Industrial IoT sensors are the measuring devices you attach to machines and utilities so their condition reaches software without anyone walking the floor with a clipboard. Choosing them means matching three things: what failure you want to catch, how the reading gets off the machine, and what keeps the sensor powered for years.

A plant engineer usually meets this question with a list of machines and a budget, and the sensors tend to be the smallest line in it. Picking the wrong network or the wrong power source is what turns a pilot into a maintenance burden, so this guide spends as much time on those as on the sensors.

In short

  • Start from the failure you want to catch, then pick the measurement: vibration for bearings and imbalance, temperature for overheating, current for load and run state, pressure for flow problems.
  • Older machines can be monitored with clamp-on and magnet-mounted sensors, without touching the machine's controller.
  • Long-range, low-power wireless networks suit slow-changing readings across a whole site; wired connections suit high-speed data and machines that already have power and cabling nearby.
  • Battery life depends mostly on how often a sensor transmits, so the reporting interval is a power decision as much as a monitoring one.

Types of condition monitoring sensors

Condition monitoring sensors measure a physical sign of a machine's health. The common types cover most plant equipment:

Sensor type What it measures Problems it typically reveals Typical mounting
Vibration (accelerometer) Acceleration, often reported as velocity RMS and peak values Imbalance, misalignment, looseness, bearing wear Stud, adhesive pad or magnet on the bearing housing
Temperature Surface or fluid temperature Overheating motors, failing cooling, friction Contact probe, strap-on sensor, or non-contact infrared
Current Electrical current in a motor's supply Run state, overload, a jammed or starved machine Split-core clamp around one phase conductor
Pressure Line or differential pressure Clogged filters, leaks, pump problems Threaded process connection
Ultrasound High-frequency sound Early bearing damage, compressed-air leaks, electrical discharge Contact probe or airborne microphone
Oil quality Water content, particles, viscosity Contaminated or degraded lubricant In-line sensor in the lubrication circuit

Two practical points don't show up in a table. First, many wireless vibration sensors don't send a full waveform. They calculate summary values on board, such as RMS velocity and peak acceleration, and transmit those, because a raw waveform is far too much data for a low-power radio. Summary values are excellent for trending and alerts; detailed fault diagnosis needs a sensor or edge device that can capture the waveform.

Second, a measurement is only as good as where it's taken. A vibration sensor belongs on a rigid part close to the bearing, not on a fan guard or a thin cover plate. A temperature probe on a motor housing reads lower than the windings inside, so its alarm limit has to reflect that offset.

It helps to work from one machine rather than from the sensor catalog. Take a centrifugal pump driven by an electric motor through a coupling. The motor has two bearings, at the drive end and the non-drive end, and the pump has two more. A sensible starting set is one vibration sensor on the motor's drive-end bearing, one on the pump's drive-end bearing, a temperature reading on each of those housings (many vibration sensors measure temperature as well), and a current clamp on the motor supply. That's three devices, and between them they cover imbalance, misalignment, bearing wear, overheating and whether the pump is running at all.

Machine monitoring sensors for older machines

Most factories run machines that were built long before anyone thought about connectivity. The good news is that machine monitoring sensors can be retrofitted without opening the control cabinet or changing the PLC program, which keeps warranties and safety approvals intact.

The usual retrofit toolkit looks like this. A split-core current clamp around one phase tells you whether a machine is running, idle or overloaded, which already answers questions about utilization. A magnet-mounted accelerometer on each bearing housing of a critical motor and pump gives a vibration trend. A strap-on temperature sensor on a gearbox or a hydraulic tank gives a thermal trend. None of these requires drilling, and all of them can be moved if the first location turns out to be the wrong one.

When comparing machine monitoring hardware, check these points against the real environment rather than the brochure:

  • measuring range and accuracy for the actual signal, for example a vibration range that covers the machine's speed;
  • ingress protection against washdown, coolant and dust;
  • operating temperature, including the hottest surface the sensor touches;
  • certification for explosive atmospheres where it applies, such as ATEX equipment approval in the EU;
  • how the sensor is configured after installation, for example whether its reporting interval can be changed over the air.

Predictive maintenance sensors are not a separate category of hardware. The same accelerometers and temperature sensors become "predictive" when their readings are trended over months and compared with limits that leave time to plan a repair.

Wireless sensor networks for factory monitoring

Wireless sensor networks for factory monitoring remove the most expensive part of a retrofit: running cable through a working plant. Each option suits different data.

Option Typical reach in a plant Power Data per message Good fit
Wired 4–20 mA or IO-Link Cable length (IO-Link up to 20 m per port) From the cabinet Continuous Fast signals, machines with nearby panels
LoRaWAN Hundreds of meters to a few kilometers per gateway Battery, often for years A few to a few dozen bytes Periodic readings across a whole site
mioty Similar to LoRaWAN Battery, often for years Small payloads Very large sensor counts, radio-noisy sites
Wi-Fi Tens of meters per access point Mains or rechargeable High Waveforms, high-rate data
Zigbee or Bluetooth mesh Tens of meters per hop Battery Small to moderate Dense indoor areas, short distances

Factory halls are hard on radio. Steel racks, machines and concrete walls reflect and block signals, and motors and welding equipment add electrical noise. Long-range LPWAN technologies such as LoRaWAN and mioty cope well because they trade data rate for robustness, so a small message gets through where a Wi-Fi link would struggle. Before buying in volume, place a gateway high and central, carry a test sensor to the worst corners of the hall, and check signal quality at each spot. Repeat the walk with the machines running, because a hall at full production is electrically noisier than the same hall on a quiet Sunday, and a marginal spot can drop out under load.

Radio rules also shape how often a sensor can report. In Europe, LoRaWAN uses the 868 MHz band, where most sub-bands allow a device to transmit for only 1% of the time. For a sensor sending a short message every few minutes that's no constraint at all, but it rules out using LoRaWAN for anything that needs a reading every second. Plans that need fast data belong on a wired or Wi-Fi connection from the start.

On Kilo, the LoRaWAN network server is part of the platform, so a factory only needs gateways that support the LoRa Basics Station protocol. mioty base stations connect either to mioty built into Kilo Cloud or to the open-source Kilo mioty Service Center that you host yourself. Either way, readings from predictive maintenance sensors on pumps and motors land on the same dashboards, with each machine's vibration and temperature trend charted next to the others.

Continuous power for factory monitoring sensors

Continuous power for factory monitoring sensors comes from four sources, and each sensor location usually makes the choice for you.

Batteries are the default for wireless retrofits. Long-life industrial sensors often use lithium thionyl chloride cells, which hold their charge for years but lose capacity in deep cold. Battery life depends mostly on transmissions. Suppose a sensor's datasheet promises eight years at one report per hour, and at that rate transmissions use 70% of its energy while sleeping uses 30%. Switch to a report every ten minutes and the transmission share grows six times: 0.3 + 0.7 × 6 = 4.5 times the daily energy, so the battery lasts about 8 ÷ 4.5 ≈ 1.8 years. The numbers are made up, but the shape holds for most low-power sensors.

Mains or 24 V DC power makes sense where the sensor sits next to a control cabinet that already has a supply, and for sensors that sample fast or stream data. Industrial 24 V DC is the standard supply for field devices, so a sensor or gateway in a panel can usually share it.

Power over Ethernet (PoE) carries power and data on one cable. The IEEE 802.3af standard supplies up to 15.4 W at the switch port, enough for most sensors, edge devices and gateways, and later versions supply more. The catch is the cable itself: each PoE device needs its own run back to a switch, so PoE pays off for a gateway or a camera on the hall ceiling, and much less for twenty sensors scattered across machines.

Energy harvesting powers a sensor from its surroundings: vibration, heat differences or light. It suits machines that run constantly, but a sensor that relies on the machine's vibration stops reporting when the machine stops, so check whether you need readings during downtime.

Battery swaps are easier to handle as planned maintenance work. Record each sensor's install date and reporting interval, and schedule replacements by area when the first sensors approach their expected life. A sensor in a hot spot, such as on top of a furnace or a compressor, may run down sooner than its datasheet suggests, because battery chemistry is sensitive to temperature in both directions.

Industrial IoT sensors FAQ

What does IP67 mean for industrial IoT sensors?

IP67 is a rating defined in IEC 60529. The 6 means the enclosure is dust-tight, and the 7 means it survives temporary immersion in water up to 1 m deep for 30 minutes. It doesn't cover high-pressure washdown, which IP69K addresses.

Do industrial IoT sensors need a gateway?

Most wireless ones do. LoRaWAN sensors talk to a LoRaWAN gateway and mioty sensors to a base station, which forward the messages to a network server over Ethernet, Wi-Fi or another backhaul. One gateway can serve hundreds of sensors, so a single hall rarely needs more than one or two.

Can industrial IoT sensors connect to an existing PLC?

Yes, if the PLC has spare inputs. A wired sensor with a 4–20 mA output can go straight into an analog input card, and the PLC then shares that value with SCADA or an edge gateway like any other signal. Wireless sensors usually bypass the PLC and report to their own network instead.

Pick the pump or motor whose breakdowns hurt most and give it the three-device starting set from the pump example, then add two vibration sensors on the next machine in line and chart both machines on one dashboard. Those five sensors fit on Kilo's free plan. Kilo Electronics stocks acceleration sensors for this kind of retrofit, and sensors from other suppliers work too, as long as they use a supported connection.