Product type
An ultrasonic level meter measures the distance down to the surface of what is in a tank, silo or channel by timing a sound pulse that travels to the surface and back. The transducer is mounted above the contents and never touches them, which is the whole point of the type: nothing is wetted, nothing corrodes and nothing has to be cleaned. Where a vessel holds sewage, a chemical, a food product or a slurry, that absence of contact is usually the reason this technology is chosen over a float, a probe or a pressure transmitter.
An ultrasonic level meter measures the distance down to the surface of what is in a tank, silo or channel by timing a sound pulse that travels to the surface and back. The transducer is mounted above the contents and never touches them, which is the whole point of the type: nothing is wetted, nothing corrodes and nothing has to be cleaned. Where a vessel holds sewage, a chemical, a food product or a slurry, that absence of contact is usually the reason this technology is chosen over a float, a probe or a pressure transmitter.
One instrument covers a very wide range of duties because the measurement does not care what the surface belongs to. Water in a sump, acid in a storage tank, grain in a silo, a river level under a bridge and the contents of a small dosing vessel are all measured on the same principle, and only the range, the mounting and the transducer material change. Practical forms add an integral display and a serial output, and a variant sends the reading over a mobile network for sites with no wiring at all.
This page covers how the type is configured: how range, blanking distance and beam angle together constrain where the instrument may be mounted, when an integral or a separate form is required, and how it is told apart from the radar level meter quoted against the same duty.
The transducer both transmits and receives. A burst of sound is sent downwards, reflects from the change in density at the surface of the medium and returns; the time between transmission and reception gives the distance, and subtracting that distance from the mounting height gives the level. Because the speed of sound in air varies with temperature, an instrument of this kind carries a temperature sensor and corrects the timing for it, which is why the temperature of the installation is part of the specification rather than an ambient detail.
Three geometric constraints follow, and together they decide whether a given vessel can be measured at all. The first is the blanking distance: close to the transducer the instrument cannot separate its own transmission from the returning echo, so a band directly under the face is unmeasurable and the highest level the vessel may reach has to stay below it. The second is the beam angle: the pulse spreads as it travels, so on a tall narrow vessel the beam can strike the wall or an internal fitting and return a false echo. The third is clearance from the wall: for a given range there is a minimum distance between transducer and vessel wall, because the wall reflection arrives close in time to the surface reflection.
All three are why the type is specified from the vessel drawing rather than from a level range alone. A range figure quoted without the mounting height, the blanking distance and the internal obstructions does not yet determine an instrument.
Most of the specification is fixed by these decisions rather than by the accuracy class. Each one constrains the next, which is why they are settled in order.
| Configuration | Options to fix | What it actually decides |
|---|---|---|
| Instrument form | Integral, with transducer and electronics in one housing, or separate, with the two joined by cable | Where the electronics can be reached and read. A separate form puts the indicator at eye level and the transducer on the vessel, which is the usual arrangement where the vessel top is inaccessible or the space above it is tight. |
| Range | A band of ranges, each with its own blanking distance | The vessel height that can be covered, and the band under the transducer that cannot be used at all. A longer range normally brings a larger blanking distance, so a tall vessel and a vessel with a high maximum level are not the same requirement. |
| Transducer material | General-purpose and corrosion-resistant faces | Whether the instrument survives the atmosphere above the medium, which is settled separately from whether the medium itself is aggressive. |
| Mounting | Flanged, threaded, bracketed and open-mounting arrangements | How the transducer is held at the right height and square to the surface, and whether the vessel can be opened for the fitting. |
| Outputs | Analogue, relay and serial outputs, in various combinations | Whether the reading drives a display, an alarm, a pump or a control system. The number of relays available decides how many actions one instrument can take. |
| Communication | A wired serial output, or an optional wireless link | Whether the site has any wiring, and whether the reading has to be seen remotely. |
| Power supply | Low-voltage DC, or mains where the separate form is used | Whether a supply exists at the vessel, which is often the deciding factor on a remote site. |
| Display and local indication | Integral display, or a separate indicator | Whether anyone reads the level at the vessel, or only in a control room. |
| Factor | Why it decides the answer | How to settle it before enquiring |
|---|---|---|
| Vessel height and the highest level | The range has to cover the working span, and the top of that span has to stay clear of the blanking distance | Give the vessel height and the highest level the contents reach, not the vessel height alone. |
| Vessel diameter and internal fittings | The beam spreads as it travels, so wall clearance and anything protruding decide whether a clean echo returns | Describe the vessel shape and what is inside it, including agitators, ladders, heating coils and filling pipes. |
| Mounting position and access | Decides the form, the range, and whether the electronics can be read locally | State where the instrument can be fixed, and whether the top of the vessel is reachable. |
| Atmosphere above the medium | Vapour, condensation, dust and foam each affect the returning echo differently from clean air | State the vapour, the temperature, and whether condensation or foam forms on the surface. |
| Temperature range | The speed of sound changes with temperature, so the range of conditions is part of the selection | Give the working and the extreme temperatures at the instrument. |
| Whether the reading is local or remote | Decides the outputs, the communication and the power arrangement | Say where the reading has to appear, and what has to act on it. |
If any of these are still open, send what is known. A quotation can be issued against a duty description and refined once the gaps are filled.
These are the types an enquiry for an ultrasonic level meter usually turns out to be, and the point at which the choice is genuinely decided.
| Nearest alternative | What separates it from an ultrasonic level meter |
|---|---|
| Radar level meters | Also non-contact and mounted above the medium, but it works on microwaves and is largely indifferent to the vapour, temperature layers and dust that disturb an acoustic pulse. It is the answer for a hot, dusty or vapour-laden vessel, and it is normally the more expensive of the two. |
| Hydrostatic level transmitters | Sits in or on the bottom of the vessel and infers level from the head of liquid above it. It is unaffected by foam, vapour and internal fittings, needs a medium whose density is known and stable, and it is wetted - which is the trade against the non-contact types. |
| Capacitive level sensors | A probe whose capacitance changes with the medium around it. Simple for a point and for small vessels, and adversely affected by build-up on the probe. |
| Float level sensors | A displacer that follows the surface. Mechanically simple and independent of foam and vapour, but the moving parts foul, and the device gives a point or a short span rather than a continuous measurement. |
| Magnetic level gauges | A float inside a chamber moves a magnetic column outside it, giving a local visual level that needs no power. It is a reading rather than a signal, and the chamber is wetted. |
| Ultrasonic level transmitters | The same measurement principle packaged for transmission rather than for local indication, which is the form chosen when the reading is only ever wanted as a signal. |
The boundary between ultrasonic and radar is normally drawn by the atmosphere above the medium and by temperature, not by the level range, which both cover.
The first reply can be a quotation rather than a set of questions if the enquiry carries these. Where a figure is not known, send the duty description and we will confirm what it implies.
Available products
SIN-MP-C (4 models) · Ultrasonic Level Meters
Non-contact ultrasonic level meter for tanks, sumps, channels and silos, in integral and separate forms, with 4-20 mA and RS-485 outputs and a relay pair.
Also in Level Measurement
Every type we quote for under Level Measurement. A type with no link yet is still quoted for - it is described on the Level Measurement overview, and gets a page of its own as soon as a model is published against it.
Frequently asked
Because the transducer has to stop transmitting before it can listen. While the pulse is going out the face cannot hear the echo coming back, so the band directly beneath it is unmeasurable - usually described as the blanking distance or the dead band. It is not a fault and it cannot be tuned away. What it means in practice is that the highest level a vessel is allowed to reach has to sit below that band, so a tank that fills to the top needs the instrument raised, a standpipe brought up above it, or a different technology.
Not through a solid roof, because the pulse travels in air and would be reflected by the roof itself. What the type needs is an opening at the top of the vessel, a mounting that holds the transducer square to the surface and clear of the highest level, and free air between the face and the surface. A closed tank with no opening cannot be measured this way; a closed tank with a nozzle can, provided the nozzle is wide enough not to act as a waveguide.
The atmosphere above the medium more than the medium itself. An ultrasonic pulse travels in air and is slowed, scattered or absorbed by vapour, temperature gradients, dust and foam, so a hot vessel, a dusty silo or a tank that gives off vapour tends to go to radar. Where the air above the surface is clean and reasonably stable, ultrasonic does the same job for less. Because the two are quoted against the same duties so often, the enquiry is normally settled by describing the vessel and the surface rather than by naming a technology.
Because the pulse spreads as it travels and the instrument reads whatever comes back first. On a narrow vessel the beam reaches the wall and returns an echo before the surface does, and the reading locks onto the wall; internal ladders, agitators and heating coils do the same. A minimum clearance between transducer and wall is therefore part of the specification, and it grows with the range. It is why a vessel drawing is more useful than a range figure when the duty is being quoted.
Send the specification and we will confirm the matching model, availability and lead time. Minimum order quantity is 1 pc.
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