1. Measurement Hardware Sensor: a device that senses a physical
stimulus and converts it into a signal.
Transducer: a device that changes the
signal into the desired form.
Signal Conditioner: a device that puts the
signal into its final form to be processed
and recorded.
Signal Processor: a device that converts
the signal typically from analog to digital
and stores the information.

2. Sensors and Transducers

3. A Simple Measurement System
liquid
stem
bulb
scale
Sensor:
liquid
Transducer:
bulb
Signal Conditioner:
stem
Signal Processor:
scale on stem

4. Some Sensors strain gage (R=rL/A) hot-film probe (or RTD)
R=Ro[1+a(T-To)]
thermistor
R=Roexp[h(1/T-1/To)]

5. LEX-2 Pressure Transducers

6. LEX-2 Pressure Transducers

7. Amplifiers
amplifiers

8. Amplifiers An amplifier is an electronic component that scales
the magnitude of a signal from its input value, Ei,
to its output value, Eo.
Functionally, this can be expressed as Eo = f[Ei],
where f is some amplification operator.
For a linear amplifier, Eo = G•Ei, where G is the gain.
For a logarithmic amplifier, Eo = G•log[Ei].

9. Figure 6.4: The LM124 Series Op Amp
Operational Amplifiers
Figure 6.4: The LM124 Series Op Amp

10. Operational Amplifiers
The complex circuit of the op amp can be modeled
as a ‘black box’ having two voltage inputs and one
voltage output.
Figure 6.5
It major attributes are:
See consequences
Top pg. (151)
[1] very high input impedance (> 107 Ω)
[2] very low output impedance (< 100 Ω)
[3] high internal open-loop gain (~105 to 106)

11. Figure 6.7

12. Differential Op Amp Equation
Kirchoff’s First Law can be applied to determine the amplification
factor for this configuration. B
at node B, (Ei1-EB)/R1 = (EB-Eo)/R2
at node A, (Ei2-EA)/R1 = (EA-0)/R2 A
Now EA = EB because the voltage difference between the inputs is
zero (a consequence of the op amp’s high internal open-loop gain).
Equating the two expressions yields the desired factor.