Hardware Reference
In-Depth Information
Figure 12.10
Strain gauge input signal conditioning circuitry
Hardware
The system can be based on a PC fitted with almost any 8-channel analogue input
card (e.g. Arcom's PCAD12/16 which is a 16-channel 12-bit ISA card). The
signal conditioning circuitry (replicated eight times) is based on a conventional
temperature compensated half-bridge with operational amplifiers to provide
voltage gain (variable from approximately 500 to 1500). To minimize noise, the
input cable from each strain gauge bridge is balanced and shielded. Figure 12.10
shows
the
signal
conditioning
circuitry
associated
with
each
strain
gauge
bridge.
Backup battery load test
The client is a manufacturer of low-power FM radio relays. Each relay is fitted
with a standby battery comprising four 2 V sealed lead-acid cells, each rated
at 2 V 80 Ah.
Specification
The battery load test is to capture backup battery voltage data at regular intervals
ranging from 10 ms to 100 s for periods of between 1 min (accelerated load test)
and 10 days (prolonged load test). Voltage readings are to be within the range
0-10 V DC and they are to be accurate to within
50 mV (
0.05 V). Data is
to captured in a form that is compatible with a standard spreadsheet (e.g. MS
Excel) for subsequent display and analysis. A dedicated PC is unavailable for
