Choosing sensors and labels for site materials: a plain comparison
Updated · 5 min read
There is no single right sensor for site materials. A drum of form release, a diesel tank, a cement silo and a fuel trailer each need something different, and the cheapest option is often a printed label. This guide compares the common choices by what they tell you, what they need, and where they let you down.
Start with the question, not the device
Before choosing hardware, write down what you need to know and how quickly:
- How much is there? Level, weight or a count.
- Where is it? Which store, which zone, or a GPS position.
- Who moved it? That needs a person to record it. No sensor knows why fuel left a tank.
- How fresh must it be? A weekly count is fine for sealant. A fuel tank feeding a fleet may need hourly figures.
Most sites end up with labels on everything and sensors on a few high-value or high-risk vessels.
The options side by side
| Option | Tells you | Needs | Watch out for |
|---|---|---|---|
| QR label | Which container, when a person scans it | A phone camera, durable labels | Only as current as the last scan |
| NFC tag | Which container, by touching a phone to it | A phone with NFC, suitable tags | Not remote tracking; some tags fail on metal |
| BLE tag | Roughly which zone a tagged item is near | Fixed gateways and site calibration | Zone-level, not a precise position |
| GPS tracker (cellular) | Position of mobile assets outdoors | A data plan, a vendor platform | Poor indoors and between tall buildings; ongoing fees |
| Ultrasonic level sensor | Distance to the liquid surface, so fill level | Tank geometry, a LoRaWAN or cellular network | Foam, vapour, condensation, a blind zone near the sensor |
| Radar level sensor | Distance to surface in tanks and silos | Correct fitting and setup | Higher cost; check chemical compatibility |
| Pressure (hydrostatic) sensor | Liquid head, so fill level | Liquid density, a sensor in contact with the product | Chemical compatibility; density changes with temperature |
| Load cells or scale | Gross weight, so net with the empty weight | A suitable scale and placement | Calibration and how the load sits |
Labels: the base layer
Labels cost little and work without any network. A durable QR label on every drum, can box, IBC and tank means anyone with a phone can bring up the container, its SDS and its history, and record a use or a count on the spot. NFC tags do the same by touch, which helps when labels get dirty or the lighting is poor.
The limit is that a label only knows what people tell it. If nobody scans, nothing is recorded. That is a process question as much as a technology one. See QR and NFC labels for site stock.
Level sensors: ultrasonic, radar and pressure
Ultrasonic sensors are the usual first choice for a fuel or water tank: affordable, battery powered and mounted on top without touching the product. They struggle with foam, heavy vapour, condensation on the face of the sensor, and narrow tank necks or internal pipework that reflect the signal. Every ultrasonic sensor has a minimum distance it cannot read, so it should not sit right at the top of a full tank.
Radar sensors handle vapour, temperature changes and dusty silos better and suit bulk solids. They cost more and need correct fitting.
Pressure sensors sit at the bottom of the tank in the product, which is accurate for clean liquids but means the sensor body and cable must suit the chemical. They read liquid head, so converting to volume needs the product's density.
Whichever you choose, the figure is only as good as the calibration: the tank's shape, its dimensions or strapping table, and where the sensor sits. See Tank level sensors on a construction site.
Weight: gas cylinders, IBCs and silos
Load cells measure mass directly, which suits liquefied gas cylinders (whose pressure says little about how much is left), IBCs on a frame, and silos on legs. You need the empty weight to get net contents, and to place the load the way the scale expects.
Location: GPS and BLE
A GPS tracker on a fuel trailer or bowser shows where it is and can raise an alert when it leaves an area. Position accuracy varies, so good software keeps the accuracy radius with each fix and does not raise a geofence alert from a fix that is too vague to tell. Indoors and in tight urban sites GPS is unreliable. BLE tags with fixed gateways can tell you which area something is near, but not where in it.
Networks: how readings get off site
- LoRaWAN suits battery sensors that report small readings every few minutes to hours. It needs a gateway within range, or a public network that covers your site, and uses a regional band (US915 in the US, EU868 in Europe). Readings reach your software through a network server such as ChirpStack or The Things Stack.
- Cellular (LTE-M or NB-IoT) needs no gateway, just signal where the device sits and a data plan. It is common for trackers.
- MQTT and HTTP are how a network server or vendor platform forwards readings onward. Check that yours can forward to the software you plan to use.
Battery life depends mostly on how often a device reports. Hourly is a sensible default for a tank. Every minute drains batteries and adds noise.
Hazardous locations
Fuel, solvents and many site chemicals can create a flammable atmosphere around a tank or store. A sensor or tracker used there must be certified for that hazardous location classification, and commodity battery devices usually are not. Have a competent person assess each vessel, substance and zone before fitting anything, and prefer certified equipment or a qualified installer where it matters.
Whatever you fit, none of this replaces a site-specific assessment of whether a device is suitable for a particular tank or zone.