MTO300 Series

MTO300 Series - Automated six-winding transformer ohmmeter

  • Automated 8-terminal/6-winding measurement capability
  • Simultaneous winding magnetization
  • Tests operation of on-load tap-changers
  • Built-in auto-demagnetization feature
  • Automatic discharge
  • Power DB software (MTO330A)

Model MTO330A shown above.

The MTO 300 series delivers full eight-terminal/six-winding resistance measurement capability. It is designed to save time for the user by testing all normal 6 windings without having to disconnect and reconnect leads during testing.

The MTO3xx series also shares the Megger TTR300 series lead set. Users who test both turns ratio and winding resistance can save time and money since only one lead set is needed to connect to the transformer.


MTO 210/330 Firmware and Software Updates

The Megger Valley Forge, USA factory and select Megger Authorized Service Centers (ASCs) can perform updates. If you do not feel capable of performing updates properly, please contact your nearest Megger sales representative for information on where to return your instrument for updates.

Carefully read all instructions and backup your data before performing any updates.

Only update the firmware or software if you are experiencing difficulty with your instrument or if you have a specific need to do so.



Incorrect installation of updates and incomplete updates may cause an error and make the equipment unusable.

If damage occurs from improper updates, customer is responsible for repair costs.


MTO 210

1. Install PowerDB Upgrade (11) [optional]:

a. Download PowerDB 11 (You will be redirected to

2. Install Firmware Upgrade:

a. MTO 210 Upgrade Instructions

b. Download MTO 210 Upgrade Installer


MTO 300/330 

1. PowerDB PC Upgrade [Optional]. DO NOT INSTALL THIS ON THE MTO 330:

a. Download PowerDB 11 (You will be redirected to

b. MTO 330 PC Quick Manual

c. MTO 330 Quick Manual

2. Download Brother PocketJet 6 Installer [Accessories]:

a. MTO 330 Brother PocketJet 6 Install Instructions

b. Download MTO 330 Brother PocketJet 6 Installer

MTO 330 Brother PocketJet 6 Install Instructions
172.4 KB | 10/12/21
Download MTO 210 Upgrade Installer
432.5 KB | 10/12/21
Download MTO 330 Brother PocketJet 6 Installer
846.9 KB | 10/12/21
MTO 210 Upgrade Instructions
387.9 KB | 10/12/21
MTO 330 PC Quick Manual
786.5 KB | 10/12/21
MTO 330 Quick Manual
435.7 KB | 10/12/21
Transformer Test Instrument Software Updates for TTR330A, MTO330A, MWA330A, DELTA4310A

The following components have been updated:

PowerDB ________________ 11.1.4_22AUG18

MTOTestXP ______________ Release_2018.8.16.2

Instrument Config ______ 1.0.18051.2001

Splash Screen __________ 1.0.18047.1404

Factory Config _________ 1.0.18054.818

Megger Update Manager __ 1.0.18043.0955

Additionally this update will force the slider bars to be wide for improved touch screen usage.



- Megger recommends that you return your instrument annually for calibration verification.
- Any instrument returned for re-calibration will be updated with the latest firmware and software versions.
- Certified Factory Calibration is valid for one year.


Incorrect installation of updates or incomplete updates may cause the equipment to become unusable.

If damage occurs from improper updates, the customer may be responsible for repair costs.


Software updates for TTR330A, MTO330A, MWA330A and DELTA4310A


Download this zip file and extract it to the root of an empty USB drive.

File Size:    ≈800 MB 

File Date/Revision:   9/17/2018  /  10.001

MD5:     6d9605365c5725d1e61b416d3b7acf19
727.7 MB | 10/12/21
Update Instructions


Please download and read these instructions before performing the update below.

File Size:   ≈200 KB

File Date/Revision:     10/9/2018  /  Rev. 2

235.0 KB | 10/12/21