DayTronic 3500 Series, Instruction Manual

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soon as the "TC TYPE" and desired measurement units are specified. For the
front-panel entry of TC type and scale, see Section 3.a.5(a). For use of the
TYPE
(TYP) and RANGE (RNG) commands to accomplish the same thing, see Section
3.a.B.
NOTE: While "absolute" calibration is sufficient for almost all applications of the
Model 3510, the "Two-Point" technique described below can also be used for
applications where it is desirable to force multiple TC readings to the same exact-
ly known temperature value (in heat balance applications, for example).* In such
cases, the two-point method can be used to improve on the "absolute" calibration
inherent in the 3510.
Also note that the internal 15-SEGMENT LINEARIZATION procedure described in
Section 4.c.4 does not apply to the Model 3510 Thermocouple Conditioner.
4.a.2 “A
CTUAL
” T
WO
-P
OINT
(D
EADWEIGHT
) C
ALIBRATION
This conventional "zero and span" procedure can be applied to all 3500 Series
conditioner models. It should be used when the transducer signal is relatively lin-
ear and when there are at least two independently and accurately known calibra-
tion values.
With "TWO-POINT" calibration, you will command the instrument's micro-
processor to compute and store two constant values: a ZERO OFFSET term ("b")
and a SCALING FACTOR coefficient ("m," also called "multiplier" or "gain" factor).
Automatically and continuously applied to all subsequent data readings, these
two calibration constants define the linear proportionality expressed by the equa-
tion "y = mx + b."**
4.a.3 “S
IMULATED
” T
WO
-P
OINT
(D
EADWEIGHT
)
C
ALIBRATION
This calibration method applies to the Model 3570 DC Strain Gage Conditioner
and the Model 3578 AC Strain Gage Conditioner . In "actual" two-point calibra-
tion (above), the second ("span") calibration input is produced by actually loading
the transducer. When this kind of "deadweighting" is impossible or inconvenient,
the same effect can be achieved for either of the two Strain Gage Conditioners by
shunting a resistor of known magnitude across one arm of the strain-gage bridge,
thereby "simulating" a particular up-scale value of mechanical input.
4.2
4
S
ETUP
: I
NSTRUMENT
C
ALIBRATION
4.a I
NTRODUCTION
: C
ALIBRATION
T
ECHNIQUES
* Note, however, that for a TC input, two-point calibration is of no advantage unless you can gen-
erate temperatures that are known to an accuracy exceeding that given in Appendix A for the
Model 3510.
** Where "y" is the reported measurement value and "x" is the ratio of the actual voltage of the
analog input signal to the positive full-scale voltage of that input (based on the selected input
range). As such, "x" is a unitless number operated upon by the ("slope") coefficient "m" and the
offset term "b" to yield a true analog measurement in the appropriate engineering units.