Once a facility decides it wants better equipment inspection data, the next question is almost always the same: do we put sensors permanently on the equipment, or send a robot to check on it? Both are legitimate predictive-maintenance strategies, and most facilities that use one eventually ask whether they should be using the other instead — or both. The honest answer is that they solve different parts of the problem, and conflating them leads to either overspending on sensors you don't need or under-covering assets a fixed network never reaches.
What Fixed IoT Sensors Do Well
A permanently installed sensor — a vibration monitor, a thermal probe, a continuous gas detector — watches one specific point on one specific asset, constantly, with no gaps and no travel time. For a small number of your highest-criticality assets, where a failure is catastrophic and you need true 24/7 continuous monitoring rather than a periodic check, that's exactly the right tool. The tradeoff is cost and coverage: sensors have to be purchased, wired or battery-maintained, and installed per monitoring point, which means the economics only work for a limited set of assets. Instrumenting every bearing, panel, and pipe run in a facility this way is rarely realistic.
What Spot Does Well
Spot flips the economics: instead of paying per sensor point, you pay for one mobile platform that walks a route and takes the same kind of thermal, visual, and acoustic readings a fixed sensor would, at every stop along that route. It doesn't watch any single point continuously — it checks dozens or hundreds of points on a repeating schedule. For the broad base of equipment that doesn't need second-by-second monitoring but does need frequent, consistent inspection, that tradeoff strongly favors the robot: far more coverage per dollar, at the cost of monitoring in intervals rather than continuously.
The practical comparison
- Coverage breadth: Fixed sensors cover only the points you've instrumented. Spot covers every stop on its route — often dozens to hundreds of check points — without per-point hardware cost.
- Monitoring frequency: Fixed sensors are continuous. Spot is periodic — readings at each route pass, not every second. For most equipment, scheduled passes that catch a developing trend over days or weeks are sufficient; for a handful of truly catastrophic-failure-risk assets, continuous fixed monitoring is worth the added cost.
- Upfront cost per monitored point: Fixed sensors require hardware, wiring or battery maintenance, and installation labor for every point. Spot's cost is concentrated in the platform itself, amortized across every asset on its route.
- Flexibility as the facility changes: A fixed sensor network is set where it's installed. Spot's route can be remapped as equipment layouts, priorities, or facility footprint change, without re-wiring anything.
- Human-equivalent checks: Spot can read a standard analog gauge face or visually confirm a condition a camera-only or vibration-only sensor can't interpret — the same way a human inspector would.
Why Most Serious Programs Use Both
The realistic answer for most facilities isn't "Spot or sensors" — it's a small number of fixed sensors on the handful of assets where continuous monitoring is genuinely worth the cost, paired with Spot covering the much larger base of equipment that needs frequent but not constant inspection. That combination gets both: true real-time monitoring where failure is catastrophic, and broad, affordable coverage everywhere else. Manufacturers running this kind of layered predictive maintenance program see real results — see our coverage of predictive maintenance for manufacturing for the data on what frequent inspection actually delivers.
What to Evaluate
Which assets actually need continuous monitoring
Be honest about which failures are truly catastrophic-and-sudden (where continuous fixed sensing earns its cost) versus which develop gradually enough that a weekly or daily robotic pass catches them with time to spare.
Total monitored points vs. budget
Price out what instrumenting your full asset base with fixed sensors would actually cost per point, and compare it honestly to a Spot route covering the same assets — the gap is usually larger than people expect.
How often your facility's layout changes
A facility that reconfigures equipment regularly gets more value from a remappable robotic route than from rewiring a fixed sensor network every time something moves.
See our robotic inspection solutions page for how Actel deploys Spot programs, or read how the economics work in our guide to robotic inspection ROI calculation.
Not sure which mix of fixed sensors and mobile inspection fits your facility? Contact Actel Robotics for a site assessment and we'll help you map it out.