TO FIND OUT WHICH CALIBRATION METHOD OR METHODS MAY BE USED
WITH A GIVEN CONDITIONER CARD, YOU SHOULD REFER TO THE RESPEC-
TIVE SUBSECTION OF
SYSTEM 10 GUIDEBOOK SECTION 1.E.2.
In very general terms, you will calibrate a signal-conditioner channel by com-
manding the system’s Central Processor to compute and store two constant
values: a
SCALING FACTOR (“m”) and a ZERO OFFSET (“b”). Automatically
and continuously applied to all subsequent readings of the given channel,
these two calibration constants define the linear proportionality expressed by
the equation “y = mx + b.”* In the following conventional “zero and span” tech-
nique, you will use the
ZERO (ZRO) and FORCE (FRC) commands to define
a channel’s “b” and “m” values, respectively. This is known as “Two-Point” or
“Deadweight” calibration.
a. In Section 8, above, you determined the CHANNEL NUMBER of the “live”
analog input channel you set up in Section 6. We will consistently refer to
this channel as “Channel No. x.” Thus, where “x” appears in the command
syntax below, you should enter the
actual Channel Number assigned to
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 your mainframe has a multichannel LCD or VFD display, use the PAG
command to invoke a display page that contains Channel No. x, as
explained in Section 5, above. If “x” is a number from 1 through 12, the
channel’s data reading should initially appear on Display Page No. 1
(unless you have already specified a new channel list for this page); if “x”
is from 13 through 24, it should appear on Page No. 2; etc.
If your mainframe does not have a multichannel LCD or VFD display, you
will have to display Channel No. x by transmitting its data reading from the
mainframe’s Computer Interface Port to a receiving computer CRT or
“dumb” terminal. You can use the
STREAM (STR) command for this pur-
pose, along with a special “header” or “tailer” that allows nonscrolling CRT
display of the “datastream” output (see Sections 1.H.2 and 1.H.3 of the
System 10 Guidebook for details). See Section 2.B of the System 10
Guidebook
for complete setup of the interface link.
c. Establish a
zero input for Channel No. x by removing all load from the
source transducer.
d. 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.
A - 15
DATA CHANNEL CALIBRATION
“O
NTHE
A
IR
” (A-S
IZED
)
* Where “y” is the measurement value reported for the channel and “x” is the ratio of the
actual voltage of the analog input signal to the positive full-scale voltage of the channel’s
chosen input “type.” As such, “x” is a unitless number operated upon by the “slope” coef-
ficient “m” and the offset term “b” to yield a true analog measurement. Both “m” and “b”
are expressed in the engineering units of the chosen input “type.”
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