Automating Manufacturing Systems - Process Control and ...

continuous sensors - 23.40
ratio. If the position of the geared down shaft needs to be positioned to 0.1 degrees, what is the
minimum resolution of the incremental encoder?
8. What is the difference between a strain gauge and an accelerometer? How do they work?
9. Use the equations for a permanent magnet DC motor to explain how it can be used as a tachometer.
10. What are the trade-offs between encoders and potentiometers?
11. A potentiometer is connected to a PLC analog input card. The potentiometer can rotate 300
degrees, and the voltage supply for the potentiometer is +/-10V. Write a ladder logic program
to read the voltage from the potentiometer and convert it to an angle in radians stored in F8:0.
23.8 PRACTICE PROBLEM SOLUTIONS
1. Temperature and displacement
2. Sensors can be found at www.ab.com, www.omron.com, etc
3. 360°/64steps, 360°/512steps, 360°/4096steps
4. data bucket, smart machines, PLCs with analog inputs and network connections
5.
V out
= α( T–
T ref
) 0.030 = α( 800 – T ref
) 0.040 = α( 1000 – T ref
)
1 800 – T
--
ref
1000 – T
= ----------------------- = -------------------------- ref
α 0.030 0.040
800 – T ref
= 750 – 0.75T ref
50 = 0.25T ref
T ref
= 200F α
V out
= 0.00005( 1200 – 200) = 0.050V
0.040
= -------------------------- =
1000 – 200
50µV
-------------
F