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Instrumentation - Second Period > 310203fA Intro To PLC's Part A > Flashcards

310203fA Intro To PLC's Part A Flashcards

1
Q

What is this symbol?

A

NC Level switch

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2
Q

What is this symbol?

A

NO Pressure Switch

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3
Q

What is this symbol?

A

NC Flow Switch

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4
Q

What is this symbol?

A

NO Temperature Switch

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5
Q

What is this symbol?

A

NC Limit Switch

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6
Q

What is this symbol?

A

NO Level Switch

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7
Q

What is this symbol?

A

NC pressure switch

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8
Q

What is this symbol?

A

NO flow switch

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9
Q

What is this symbol?

A

NC temperature switch

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10
Q

What is this symbol?

A

NO Limit Switch

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11
Q

What is this symbol?

A

Relay coil

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12
Q

What is a form A relay?

A

A relay with one or more normally open (NO) switches

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13
Q

What is a form B relay?

A

A relay with one or more normally closed (NC) switches

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14
Q

What is a form C relay?

A

A relay that has both normally open (NO) and normally closed (NC) contacts

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15
Q

What are the 4 major hardware components of a modular PLC system

A
  1. Power supply
  2. Backplane
  3. Central processing unit (CPU)
  4. Input and output modules (I/O)
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16
Q

What is the purpose of the backplane in a PLC?

A

The backplane consists of the address data and control buses.
The back plane allows the controller to communicate with the IO module’s within the chassis and provides power for the internal operation of the controller and the I/O modules.

17
Q

How are PLC chassis selected?

A

According to the number of slots available for IO modules.

18
Q

What are the 3 types of processor memory?

A
  1. Read only memory (ROM)
  2. Random access memory (RAM)
  3. Electrically erasable, programmable memory (EEPROM)
19
Q

What is the difference between non-volatile and volatile processor memory?

A

Non volatile processor memory retains information after a power loss
Volatile processor memory loses its information on a power loss

20
Q

Is read-only memory (ROM) volatile or non-volatile memory?

A

Read-only memory is non-volatile (retains information after power loss)

21
Q

Is random access memory (RAM) volatile or non-volatile?

A

Random access memory (RAM) is volatile (loses its information on power loss)

22
Q

What is electrically erasable programmable memory (EPPROM)

A

EEPROM is retentive memory that saves user programs and data when the PLC is turned off or loses power unintentionally

23
Q

The key switch allows you to put the PLC into 3 different modes. What are these modes?

A
  1. Programming (PROG)
  2. Operation (RUN)
  3. Remote (REM)
24
Q

What are the 3 steps in a PLC scan cycle?

A
  1. Input scan
  2. User-program scan
  3. Output scan
25
Q

Discrete input modules are specified by 3 things:

A
  1. The operating voltage (24vdc, 120ac, 240vac)
  2. The number of points they have (8, 16, 32)
  3. The way power is connected (sinking or sourcing, isolated or non-isolated)
26
Q

Describe the field side operation of a current sinking DI module

A

With optical isolation and external power supply is required to power the field side connections of the DI module
To properly biased the LED the power supply’s positive terminal must be connected to the field device, and its common terminal must be connected to the PLC’s common terminal
Conventional current flows INTO the field terminal from the field switch and is called current sinking.

27
Q

Describe the field side operation of a current sinking DI module

A

With optical isolation and external power supply is required to power the field side connections of the DI module
To properly biased the LED the power supply’s positive terminal must be connected to the field device, and its common terminal must be connected to the PLC’s common terminal
Conventional current flows INTO the field terminal from the field switch and is called current sinking.

28
Q

Describe the field side operation of a current sourcing DI module

A

With optical isolation an external power supply is required to power the field side connections
To properly bias the LED the power supply’s common terminal must be connected to the field device, and it’s positive terminal must be connected to the power terminal (V) on the DI module

29
Q

What is the difference between a current sinking and current sourcing DI module?

A

A current sinking module has a common terminal connected to the negative of the power supply supplying the DI module. The positive terminal on the power supply is connected to the field device/process switch and then from the switch to the field terminals of the DI module
Current sinking = field terminals are positive (+) with one common (-) terminal
A current sourcing module has a positive voltage terminal connected to the positive of the power supply supplying the DI module. The negative of the power supply is connected to the process switch, and then from the process switch to the field terminals on the DI module.
Current sourcing = field terminals are negative (-) with one positive terminal (V)

30
Q

Discrete output modules are specified by 4 things:

A
  1. The operating voltage
  2. The number of points they have
  3. The field interface circuit technology
  4. The way power is connected
31
Q

Which part of an AC DO Module may cause a faint glow with pilot lights, a detectable hum with small coils and relays or solenoids, and false meter readings?

A

AC switching DO modules use a TRIAC as a switch that allows AC current flow went on and no current flow went off.
TRIAC’s allow a small leakage current (a few milliamps) in their off state, which can cause these problems.

32
Q

Analog input modules are specified by 3 things:

A
  1. The signal input range
  2. The number of points they have
  3. The way the power is connected
33
Q

Define analog input resolution

A

The resolution of an analog input point is the smallest amount of change in the analog to digital converter (ADC) chips input electrical signal that results in a change of one count
To determine the resolution, divide the input ranges span by the number of counts
For example, a 16-bit ADC chip with a full input range of 0 mA to 21.09 mA has a resolution of 0.32 micro-amps
A 16-bit binary word represents 65,536 counts

34
Q

True or false
If you use a sensor with a limited range, the you do not change the module’s resolution.

A

True
Resolution is based on the module hardware and range selected. If you use a sensor with a limited range, you do not change the module resolution.

35
Q

Analog output modules are specified by three things:

A
  1. The signal output range
  2. The number of points they
  3. The outputs (isolated or non- isolated)
36
Q

How many counts does a 12-bit binary word represent?

A

4096 counts

37
Q

How many counts does a 16-bit binary word represent?

A

65,536 counts

Instrumentation - Second Period (30 decks)

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