- How the 11 Content Areas Are Organized
- PMMI PLCs 1 Exam Snapshot
- Domains 1-3: Operation, Memory, and Discrete I/O
- Domains 4-6: Monitoring, Logic, Timers, and Counters
- Domains 7-9: Motor Control, Sequencing, and Machine Applications
- Domains 10-11: Troubleshooting
- Original Practice Questions Mapped to Domains
- A Four-Week Editorial Plan Built Around the Domain Order
- Frequently Asked Questions
- PMMI publishes 11 test-competency groups for PLCs 1, listed in sequence from PLC operation through hardware and software troubleshooting.
- The public page lists 100 questions and a 70% passing score; the roughly two-hour length is an estimate, not a verified timer.
- The 11 domains are unweighted public objective groups, so don't assume any one area carries more points.
- Relay logic, ladder programming, and input/output knowledge are the emphasized foundations for entry-level packaging technicians.
How the 11 Content Areas Are Organized
The PMMI Mechatronics: Programmable Logic Controllers 1 (PLCs) test publishes its scope as a list of eleven competency groups under its "Test Topics & Questions" section. Read in order, they follow the way a technician actually grows on the job: first you learn what a controller does, then how it stores and addresses data, then how it talks to field devices, then how to write and test logic, and finally how to diagnose a machine that has stopped running.
One point deserves emphasis before you build a study plan. PMMI's public page presents these groups as unweighted headings. There is no published percentage breakdown, so you cannot responsibly say that Domain 5 is worth more than Domain 9, or that timers and counters make up a particular share of the test. Treat all eleven as fair game and prepare evenly, with extra time wherever your own on-the-job experience is thinnest. For a broader view of what the exam feels like in practice, see How Hard Is the PLCs Exam? Complete Difficulty Guide 2026.
PMMI PLCs 1 Exam Snapshot
Before diving into the domains, it helps to anchor on the logistics PMMI actually publishes. The table below separates what is verified from what was not confirmed in the public sources.
| Item | What the public PMMI page shows |
|---|---|
| Governing body | Packaging Machinery Manufacturing Institute (PMMI) |
| Number of questions | 100 |
| Passing score | 70% |
| Listed time | "Approximately 2 Hours" (a completion estimate, not a verified hard timer) |
| Test price | USD 125, one attempt per purchase |
| Delivery | Online certification test; candidates are directed to PMMI Education Partners for examination arrangements |
| Domain weights | Not published |
| Pass-rate statistic, renewal rule | Not verified from public sources |
Because each purchase covers a single attempt, there is real value in arriving prepared. Our PLCs Certification Cost 2026: Complete Pricing Breakdown walks through the fee mechanics, and PLCs Passing Score 2026: Exactly What You Need to Pass explains what a 70% threshold means across 100 questions.
Domains 1-3: Operation, Memory, and Discrete I/O
The first three domains build the vocabulary everything else depends on. Candidates who skim here usually struggle later, because ladder logic is just a way of manipulating the memory locations and I/O points defined in these areas.
Domain 1: Operation of a PLC
This area is about how a controller works as a system, not about any single instruction.
- The major hardware blocks: processor, power supply, input modules, output modules, and programming interface
- The repeating scan cycle: reading inputs, executing the program, updating outputs
- Run, program, and fault states, and what each means for the machine
- Why a PLC replaced hardwired relay panels on packaging lines
Domain 2: Memory Organization and Addressing
Expect questions that ask you to interpret an address and say what it refers to.
- How memory is divided between program storage and data storage
- Address structure for input, output, internal (bit), timer, counter, and integer data
- Bits, words, and number systems such as binary and decimal as they relate to data
- Why addressing conventions differ by platform, so focus on the concept of mapping a physical terminal to a memory location
Domain 3: Discrete I/O Interfacing
This is where the controller meets the real machine, and it connects directly to the relay logic and input/output emphasis PMMI calls out for entry-level candidates.
- Discrete (on/off) devices: pushbuttons, limit switches, proximity sensors, photoeyes, solenoids, contactor coils, indicator lamps
- Sinking versus sourcing, and AC versus DC module considerations
- Normally open versus normally closed field devices and how that choice changes what the PLC "sees"
- Wiring a device to the correct input or output terminal and tying it to its address
Domains 4-6: Monitoring, Logic, Timers, and Counters
Domain 4: Function and Use of Monitoring Devices
Monitoring devices give a technician visibility into what the controller and machine are doing. Think of this domain as the "how do I see what's happening" group: status indicators on modules, programming-software online views, operator displays, and the other tools used to observe bit states and data values while a machine runs. Understanding what each device can and cannot tell you sets up the troubleshooting domains at the end of the list.
Domain 5: Basic PLC Logic Instructions
This is the heart of ladder programming and the domain most candidates expect to see. Master how a rung evaluates left to right and how logical conditions combine.
Core ladder concepts to master
- Examine-if-closed and examine-if-open contacts, and output energize instructions
- Series contacts as AND logic and parallel branches as OR logic
- Latching and unlatching, and the classic seal-in (holding) circuit using an output's own contact
- Translating a relay ladder diagram into a PLC ladder rung, and back again
Because PMMI highlights relay logic knowledge, practice drawing the same circuit both ways. If you can convert a start/stop motor circuit from hardwired relays to a PLC rung without hesitation, you are well placed here.
Domain 6: PLC Timer and Counter instructions
Domain 6 covers time-based and count-based control, which show up constantly in packaging: dwell times on a sealing jaw, delays before a conveyor restarts, counts of product per case. Know the behavior of the common timer types (on-delay, off-delay, and retentive variants where relevant), the presettings, accumulated values, and the status bits that indicate timing or completion. For counters, understand count-up and count-down behavior, reset conditions, and how presets and accumulators interact.
Key Takeaway
Work timers and counters as small stories: "what is true at 0 seconds, at half of preset, and at preset?" Walking through the status bits at each moment is the fastest way to stop mixing up on-delay and off-delay behavior.
Domains 7-9: Motor Control, Sequencing, and Machine Applications
The middle-to-late domains shift from individual instructions to complete control tasks. These are where earlier skills combine, and they reward candidates who have actually touched packaging equipment.
Domain 7: Basic PLC Motor Control Applications
- Start/stop control with seal-in logic and overload or stop-circuit considerations
- Forward/reverse control with interlocks that prevent both directions energizing together
- Jog functions and permissive conditions before a motor may run
- How PLC outputs drive motor starters and contactors rather than the motor directly
Domain 8: Basic PLC Sequencing Applications
- Step-by-step control where one action must complete before the next begins
- Using internal bits or step indicators to track where a process is in its cycle
- Combining timers, counters, and sensor feedback to advance a sequence
- Resetting a sequence safely after a stop or fault
Domain 9: Basic PLC Machine Application
This heading uses the singular "Machine Application" in PMMI's list, and it pulls everything together into scenarios resembling real equipment.
- Reading a machine description and identifying the inputs, outputs, and conditions involved
- Selecting the right instruction combination to produce a described machine behavior
- Recognizing how conveyors, fillers, sealers, and similar packaging functions map to basic logic
If your day job is on packaging machinery, these three domains will feel familiar. If you are coming from coursework, supplement with diagrams of real machine cycles. Our PLCs Study Guide 2026: How to Pass on Your First Attempt suggests ways to structure that practice.
Domains 10-11: Troubleshooting
The final two domains separate people who can write logic from people who can fix a down machine. PMMI divides troubleshooting into two groups: the larger system and the controller's own hardware and software.
Domain 10: Troubleshooting PLC Based Systems
Think system-level. When a machine stops, the cause could be a field device, wiring, power, a mechanical issue, or the program. Candidates should be comfortable with a methodical approach: observe symptoms, isolate whether the fault is on the input side, the output side, or in the logic, and verify with the monitoring tools covered in Domain 4.
Domain 11: Troubleshooting PLC Hardware and Software
Here the focus narrows to the controller itself: module status indicators, processor fault conditions, power problems, communication or programming-connection issues, and logic errors found while viewing a program online. Knowing what a fault light pattern implies, and what to check first, is the kind of practical judgment this domain targets.
For a sense of how the troubleshooting areas typically feel relative to the rest, see our difficulty guide, and use the PLCs Cheat Sheet 2026 for a compact refresher the night before you test.
Original Practice Questions Mapped to Domains
The questions below are original and written only to illustrate the style of reasoning each domain calls for. They are not actual exam items.
- (Domain 3) A normally closed stop pushbutton is wired to a PLC input. When nobody is pressing the button, is the corresponding input bit on or off? Answer: on, because the closed contact passes power to the input.
- (Domain 5) Two examine-if-closed contacts are placed in series before an output. Under what condition does the output energize? Answer: only when both input conditions are true.
- (Domain 6) An on-delay timer has a preset of 5 seconds. What is the state of its done bit while the accumulated value is 3 seconds and the rung is still true? Answer: off; the done bit turns on only after the accumulated value reaches the preset.
- (Domain 7) In a forward/reverse motor circuit, why is an interlock placed between the two direction outputs? Answer: to prevent both directions from energizing at once, which could damage equipment.
- (Domain 10) A conveyor will not start, and the output's status indicator shows it is commanded on. Where should you look first? Answer: the output side, such as the contactor, wiring, power, or overload, since the controller is already issuing the command.
A Four-Week Editorial Plan Built Around the Domain Order
This schedule is an editorial suggestion, not an eligibility requirement and not a pass guarantee. It simply follows PMMI's published domain sequence so each week builds on the last.
Foundations (Domains 1-3)
- Learn the scan cycle and hardware blocks
- Practice reading addresses until mapping a terminal to memory is automatic
- Drill NO versus NC device behavior against input bit states
Logic and Timing (Domains 4-6)
- Convert relay diagrams to ladder rungs and back
- Walk timers and counters through their status bits step by step
Applications (Domains 7-9)
- Build start/stop, forward/reverse, and simple sequence logic on paper or in a simulator
- Describe a packaging machine cycle and map its I/O
Troubleshooting and Review (Domains 10-11)
- Practice isolating input, output, and logic faults from symptom descriptions
- Take timed practice sets on the main practice test site and revisit weak domains
If you want to confirm whether you qualify and how to arrange your sitting, read PLCs Requirements 2026: Eligibility, Prerequisites & How to Qualify and PLCs Exam Dates 2026: Testing Windows, Deadlines & Scheduling. PMMI directs candidates to its Education Partners for examination arrangements, and its proctor guidelines could not be verified here, so confirm the specific rules with your partner rather than assuming unrestricted at-home testing.
When you are ready to test your recall across all eleven areas, our PLCs practice questions are organized to mirror these domains.
Frequently Asked Questions
PMMI publishes 11 test-competency groups, running from Operation of a PLC through Troubleshooting PLC Hardware and Software. They are listed in sequence on the public test page.
No weights are published. The domains are unweighted public objective groups, so you should not assume any one carries a larger share of the 100 questions.
The public PMMI page lists a 70% passing score on a 100-question test. See our passing score guide for details on interpreting that threshold.
PMMI describes the test as taking "Approximately 2 Hours," which is a completion estimate. A fixed, enforced timer was not verified, so confirm timing details with your Education Partner.
The intended audience includes entry-level technicians with PLC experience on packaging equipment and students who have completed coursework covering the tested competencies. This is audience guidance, not a published minimum degree or experience requirement.