Electronic Fundamentals

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The interaction between the electrical components of the SRM – High Performance Ergometer allows precise power control for performance diagnostic examination and scientific data acquisition.

The PowerMeter

The PowerMeter is the central part of the ergometer. It is responsible for measuring the power output. The PM transmits a particular frequency (500 - 12.000 Hz) proportional to the actual torque and also a frequency proportional to the actual angular velocity via a transmitter to a receiver located on the frame. The signal is digital to eliminate transmission errors. Power supply of the PM is by a Lithium battery lasting 1800 hours.

Important: If there is no torque on the chain, the PM does not measure any frequency, which means the angular velocity is zero. Setting this zero offset correctly is important to receive the right measurement of power output.

In the factory we calibrate all SRM PowerMeters in order to determine the frequency change of PowerMeter when changing the torque on the cranks. This frequency is called slope. This slope, measured in Hz/Nm, has to be entered initially into the PowerControl. The slope only has to be reentered if a different PowerMeter is employed, which normally has also a different slope.

Connecting the Ergometer (Ports)

  1. Power Supply
  2. Serial Port
    The serial port is only for the external control by CPX/CPET, EKG or other medical devices by the so called “ergoline” protocol. The idea is to specify the protocols in the CPX/CPET or EKG software to be independend of the SRM Ergometer software.
    Please connect the SRM ergometer via the serial port and the USB-to-Serial Adapter to the controlling computer.
    Please note: If you like to control the protocol by an external device don’t start the performance diagnostics in the SRM ergometer software. The SRM ergometer software are dominant.
  3. Torque Analysis
  4. Ethernet Ergometer

Ethernet hub

An Ethernet hub is a network hardware device for connecting multiple Ethernet devices together and making them act as a single network segment. If, for example, a notebook has only 1 Ethernet port this offers a solution. Because if you want to you use both the Ergometer and the Torque Analysis you will need 2 Ethernet ports. It is most likely is does not matter which Ethernut hub you will use but we recommend to take the Dexlan Ethernet hub because is has been tested with the SRM Ergometer.

The PowerControl Ergometer

The PowerControl Ergometer is the new version of the PowerControl and can be used only with the new ergometer control. It receives and displays the HR data.

To employ the PowerControl on the Ergometer the user has to ensure that the zero-offset is correctly entered. All other values such as slope, circumference of tire, etc. are in this case not applicable and has to be changed in the settings of the ergometer software.

Main menu

The main menu shows real-time data as the athlete trains.

Real-time Training Data Menu:
  • Top Line: Time - total training time [h:min:sec].
  • Middle Line: Power [Watt], Heartrate [bpm].
  • Bottom Line: Speed [km/h], Cadence [rpm].
If no signal from a sensor is picked up, the display shows “-“ for this data instead of a number (for example “Heartrate -“ if heartrate sensor is not paired/connected).

Sensor Pairing

You need to pair the PowerControl Ergometer with the heartrate sensors. If you don’t do this, no heartrate data will be received by the PowerControl Ergometer and can't be saved in the ergometer software.

Please follow these steps:

  • Connect the ergometer to the power supply.
  • Switch on heartrate sensor by putting the belt on your chest. Please moisten the electrodes to improve contact.
  • Switch on the PowerControl by pressing the MODE and PRO buttons simultaneously.
  • Select the heartrate sensor you like to pair: Possible heartrate sensors are SUUNTO or the PLUS (the PLUS-SRM heartrate sensor belongs to the ergometer standard accessory)
  • Press SET for searching the heartrate sensor; the search bar of the display shows the progress of the search and the antenna symbol is flashing.
  • If the heartrate sensor is found, the search bar is completed, the antenna symbol is displayed continuously and in the bottom line the sensor’s serial number is displayed.
  • Hold MODE for about 3 seconds to get back in the main display chart, the heartrate should be displayed after a short time.

If no signal is picked up, please check and repeat pairing from the beginning:

  • Damp the heartrate belt at the skin sensors to ensure that the heartrate data can be recorded by the heartrate belt.
  • If the sensor is working e.g. with another receiver (e.g. heartrate watch, PC8).
  • Check the battery of the hartrate sensor.
  • If it is still not working, please get in touch with the SRM Service Center.

Control test with PowerControl keys

You have the possibility to start and stop the test (or the training session) with the keys of the PowerControl.

Keybord Shortcuts
  • PRO (short): Test Start
  • SET (short): Test Pause
  • PRO (long): Test Resume
  • SET (long): Test Stop

The Power Supply

Power Supply

The power supply has been especially designed to suit the SRM Performance Ergometer. It supplies power to the ergometer, including the PowerControl Ergometer. The operating mode of the power supply is indicated by a green LED display.

Place the power supply in dry, well aired condition. Avoid switching the power supply on and off in quick succession. The power supply does not need any maintenance.

Light Barrier

The light barrier measures the speed of the fly masses. It is a necessary for the power measurement. If speed is not measured correctly, the power measurement is not correct either. The speed values are displayed in the SRM ergometer software and on the PowerControl Ergometer. The speed data do not correspond to real speed values.


It is possible to do some adjustments to the SRM Ergometer if it is necessary.

Relocating Plug

The cable of the PowerControl could be too short with the new SRM Ergometers. This occurs by pulling up the steering wheel of the Ergometer. In order to solve this the plug of the PowerControl will be relocated.


Not every SRM Ergometer has been grounded thoroughly for international standards. This could be fixed easily by adding some more grounding like in the images below.