Campbell Scientific ST350 Strain Transducer for Structural Testing - Manual (Page 13)

Section 4. Wiring
4.1 Initial Check-Out
Upon receiving new transducers, it is important to check that they are in proper
working order. Using an ohmmeter, read the resistances between the black and
red wires and then the green and white wires, both readings should be very
close to 350
Ω. If they are not, the unit may be unusable and should be returned
to BDI either for repair or replacement. This test should be performed on a
periodic basis, especially if the transducer has been dropped or otherwise
mishandled.
Campbell Scientific, Inc. data acquisition systems support the use of a full
Wheatstone bridge sensor. The ST350 strain transducer has four active arms
consisting of 350
Ω strain gages. This configuration provides approximately 3
to 3-1/2 times the output of a standard 1/4-arm foil gage installation for a given
strain level. The connection sequence is shown in the following figure.
FIGURE 4-1. ST350 Electrical Wiring Diagram
Output = V
diff
is defined as ((+ Sig) – (- Sig)) NOTE
Therefore, [+ Output = Member in Tension] and [- Output = Member in
Compression]
4.2 Excitation Voltage
The recommended excitation voltage is generally between 2.5 and 5 volts DC.
When programming this transducer use Reverse Excitation to
cancel effects of Lead Resistance. CSI recommends performing
a reverse measurement to eliminate any hardware offsets. See
datalogger programming example for further information. NOTE
Once the transducer has been connected to the data acquisition system, the user
should verify output by monitoring the signal in real time while gently placing
the transducer in tension and compression by hand. This will ensure that
4-1