VTM-System Measuring the valve motion in real-time

Automotive development engineers are increasingly focusing on valve trains. Especially with regard to complex valve trains, measurement technology is necessary in a real environment.

The valve train-measurement system offers vehicle developers new opportunities – measurement in combustion engines. 

Modern GMR sensors in combination with powerful evaluation electronics solve a highly complex measurement task in an astoundingly easy and effective way.

The VTM system consists of the following components:

  • Sensor with cable length of 1 m or 1.5 m
  • Amplifier unit
  • Evaluation unit with user software

The support and service provided by Sensitec will assist you throughout the entire service life of your VTM system.

Our team of specialists will provide you with competent support: From planning and development to commissioning and maintenance – we are committed to individual service for all concerns.

General information

The automobile industry wants motors with less emission, lower consumption and more power. What may initially sounds like trying to square the circle can be achieved if engine developers are aware of the engine in every load case. High up on the wish list for engineers is measurement at valve trains, as this is where very effective optimizations are possible.

The VTM system (valve train-measurement system) is the perfect measuring device for this.


  • Measurement system for valve lift or valve rotation in real-time
  • No impact of the measuring equipment on operation.
  • High accuracy and durability

We offer support and know-how for the integration of the sensor into the engine.

Selection criteria

The VTM system was initially developed for measurements at the valve stem. The measurement principle can, however, also be used for other applications, especially if motion needs to measured extremely precisely in confined spatial conditions in harsh environments.

The deciding criteria for other applications can be derived very well based on the valve train measurement:

Selection criteriaMeasurement at the valve

Precise measurement scale

  • Ferromagnetic
  • Non-magnetic
The valve stem is machined very precisely and is ideal as measurement scale. The retrofitted mechanical structure does not lead to any restrictions for operation. Valves are predominantly produced from ferromagnetic material. Non-magnetic variants (e.g. titanium) can also be used as the measurement scale, although the process involved is slightly more time-consuming.
Precise controlThe distance between the measurement scale (mechanical structure) and sensor is only a few 100 µm. The distance fluctuation must be tightly tolerated. The valve guide provides an optimal prerequisite for this.

Measurement principle

The measurement is based on a magnetically preloaded GMR sensor which scans a ferromagnetic measuring structure at the valve. This scanning also functions for non-magnetic materials with a modified arrangement. The sensor works very precisely, has no hysteresis and allows measuring accuracies in a range of <10 µm.

The sensor is integrated directly into the valve guide for measurement data recording. The valve itself has a precise mechanical structure without compromising stability. The sensor provides path information from a standstill up to the highest speeds. The measuring signal is amplified, digitized by the evaluation unit and issued as a high-resolution displacement proportional voltage of 0-10 V. These analog output interfaces allows the VTM system to be easily incorporated into an existing test environment.


  • Measurement of valve lift or valve rotation in real-time
  • Durable sensor technology
  • The sensors do not restrict the motor’s operation
  • Measurement resolution < 10 µm
  • High measurement data quality from standstill to the highest speeds
  • Path or angle-proportional power output 0-10 V
  • USB interface
  • Fast integration into existing test environments
  • Windows user interface for simple configuration and calibration


The VTM system consists of the following components:

  • Sensor with cable length of 1.5 m
  • Evaluation unit with user software

Name of the components

SensorAmplifierEvaluation unit
GLM711 AVA-UA / GLM711 AVB-UA-SPP-3001


The latest GMR sensor technology with integrated magnets, optimized for use at high temperatures. The cable is ready made for connection.

Sensor typeHousingOutput signalPlug connectionCable type

3.6 x 7.0 x 3.2 mm
completely sealed

Sine/cosine differentialLemo 6 pol.
(shield placed on the housing)

PFA (Teflon®), Shielded
Cable diameter: 1.4 mm
Temperature range: -200°C to 196°C


The standard cable length of the sensor can be extended to a maximum of 3.5 m. In critical cases it may be necessary to use a signal amplifier. We offer a low-noise signal amplifier unit that amplifies the sensor signal by a factor of 5.5.

HousingAmplificationInput signalOutput signalPlug connection
30 x 35 x 115 mm
5.5Sine/cosine differentialSine/cosine differential, amplifiedLemo 6 pol.
(shield placed on the housing)

Evaluation unit and software

The evaluation unit SPP-3001 assumes complete signal conditioning of the sensor signal and calculation of the measured distance. The calculated distance or angle information is scaled to 0-10 V as analog output voltage and emitted at the BNC output.

The SPP-3001 has a high sampling frequency (1 MHz) and can be expanded to 32 measuring channels. The valve position is measured within 1 μm in real time and output as analog voltage. This means that even very fast movements can now be detected reliably.

Before the start of measurement, the system is configured and calibrated in just a few steps. A graphic user interface is provided for this purpose. The evaluation unit communicates with a Windows PC via USB during the setup phase. After switching to the "measure" mode, the analysis operates autonomously and there is no need for a connection to the PC. The "setup" and "measure" modes are each displayed on the evaluation unit with an LED.

The software offers the following setting options:

  • Automatic and manual adjustment to sensor offset and sensor amplitude
  • Amplification setting
  • Adjustment to the tooth pitch of the measured distance
  • Real-time signal monitor during setup phase
  • DAC test
  • Selection of communication interfaces (virtual COM ports)


More information


We help you to integrate the sensors into your engine.
We offer individual service packages whose scope you can determine yourself. After you have used the VTM system a number times, your know-how will also increase so that you can carry out these tasks yourself.

Example of a typical schedule for integrating the VTM sensors into the motor:

  • Non-disclosure agreement
  • Decide on product specifications (measurement task, customer expectation, requirements)
  • Customer provides sectional drawing of the parts to be processed
  • Exchange of further relevant information
  • Customer / Sensitec produces production drawing
  • Customer / Sensitec processes valve, valve guide, and if necessary cylinder head
  • Sensitec integrates the sensor into valve guide and tests the function
  • Customer / Sensitec builds modified valve guide into the cylinder head
  • Customer / Sensitec cable laying and potting of measuring point with the customer
  • Measurement by the customer

Data sheets

To the download area

Product information

Further information

Your contact person