Showing posts with label Disadvantages. Show all posts
Showing posts with label Disadvantages. Show all posts
Sunday, 5 March 2017
Types of Actuators used for Motion in Automation with Advantages Disadvantages
Types of Actuators used for Motion in Automation with Advantages & Disadvantages
The actuators used for performing motion (which includes control of speed, positional accuracy or torque) are
• Air Motors
• AC Induction Motors
• Clutch/Brake
• Stepper Motors
• Hydraulic Motors
• Servomotors
1) Air Motors –
This uses “compressed air” to create motion. Pressure and flow determine speed and torque. Positional accuracy is not a required.
Advantages:
1. Low cost
2. Available components
3. Maintenance easy
4. Simple
5 .Centralized power source
Disadvantages:
1. Audible compressor noise
2. Difficult to regulate speed
3 Prone to contamination
4. Energy inefficient
2) Hydraulic motors –
This uses “pressurized oil” to move a piston. Higher pressure results in higher torque (i.e. brute force).
Advantages:
1 .Easy to apply
2. High torques
3. Centralized power source
4. Simple
Disadvantages:
1. Audible noise
2. Difficult to control speed
3. Slow positioning
4. Prone to leaks
5. Energy inefficient
6. High maintenance required
3) Clutch/Brake –
A device couples a continuously rotating shaft and a load. Uncoupling the load results in stopping of shaft. Varying on/off time results in varying distances
Advantages:
1. Easy to apply
2. Low cost
3. Good for start/stop (not used with high loads)
4. Easy to provide speed matching
Disadvantages:
1. Uncontrolled acceleration
2. Inaccurate
3. Prone to wear
4. Non-repeatable performance
4) Stepping Motors –
Electromechanical device which converts one digital pulse into a specific rotational movement/Step or displacement. A "train of pulses" results in rotational speed.
Advantages:
1. Simple control
2. Moderate cost
3. Good for constant loads
4. Good positional accuracy
Disadvantages:
1. Prone to losing steps
2. Not good for varying loads
3. Energy inefficient
4. Large motor size
5. Resonance problems
5) AC Induction Motors –
Widely used for constant speed requirements. Electric "starters" provide connections/start-up/overload protection. Newer technology provides variable speed Drive capability.
Advantages:
1. Simple motor
2. Low cost
3. Mature technology
4. Straightforward on/off control
5. Affordable coarse speed control
6 .Simple wiring
7. Wide product variety
8. Many vendors available
Disadvantages:
1. Limited position control
2. Relatively larger size
6) Servomotors –
A motor with a "feedback" device called as encoder. High speed and position accuracy
Advantages:
1. High performance
2. Small size
3. Wide variety of components
4. High speeds available with specialized controls
Disadvantages:
1. High cost
2. High performance limited by controls
3. High speed, torque is limited.
Sunday, 15 January 2017
Advantages Disadvantages of RTD Thermocouple Thermistor Temp IC Sensors
Hi Greeting,
Friends we always come across various temperature sensors like RTD, Thermocouple, Thermistor, temperature sensing IC’s while doing automation of process plants. It’s very essential to know about advantages & disadvantages of the entire sensors so that we can select them with ease.
So let’s start with Thermocouple.
Thermocouple:
Advantages of Thermocouple:
- Self Powered
- Simple
- Rugged
- Inexpensive
- Wide Variety
- Wide Temp Range
Disadvantages of Thermocouple:
- Non Linear
- Reference Required
- Low Voltage
- Least Stable
- Least Sensitive
RTD:
Advantages of RTD:
- Most Stable
- Most Accurate
- More Linear than Thermocouple
Disadvantages of RTD:
- Expensive
- Current Source Required
- Small ∆R
- Low absolute Resistance
- Self heating
Thermistor:
Advantages of Thermistor:
- High Output
- Fast
- Two wire ohms measurement.
Disadvantages of Thermistor:
- Non Linear
- Limited Temperature Range.
- Fragile
- Current Source required.
- Self heating
IC Sensors:
Advantages of IC Sensor:
- Highest Output.
- Inexpensive.
- Most linear.
Disadvantages of IC Sensor:
- T< 200C.
- Power supply required.
- Slow.
- Limited Configuration.
- Self heating
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