Cheap digital spirit level accuracy

[Mick BaileyParticipant @mickbailey28509]

The market is awash with cheap digital levels with good claimed accuracy. When setting up for milling/drilling angles I use a M&W vernier protractor, but this is difficult to read and not ideal.

I wonder if the cheap digital spirit levels are good enough for the job – zero the level on the workpiece and then set it to the required angle. I don’t need laborarory accuracy – something equivalent to my old manual protractor would be fine. Most of the cheap digital stuff seems to be fine but I dont have experience of this type of device.

[John HaineParticipant @johnhaine32865]

I tried mine using a digitallly controlled Myford dividing head (Ward Indexer), mounting a flat plate in a chuck on the spindle and sticking a Wixey angle gauge to the plate and rotating the divider through known angles.  As I recall it was accurate to 0.1 degrees or so – I may have posted on here about it at the time.

[old martParticipant @oldmart]

I have one at the museum, and it gets used for jobs which are not critical, having a claimed resolution of 1/10 degree. It is easy to check if you have some parallels and slips to tilt the parallels a known amount. The short base is more likely to be a source of errors, but is also an advantage for small jobs. Most of the angles that we would require would be +- 1/2 degree, rarely smaller.

[JasonBModerator @jasonb]

They work for me, others wanting to get their spaceship to the moon without going wide of the mark may feel the need for better accuracy but OK for making models.

[bernard towersParticipant @bernardtowers37738]

To be honest using the old protractors are fraught with user misreading but you can’t with a little up screen and as far as accuracy is concerned I have retired from NASA, tee hee.

[Howard LewisParticipant @howardlewis46836]

The way to check a level for accuracy, is to place it on a surface which is as level as possible. Note the reading; and then rotate through 180 degrees.

Ideally the reading should be the same in both directions, (SAY : 0.25 degrees UP at one setting, 2.5 degrees DOWN at the other. (On a perectly level surface, should read ZERO when facing either way)

If this is not the case,, if possible, adjust until both readings are of the same value.

This is how, when completed, my College Engineering Supplies level was adjusted, on a surface table in the Standards Room, at work.

Howard

[Mick Bailey]

On 5 June 2026 at 14:08 Mick Bailey Said:

[…]

I wonder if the cheap digital spirit levels are good enough for the job – zero the level on the workpiece and then set it to the required angle. […]

Entirely adequate for many jobs … but useless for others

Just try using one to measure, or transfer, the taper angle of a Taylor Hobson engraving cutter [as discussed in a concurrent ‘topic’]

MichaelG.

[Howard Lewis]

On Howard Lewis Said:

SAY : 0.25 degrees UP at one setting, 2.5 degrees DOWN at the other.

If you have one that reads those figures, I would consider returning it for a refund.

Also, given they display in 0.1 degree increments, how would it ever read 0.25 degrees?

[Robert Atkinson 2Participant @robertatkinson2]

Hi Howard,
While correct, that process only checks the zero or “level” condition. It does not check the angular accuracy (range and linearity). To check angular accuracy you need a known angle. A Sine bar, surface plate and “slip” gauges is the classic way to do this over small angles. A reasonably stiff straight piece of material and a block of known (measured) height is a good substitute. A length of rectangular or square light alloy tube or I section will do. Set one end of the straight on the block and us trigonometry to calculate the angle. Zero the instrument on the surface and then place on the angle and compare to the calculated angle. To be fussy test on different positions and with the straight turned over.

I can’t help with how good the cheap Chinese ones are, my digital is a Mitutoyo. That does match my Hilger and Watts mechanical vernier one. (I’m a bit of a metrology nut).

Robert.

[DC31k]

On DC31k Said:

Also, given they display in 0.1 degree increments, how would it ever read 0.25 degrees?

There are quite a few that read to 0.05.

[Andy StopfordParticipant @andystopford50521]

Mine matches the readings from my Mitutoyo vernier protractor – the only thing to watch for is that it takes a few seconds to settle on the correct value – I don’t know whether that applies to all of them.

For some applications the size and magnetic base is handy, others, as Michael suggests, not so much.

[Michael GilliganParticipant @michaelgilligan61133]

Digressing somewhat from ‘cheap’

The spec for this one is impressive !

https://www.leveldevelopments.com/products/engineers-level/precision-digital-levels/eel-200-h-high-precision-digital-level-with-bluetooth-and-app/

MichaelG.

[Michael Gilligan]

On Michael Gilligan Said:

Digressing somewhat from ‘cheap’

The spec for this one is impressive !

https://www.leveldevelopments.com/products/engineers-level/precision-digital-levels/eel-200-h-high-precision-digital-level-with-bluetooth-and-app/

MichaelG.

It’s very sensitive but with a +- 300 arc second operating range you have to be level to better than 0.08 of a degree before it will start to work.
It’s cheaper than the list price of my Mitutoyo Pro 3600…
EDIT: I note they sell an inclinometer identical to the Mitutoyo for a bit less:
https://www.leveldevelopments.com/products/inclinometers/digital-inclinometers/pro3600-digital-protractor-range-360-resolution-0-01/

 

[Michael GilliganParticipant @michaelgilligan61133]

“Horses for Courses”

MichaelG.

[Robert Atkinson 2Participant @robertatkinson2]

More like Apples and Oranges. One is a level the other is an inclinometer. The OP talks about levels but what he wants (a protractor replacement) is an inclinometer. Specifically one that can easily zeroed to a non-level datum.

Robert.

[Kiwi BlokeParticipant @kiwibloke62605]

How do the digital gizmos work?

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Mick Bailey, Checking true accuracy at home is quite difficult, as everything has to be on a solid stable base in a temperature controlled room, where everything has to climatise, and you should not handle anything with your bare hands. However, for the likes of what we do in our workshop, levels can be reasonable checked, take the digital ones, which can in most cases, be zeroed to whatever you starting surface is, and an easy way of seeing how true a digital one is, is shown in my photos below, the results show a small difference, but it doesn’t mean the digital device is in error, or even if it is level or not, as the first 2 photos show it reset to 0.0, but when turning the first photo, the error shown could be the block it is sitting on, or any small difference between the block and the surface plate or even the device or a slight temperature change. The same goes for the second two photos, but that vee block is not in pristine condition , but for what the most of us do, and the machines we have, these errors are plenty good enough.

The Wixey was not what I would call expensive, nor was it what I’d call cheap, and I’ve had it for 20 odd years.

Regards Nick.

[Kiwi Bloke]

On Kiwi Bloke Said:

How do the digital gizmos work?

They normally use a capacitive rotary encoder. A bit like the old variable capacitors seen in radios. Except that there are only two plates, one moving and one fixed, and the ‘plates’ are copper areas on PCBs.

Julie

[Robert Atkinson 2Participant @robertatkinson2]

Other technologies for inclinometers include circular digital encoders with a weight. Basically the same as a linear scale so can be optical or inductive.

Electronic levels can use “bubbles” the same a a spirit level with the bubble position detected electronically using capacitance (non-invasive of the capsule) or resistance (requires electrodes inside the capsule) or pendulums e.g talyvel.

Robert.

[Kiwi BlokeParticipant @kiwibloke62605]

Thanks Julie Ann and Robert. So, in some cases, an analogue transducer and ADC? Presumably consistency depends to an extent on bearing quality and freedom from ‘stiction’ (is that how you spell it?)?

[Robert Atkinson 2Participant @robertatkinson2]

One thing to note on accuracy of digital inclinometers (or any other digital measurement device) is that the accuracy can never be better than plus or minus one count of the lst digit. This is quantisation error.
So a digital “level” reading to to 0.1 degrees can never be better than 0.1 degrees accuracy*.
Typically they are worse. For example my 0.01 degree resolution inclinometer only has a accuracy of 0.05 degrees.

Robert.

* There are ways to improve this if the measurement is “noisy” i.e changing between two or more values. You can record the readings and apply statistics to remove the noise.

[Andy StopfordParticipant @andystopford50521]

I made one using an MPU6050 accelerometer chip and an ESP32 microcontroller (and a load of other stuff).

As far as I remember, it worked OK, but there were separate issues with the ESP32-clone’s WiFi hardware, and my original use-case for it faded away, so I never pursued it further, or made any serious attempt to measure its accuracy and repeatability.

edit: seeing Robert’s post above, I think the MPU6050 had built-in routines for dealing with noise

[Robert Atkinson 2]

On Robert Atkinson 2 Said:

More like Apples and Oranges. One is a level the other is an inclinometer. The OP talks about levels but what he wants (a protractor replacement) is an inclinometer. Specifically one that can easily zeroed to a non-level datum.

Robert.

Sorry Robert … I posted my remark before you edited #850908

I was specifically referring to the ‘operating range’

MichaelG.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, This digital protractor is reasonable good, it cost quite a lot more than my Wixey, and has a built in calibrator, and calibration can be done on any flat surface that doesn’t have to be level. As you can see in the photo below, the surface plate it is on, is near enough 4.2mm low on the left hand side, the protractor is 150mm long. When it is level, the ABS is showing, at the right of the digits, but it can be put into relative measurement on a surface that is not level, by pressing the zero button, and an angle can then be measured from there, pressing the zero again will bring it back to ABS.

Regards Nick.

[vintagengineerParticipant @vintagengineer]

As they contain no spirit, surely the are digital inclinometers?😉

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