Minoura Japan – Watt-Master

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Cycle-computer for training on GYRO series trainer

It is highly recommended to try to achieve the target strength of your indoor training for maintaining it as effective as possible.
For this purpose, Watt-Master provides various kinds of data on its big size 2" LCD screen;

Current, Average, Max
Current, Average, Max
Elapsed time (Auto start/stop)
Odd, Trip
Pace Arrow
(to show if your current speed is faster or slower than the average speed)
Course Bar
(to show where you are in the pre-programmed 20 km/miles training course)
Resistance Level
(to show which level you need to set in this 1 km/mile block according to the program)

* Watt data is correct only when you use Watt-Master on Minoura GYRO series trainers (V270/V150/V130). Not compatible with any other models.
Watt data will not be indicated in "Cycling Stage".

The unique and epoch-making feature on Watt-Master is course programming.
You can design a totally 20 km/miles training course, and you can set your favorite resistance level in each 1 km/mike block.
As per every 1 km/mile passed, red LED light blinks and the next pre-programmed resistance level will be shown in the top-left window. You will operate the remote shifter to switch the resistance level as per indicated.
When you finish the course, the computer will stop measuring the data, and you can compare the time to your past records.

To calculate your desired training level, use the supplied PowerChecker calculation disc.


Click to enlarge images

Measured on Rear Wheel

Speed data is picked up from the rear wheel

The standard cycle-computer picks up the speed data from the front wheel, but the front wheel won't move on stationary trainers. Watt-Master picks up the data from the rear wheel so you can use Watt-Master on both trainer and road.

Speed data is measured by the magnet on spoke, and cadence data is measured by the magnet on the left-side crank arm. Both signals are transmitted to the computer through the cable. It's not wireless.

Why Wired Computer?

Wired is more reliable on transmitting signals

Actually, it is true that the wireless system provides much sleeker looking and easier setting up than wired system. However, it is also a fact that any wireless system in either Digital or Analog still have jammed signal problem during transmission even with the current technology.
Every computer company is trying to avoid this problem in the method like adding secret pairing code or repeating data when transmitting, but every system still cannot 100% guarantee the correct data transmission. It's not reliable yet.

There is also a kind of secret among cycle-computer companies that the carbon material on the frame or front fork absorbs the signal wave and it causes the data lacking problem.
Therefore, most major professional riders are still using old fashioned wired computer in the race events to avoid data problem.

We are working very hard to develop our own reliable wireless system, but we are focusing on providing more reliable system at reasonable price rather than unreliable and expensive wireless system. That's the reason why Watt-Master is still a wired model.

Why So Big?

Large LCD screen for easier data view

The time for viewing the data while riding is quite limited. It's dangerous if you keep watching the screen to read out the data due to too small font size on the screen.
Watt-Master shows every data in big size text in its 2" LCD screen for easier and quicker data scan.

Also the course progress bar in the left-side of the screen and an LED on top of the body are the reason for the big body.

The 2-button operation is simple and easier even by the fingers in grove.

Dual Computer

Two computers in just one body

Watt-Master has two different stages (Training Stage & Cycling Stage) and each stage is driven by its own computer system. You switch two computers depending on the stages. Therefore, the total distance or total elapsed time is different in each stage.

You can record the data separately between indoor training and on-road riding.
All data will be reset to zero at once.

About Watt Data

Not actually measured power, it's calculated data

Watt-Master doesn't measure your pedaling power actually.
We already precisely measured the unit power in our lab, and keep it in the memory as a preset data. We adjust the preset data with adding the speed factor, then show it on the screen.

It's completely different from the actual measuring system such as super-expensive SRM or PowerTap, but it's no problem to use Watt-Master for your usual purpose that you compare the present data to your past record.

According to Ergomo (a German power measuring company), the liability of PowerTap is less than 90% and its data is more rough than SRM or Ergomo.

The main theme on our Watt-Master project is "How we can provide the training circumstance on focusing on output power at reasonable price". It's not our mission to show exact precise power data.
We put priority on helping you grow up "Faster than yesterday". Please do not misunderstand our wish.

Purpose on PowerChecker

To know your power or desired resistance level

PowerChecker is constructed with 3 discs, and can be used for 4 purposes by turning these discs as follows;

  1. To know the current power
    • By setting the total weight of your body and bike and the current resistance level, you will see your output Watt power.
  2. To know the simulated gradient in the current power
    • In the same procedure. you will see how much % of gradient you are simulating.
  3. To know which resistance level you need to set for simulating your desired Watt power
    • By setting the total weight of your body and bike, and set your desired Watt power by turning the middle disc, then the suitable resistance level will be indicated.
  4. To know which resistance level you need to set for simulating your desired gradient
    • By setting the total weight of your body and bike, and set your desired gradient by turning the middle disc, then the suitable resistance level will be indicated.

Every data is in the condition when you are riding at 30 km/h.


Net Weight
40 grams(excluding battery)
L 70 x W 53 x H 20 mm
LCD Screen
B/W, 2.0" (34 x 39 mm)
CR2032 x 1
Expected Life = 1 year
Water Resistant
Rain resistant(cannot be used in water)
Warranty Period
1 year(not responsible to any trouble after installation)


Watt-Master is compatible with the following models only

  • V270 / V270-2
  • V150 / V150-2
  • V130
  • M20-V

Watt data is NOT correct on any other models, including V100 and Magteqs Twin.
Speed and cadence are usable on any trainers.

Warranty Parts

Sensor Kit with magnets
SKU: 400-5001-00
Item: Computer mount, Speed & Cadence sensor, Wheel magnet, Crank magnet, Zip-tie
Sensor Kit without magnet
SKU: 400-5004-00
Item: Computer mount, Speed & Cadence sensor, Zip-tie
Wheel Magnet
SKU: 400-5002-00
Item: Magnet for wheel
Crank Magnet
SKU: 400-5003-00
Item: Magnet for crank arm, Zip-tie


Important Notices

  • Watt-Master comes with two different base brackets for handlebar or stem. Once you install it to the computer holder, it cannot be removed. Be careful which type you should set.
  • The speed sensor magnet is compatible with aero-type spoke, but its max width is 3.2mm so it may not fit MAVIC spokes.
  • Watt-Master is water resistant and can be used under rain, but do not sink in the water.
  • The provided watt data is the calculated number. It's not the actually measured data. Do not use for any academic purpose.
  • We don't guarantee the 1-year battery life. The battery in the kit is just for checking the computer functions and may expire within this period.
  • Do not use too cheap battery. Such battery usually doesn't keep proper voltage and may cause trouble.

Data Download

  • Instructions Manual (PDF 718KB) Doticon_grn_Down.gif
  • Course Design Sheet (original) (PDF 105KB) Doticon_grn_Down.gif
  • Course Design Sheet (A4) (PDF 76KB) Doticon_grn_Down.gif

Data not appear

Speed or cadence data is not shown on the screen

Watt-Master is a wired computer, so if you have pulled the cable strongly and accidently, the cable will have to be cut off in the sensor then it won't be able to send signals.
It is rare the computer itself has problem. 99% case is due to this damaged cable.

Please be careful not to pull the cable when you fully steer the handlebar when wiring.
And if the cable has been loosened, you may hook it and cut the cable. Hold the cable with zip-ties as many as possible.

To get replacement sensor cable, place an order to your local Minoura dealer.

Switching Level

Can I see the wattage data according to my current resistance level?

We are sorry Watt-Master just shows the wattage according to the pre-programmed course only.
The function to show the current wattage at your favorite resistance level without pre-programming shall be supplied in the next version.

Watt-Master doesn't measure the wattage in Cycling Mode, so the watt data stays at zero at all times.

Data Accuracy

It seems Watt-Master shows lower data than SRM

Watt-Master is designed for showing wattage data for more effective training at reasonable price, so its data is not actually measured, but the calculated one.
Watt-Master contains the data map in the memory and calculates the wattage by adding the current speed factor.
This data is the fixed one and it doesn't consider about your actual body weight, so it may show lower data than the system which actually measures the spinning torque. It's not a defect.

We shall add some more factors such as your body or bike weight in the next version for more accurate calculation.