A small Polish company invented a new, very quick and very convenient method for stay ropes tension measurement. The instrument measures the frequency of the first harmonic of the oscillating rope and uses dependency between the frequency of oscillation and tension of the rope. The company seeks both the technology receiver (manufacturing of electronic devices) or/and a financial partner, which will invest in further development of the product.

The instrument developed by a Polish company measures frequency of the first harmonic of the oscillating rope and uses dependency between the frequency of oscillation and tension in the rope.
A mathematical formula expressing this dependency includes many coefficients describing parameters of the rope as the frequency of the rope depends not only of its tension but also of the length and diameter.

To execute the measurement, the user has to clip the sensor to the rope at the height of ca. two meters above the bottom anchoring of the rope and select appropriate type, length and diameter of the rope form the device's list. Then the rope has to be swayed and let sway freely so that the instrument can measure the frequency of the oscillation of the rope and thus calculate its tension using the mathematical formula. In a couple of seconds the reading will appear on the LCD (liquid crystal display) display indicating the tension in kN.

In order to minimise error and increase accuracy of the measurement following methods can be used:

1) Calibration in a certified laboratory.
The instrument should be calibrated for each rope type, length and diameter the operator is about to use. Each rope should be measured for its oscillation frequency at the maximum tension applied and results should be stored in the instrument's memory.
The device's maximal occurring error in this method of calibration is 8% or less depending on the range of tension the instrument was calibrated for.

2) Calibration by comparison.
In a group of identical ropes the user chooses one and uses a dynamometer to measure its tension.
Now he clips the sensor of NL-1 to the rope with dynamometer, swings it and measures its frequency.
He adjusts the tension of other ropes without dynamometer simply by swinging each of them and using NL-1 to achieve the same reading as for the first rope with dynamometer.
Resulting accuracy in this method is comparable to the one of the used dynamometer.

Calculating results from the sensor.
The frequency of oscillation is detected by a circuit based on the accelerometer built in the sensor clip.
The device is calculating the mean value of several consecutive periodically similar oscillations differing only by a previously defined margin. The user is able to set up this margin as well as the number of periods when the mean value is calculated.

The resulting average frequency along with rope parameters is put into equation, which gives the value of the tension of the rope. The result will appear on the display (with the accuracy of 0.1 kN) as soon as the desired number of periods contained within the predefined margin is detected and the calculations succeed.

Specifications:
- Operating voltage: 4,0 V – 5,5V
- Battery: 4 x R6 or equivalent
- Supply current (without LCD backlight): ca.16 mA
- Supply current (with LCD backlight): ca. 33 mA
- Display: 2 x16 alphanumeric LCD display
- Accuracy: Max. 8% (dependent on calibration method)
- Dimensions: 100x195x140 mm
- Weight: 200 g

Innovative Aspects:
This is the first device that utilises the oscillation period measurement method for rope tension measurement.

Main Advantages:
- Simple and user-friendly instrument for non-invasive measurement of tension forces in cables, ropes and guy wires for all kind of masts, chimneys and other guyed constructions
- The most convenient and quickest method for tension measurement, especially for periodic inspection and regulation

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