SIT TEN-SIT Light Belt Tension Meter
Electronic gauge with optical sensor; measures belt span frequency 8-600 Hz; 90 cm cable for hard-to-reach drives; suitable for any belt type.
SIT TEN-SIT Light Belt Tension Meter
The SIT TEN-SIT® Light is an electronic belt tension meter for checking the tension of power transmission belts. It works on the relationship between belt tension and the natural vibration frequency of a free belt span: an optical sensor reads the vibration frequency of the span without touching the belt, and the frequency is converted into belt tension. Together with pulley alignment (see LINE-LASER), correct belt tension is essential for the performance and service life of a belt drive.
Features
- Reliable and accurate frequency measurement
- Suitable for all belt types: synchronous (timing) belts, V-belts, banded and Poly-V belts
- Easy to handle and versatile
- Lightweight and compact
- Frequency range 8 - 600 Hz
- 90 cm sensor cable for measurements in hard-to-reach locations
How to measure belt tension
- Stop the drive: measure only with stationary pulleys.
- Hold the sensor as close as possible to the back of the belt without touching it, centred on the chosen free span (Lf) and perpendicular to the belt. If a guard is in the way, aim at the inside of the belt in the same manner.
- Make the span vibrate by striking it with a rigid object (for example a screwdriver) while keeping the sensor in position.
- Read the frequency (Hz) after the acoustic signal. Repeat several times and use the average value.
- Check the tension again after one or two minutes of drive operation and correct it if it differs from the calculated value.
Belt tension and vibration frequency - formula
With T = static belt tension [N], M = linear belt mass [kg/m], Lf = free span length [m] and f = span vibration frequency [Hz]:
f = 1 / (2 · Lf) · √(T / M) and T = 4 · M · Lf² · f²
From the required static tension, the target frequency can be calculated; from a measured frequency, the actual tension. If the measured frequency is lower than the calculated one, tighten the belt; if it is higher, loosen it.
Example (SIT leaflet): belt 3150 Hi-PERFORMANCE Pd Plus 14M 55 - linear mass M = (0.412 / 40) · 55 = 0.566 kg/m, required tension T = 2,150 N, free span Lf = 0.65 m. Target reading on the TEN-SIT Light: f = 1 / (2 · 0.65) · √(2150 / 0.566) ≈ 47.4 Hz.
Linear mass of common belt types
| Belt type | Pitch / section | Width | Linear mass (kg/m) |
|---|---|---|---|
| Hi-PERFORMANCE Pd® Plus | 8M / 14M | 20 / 40 mm | 0.114 / 0.412 |
| MUSTANG® SPEED HTD | 3M / 5M / 8M / 14M | 6 / 9 / 20 / 40 mm | 0.022 / 0.031 / 0.114 / 0.412 |
| MUSTANG® TORQUE HTD | 8M / 14M | 20 / 40 mm | 0.112 / 0.408 |
| Classical timing belts (imperial pitch) | XL / L / H / XH / XXH | 6.35 / 12.70 / 19.05 / 50.80 / 50.80 mm | 0.056 / 0.082 / 0.120 / 0.282 / 0.406 |
| MAXSTAR envelope narrow V-belts | SPZ / SPA / SPB / SPC | - | 0.087 / 0.120 / 0.240 / 0.400 |
| MAXSTAR / EXCELITE ES® envelope classical V-belts | Z / A / B / C / D / E | - | 0.059 / 0.118 / 0.197 / 0.335 / 0.630 / 1.000 |
| TORQUE FLEX® moulded cogs narrow V-belts | XPZ / XPA / XPB / XPC | - | 0.071 / 0.123 / 0.185 / 0.382 |
For synchronous belts of another width, scale the mass in proportion to the width. For banded and Poly-V belts, multiply the value per rib by the number of ribs. The full table (polyurethane, WEDGE, banded and Poly-V belts) is available on request.
Source: SIT S.p.A. leaflet "TEN-SIT® Light", 534.00 - 07/26. Brand names are used for identification and technical reference.
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