Bridge Amp Operation - ADInstruments Bridge Amp Owner's Manual

Figure A–1
Block diagram of the
ML221 Bridge Amp. The
ML224 and 228 Bridge
Amps are similar but with
four or eight inputs,
respectively
42
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Bridge Amp Operation

The Bridge Amp and other ADInstruments front-ends have been
designed to integrate fully with the PowerLab system. The Bridge
Amp is essentially an extension of the PowerLab's input amplifiers, so
the amplification (and hence the ranges) offered in LabChart and
Scope are the combination of both pieces of hardware. The
Bridge Amp provides:
• the additional amplification necessary to deal with the low signal
outputs of most transducers
• additional programmable filtering, to remove unwanted signal
frequencies
• a stable DC excitation voltage supply for powering the transducer
• digitally-controlled transducer zeroing circuitry.
Transducer
plug
Transducer
Pre-amp
signal inputs
Overload
indicator
+ Bridge
Excitation
excitation
voltage
–
driver
Excitation voltage
setting resistor
Online indicator
Gain
control
5th-order
8 kHz
Prog.
Butterworth
Amp
low-pass
filter
16-bit
control
DAC
interface
V
ref
Bridge Amp Owner's Guide
Signal
Output
2
I C
2
I C
Outpu t
+
power
2
I C
supply
Input