Applications
Remote Fuel and Tank Level Monitoring
Read the level transmitter already fitted to a tank, correct it for the shape of the tank, and know what is in it without anyone driving out to look.
A dipstick tells you one thing, once
Tank levels are usually checked the way they have always been checked: somebody drives out, looks, and writes a number down. The number is accurate and almost useless — it describes one moment, it is already old by the time anyone reads it, and it says nothing about the rate the tank is emptying at, which is where both the warning and the leak show up first.
The cost is rarely the fuel. It is the generator that did not start, the emergency delivery at a premium, the plant stopped waiting on a tanker, and the trip that confirmed everything was fine.
What changes
A level transmitter already fitted to the tank, wired to a controller that reads it continuously, corrects it for the tank’s shape, acts on it locally, and tells you before it matters rather than after.
The part most systems get wrong
Depth is not volume
In a horizontal cylindrical tank — which is most bulk fuel storage — the relationship between how deep the liquid is and how much of it there is changes continuously. The same ten millimetres of depth represents a much larger volume across the middle of the tank than it does near the top or the bottom.
A system that simply scales the transmitter’s output reads roughly right at half full and noticeably wrong at both ends. Which is unfortunate, because both ends are where the decisions are: the low-level alarm, and whether the delivery that just arrived was the volume on the docket.
Sentor lists non-linear input as a distinct input type alongside linear, current-loop and voltage inputs, and each analogue input is calibrated against the actual device during configuration rather than assumed. The reading is corrected for the shape of the vessel.
Tell us the tank geometry and the transmitter and we will confirm the arrangement before you specify it.
What it connects to
The instrumentation is usually already on the tank
| Input | Range or capacity | Detail |
|---|---|---|
| Current loop | 0–20 mA, and protected loop | Takes the 4–20 mA level transmitters fitted to most tanks |
| Voltage | 0–1 V, 0–10 V and 0–30 V | Three ranges, so a low-output probe is matched rather than scaled away |
| Non-linear input | A distinct input type | For tanks whose volume does not change evenly with depth — see below |
| Resolution and rate | 9-bit, up to 20 samples per second | Accuracy better than 0.5% |
| Capacity | Up to 80 inputs per controller | Reached by adding ST317 expansion cards, so more tanks do not mean another controller |
| Outputs | 8 SPCO relay contacts | 1 A at 48 VDC or 24 VAC — pumps, valves, solenoids, alarms |
Figures from the Sentor specification sheet. Full controller and module specifications.
Where it is used
Four situations, one input
Generator fuel at unmanned sites
The tank that matters most on the night the mains fails is the one nobody has looked at since the last service visit. Level, consumption rate and a low-level alarm turn a generator from an assumption into a reading.
Bulk diesel and farm fuel storage
A bulk tank that empties faster than it should is either a busy month or a leak, and the difference is visible in the rate rather than the level. Deliveries can be scheduled against a real figure instead of a dipstick and a guess.
Water, chemical and process tanks
The same input reads any level transmitter — water storage, dosing chemicals, effluent, process liquids — and the same relay outputs start and stop the pump that fills or empties it.
Tanks across many sites
One controller per site, every site on one screen, and the alarm raised against the site name rather than a number somebody has to look up.
At the site
It keeps deciding while you are out of contact
Fuel tanks sit where fuel is needed, which tends to be where the mains and the network are not. The controller holds its scenario logic on board and acts on it locally — raising a low-level alarm, starting a transfer pump, isolating equipment — so a communications failure costs you visibility rather than control.
Alarms travel over cellular, radio, microwave, satellite or landline, and can be sent as an SMS text. The history log is written at the site, so the hours you could not see are handed back to you when the link returns.
Power is not an obstacle
Solar, wind, generator or battery bank — each can run the controller and each can itself be monitored. An optional standby battery covers up to 24 hours, and a total power loss does not cost you the programming.
Common questions
Fuel and tank monitoring, answered
Will it read the level sensor already on our tank?
Usually. The analogue inputs take 0–20 mA current loops — which covers the 4–20 mA level transmitters fitted to most tanks — along with 0–1 V, 0–10 V and 0–30 V instruments, and both linear and non-linear sensor curves. Each input is calibrated against the actual device through the Sentor configuration screens rather than assumed. Tell us the transmitter model and the tank and we will confirm it before you order anything.
Our tank is a horizontal cylinder. Does that matter?
It matters a great deal, and it is the most common reason a tank gauge is distrusted. In a horizontal cylindrical tank the same 10 mm change in depth represents a much larger volume near the middle than near the top or bottom. A system that treats depth as proportional to volume will read roughly right at half full and noticeably wrong at both ends — which is precisely when you care. Sentor lists non-linear input as a distinct input type for exactly this, so the reading is corrected for the shape of the vessel rather than reported raw.
Can it warn us before the tank runs out, not after?
That is what the scenario logic is for. Rules are written as plain if-this-then-that statements and run on the controller at the site, so a threshold alarm, a rate-of-change alarm, or a rule that only fires outside expected hours all behave the same way — locally, and whether or not the site is in contact with anyone. Alarms can be sent as an SMS text over a cellular network as well as appearing in the software.
What if the site has no power and no internet?
Both are normal at a fuel tank. The controller runs from whatever supply the site has — solar, wind, a generator or a battery bank, each of which it can also monitor — and an optional sealed lead-acid standby battery carries it for up to 24 hours through a supply failure. It reports over cellular, radio, microwave, satellite or landline. If power fails completely, an on-board lithium cell retains the programs, the history log and the clock, and the controller restarts itself when power returns.
Does it keep a record we can go back to?
Yes, and it is written at the site rather than on a server. Each entry carries a date and time, the log size is user definable, and a controller running standalone holds around 500 entries — up to 1,000 across two rotating files when connected to a PC. That is what lets you answer the question that usually follows a shortfall: not what the level is now, but what it was doing last Tuesday night.
Can it control the pump as well as watch the tank?
Yes. Each controller carries eight single-pole double-throw relay outputs rated at 1 A at 48 VDC or 24 VAC, switched by an operator or automatically by the scenario logic — starting a transfer pump, closing a valve, or isolating equipment on a low-level condition.
Related
Where tank monitoring usually sits
Utilities, water, oil and gas
Process values, plant status and SCADA reporting across distributed infrastructure. Read more
Agriculture and off-grid sites
Bores, troughs, tanks and pumps at sites with no mains and no fixed line. Read more
Tower and broadcast sites
Generator fuel alongside RF power, batteries, rectifiers and site access. Read more
Tell us about the tank and we will tell you what it takes.
Send us the tank dimensions, the level transmitter fitted to it and how the site is powered and connected, and we will confirm what connects directly before you commit to anything.