DayTronic 3500 Series, Instruction Manual

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Press the CAL button again. This will return you temporarily to a display of the
"live" analog input.
h. Apply a second accurately known value of input loading—a value from 80% to
100% of the transducer's nominal full-scale rating.
i. Now press ANY KEY EXCEPT CAL OR SETUP . This will freeze the displayed
data value, which should be the value of input loading at your second ("force")
calibration point.
NOTE: THOUGH THE DISPLAYED INPUT VALUE IS FROZEN, THE INPUT
ITSELF IS NOT. "FORCE" CALIBRATION WILL BE BASED ON WHATEVER
ACTUAL INPUT EXISTS WHEN THAT CALIBRATION POINT IS ENTERED.
j. Again using the NUMERIC BUTTONS, change the displayed value to the
desired measurement reading for the known input, in the desired engineering
units, and with appropriate polarity. This "forces" the data reading to equal
this value, thereby determining the SCALING FACTOR to be applied to all sub-
sequent readings. Like the offset entry, above, the "force" entry cannot
exceed the inherent number count of ±32700. Also, if you try to "force" a num-
ber that is less than 50% of full scale, you will get an "INPUT INSUFFICIENT"
error.
NOTE: The second calibration entry also sets the desired measurement pre-
cision. If, for example, you're measuring "millimeters," and enter a "FORCE"
value of "10," then all subsequent readings will be rounded to the nearest mil-
limeter. If you enter "10.0," then all readings will be rounded to the nearest
tenth of a millimeter. This same precision will be automatically reflected in the
LIMIT parameters ("HIL" and "LOL"—see Section 3.a.8).
k. Press ENTER to establish your second calibration point. The display will
return to "FORCE." Press SETUP to return to the "Setup" display.
4.c.3 “S
IMULATED
” (S
HUNT
) C
ALIBRATION FOR A
S
TRAIN
G
AGE
C
ONDITIONER
(M
ODEL
3570
OR
3578)
This is an easier though generally less accurate technique than "actual" two-point
calibration. It is useful, however, when overall "deadweighting" is impossible or
inconvenient, and is good for an accuracy of about 0.2% (depending, of course,
on the accuracy of the specified EQUIVALENT INPUT, and on the resistor/ bridge
tolerance and temperature). The known calibration input is not produced by load-
ing the transducer, as in the "deadweight" method, but 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. This known EQUIVALENT INPUT
then serves to determine the SCALING FACTOR for the channel.
Every Model 3570 or 3578 is equipped with a 100-k
Ω
, 0.1% calibration resistor
which you may, if you wish, replace with a resistor of some other value (strain-
gage transducer manufacturers often supply such resistors with their instru-
ments, along with the exact values of EQUIVALENT INPUT thereby produced).
See Fig. 11(c) for resistor installation.
4.10
4
S
ETUP
: I
NSTRUMENT
C
ALIBRATION
4.c C
ALIBRATING
T
HROUGH THE
F
RONT
P
ANEL