Ultrasonic vs. Pressure Water Level Sensors: Which Is Better?
The core difference is contact. A pressure (submerged) sensor sits in the water and reads the weight of water above it; an ultrasonic sensor mounts above the water and measures the distance down to the surface. On a tank you keep clear, non-contact ultrasonic is usually the better choice, because nothing is submerged to corrode, foul with algae, or crack in a freeze — that's why Meterra uses it on tanks. A submerged pressure sensor earns its place wherever you need to read the water itself: troughs and open water that ice over, where reading beneath the surface beats reading the top of the ice, plus deep wells and pipes you can't see into from above. Meterra uses a submerged sensor on troughs, dams, and ponds for exactly that reason.
How each one works
The two technologies measure the same thing — water level — in opposite ways.
- Ultrasonic (non-contact). The sensor mounts above the water and sends a pulse of sound straight down. It times the echo off the surface to calculate the distance, then converts that to level, percentage full, and volume for your tank’s dimensions. Nothing is ever in the water.
- Pressure (submerged / hydrostatic). The sensor sits at the bottom and measures the pressure of the water column above it. More water means more pressure, which converts to depth. The probe lives in the liquid full-time.
There’s also a difference in what each can measure. Ultrasonic just reads the distance to a surface, so it works on almost any material — water, fuel, and fertilizer, but also dry, granular solids like grain or feed in a silo. A pressure sensor depends on the weight of the column above it, so it only works in a liquid. Think of ultrasonic as the swiss-army-knife and pressure as the liquid specialist.
Both are accurate when they’re working. The real difference is what happens to them over months in the field.
Why contact is the deciding factor
On a farm or ranch, the sensor has to survive algae, sediment, livestock, sun, and frost — and that’s where the submerged probe is at a disadvantage:
- Fouling. Algae, scale, and sediment build up on a submerged probe and drift its readings; a non-contact sensor never touches any of it.
- Corrosion. Constant immersion — worse in fertilizer or brackish water — eats at submerged hardware over time. Above the water, there’s nothing to corrode.
- Freeze durability. A shallow submerged probe can freeze into the ice and crack, so on a tank an above-surface ultrasonic unit is the more durable hardware. The catch: an above-water sensor only reads the top of the ice, while a submerged sensor reads the water beneath it — which is exactly why Meterra puts a sealed submerged sensor on troughs, dams, and ponds that freeze (see below).
- Damage and access. A submerged sensor and its cable sit in the water, so they can foul or be disturbed; an above-mounted unit sits clear. It’s a real trade-off — you accept it where reading depth directly, and under ice, matters more.
Where a pressure sensor still wins
Non-contact only works when the sensor can “see” the surface from above. When it can’t, pressure is the right tool:
- Deep, narrow wells and bores, where there’s no clear line to the surface — this is how Meterra reads bore and groundwater depth.
- Inside pipes and pressurized lines, where there’s no open surface at all.
- Troughs and open water that ice over — stock troughs, dams, and ponds in winter. A surface sensor reads the top of the ice; a submerged depth sensor keeps reading the actual water beneath it. This is why Meterra’s trough, dam, and pond monitors use a submerged sensor.
For a tank, non-contact ultrasonic is usually the better call. For troughs, dams, and ponds — especially water that freezes over — a submerged depth sensor that reads beneath the ice often fits better.
Which should you choose?
For an above-ground tank, ultrasonic is the more durable choice: nothing submerged to foul or corrode, and the same unit handles water, diesel, and fertilizer. Reach for a submerged depth sensor where you need to read the water itself — troughs, dams, and ponds that ice over, where reading beneath the ice is exactly the point, plus deep wells, bores, and closed pipes you can’t see into from above. Meterra uses non-contact ultrasonic on tanks and a submerged pressure sensor on troughs, dams, and ponds.
The winter test
When the surface freezes over, we keep reading.
An ultrasonic sensor reads the first surface it hits — in a hard freeze, that’s the top of the ice. Meterra’s submerged pressure sensors read the water itself, so troughs, ponds, and dams keep reporting straight through winter, and a high-level alarm can still fire before an iced-over pond overflows.
One honest note: extreme cold shortens battery life on any electronics. We’ll help you plan for your climate.
The hardware this guide covers
Every device reports to the same Meterra dashboard and app.
Tell us what you need to keep an eye on and we'll map the right sensors and coverage.
Frequently asked questions
What's the difference between ultrasonic and pressure water level sensors?
An ultrasonic sensor mounts above the water and measures the distance to the surface with sound, so nothing touches the liquid. A pressure (hydrostatic) sensor sits submerged and measures the head of water above it. Ultrasonic is non-contact; pressure is in the water — and that's what drives most of the practical differences.
Which is better for stock tanks, troughs, and dams?
It depends on the vessel and the weather. On a tank you keep clear, ultrasonic wins — no submerged probe to foul with algae, corrode, or freeze and crack. On troughs, dams, and ponds, Meterra uses a submerged pressure sensor instead, because it reads the depth from in the water and keeps reading beneath the ice — when those sources are most likely to freeze and most critical to watch.
When is a pressure sensor the right choice?
When you can't get a clear shot at the surface from above — deep, narrow wells and bores, or inside pipes. There, a submerged pressure sensor is often the only practical option, and depth sensors are exactly how Meterra reads bore and groundwater levels.
Does ultrasonic work on fuel and fertilizer, not just water?
Yes — and it goes beyond liquids. Because it simply measures the distance to a surface, the same ultrasonic sensor reads water, diesel, and liquid fertilizers like UAN, plus dry, granular materials like grain or feed in a silo. A pressure sensor, by contrast, works by the weight of the water column above it, so it only reads liquids — which is why ultrasonic is the more versatile of the two.
Do ultrasonic sensors work in freezing weather?
An ultrasonic sensor's hardware handles cold well — with nothing submerged, there's no probe to freeze in and crack. But once the surface freezes over it reads the top of the ice, not the water beneath, so it won't track the level under a sheet of ice. For a heated tank that's fine; for troughs, dams, and ponds that ice over, a submerged depth sensor that reads beneath the surface is the better tool — which is what Meterra uses on those.
Related Meterra pages
- Water Level Monitoring — how non-contact level sensing works across all your water.
- Tank Level Sensor — the ultrasonic sensor for tanks, fuel, and fertilizer.
- Dam Level Monitor — submerged pressure level for dams and ponds.
- How to Monitor Livestock Water Remotely — putting the sensor to work across a property.