Do these 3 things before closing this tab:
1Clear out junk files and repair common Windows errors2Scan for outdated or missing drivers - takes under a minute3Repair Windows errors before they cause bigger problemsmwkeithley.dll is a legacy Keithley adaptor used by MATLAB Data Acquisition Toolbox, not a Windows system file. If Windows reports that mwkeithley.dll is missing, the real repair is usually restoring a compatible MATLAB and Keithley hardware installation, not copying a DLL into a system folder.
| Item | Verified identification |
|---|---|
| File | mwkeithley.dll |
| Description | Keithley adaptor for MATLAB Data Acquisition Toolbox |
| Publisher | The MathWorks, Inc. |
| Type | Application component |
| Used by | Legacy MATLAB Data Acquisition Toolbox and Keithley data-acquisition hardware |
| Windows component | No |
| Architecture concern | The documented Keithley adapters are 32-bit |
| Current support | MathWorks limits Keithley hardware support to Data Acquisition Toolbox R2015b and earlier |
The filename may appear in messages such as “mwkeithley.dll was not found,” “mwkeithley.dll is missing,” or “Error loading mwkeithley.dll.” These are common reported variants, not necessarily standardized Microsoft error wording.
What mwkeithley.dll actually does
Older MATLAB Data Acquisition Toolbox installations used adaptors to connect MATLAB’s acquisition commands to particular hardware vendors. The legacy adaptor was identified as:
- Adaptor:
keithley - DLL:
mwkeithley.dll - Hardware: Keithley Instruments data-acquisition devices
- Older dependency: DriverLINX in the documented adaptor implementation
- Older location: the Data Acquisition Toolbox private adaptor directory
That makes this a hardware-integration file. It is not a general-purpose Microsoft runtime, a DirectX component, or a DLL shared by ordinary games.
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The adaptor sits between MATLAB and the Keithley driver layer. A failure can therefore mean several different things:
- The adaptor itself was removed.
- Data Acquisition Toolbox was never installed.
- MATLAB is the wrong release or architecture.
- A Keithley driver or supporting runtime is missing.
- MATLAB’s legacy DAQ registration is broken.
- Antivirus software quarantined the file.
- A third-party application bundled old MATLAB components and is calling them incorrectly.
The most important clue is what launches the error. If it appears when MATLAB starts, when an old daqhwinfo command runs, or when an analoginput object is created, the MATLAB DAQ installation is the primary suspect. If an unrelated program displays it, that program may contain or depend on an embedded MATLAB workflow.
Compatibility comes before repair
MathWorks identifies Keithley hardware support as limited to Data Acquisition Toolbox R2015b and earlier because the existing Keithley adapters are 32-bit only. MATLAB stopped being available as a 32-bit application beginning with R2016a.
That creates a hard architecture boundary:
- A 32-bit
mwkeithley.dllcan be loaded by a 32-bit MATLAB process. - A 32-bit MATLAB process can run on 64-bit Windows.
- A 64-bit MATLAB process cannot load a 32-bit adaptor.
- Installing the file in
System32orSysWOW64does not change its architecture.
Before reinstalling anything, confirm what you are actually running.
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Check the MATLAB release and process architecture
Open MATLAB if it still starts, then enter:
version
computer
Older MATLAB releases normally report a 32-bit or 64-bit platform in the output. You can also open Windows Task Manager:
- Press
Ctrl+Shift+Esc. - Select the Details tab.
- Find the MATLAB process.
- On many 64-bit Windows installations, a 32-bit process is marked with “32-bit” or “*32”.
If the installation is a modern 64-bit MATLAB release, continuing to replace mwkeithley.dll will not make the old adaptor load. Plan to use a supported Keithley interface instead, such as VISA, serial, TCP/IP, or another interface appropriate to the instrument.
Fix 1: Reinstall the matching MATLAB and DAQ products
This is the safest and most likely fix when the file is genuinely missing.
Do not begin by downloading the DLL. Restore the software package that owns it.
- Identify the MATLAB release used by the project or instrument computer.
- Confirm that Data Acquisition Toolbox was included in that installation.
- Obtain the installer or licensed installation files from MathWorks or the organization that supplied the MATLAB installation.
- Start the installer.
- Select the matching MATLAB release.
- Select Data Acquisition Toolbox in the product list.
- Complete the installation using the original installation location where practical.
- Restart Windows.
- Install the matching Keithley hardware driver and adaptor package supplied for the device and MATLAB release.
- Reconnect the Keithley hardware only after the driver installation completes.
MathWorks’ current installation process installs licensed products selected in the official installer. There is no current official standalone mwkeithley.dll download that should be treated as a universal repair package.
Verify the installation
After restarting MATLAB, test the legacy DAQ layer with the commands supported by that release. For older installations, the following may be useful:
daqhwinfo
If the adaptor is present but unregistered, the older DAQ system may support:
daqregister('keithley')
Do not assume that command exists in modern MATLAB. The legacy DAQ API changed, and a command that worked in an older release may be unavailable now.
A successful repair should produce one of these results:
- MATLAB starts without the missing-file message.
daqhwinforuns instead of reporting a missing adaptor.- The Keithley device appears in the DAQ hardware information.
- The old acquisition application reaches its hardware connection stage.
If MATLAB still names mwkeithley.dll, inspect the installation directory and confirm that the file belongs to the same release and adaptor package as the calling MATLAB process. If the file is present but the message says “specified module could not be found,” Windows may be unable to find a dependency rather than the named DLL itself.
Fix 2: Install the correct Keithley driver package
A working adaptor is not enough. The adaptor may depend on Keithley hardware software, Open Layers components, or an older DriverLINX layer.
The exact package depends on the hardware and the MATLAB integration. A Keithley manual for a separate MATLAB DAQ adaptor, for example, requires Keithley hardware drivers and Open Layers before the adaptor can work. That documentation concerns the dtol adaptor and does not prove that every mwkeithley.dll installation uses the same package.
Use the driver package supplied for the specific Keithley device and the legacy MATLAB release.
Reinstall through the vendor package
- Disconnect the Keithley device.
- Open Settings with
Win+I. - Select Apps.
- Open Installed apps or Apps & features.
- Search for Keithley, Tektronix, DriverLINX, Open Layers, or the device-specific driver.
- Uninstall only the damaged or mismatched package identified by the hardware documentation.
- Restart Windows.
- Run the original Keithley driver installer as administrator.
- Reconnect the hardware when the installer requests it.
- Restart again.
- Launch the matching 32-bit MATLAB installation and test the DAQ commands.
Check Device Manager
- Right-click Start.
- Select Device Manager.
- Expand Data acquisition devices, Universal Serial Bus controllers, Ports (COM & LPT), and Other devices.
- Look for the Keithley instrument, a USB interface, or a device with a warning icon.
- Right-click the relevant entry and select Properties.
- Read the Device status message on the General tab.
- Open the Driver tab and note the provider and date.
- If the device is absent or marked with a warning icon, reinstall the vendor driver rather than replacing
mwkeithley.dll. - If the device appears correctly, test MATLAB again.
The Windows driver and the MATLAB adaptor are separate layers. Device Manager can show a healthy USB device while MATLAB still lacks its adaptor, and MATLAB can contain the adaptor while Windows lacks the hardware driver.
Manually searching for the correct Keithley driver version means matching the instrument, connection method, operating system, MATLAB release, and 32-bit process. Outbyte Driver Updater can scan for driver problems and show what needs attention, while the full version performs the driver installation; it is optional, and reinstalling the vendor’s official Keithley package remains the definitive fix for this MATLAB-specific component.
Fix 3: Repair legacy adaptor registration
If mwkeithley.dll exists in the expected MATLAB toolbox directory and the Keithley driver is installed, the failure may be registration or path-related.
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Older Data Acquisition Toolbox adaptors were registered through MATLAB’s DAQ mechanism rather than ordinary Windows COM registration.
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Try this only from the matching legacy MATLAB release:
daqregister('keithley')
Then close and reopen MATLAB and run:
daqhwinfo
If MATLAB reports that daqregister is undefined, do not force the issue with random scripts. That usually means the release uses a different DAQ API or does not include the old toolbox. Reinstall the matching Data Acquisition Toolbox release instead.
If the command reports that the adaptor cannot be found, check:
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- The MATLAB process is 32-bit.
- The adaptor belongs to the same release as MATLAB.
- The Keithley driver package is installed.
- MATLAB is not using a copied or partially restored toolbox directory.
Fix 4: Check antivirus quarantine
Security software can remove a legacy DLL because old binaries are unusual, unsigned, or rarely seen. That does not prove the file is safe, so verify its source before restoring it.
Windows Security Protection History
- Open Start.
- Type Windows Security.
- Open the app.
- Select Virus & threat protection.
- Select Protection history.
- Look for an event involving
mwkeithley.dllor the MATLAB installation directory. - Open the event details.
- Check the detected path and action.
- If the file came from the original licensed MATLAB installation and you have confirmed its authenticity, use Restore or Allow on device as appropriate.
- Restart MATLAB and test the DAQ function.
Microsoft warns against restoring quarantined files unless their safety is established. Prefer reinstalling the file from the official MATLAB or Keithley installer. If the file’s origin is uncertain, leave it quarantined and submit it to the security product for analysis.
Also check whether a cleanup utility removed the old MATLAB private directory. A missing folder after disk cleanup or backup restoration points to software recovery, not Windows repair.
Fix 5: Remove and reinstall MATLAB cleanly
MathWorks does not provide a conventional repair-installation button for MATLAB. If the installation files are corrupted, the supported recovery path is uninstalling and reinstalling the affected products.
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- Open Settings with
Win+I. - Select Apps.
- Select Installed apps.
- Search for MATLAB.
- Select the release you need.
- Choose Uninstall.
- Follow the MathWorks uninstaller.
- Restart Windows.
- Run the official installer for the same licensed release.
- Select MATLAB and Data Acquisition Toolbox.
- Install the matching Keithley adaptor and hardware driver.
- Restart again.
- Test from the legacy MATLAB environment.
If the uninstaller is unavailable, use the original MATLAB installation media or the official uninstaller associated with that release. Do not delete random MATLAB directories first, because projects, licenses, and shared configuration may be stored separately.
Fix 6: Repair broader Windows component corruption
Windows system repair is lower on the list because mwkeithley.dll is a third-party MATLAB component. System File Checker will not normally recreate it.
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Use these commands only if Windows itself is showing broader corruption, failed updates, damaged system applications, or multiple unrelated system errors.
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- Install pending Windows updates.
- Restart the computer.
- Right-click Start.
- Select Terminal (Admin) or Command Prompt (Admin).
- Approve the User Account Control prompt.
- Run:
DISM.exe /Online /Cleanup-Image /RestoreHealth
- Wait for it to finish.
- Then run:
sfc /scannow
- Restart Windows.
- Test MATLAB again.
Microsoft recommends running DISM before SFC. If both commands complete successfully but MATLAB still reports mwkeithley.dll, return to the MATLAB, architecture, and Keithley driver checks.
Repeating SFC and DISM cannot substitute for reinstalling a missing application file. If you want a guided scan of Windows problems rather than repeatedly guessing which component changed, Outbyte PC Repair can identify issues in its free scan, while repair actions require the full version; it is optional, and reinstalling MATLAB remains the definitive fix for this application DLL.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Fix 7: Consider migration instead of forcing the old adaptor
If the computer uses a 64-bit MATLAB release, the old 32-bit adaptor is not a viable loading target. Do not downgrade random DLLs or try to bypass Windows loader checks.
Check whether the Keithley instrument supports a current communication route:
- VISA
- Serial communication
- TCP/IP
- A supported vendor interface
- A newer Data Acquisition Toolbox integration
The correct replacement depends on the instrument model and the existing MATLAB code. A migration may require changing old DAQ calls rather than restoring the original adaptor.
If the legacy application is essential, keep a controlled 32-bit MATLAB environment on compatible 64-bit Windows hardware, with the matching toolbox, adaptor, and driver package. Avoid updating individual pieces independently once the acquisition system works.
What not to do
Do not copy the file into System32
System32 and SysWOW64 are Windows loader directories, not generic DLL repair locations. Copying mwkeithley.dll there can create a second, wrong copy while leaving MATLAB’s private adaptor directory broken.
Do not use random DLL download sites
A loose download may contain the wrong architecture, incompatible exports, missing dependencies, altered metadata, or malware. It may also hide the real problem, such as a missing Keithley driver or an unsupported 64-bit MATLAB process.
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Do not run regsvr32 on this adaptor
regsvr32 is intended for self-registering COM and ActiveX DLLs. A MATLAB DAQ adaptor is handled through MATLAB’s DAQ subsystem, not ordinary Windows COM registration.
Running this command:
regsvr32 mwkeithley.dll
will not normally repair the adaptor and may produce an entry-point error. Use the legacy MATLAB registration mechanism only when that release documents it, such as:
daqregister('keithley')
Do not install Visual C++ runtimes blindly
A .dll extension does not mean that a Microsoft Visual C++ Redistributable is missing. Install a redistributable only when the actual error names a Microsoft runtime dependency or the vendor installer requires it. If one is required, its architecture must match the application process.
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Do not assume the named file is the missing dependency
Windows may name mwkeithley.dll while a dependency beneath it is absent. If the file exists but still will not load:
- Check the MATLAB installation path.
- Confirm the MATLAB process architecture.
- Review the Windows Event Viewer application log.
- Identify dependent DLLs with a trusted dependency-analysis tool.
- Reinstall the Keithley driver package.
- Reinstall MATLAB and Data Acquisition Toolbox.
FAQ
Is mwkeithley.dll part of Windows?
No. It is a legacy MATLAB Data Acquisition Toolbox adaptor associated with Keithley hardware. Windows does not provide it, and SFC will not normally restore it.
Is it a Microsoft runtime?
No. It is not a general-purpose Microsoft runtime or Windows library.
Which MATLAB versions support it?
MathWorks identifies Keithley hardware support through Data Acquisition Toolbox R2015b. The existing Keithley adapters are 32-bit, while MATLAB became 64-bit-only beginning with R2016a.
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Can a 32-bit adaptor run on 64-bit Windows?
Yes, a 32-bit MATLAB process can run on 64-bit Windows. A 64-bit MATLAB process cannot load the 32-bit mwkeithley.dll adaptor.
Why does the message say “specified module could not be found” when the file is present?
That wording can indicate a missing dependency below the named DLL. Check Keithley drivers, Open Layers or DriverLINX components where applicable, and the adaptor’s architecture.
Should I restore it from antivirus quarantine?
Only after confirming that it came from the original licensed MATLAB installation or a known-good backup. Otherwise, reinstall it from the official installer.
Can I fix it with regsvr32?
Usually no. MATLAB DAQ adaptors are not ordinary COM servers. Use the matching legacy MATLAB registration process or reinstall the toolbox and adaptor.
Do these 3 things before closing this tab:
1Clear out junk files and repair common Windows errors2Scan for outdated or missing drivers - takes under a minute3Repair Windows errors before they cause bigger problemsWhat if I no longer use MATLAB?
Uninstall the program that is requesting the file, or remove the obsolete startup entry or application that launches it. Do not add a replacement DLL to Windows just to silence an old program.
What is the final diagnostic question?
Ask which process is requesting mwkeithley.dll, which MATLAB release it uses, whether that process is 32-bit, and whether the matching Keithley driver is installed. Those four answers usually distinguish a missing adaptor from an unsupported installation.
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