Belt Tension Meter RTM-400

Measuring range max. 10 - 800 Hz

Trummeter for measuring belt tension and for control the strand force of V-belts, tooth belts, power belts or similar. The optimal life time of a belt is depending on the correct belt tension.

The measured value is shown as frequency in Hz or strand force in N.

Non-contact measuring occurs by infrared light

CE mark

Special Features

Measuring principle: Frequency measurement by LED light while the belt is not moving. The belt is toughed by hand to create vibration.

The readings can be displayed as frequency (Hz) or strand force (N or lbf)

The belt tension meter RTM-400 includes a display unit as well as 2 measuring probes:
– plug in probe for one-hand operation
– measuring probe with cable for limited access space

For determinating the belt force in Newton, 2 parameters are needed. Thereby the following restrictions are obtained:
– free strand length 9.99 m
– belt mass up to 9.999 kg/m

Belt tension meter with measuring range 10 – 800 Hz

Belt tension tester with multilingual operator guidance and display (German, English, French, Italian, Spanish, Portuguese, Swedish, Norwegian, Danish, Finnish)

Manufacturer`s calibration report is included

Standard Features

Belt tension devise for easy and safe operation

Trummeter with rugged, handy plastic housing

Microprocessor controlled belt tension meter

Belt tension tester for measurements with highest precision

Available Models

ModelMeasuring Range
RTM-400max. 10 – 800 Hz

Measuring range: 10 – 800 Hz
Digital sampling error: < 1 %
Indicator error: ±1 Hz
Total error: < 5 % of measuring value
measuring units:
Hz (Frequency) or
N, lbf (Strand force)
Measuring distance: 3 – 20 mm
Display: 2 line LCD, 16 characters per line
Languages: 10 languages (German, English, French, Italian, Spanish,
Portuguese, Swedish, Norwegian, Danish, Finnish)
Input ranges: Free strand length: up to 9.99 m
Belt mass: up to 9.999 kg/m
Temperature ranges: Operation: +10 °C … 50 °C, Transport: -5 °C … +50 °C
Air humidity: 85 % RH, max.
Power supply: 9 V – Battery
Housing: Plastic (ABS)
Dimensions: 126 x 80 x 37 (LxWxH)
Weight net (gross): Approx. 170 g (approx. 660 g)

Specifications subject to change without notice!

Belt Masses

Ribbed V-belts PJ = 0.082
PM = 1.100
PL = 0.320kg/m per 10 ribs
V-belts SPZ = 0.074
SPB = 0.195
10 = 0.064
17 = 0.196
22 = 0.324
32 = 0.668
SPA = 0.123
SPC = 0.377
13 = 0.109
20 = 0.266
25 = 0.420
40 = 0.958
kg/m per belt
Power belts SPZ = 0.120
SPB = 0.261
3V/9J = 0.120
8V/25J = 0.693
SPA = 0.166
SPC 0 0.555
5 V/15J = 0.252
kg/m per rib
Toothed belts
T 2.5 = 0.015
T 10 = 0.045
AT 3 0 0.023
AT 10 = 0.063
T 5 = 0.024
T 20 = 0.084
AT 5 = 0.034
AT 20 = 0.106
kg/m per 10 mm width

To measure the belt mass precisely, we recommend that you weigh the drive belt and then recalculate this weight based on a belt length of 1 meter.

The table above contains comparison values for some belts.

Operation of belt tension meter RTM-400The belt tension can be measured only when the drive is stationary. Preferably, the belt tension should always be measured at the center of the longer belt strand between the two drive pulleys. The distance to the belt can be 3 – 20 mm. Depending upon ambient light and surface of belt, the measurement can occur from a distance of max. 60 mm, whereas darker light and better reflection (can be obtained by attaching a reflective tape) admit a larger measuring distance.

The belt is tapped in order to make it natural oscillating. This static natural frequency is then measured by the probe with the aid of pulsed light. Care must be taken to ensure the light is sufficiently reflected by the belt. A reflective tape must be fixed if necessary.

General information:
To measure the belt mass precisely, we recommend that you weigh the drive belt and then recalculate this weight based on a belt of 1 meter. The strand force is calculated using the formula:

formula for calculating the strand force

F= strand force in N
m= linear belt mass in kg/m
L= length of the free belt strand in m
f= natural frequency of the free belt measured in Hz

Measurement deviations of up to ±10 % for several measurements taken on the same drive belt are as a rule not caused by a measurement error or fault in the unit. In most cases, measurement deviations are due to the mechanical tolerances of the drive systems.

Newton- or poundforce-calculations have a square factor higher error result!

Set point:
The set point for belt tension is specified as natural frequency in Hz or as strand force in N.
It is depending to the characteristics of the drive. Alternative the set point can be calculated with the formula:

Calculating the set point for belt tension

P= motor power in kW
z= number of belts
v= speed of belt = D x n/19100
D= effective diameter of the small pulley in mm
n= revolution of the small pulley (Upm)
m x v²= centrifugal force (relevant for revolutions > 800 Upm)
m= weight of belt in kg/m according the table (for a belt)

Delivery Includes

Scope of delivery belt tension meter RTM-400Belt tension meter  RTM-400 with carrying case, 2 measuring probes, 1 battery, manufacturer`s calibration report and operating instruction in German and English

Instruction Manual

Download the instruction manual for belt tension meter RTM-400:

If you want to get a quote or want to place an order, please contact us!

+49 (0)8638 9410-0

+49 (0)8638 4825