The Right Cable for Your Force Measurement

Measuring cables are a key component of the measuring chain and significantly impact the accuracy of the result. Potential interferences such as the electromagnetic fields of electronic devices, inverters, or electric motors play a major role in this context.

A strain-gauge bridge has a low output signal, owing to its design principle: Typically, strain-gauge transducers have an output signal of 2 mV/V. Versions with an output signal of 4 mV/V are also available (for instance, U10M and C10 from HBM). The usual excitation voltage (supply voltage) is 5 V. Hence, when the measuring range is fully utilized, 10 mV are available (20 mV with sensors with a high output signal). Modern electronics enable measurement uncertainties to be achieved that can be significantly smaller than 0.1 %, depending on the ambient conditions. It is obvious that this small signal must be safely protected from the impact of their electromagnetic environment.

To achieve this, HBM's accredited in-house EMC laboratory, established many years ago, is available to check our force sensors’ behavior under the influence of electromagnetic fields.

Measures to improve EMC

The sensor cable’s shield is galvanically connected to the sensor housing and amplifier housing, creating a Faraday cage to achieve a high standard. Therefore, all components of the measurement chain are shielded. HBM offers a double-shielded cable (type 139B), particularly immune to interference in cases where extremely strong electromagnetic fields occur.

Cable assembly requires a high standard of cleanliness and protection. Make sure to thoroughly clean the installation surfaces by removing remaining fluxing agent, safely shield the installation from high-frequency interference signals, and create proper solder joints. Detailed work specifications are provided for cable assembly to ensure full protection from electromagnetic interference and a high standard in production. Measuring leads produced in this way ensure reliable results in any environment.

Other important technical properties besides EMC:

  • Low-capacitance cables should be used to minimize capacitive crosstalk.
  • The cables’ capacitive and isolation properties should change as little as possible due to temperature variations to ensure that the cable has no (or as little as possible) impact on the temperature-dependent measuring properties.
  • Cables that shall be used with drag chains must be mechanically robust.
  • A key requirement is that cables should be resistant to the common consumables required for operation in the measurement environment. This applies, in particular, to oils that can be present in applications near hydraulic devices.
  • Eventually, it is essential that with small forces, the cable is as flexible as possible. Otherwise, there is the risk of forces needed to move the cables being measured even though they are not related to the process.

In general, measuring cables from HBM offer the better part of the demanded properties; however, no cable can fully meet all requirements. For instance, the double-shielded cable is slightly stiffer and therefore, not fit for use with drag chains or small sensors. 

In general, there is always a solution, regardless of whether the application involves high temperatures, requires high precision, or demands mechanically robust cables. This is why HBM has restructured the measuring cables for force transducers:

  • HBM installs the cables and plugs in compliance with requirements for reduced sensitivity to interference

  • Solutions for all types of force sensors and amplifier systems are available

  • Three different cables with different characteristics offer a solution to virtually any measuring task in any environment

Every chain is only as strong as the weakest link! Therefore, the individual components are described in detail in the data sheet. To facilitate your choice, all cables can be combined with all plugs on both the sensor and amplifier sides. We are happy to consult with you in person. 

K-CAB-F cable types:

Standard cable

Robust, thermally and chemically resistant measuring cable that offers good metrological properties.

  • Up to 85 °C
  • Suitable for outdoor use
  • Resistant to machine oil, oil emulsions, seawater, diluted alkaline solutions, and ozone

Double-shielded cable

Double-shielded measuring lead that offers excellent capacitive symmetry for highly precise measurements.

  • Suitable for reference measurement tasks and long distances, high carrier frequencies, and temperature variations
  • Not suitable for drag chains and applications in which the cable is subject to constant movement
  • Resistant to many alkaline solutions, acids, and seawater

Highly flexible cable

Highly flexible measuring lead with a small outside diameter, suitable for applications in which it is subject to constant movement with a low force shunt.

  • Suitable for drag chains and measuring small forces, with stable temperatures and low carrier frequencies
  • Suitable for outdoor use
  • Resistant to many machine oils, oil emulsions, saltwater, seawater, diluted alkaline solutions, and ozone

Technical Documentation K-CAB-F

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