IMU Comparison

This page is built on large amounts of community feedback, compared against a community survey, alongside side-by-side IMU tests conducted by various community members. After completing your own trackers, you can complete an extended version of that original survey yourself, or view previous responses on the SlimeVR Experience Survey page.

Table of Contents

• IMU Tier Rankings
  • 🟢 Recommended IMUs
    • 🟢 ICM-45686
    • 🟢 LSM6DSV
    • 🟢 LSM6DSR
  • 🟠 Acceptable IMUs, but better options exist
    • 🟠 LSM6DSO
  • 🔴 Poor IMUs, generally not recommended
    • 🔴 BNO085
    • 🔴 BMI270
    • 🔴 ICM-42688
    • 🔴 ICM-20948
    • 🔴 BNO055
  • 🚫 Avoid IMUs, do not use in new designs
    • 🚫 BMI160
    • 🚫 MPU9250
    • 🚫 MPU+QMC5883L
    • 🚫 MPU6500
    • 🚫 MPU6050
• Additional Info
  • Rating Criteria
  • What's the difference between an IMU with a magnetometer (9 DOF) and an IMU without a magnetometer (6 DOF)?
  • How can I check if I have an acceptable magnetic environment?
  • My app shows around X uT, is that okay?
  • What determines a "poor magnetic environment"?
  • Does magnetic interference cause drift?
  • Can I still use my IMU with a magnetometer if I don't have a stable magnetic environment?
  • IMU Calibration
    • Credits

IMU Tier Rankings

Ordered from best to worst with current firmware.

🟢 Recommended IMUs

These IMUs are recommended choice for new SlimeVR tracker builds.

🟢 ICM-45686

ICM-45686 is a very good IMU for DIY SlimeVR. It performs slightly better than LSM6DSV and much better than BNO085, but at a lower price. It can be purchased directly from the SlimeVR store.

🟢 LSM6DSV

LSM6DSV is a very good IMU for DIY SlimeVR. It seems to perform just as well as the BNO085, but at a lower cost.

🟢 LSM6DSR

LSM6DSR is a good IMU for DIY SlimeVR. It seems to perform a little worse than the ICM-45686, mostly in sensitivity, while being cheaper. Like the ICM-45686, this comes with the QMC6309 magnetometer built into the module.

🟠 Acceptable IMUs, but better options exist

Not recommended: These IMUs are acceptable to use if no other option is available.

🟠 LSM6DSO

LSM6DSO has average drift times and there is no reliable seller for breakout boards. It is not recommended to purchase new trackers equipped with this IMU from a third-party SlimeVR seller. There are trackers with better IMUs available at the same price or lower.

🔴 Poor IMUs, generally not recommended

These IMUs are generally not recommended for new SlimeVR trackers.

🔴 BNO085

This is the IMU used in versions 1.0 and 1.1 of the official SlimeVR trackers. This IMU has been discontinued from the SlimeVR store, making it difficult to obtain or to estimate its price. It also suffers significantly from the stomp bug.

🔴 BMI270

BMI270 has well below average drift times, and there are no reliable sources for SlimeVR-ready boards. It is not recommended to purchase new trackers equipped with this IMU from a third-party SlimeVR seller. There are many trackers with better IMUs available at the same price or lower.

🔴 ICM-42688

ICM-42688 is currently not recommended for new SlimeVR trackers. While it is a newer IMU, it is temperature sensitive and drifts fairly quickly.

🔴 ICM-20948

The ICM-20948 is a relatively modern chip. While early testing results are promising, the chip has not yet seen enough real-world use to draw conclusive results.

There are quite a few variants of the ICM-20948, most of which operate at 3.3v.

• Pimoroni ICM-20948: Requires cutting a bridge on the back to change the I2C address.
• Adafruit ICM-20948: Requires soldering a bridge on the back to change the I2C address.
• SparkFun ICM-20948: Also requires soldering a bridge to change the I2C address.
• GY-912: Requires bridging SD0 to GND to change the I2C address.
• CJMCU-20948: Operates at 1.8V and is not recommended. It requires both a 1.8V linear voltage regulator and a logic level converter to function.

🔴 BNO055

This is an earlier version of the BNO085 without stabilization firmware.

This chip lacks sufficient testing to provide a conclusive summary.

🚫 Avoid IMUs, do not use in new designs

Not recommended for use in new designs! You should absolutely avoid using these IMUs!

🚫 BMI160

BMI160 should not be used for new SlimeVR trackers. It is very outdated with almost all modern IMUs surpassing it in performance.

🚫 MPU9250

MPU9250 (currently run in several modes) is a newer installment of the MPU lineup.

🚫 MPU+QMC5883L

This is a highly experimental setup intended to approximately replicate the functionality of an MPU9250. Unlike other IMUs, which consist of a single PCB, this setup relies on connecting a magnetometer to an MPU6050 or MPU6500. That said, a breakout board that includes both an MPU6050 and an HMC5883L does exist: the GY-87. Both the QMC5883L and HMC5883L may be used; however, the QMC5883L may perform better.

🚫 MPU6500

MPU6500 is the middle ground of the MPU chips available. The drift time of this IMU may be a slight improvement over the MPU6050.

🚫 MPU6050

MPU6050 should be avoided. It loses accuracy within minutes and has poor motion sensitivity. It should not be used for any SlimeVR tracker.

Additional Info

Rating Criteria

We rank these chips in the following categories: Drift Time, Cost, Availability, and Build Quality. Drift time can be described by the time it takes for the tracker to lose tracking accuracy due to accumulated errors from its IMU.

These factors are meant to give a quick indication as to what to expect from various IMUs; your mileage may vary. For clarification purposes: If two out of ten chips or breakout boards are dead on arrival or die during early use, we refer to that as poor build quality.

What's the difference between an IMU with a magnetometer (9 DOF) and an IMU without a magnetometer (6 DOF)?

IMUs with a magnetometer, like a compass, use the Earth's magnetic field as a reference point to reduce gyroscope drift, however they require a stable magnetic environment or else they will perform erratically. IMUs without a magnetometer don't require a stable magnetic environment, but are prone to gyroscope drift over time due to being unable to differentiate sensor noise from actual movement, which means will slowly spin in the yaw axis over time. For SlimeVR's purposes, neither is inherently better or worse than the other. The BNO085, which is the IMU used in the official SlimeVR trackers, is used in 6DOF mode and yet performs the best out of all supported IMUs, for example.

How can I check if I have an acceptable magnetic environment?

You can check by using any magnetometer app that displays magnetic field strength in µT while walking around your playspace. You may want to check at varying heights, such as at chest level, waist level, and ankle level. One option available on both iOS and Android is Physics Toolbox Magnetometer. If you do use Physics Toolbox Magnetometer, you only need to pay attention to the total, not the X, Y, or Z components. Most phones include a magnetometer. If yours does not, you won’t be able to check directly, but you can still make educated assumptions based on known sources of magnetic interference.

My app shows around X uT, is that okay?

There’s no single 'safe' value; what matters is the fluctuation range. There is currently limited data to give an exact range, but a good baseline appears to be a fluctuation range of 5 µT or less. For example, 20-25 uT would be okay as would 40-45 uT, but a range from 20-40 uT would likely be too unstable to use.

What determines a "poor magnetic environment"?

Often objects made of steel or other ferromagnetic materials contribute most to a poor magnetic environment. Some common examples of things that might affect your magnetic environment include, but are not limited to: spring mattresses, radiators, PC cases, desktop speakers, or furniture made of steel. In most cases, the effect that these things will have extends about 15-30 cm (6-12 inches) and within that range may cause the IMU to rotate incorrectly. The size and amount of mass directly impacts the size of the affected area; a paper clip might only affect your IMU if it's directly next to it, whereas a steel bedframe might affect an area 15-30 cm (6-12 inches) away as previously mentioned. In most cases, depending on the size of your playspace, these issues of certain objects causing interference can be mitigated by avoiding or repositioning these items. Regardless, other factors such as the wiring, plumbing or rebar in your building could also affect your magnetic environment. These last few examples are harder to predict and illustrate why it's important to test with an app before assuming you might have a stable magnetic environment.

It's also worth mentioning that some controllers have magnets in them, either to hold the battery door closed or for the trigger. As such, placing your controller near a tracker with a magnetometer may cause it to spin slightly.

Does magnetic interference cause drift?

No, but you may still need to reset. When in an area of magnetic interference an IMU with a magnetometer will reorient itself the same way a compass will when put near a magnet; if you take the magnet away from the compass, the compass will return pointing towards magnetic North. As mentioned though, you may still find yourself needing to reset. For instance, if your bed has a steel bedframe you'll likely need to perform a reset so that your trackers are facing the correct orientation. If you then move somewhere else within your playspace you'll likely then need to reset once again.

Can I still use my IMU with a magnetometer if I don't have a stable magnetic environment?

This cannot be recommended. When run without the magnetometer, IMUs with magnetometers such as the MPU9250 and ICM20948 will perform much worse. That said, if for whatever reason you do want to use your IMU without the magnetometer, the MPU6500 or MPU6050 firmware can be used on the MPU9250 instead, and the ICM20948 can run in 6DOF mode.

Note that the IMUs mentioned in this subsection have more issues than just their magnetometer. Do not use them.

IMU Calibration

Some IMUs, such as the BMI270, BMI160, MPU9250, and MPU+QMC5883L, require manual calibration. This only needs to be performed once upon first setting up your SlimeVR tracker, however, you may need to perform the calibration multiple times before reaching satisfactory results. More information on how you would calibrate your IMUs can be found here.

Credits

Created by smeltie, edited by calliepepper, nwbx01, Aed, Amebun and Depact

A big thanks to everyone who took the time to fill out the survey.