CONFIGURATION AND CALIBRATION
OF
ANALOG INPUT CHANNELS
1.G
The most likely reason you would have for changing a “real” channel’s current
EMM value would be to change the effective decimal-point precision for that
channel’s data reading. However, if you wish to
calibrate a channel by directly
entering its two calibration constants, you will have to use an “x” value that is, as
mentioned above, the ratio of the actual input to the stated positive full-scale
range. For example, if the channel is assigned a “TYPE” designation of “61” (=
VOLTAGE INPUT CHANNEL, 50 mV-DC full scale), and the actual input is currently
+45 mV, then x = 0.9 (and NOT “45”). If the 45-mV input corresponds to a mea-
surement of, say, 1000 kPa, then for “y = mx + b” we can write
1000 kPa = m (kPa) (0.9) + 0 (kPa)
which yields an “m” (to the nearest kPa) of “1111” for the ±50-mV range, plus-or-
minus the inherent initial accuracy of the conditioner. There are exceptions to this
procedure, including certain VOLTAGE and CURRENT conditioners (10A60-4,
10A61-2) and THERMOCOUPLE conditioners that have their own linearization
standards. Contact the factory for precise instructions.
As the examples given below will make clear, the
PRECISION (i.e., decimal-point
location) of the measurements reported by a given “real” channel will always
match the precision of one of the numbers entered by the operator or computer
during the calibration procedure.
The basic System 10 calibration methods are listed below, and are described in
the following Guidebook sections. TO FIND OUT WHICH CALIBRATION METHOD
OR METHODS MAY BE USED WITH A GIVEN CONDITIONER CARD, YOU SHOULD
REFER TO THE RESPECTIVE SUBSECTION OF
SECTION 1.E.2 OF THIS GUIDE-
BOOK.
•
ABSOLUTE CALIBRATION (CPU)—see Section 1.G.3(a)
•
ABSOLUTE CALIBRATION—see Section 1.G.3(b)
•
CALCULATED CALIBRATION (FRQ)—see Section 1.G.4(a)
•
CALCULATED CALIBRATION (MVV)—see Section 1.G.4(b)
•
CALCULATED CALIBRATION (OTHER)—see Section 1.G.4(c)
•
TWO-POINT (DEADWEIGHT) CALIBRATION—see Section 1.G.5
•
SIMULATED (SHUNT) CALIBRATION—see Section 1.G.6
1.G.3 ABSOLUTE CALIBRATION
a. CPU-BASED ABSOLUTE CALIBRATION
This form of “ABSOLUTE” CALIBRATION applies primarily to temperature-mea-
suring channels
. Here, the zero and scaling characteristics of the sensor/condi-
tioner combination are fixed and known (by the System 10 Central Processor).
Since the “m” (
EMM) and “b” (BEE) values for such channels are prestored in
System 10 memory, with suitable engineering-unit scaling, THERE IS NO NEED
FOR ANY FURTHER CALIBRATION PROCEDURES ON THE PART OF THE USER,
once the channel’s TYPE CODE has been specified.
Note that for a thermocouple-based “real” channel or other channel capable of
CPU-base absolute calibration, specific
EMM and BEE values are automatically
loaded as soon as the channel is “typed.” THESE INITIALLY LOADED CALIBRA-
TION CONSTANTS SHOULD NOT NORMALLY BE CHANGED.
1-35
1.G.3 ABSOLUTE CALIBRATION
To Next Page
Loading...