How Accurate and Precise Is the BLTouch Sensor? (How to Increase It?)

There is no denying that an auto bed leveling sensor, such as the BLTouch, changes the bed leveling from a grueling and tedious experience to a smooth and user-friendly one that doesn’t take any effort other than initial configuration.

On the other hand, while the improvement in the user experience is pretty valuable, we shouldn’t forget that the most vital parts of bed leveling are accuracy and precision, as the improved user experience doesn’t mean much if the bed isn’t correctly leveled.

In today’s article, we will take a deep dive into the accuracy and precision capabilities of the BLTouch sensor, where we will try to find out if the BLTouch is accurate and precise enough to perform the bed leveling process in a more reliable way than manually leveling the bed instead.

So, how accurate and precise is the BLTouch sensor?

As long as you use the original product and set it up correctly, the BLTouch auto bed leveling sensor is highly accurate and precise, capable of producing satisfactory results that fall within a standard deviation of 0.005 mm between distinct iterations of the bed leveling process.

Next up, we will analyze the accuracy and precision of the BLTouch sensor in greater detail, find out what we can do to increase the precision as much as possible, and take a look at the process of running precision tests to obtain concrete figures about the precision of the sensor.

How Accurate and Precise Is the BLTouch Sensor?

The sensor’s accuracy and precision essentially determine how successful it is, as we need the sensor to be as accurate and precise as possible for the bed leveling to be successful and not cause us issues during the printing process.

The accuracy and the precision of a genuine BLTouch sensor that has been set up according to the manufacturer’s instructions are very high, with the manufacturer stating that the sensor is capable of reaching a standard deviation value of 0.005 mm in repeatability.

While there isn’t a concrete figure about the accuracy capabilities of the BLTouch, our tests and the consensus from the community show us that the BLTouch is indeed highly successful in terms of accuracy, making bed leveling issues non-existent.

On the other hand, the standard deviation figure tells us that the margin of error between different iterations of the bed leveling process can be as little as 0.005 mm when the sensor is working as intended, which proves that the BLTouch is extremely precise.

How to Run Precision Tests for the BLTouch Sensor?

Running precision tests to find out exactly how precise your BLTouch is is the most efficient way to know whether your BLTouch is performing as it should or not, as problems with precision may not always be easy to notice.

Marlin Firmware offers a G-code command to run precision tests for your BLTouch sensor (or any other bed leveling sensor), called the Probe Repeatability Test, which you can run by invoking the M48 G-code.

Running the M48 G-Code causes the BLTouch to go through several iterations of the bed leveling process, makes the 3D printer record the results after each iteration, and instructs it to display all of these results alongside the standard deviation between these results as the output.

While higher standard deviation values tell us that there are inconsistencies between the readings in different iterations, lower standard deviation values tell us that the BLTouch sensor is operating correctly and finding similar results regardless of how many iterations it performs.

Despite it coming with many parameters that you can use to configure how the M48 G-code runs, we recommend running it with the default parameters and only passing the V4 parameter for it to display detailed results, which would yield the command:

M48 V4

After running this command, all you have to do is wait for the BLTouch to complete the test, at which point the 3D printer will produce the detailed output that you can use to find out if your BLTouch is working as it should.

How to Increase BLTouch Sensor Precision?

Do not be worried just yet if your BLTouch isn’t performing as precisely as it should, since in most cases, it’s possible to improve the sensor’s precision by following the appropriate steps for tuning it.

Here is a step-by-step guide we recommend following to increase the precision of your BLTouch:

  1. Run the Probe Repeatability Test (M48) a few times to confirm that there is indeed an issue with your BLTouch’s precision. Consistently finding standard deviation figures above 0.05 mm is a good sign that something is wrong.
  2. Bring the BLTouch to an idle state where the pin sticks out and measure the length of the part sticking out.
  3. Unscrew the magnetic screw on top of the BLTouch to release the pin.
  4. Remove the pin from the sensor’s body.
  5. Re-magnetize the screw and the pin with the help of a magnet. The longer the parts stay stuck to the magnet, the more magnetized they will be.
  6. Put the pin back in and screw it with the magnetic screw while ensuring that the measurement is the same as what you have found in step 2.
  7. Re-run the Probe Repeatability Test, and compare the results to the test results from step 1.

While this process should almost always increase the precision of your BLTouch by a great deal, in cases where the standard deviation remains way too high even after this process, we recommend reinstalling the BLTouch first and purchasing a new BLTouch sensor from an authorized seller to eliminate the possibility of buying a clone as a last resort, which is also likely to help with the accuracy.

Wrapping Up

Accuracy is definitely a very significant metric for auto bed leveling sensors, as the bed leveling that the sensor provides should be flawless for the printing process to run smoothly and successfully.

To quickly recap, the BLTouch auto bed leveling sensor should always provide a more accurate and precise result than manually leveling the bed, with figures with a standard deviation value that goes down to 0.005 mm between distinct iterations.

On the other hand, in cases where you come across a great deal of inconsistency between measurements, which increase the standard deviation figure to levels above 0.05 mm, taking the necessary steps to improve the accuracy of your sensor or replacing it may be required.

Happy printing!