b
c
Remote Calibration Check:
The instrument can be placed in the calibration mode (positive or negative) by
shorting terminals Power Common and SHP for positive or SHN for negative on the lower I/O connector.
Figure 4 indicates two methods of remotely entering the calibration mode (external switch, or push
button control). The Remote Cal function provides a convenient method of periodically monitoring
calibration of the instrument in the positive or negative realm.
Master/Slave Connections
.
: When more than one IL78A is being used in a measurement setup
(instruments are closely mounted or the transducer cabling is in a common conduit or raceway),
beat frequencies may be produced from the 3-kHz oscillators used in the instruments to develop the
excitation. To prevent beat frequencies from occur-ring, one unit can be designated the master, and
the remaining units can be driven from the oscillator contained in the master unit. The remaining
units are designated as slave instruments. To perform master/slave wiring, refer to Figure 7.
3.
CALIBRATION
(cont.)
Switch 1 - Mode -
current (I) or voltage analog output
Switch 2 - Volts -
+/- 5 or +/- 10 Vdc when mode is voltage
Switch 3 - Current -
4-12-20 or 4-20mA when mode is current
Switch 4 - Filter -
650 Hz or 100 Hz at 3 db, for 100 Hz switch 5 must be set down
Switch 5 - Filter -
10 Hz or 100 Hz at 3 db, for 100 Hz switch 4 must be set down
Switch 6 - Sync -
excitaton clock to slave from a master module or to be master
Switch 7 - Zero Adj. -
extended (100%) or normal (25%) zero authority
Switch 8 - Aux Output -
SYC terminal output for use by other modules
Coarse Zero -
16 position switch adjustment for stepped zero
balance control marked for calibration default position
Fine Zero -
18 turn potentiometer for fine zero balance control
Coarse Span -
16 position switch adjustment for stepped gain
contr ol marked for calibration default position
Fine Span -
18 turn potentiometer for fine gain - span control
Symmetry -
adjust the negative output span to be equal
to the positive output
Phase -
adjustment for phasing the AC modulated signal to its
highest level at load
Over Range -
indicates when the analog output is 2% greater
than mode selected
Power -
indicates the power input voltage is ON
Fig. 2 Front Panel Settings and Indicators
Calibration IL78A.3
AC Strain Gage Conditioner
Module
IL78A
