck the transducer connection, the channel number, and the channel
TYPE and LOCATION assignments; also make sure that Channel No. x is
in fact within the current scan range (see Sections 6, 7, and 8, above).
This command sets the “BEE” value for Channel No. x—that is, the ZERO
OFFSET to be applied to all subsequent channel readings.
f. Now apply an
accurately known value of input loading to the source trans-
ducer—a value (positive or negative) from 80% to 100% of the nominal full-
scale rating.
g. Enter a command of
FRC x = z [CR]
where “z” is the numerical value of the known input applied in Step e, in
desired engineering units and with appropriate polarity. This command
“forces” the data reading of Channel No. x to equal the value “z.” It there-
by sets the “EMM” value for Channel No. x—that is, the SCALING FACTOR
to be applied to all subsequent channel readings. Check the “live” display
of Channel No. x to make sure that it reads the number “z.”
The
FRC command also set the desired precision of Channel No. x. Sup-
pose, for example, that you’re measuring “pounds,” and enter a “z” of
“300.” All subsequent readings of Channel No. x will be rounded to the
nearest pound. If, however, the entry is “300.0,” then all readings will be
rounded to the nearest tenth of a pound.
B - 21
DATA CHANNEL CALIBRATION
“O
NTHE
A
IR
” (B-S
IZED
)
* Please note that these rates are approximate only.
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