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Magnetic vs ultrasonic gas bottle level indicator

Updated: 22 October 2026

The price gap looks like quality. A magnetic card in this amazon.co.uk set costs about £3.95 to £9.99, and the Truma LevelCheck costs £74.99. A magnetic vs ultrasonic gas bottle level indicator choice is really three answers. The card says where the steel wall cooled while gas was flowing. The probe says whether liquid is present at the height you are holding. Scales say how many kilograms are left after you subtract the tare. On the [gas bottle level indicator comparison](/hub/measuring-equipment/gas-bottle-level-indicator) there are eleven cards and one probe. Nothing was laboratory-tested. If you buy through our links, we may earn a commission at no extra cost to you.

The price gap looks like quality. A magnetic card in this amazon.co.uk set costs about £3.95 to £9.99, and the Truma LevelCheck costs £74.99.

Our top picks

Truma Truma LevelCheck

Best overall

Truma Truma LevelCheck
9.2/10about £74.99
View offer
Volnamal Volnamal magnetic strip

Best value

Volnamal Volnamal magnetic strip
6.6/10about £3.99
View offer
Cowiny Cowiny 3-pack magnetic strips

Alternative

Cowiny Cowiny 3-pack magnetic strips
4.3/10about £6.49
View offer
On this page
  1. 1.What the £4 card detects
  2. 2.What the probe detects
  3. 3.What neither one tells you
  4. 4.Which one to buy

What the £4 card detects

A magnetic strip is a liquid-crystal thermometer with a magnet on the back. Thermographics says the colour boundary lines up with the liquid level, and it appears only while gas is being used. Steel holds the card. Aluminium does not. A composite shell such as Flogas Gaslight is semi-translucent, so you look at the liquid. Volnamal at £3.99 and OOBRAN at £3.95 tell you to wait 10 minutes with the gas on. The card stays blank when the liquid line is above it or the appliance is off, and it can look fully coloured when the whole wall is warm. Buyers of the Volnamal card, 3.6 from 417 ratings, report both a useful warning and a card that still said full on an empty bottle.

What the probe detects

The LevelCheck sends a pulse into the wall and lights an LED. Truma's UK page describes one height at a time: green when liquid is at that point, red when it is not or the reading is rejected. The stated cylinders are steel and aluminium from 200 mm to 350 mm. The listing bullets do not require gas to be flowing. The head has to sit square, and you clean the tip because aluminium wipes dust onto the sensor. A 47 kg cylinder is wider than 350 mm on published UK dimension tables. Plastic, refillable tanks, and Campingaz-type butane are outside the manufacturer's description. Amazon shows 4.3 from 686 ratings. The listing says 200 g and gas powered. The manufacturer page says about 100 g including a 9 V battery.
Truma Truma LevelCheck

Testsieger

Truma Truma LevelCheck
9.2/10about £74.99
View offer

What neither one tells you

A green light at one spot is liquid there. It is a full bottle only after you have found red above it. A field that says 10 percent, digital, or ±2 °C on a battery-free card does not add a third kind of sensor. YG-YUNCHUANG and Linswell print those fields and have no reviews in this set. The extra £70 buys a different question, a diameter rule, and aluminium. It does not buy kilograms. A regulator gauge is the other false percentage. GOK says the needle stays high while any liquid remains, then falls when that liquid has gone. Halfway through a 13 kg bottle can still look full. If you need a mass, Flogas tells you to subtract the tare on the collar disc. A scale can state its own limits, such as a rim of about 18–32 cm and a total up to about 45 kg. That example is not an ASIN in this set.

Which one to buy

Put a magnet on the wall. If it fails, the cards are out. If the bottle is see-through, look at the liquid and skip both tools. If the magnet holds and a late colour warning is enough, the Volnamal card at £3.99 is the best value in this set: a printed 10-minute gas-on method and 417 ratings. If you have several bottles, aluminium as well as steel, inside 200–350 mm, the LevelCheck is the top pick in this set. Buy scales when the answer has to be a kilogram for a trip. The tare weight is the figure. The wider method choice, including Gas Trac on patio bottles, is on the buying guide. Who the unread multi-packs are for is on the best gas bottle level indicator page. The separate sequences are on how to use a gas bottle level indicator.

Common questions

Is the ultrasonic meter more accurate?
It is accurate at a different job. The LevelCheck answers whether liquid is at one height on steel or aluminium, inside 200–350 mm, in the way Truma states and in a review file of 4.3 from 686. The card answers where a steel wall has cooled. Neither was laboratory-tested for this page. If accurate means kilograms left, both lose to scales and the tare disc.
Will either work on aluminium?
The probe is the one that states aluminium, from 200 mm to 350 mm, with a clean tip because aluminium dusts the sensor. A magnetic card needs a wall the magnet will hold. Aluminium fails that test. A see-through composite needs neither: you look through the shell.
What does green actually mean?
On the LevelCheck, green means liquid at the measuring point, not this bottle is full and not you have 6 kg left. Red means no liquid at that point, or a bad contact. Repeat the check higher and lower. A green light with the head on a sticker is a contact problem until you have cleaned the wall.
Why does a regulator gauge stay on full?
It is reading pressure at the inlet, and vapour pressure stays high while liquid remains. The needle drops when the liquid has gone, which is late if you were hoping for a half-full warning. GOK sets that limit out for LPG regulators. Use the gauge as an end-of-bottle signal, and use a card, a probe, or scales for anything earlier.
Is the extra £70 buying a percentage?
No. The gap from about £4 to £74.99 buys ultrasound, a stated diameter, steel and aluminium, and one meter for several bottles. It buys an LED, not a kilogram and not a percent full. Percentage fields on the cheap cards are listing text. If you need a number you can plan a week around, weigh the cylinder and subtract the tare.

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Sources

Public UK sources from the research digest, last checked around 20 October 2026. Shelf prices and star lines are the amazon.co.uk figures captured with these twelve listings. The price bands are this set, not a market average.

  1. Thermographics: gas level indicator theory (retrieved 20 October 2026)
  2. Liquid Gas UK: cylinder guidance for consumers (retrieved 20 October 2026)
  3. HSE: LPG legal framework (retrieved 20 October 2026)
  4. GOV.UK: LPG general information (retrieved 20 October 2026)
  5. Flogas: how to tell if a cylinder is empty (retrieved 20 October 2026)
  6. Truma LevelCheck product page (retrieved 20 October 2026)
  7. Gas Safe Register: frequently asked questions (retrieved 20 October 2026)
  8. Calor: gas bottles and Gas Trac (retrieved 20 October 2026)