Block 5 3E

Sensor Definition

Device that responds to a change in the following conditions temperature, velocity of air, Humidity, water level, pressure,

Control Loop

1 The information flow within a control system

2 Sensor detects condition

3 Controller alters information

4 Controlled device responds

5 A control loop can maintain only one of pressure, temperature, humidity, lightning valve

Control System Configurations

1. Two Configuration open loop and closed loop

1 Sensor location determine loop type

2 Open loop Configuration sensor is upstream of control agent action on medium

3 Closed loop sensor located downstream maintains controlled variable feedback loop concepts

Active Sensors

Send info in millilamps (mA) or Volts

Not affected by wire length

Typically output 0-10V or 4-20mA

Passive Sensors

Sends info in resistance (ohms)

Convert temperature to resistance

Limited by wire resistance

Typical sensor 1000 nickel sensor

Binary (Digital)

Can be open or closed, on or off used for status proof safety and limits

Examples

Yes no

Open closed

On off

Start stop

Analog

Measure a range of values over time

Examples Temperature, Pressure, Humidity, Flow, Light