How I picked these: how they work, specs and buyer reviews. I haven't owned every one of them.
What to expect
- The needle meter is battery-free for volts and current only. Measuring resistance means pushing current through the part under test, so that range uses a battery inside the meter. Everything else works with the battery out.
- A needle is less precise than digits. You read it to a small fraction of the scale, not to three decimal places. In return you can see a value change and drift, which digits hide.
- A compass points to magnetic north, not true north. In Britain the difference is small at the moment, but it changes year by year. Steel, magnets and phones nearby will pull the needle.
- A sundial tells solar time, not clock time. Through the year it runs up to about 16 minutes fast or slow against the clock, and in summer it's an hour behind British Summer Time. Both are easy to correct.
Why these
A moving-coil meter takes its power from the circuit it's measuring, so for volts it needs no battery at all. That makes it ideal for tiny home-made power sources like an earth battery or a lemon cell.
A common, cheap needle multimeter with many ranges. It's a sensible way to try analogue measuring before spending money on a vintage Avometer.
A clear plastic base with a turning dial lets you take a bearing straight off a map with no protractor. It's the type taught in UK schools, Scouts and the Duke of Edinburgh's Award for that reason.
Silva's Starter is for learning and children. The Ranger 3 sits in the middle. The Expedition 4 is the classic full-size one, with map scales for grid references and a magnifier.
A larger dial is easier to read: the shadow moves further across it each hour. Slate stays flat and doesn't rust or rot outdoors.
Each one shows the thing it measures directly: a coil turning in a magnet, a needle lining up with the Earth's field, a shadow following the Sun. Nothing is hidden in a chip.
How they work
The moving-coil meter
A small coil of fine wire sits on a pivot between the poles of a permanent magnet. When current flows through the coil, it becomes a weak magnet and the big magnet pushes it round. Two fine hairsprings push back. The more current, the further the coil turns before the springs balance it. A needle on the coil shows how far.
That's the only thing the movement measures: current. Everything else is clever wiring around it:
- Volts: a large resistor in series with the coil. A known voltage drives a known current, so the scale can be marked in volts.
- Bigger currents: a low resistor (a "shunt") in parallel, so most of the current goes round the coil and only a set fraction goes through it.
- AC volts: a small rectifier turns AC into DC first. Still no battery.
- Resistance: the meter has to supply the current itself, from its battery. That's the one range that needs it.
The compass
The needle is a thin magnet on a jewel pivot, sitting in liquid that stops it swinging about. It lines up with the Earth's magnetic field, so its red end points to magnetic north. A baseplate compass adds a clear base with a direction of travel arrow, and a turning dial (the housing) with north-south orienting lines printed inside it.
To take a bearing from a map, you don't need the needle at all at first. You line the base up with your route and turn the dial until its orienting lines match the map's grid lines. The number at the index line is your bearing. Only then do you use the needle to walk it.
The sundial
The pointer that casts the shadow is the gnomon. Its sloping edge has to point at the celestial pole, the spot in the sky that the Sun seems to circle around once a day. That means it points to true north, tilted up at an angle equal to your latitude. Set up like that, the shadow moves at an even rate around the dial's hour lines.
What to buy
These are on Amazon UK, checked 7 November 2026. Listings change, so check each one before you order.
These are affiliate links. If you buy through them I make a small commission, at no extra cost to you. It helps cover the cost of running this site. This is a hobby, not a shop.
Needle meter
Compasses
Sundial
Not on Amazon
Set them up
Needle meter
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Zero the needle
With nothing connected, lay the meter in the position you'll use it. Turn the small screw under the needle until it sits exactly on zero.
Why: the hairsprings settle over time and with position. A needle that starts slightly off adds that error to every reading.
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Start on the highest range
Pick DC volts (or DC current) and the highest range. Connect, then step down until the needle sits in the right-hand half of the scale.
Why: a too-sensitive range slams the needle against the stop, which can bend it. Readings are most accurate in the upper part of the scale.
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Mind the polarity
Red lead to positive, black to negative. If the needle tries to go below zero, swap the leads.
Why: the coil turns one way or the other depending on current direction. A digital meter just shows a minus sign; a needle hits the stop.
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Read it square on
Look straight down at the needle. If your meter has a mirror strip on the scale (the MF47 usually does), move your head until the needle hides its own reflection, then read.
Why: looking from an angle makes the needle seem to sit over a different mark. This is called parallax.
Compass: take and walk a bearing
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Edge on the route
Lay the compass on the map with one long edge joining where you are (A) to where you want to go (B). The direction of travel arrow must point from A towards B.
Why: the edge is now your route, and the arrow fixes which way along it you're going.
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Turn the dial to the grid
Hold the base still. Turn the dial until its orienting lines run parallel to the map's north-south grid lines, with the dial's north arrow pointing to the top of the map. Ignore the needle.
Why: this measures the angle between grid north and your route. The map is the reference here, not the Earth.
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Read and correct the bearing
Read the number at the index line. Your OS map gives the difference between grid north and magnetic north for that sheet, and which way to adjust. In Britain right now it's a small figure, but check: it changes every year.
Why: the map's grid and the Earth's magnetic field don't point quite the same way, and the gap changes over time.
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Walk it
Hold the compass flat at your chest, arrow pointing ahead. Turn your whole body until the red end of the needle sits inside the orienting arrow ("put red in the shed"). Walk where the travel arrow points. Pick a landmark on that line, walk to it, repeat.
Why: turning your body, not the dial, keeps the bearing you set. Walking landmark to landmark stops you drifting off the line.
Sundial
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Level the dial
Put it on a solid base in full sun for as much of the day as possible. Level it with a spirit level in two directions.
Why: a horizontal dial's hour lines are worked out for a level plate. Tilt it and every hour reads wrong.
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Point the gnomon to true north
The easiest reliable method: on a sunny day, look up the time of solar noon for your town (many sunrise and sunset websites list it). At that moment, turn the dial so the shadow falls exactly on the 12 line. A compass gets you close first; correct it for magnetic variation.
Why: at solar noon the Sun is due south, so the shadow points due north. That's more accurate than a compass, which can be pulled by nearby steel.
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Check the gnomon angle
Measure the angle of the gnomon's sloping edge with a protractor. Compare it with your latitude (Fig 3).
Why: if the angle is wrong for where you live, morning and evening readings drift off. Then it's an ornament that's roughly right, and that's fine as long as you know.
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Turn solar time into clock time
Add 4 minutes for every degree you are west of Greenwich (about 9 minutes in Manchester, about 12 in Liverpool). Then correct for the time of year: the sundial is up to about 16 minutes fast in early November and about 14 minutes slow in mid-February, close to right around mid-April, mid-June, the start of September and late December. In summer add an hour for BST.
Why: the Earth's tilted axis and oval orbit make the Sun's noon wander a little across the year. Clocks use an averaged time instead. This correction is called the equation of time.
Looking after them
- Meter: switch to OFF or a high volts range after use. On some meters the OFF position shorts the movement, which damps the needle when it's carried.
- Meter: take the battery out if you won't use the resistance ranges for a while. A leaking battery is the most common way old meters die.
- Compass: keep it away from magnets. Phone cases with magnets, speakers and magnetic clasps can weaken or even reverse the needle. Store it apart from them.
- Compass: watch for a bubble. A small bubble can appear in cold weather and often goes away when warm. A large one that stays means it has leaked.
- Sundial: keep it clean and level. Check the level each spring. Ground frost can shift a base over winter.
Battery-free things to measure with the meter: an earth battery or lemon cell on the DC volts range, or the current from a crystal radio.
Common problems
| What you see | Likely cause | Fix |
|---|---|---|
| Needle won't move on volts | Wrong socket, wrong range, or a blown fuse | Check the leads are in the volts sockets. Try a known source, like a battery. Check the internal fuse. |
| Needle goes below zero | Leads swapped | Swap red and black. |
| Resistance range won't zero | Flat battery inside | Replace it. Volts and current still work without it. |
| Reading lower than expected on a tiny source | The meter draws a little current itself | Use a higher range, which draws less. Normal for any needle meter. |
| Compass bearing is way off | Steel or a magnet nearby | Move away from cars, fences, phones and belt buckles. Check again. |
| Needle sticks or is sluggish | Not held flat, or damaged | Hold it level. If it still sticks, the pivot is damaged; replace it. |
| Sundial right at noon, wrong morning and evening | Gnomon angle doesn't match your latitude, or plate not level | Re-level. If the angle is wrong, accept it or buy a dial made for your latitude. |
| Sundial wrong by the same amount all day | Not pointing true north, or longitude not corrected | Redo the solar-noon check. Apply the 4 minutes per degree correction. |
Safety
- Don't use a cheap meter on mains. Budget meters may not have the insulation or fuses for it. If you must measure mains, use a meter rated for it (look for a CAT II or CAT III rating on the case) and know what you're doing.
- Never measure current across a supply. On a current range the meter is almost a short circuit. Across a battery or socket it blows the fuse at best.
- Carry a map with the compass, and know how to use both before relying on them on hills.
- Never look at the Sun when setting a sundial. Work from the shadow.
Notes
The moving-coil meter is often called a d'Arsonval or Weston movement, after the people who developed it in the 1880s. The compass method is the standard one taught by Silva and in UK navigation courses. The longitude and equation-of-time figures are standard astronomy; the equation of time values are rounded to the nearest minute.
Magnetic variation in Britain changes every year. Always use the figure printed on a current map, or the British Geological Survey's online calculator.
Related guides: earth battery and lemon cells, barometers and weather glasses, slide rules and the abacus.