DayTronic 3000 series, Instruction Manual

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Model 3178
from the
+Signal
terminal of the transducer to the + or –
Excitation
terminals. The
Excitation
terminal to which the connection is made is
determined by the direction of the loading or off-zero reading.
(c) The inability to balance correctly where the instrument output reads
totally off scale and the BALANCE controls have no authority can very
likely be the result of a damaged or defective transducer or cable. This
possibility can be confirmed (or eliminated) by substituting a transducer
and cable known to be in good condition or by simulating a balanced
transducer, using either a commercially available transducer simulator
or the simple
star bridge
arrangement shown in Figure 7. The
star bridge
simulates a conventional four-arm bridge in an exact condition of bal-
ance. To construct a
star bridge
connect four 10% carbon resistors as
shown in Figure 7. Use 180-ohm resistors to simulate a 350-ohm bridge
and use 56-ohm resistors to simulate a 120-ohm bridge. Neither the
resistor values nor temperature characteristics are critical since the
balance condition of a
star bridge
is not determined by the resistance
Figure 7. Star Bridge Construction
20