Physics: take measurements and capture behaviour in mathematical form
Deviations from mathematical form implies the need to revise something
ideas of planning, executing and assessing measurements
Progress in physics
Insights
- Transducer should not affect system/device seen
- Track changes easily
- Deal with noise
- Equivalent output circuit: ideal voltage source + output impedance
- Equivalent input circuit: ideal voltage metre | input impedance
- Desirable:
- Transducer with low output impedance
- 'scope with high input impedance
Compensate the transducer with a complex impedance probe to avoid degrading of
at high f
For other measurements:
- Current: small
for 'scope
- Power:
to get the same maximum power measurable
- Operational amplifier: high gain, high input impedance
For an ideal OP:
- Golden rules for an ideal OP:
- GR1:
- GR2:
if not saturated (proof by considering the non-inverting amplifier to calculate using current conservation and Ohm's Law)
- Inverting voltage amplifier
- Closed loop gain:
- Non-inverting voltage amplifier
- Closed lop gain:
- Other persepctive: potential divider
- NB:
- Needs negative feedback
-
e.g. not saturated. After saturation
- Make
frequency-dependent to perform filtering and selected amplification
