Section 1.1-1.2

Why electrical sensing over mechanical

Ease of signal transmission to data collection

Ease of signal modification

Ease of recording data

Electrical Signal Measurement Stages

1. Measurend

2. Sensor/Transducer

3. Signal Conditioner

4. Recorder/Display/Processor

Transducer

Changes or converts information in the measurement process

Sensor

Produces an output in response to a measurand (sensor is a transducer

Sensing Stages

1. Measurand causes a physical but nonelectrical change in the sensor

2. Physical change is converted to electrical signal

Types of Signal Conditioning

– Amplification

– Attenuation

– Filtering

– Linearization

– Converting Resistance to Voltage

Amplification

Increasing the amplitude of signals

Gain

Degree of amplification

How amplifiers affect signals

• Frequency distortion

• Phase distortion

• Source loading

Bandwidth

Range of frequency with close to constant gain

Fcl and Fcu

• Cutoff frequencies

• All amplifiers will have upper but not all will have lower

Causes of Frequency Distortion

Narrow Bandwidth

Impedance

When connecting, it occurs because of the tendency to drop voltage as current is drawn

Operational Amplifier (Op-Amp)

Practical, low-cost, integrated component used for signal amplification

Buffer/Follower Op-Amp

Prevents current from running to circuit (acts as a wall)

Why we need Buffer/Follower Op-Amp

Very high input impedance and low output impedance allows less current drawn from circuit

Range of resistors in Op-Amp

1k ohms to 1M ohms

Resistors in Op Amps

• Lower resistance increases power consumption

• Higher resistance affects impedance

Voltages in Op-Amps

Supply voltage limits the voltage output

When output saturation occurs

As 𝑉𝑜 approaches supply voltage

Attenuation

Reduction of signal amplitude

Simplest method of attenuation

Voltage divider is simplest method