Tesa Electronic Probes
made in Switzerland

(Most of the following text is taken from the Brown & Sharpe 2003 Metrology Catalog. The technical prose couldn't possibly be improved upon—although we did take one or two editorial liberties. Our compliments to the anonymous author.)

Key components in any electronic linear measuring system, Tesa inductive probes detect the slightest variation in size with absolute reliability. Whether fixed to a simple measuring support or integrated by the dozen into a complex installation, they record dimensions with unvarying precision. Rugged and virtually insensitive to temperature variation and electromagnetic interference, Tesa inductive probes are compact, can be used in any position and are easily brought into contact with the work to be checked.

These standard half-bridge probes are compatible with Brown & Sharpe and Tesa amplifiers. Most are also compatible with earlier Brown & Sharpe series 960, 990 and 1020 amplifiers.

• All electronic probes are mounted on ball bearings, except for miniature axial probes.
• Ball bearing measuring bolts are virtually insensitive to radial forces.
• Probe guide system is efficiently protected against the penetration of solid and liquid contaminants by sealing rubber bellows. In normal conditions of use, Nitrile elastomer rubber bellows are sufficient. For applications where the probes remain permanently in contact with cooling and lubricating agents, we would recommend the use of Viton rubber bellows.
• Sealing bellows ensure full air tightness so that the measuring bolt is retracted by throwing off the air contained in the probe. This provides optimum protection of the guiding system because no mechanical means are used.
• Electronic signal amplification with no use of any other mechanical component produces excellent repeatability and low hysteresis.
• Maximum resolution is 0,01 µm

Functioning Principle

All Tesa electronic probes (value sensors) work on the inductive principle with mechanical contact of the workpiece. They are fitted with a coil system inducing an alternating output voltage that depends on the position of the ferromagnetic core. With a symmetric position, i.e. at electrical zero, no voltage is impressed. A move of the core, which may be attached to the measuring bolt while the measurand is being taken, leads to a change in the inductance. This change generates a signal that is amplified and rectified before being displayed and further output. Depending on the instrument type, the analog signal will be shown on a voltmeter or a numercial display after its digital transformation.

Unambiguous assessment of the measurand (at bolt position) to the signal (displayed value) is the main characteristic of the analog value acquisition. One of its distinct advantages is that the value primarily displayed will be reproduced in the event of a power cut (switch-off or power failure).

About Standard Tesa half-bridge probes designed for use with Tesa measuring instruments.

These probes have two serial coils with middle output mounted side by side and energized by a sinusoidal alternation at 3 kHz. Both are linked together to a Wheatstone bridge over an additional half-bridge.

Tesa 8mm diameter axial probes

• Measuring range: ±2 mm
• Travel: 4,3 mm
• Possible resolution: 0,01 µm
• Nominal value of the measuring force at electrical zero (maximum deviation ±25%): 0,63 N
• Moving mass: 6 g
• Frequency limit: 60 Hz (mechanical frequency limit valid for the final value of the measuring range with an amplitude of 10%).
• Dismountable: yes
• Repeatability limit: 0,01 µm
• Hysteresis limit: 0,02 µm
• Operating temperature: -10 to 65°C
• Protection rating: IP65
• Nominal sensitivity (half-bridge): 73.75 mV/V/mm.
• Linearity error: typically half the maximum error as shown below
• All of the characteristics given for these probes are valid for a reference temperature of 20°C. These technical specifications are applicable to probes fitted with the standard contact point.

These electronic probes are imported from Switzerland. They are usually in stock. No test data comes with the probe. There is a certificate of conformance only.