M91 firmware update

Teslameter softwareLatest versionRelease dateSizeDownload
(OS update required)
2024-01-1278 MBfasthall.lsfw
Operating system3.0.02024-01-12575 MB


XIP OS update instructions

Firmware update process

This process is not capable of handling a full OS update, which is required for some versions of firmware. See instructions for the update process.

NOTE: OS version 3 and higher requires the firmware to be version 2 and higher.

The easiest way to update instrument firmware is online:

  1. Provide the instrument with an Internet connection using Wi-Fi or Ethernet
  2. Access the update screen (System settings > Update)
  3. The instrument will detect the latest firmware version, follow on-screen prompts to download and install the update

Updating an offline instrument is accomplished with the following steps:

  1. Click on the desired version number below, which links to the .lsfw firmware update file.
  2. Copy or save the .lsfw file onto the root directory of a USB flash drive. Make sure it is the only .lsfw file in that location.
  3. Plug the flash drive into the USB-C port on the back of the instrument; if you don't have a newer flash drive with a USB-C connection, use the adapter supplied with the instrument.
  4. On the M91 front panel, tap the gear icon (top left corner of the screen). Then tap System settings. Touch Update.
  5. Click “Updates are available. Click here to install” and follow the on-screen instructions to update the firmware.

Note: Firmware comprises many files aggregated to form a Lake Shore firmware (.lsfw) package. The instrument stores versions of its .lsfw packages in its internal memory. This local memory location is called the “local repository.” This allows you to downgrade the firmware to older versions that remain on the instrument in the local repository.

M91 firmware changelog

Rev 2.0.2023121202 (OS update required) — 2024-01-12

Minor bug fixes and housekeeping

Rev 1.7.2023042602 - 2023-05-11


  • SCPI command to report if USB drive is attached
  • Replaced JSON.NET with System.Text.Json
  • Enhanced LscpLogFilter


  • Send of stop byte during twi read multiple bytes
  • Unable to query CCHECK:RESULT:JSON? when optimization not run
  • System error when tapping update icon in toolbar from various pages
  • Unable to write error log
  • Sending SYSTEM:DATE or SYSTEM:TIME caused system error
  • System error when update page fails when checking for updates
  • Valid IP address settings with leading zeroes such as not accepted

Rev 1.6.2021010603 - 2021-02-04


  • GPIB terminators detail moved to info circle
  • GPIB now works at 3 MB for higher throughput
  • Memory conservation processes improved


  • :RESult[:STANdard][:SUMMary]? query inconsistencies and errors
  • Link commands missing and ignoring Sampling Time parameters
  • Sheet Hall Coefficient Standard Error units naming is incorrect
  • GPIB comms timeout issue
  • Broken wire detection with high resistance samples inconsistent
  • GPIB info circle sometimes does nothing when adapter is unplugged
  • Cancel button on GPIB address selection dialog does not cancel the selection
  • DC Hall standard result query order is incorrect
  • DC Hall missing RESult[:STANdard]:POINts? query

Rev 1.4.2020073106 - 2020-08-07


  • Allow user settable sampling time on all measurements
  • Add support for external GPIB connection. Implement SCPI commands for display settings and display lock
  • Remove redundant Contact Check from optimization sequence
  • Add enhanced error messages and diagnostic data to optimization process
  • Modify current autoranging sequence to optimize hardware performance
  • Improve display formatting of numerical values
  • Change default initial excitation current in Contact Check Optimization to 100 mA
  • Improve blanking (settling) time determination
  • Add minimum SNR check to DC Hall measurement
  • Display "High Resistance" on main page when option is enabled
  • Determine if broken wire exists during contact check and notify user
  • Allow for full factory reset of instrument


  • Update broken wire check logic to account for high resistance option license
  • Fix off by one issue when calculating DC hall results with field reversal
  • Allow contact check to be properly canceled when blanking (settling) time is being calculated
  • Clear out previous four-wire measurement results before next test is run
  • Fix incorrectly reported carrier type in DC Hall measurement
  • Improve measurement auto-ranging when using voltage excitation (Hi-Res) mode
  • Update four-wire measurement to accept excitation measurement range

Rev 1.3.20191119x - 2019-11-19


  • Zero and negative field values can be entered for DC Hall and FastHall applications
  • Improved measure autorange setpoints to enhance measurement linearity

Rev 1.3.2019091701 - 2019-09-17


  • Default sample thickness setting now dependent upon if resistivity measurement was run prior in sequence or not
    • DEFault = Set to 0 m if resistivity test not run (added)
    • DEFault = Set to measured resitivity result (no change)


  • Incorrect displayed measurement range (not identical to programmed range in all states)
  • Improved error messaging when user entered sample thickness is invalid value or format

Rev 1.3.2019080101 - 2019-08-01


  • When using optimized setting and in voltage source mode, improved range and compliance auto parameter selection


  • Improved functionality when cycling into and out of sleep mode

Rev 1.2.2019053002 - 2019-05-30

Initial release