The impact of contact force on the accuracy of hand-arm vibration measurement

We recently attended the 52nd Human Response to Vibration Conference & Workshop at Cranfield University where Svantek Poland’s Marketing Manager, Jacek Kuczynski, gave a presentation on ‘The impact of contact force on the accuracy of hand-arm vibration measurement’.

https://www.cranfield.ac.uk/events/events-2017/52nd-uk-conference-on-human-response-to-vibration

Below is an abstract from a paper produced by Jacek and Piotr Kowalski Ph.D (Eng) from the Central Institute for Labour Protection in Warsaw which details a recent study into the use of hand-arm vibration adapters and the accuracy of hand-arm vibration measurements, in function of the contact force. The Institute performed 240 measurements where the impact of coupling force on vibration magnitudes was assessed using Svantek’s SV106 human vibration meters and SV105AF hand-arm adapters.

The two Svantek SV106 human vibration level meters meet ISO 8041:2005 requirements, and are designed to perform measurements in accordance with ISO 5349-1 and ISO 5349-2 standards, with special SV105AF hand-arm adapters mounted on handles of vibration exciters.

Abstract

Measurement of hand-arm vibration with the use of a hand mounted sensor ensures the most representative measurements, taken at the point of contact of hand with a vibrating tool.

When measuring vibration on a hand, simultaneous measurement of contact force verifies whether the force magnitude is sufficiently rigid. The contact force also provides information on operator’s work schedule and may help to instruct users if they are using excessive or too little force when working with hand-held tools.

Additionally, by knowing both the coupling force value and the vibration acceleration, it is possible to calculate actual vibration energy dose that has been transferred to a hand.

The results proved that measurements taken with hand-arm adaptors provide correct vibration results regardless of contact force changes and type of vibration signal. The study has also indicated that it is necessary to define a minimum force threshold in order to mitigate the uncertainty related to the contact between hand and a vibrating tool.

Conclusion

The study proved that the effect of changes of the force thresholds applied by the operator are irrelevant to the measured vibration acceleration values. This assumption is valid for the forces above threshold of 20 N, below which it is necessary to ensure the correct coupling between hand-arm adaptor and vibrating surface. Together with the force level drop below 20 N, the uncertainty related to the coupling increases rapidly. However it is necessary to note that in practise, for tools generating high vibration amplitudes, the threshold of 20 N may not guarantee the perfect coupling, therefore higher threshold levels should be established.

Summary

At the time the ISO 5349 standard was introduced it was practically impossible to perform force measurements together with tri-axial vibration measurements due to limitations in hardware.

At the moment very small force transducers can be fitted right next to the MEMS-technology-based vibration accelerometer in a form of hand-arm adaptor as specified by ISO 5349-2 and ISO 10819 standards. In comparison to the technique of mounting sensor on a tool, the use of contact force allows defining the actual vibration exposure, whereas mounting on a tool bears the uncertainty of including into tests the periods when there was no contact with the operator’s hand.

As it has been proven, the use of hand-arm adaptors provides the same accuracy of vibration amplitudes as in case of standard piezoelectric vibration sensors mounted on a tool, but additionally offers the advantage of the best possible location of the measurement point – exactly at the point of transmission of the vibration signal to the hand of an operator and provides information on the actual exposure to the vibration.

The Importance of Workplace Monitoring

Every year in the UK, 1.3 million people suffer from a work-related illness or ill health caused or worsened by their working conditions. Plus some 13,000 workers per year die from occupational exposure to harmful substances and 30.4million working days are lost due to work-related illness and workplace injury. The estimated cost of injuries and ill health from current working conditions is over £14.1billion. (Source: HSE)

Health & Safety in the workplace is a bit of a minefield at the best of times but when you add all the extra complexities of monitoring for noise, vibration, dust and heat stress then setting up a regime correctly can be daunting and stressful.

However, occupational monitoring is a fundamental requirement as workplace noise, dust, heat stress and vibrations are potential hazards to an employee’s health. As an employer, it is necessary to ensure compliance with those industry regulations which impose stringent limits to protect workers.

Employees can be exposed to high vibration levels as a result of using power tools or by driving forklifts. Excessive exposure of workers to vibration has been known to cause serious health problems such as hand-arm vibration syndrome or white finger, back pain, carpal tunnel syndrome, and other vascular disorders.

Overheating in the workplace can lead to a range of adverse effects. Mild thermal stress, for example, can cause skin problems, fatigue, fainting and nausea whilst more serious overheating can lead to unconsciousness.

FREE seminar

AcSoft Health & Safety has run a number of seminars near its office in Bedfordshire and they’re always very popular.  The next one is being held on the 12th September  at The Sharnbrook Hotel in Bedford and will cover many aspects of workplace monitoring for noise, vibration (hand arm and whole body), dust and heat stress.

Experienced speakers will cover many key topics including the standards employers need to adhere to, which instruments to select and how to generate a report at the end.

Speakers at the event include John Shelton BSc (Hons) MSc MIOA who chairs the instrumentation working group for the Institute of Acoustics.

 

The seminar will cover:

 

  • An introduction to noise – what is the Noise at Work Act an how do I comply?
  • What is the difference between a noise dosimeter and a sound level meter and when do I use which?
  • Selecting hearing protection: there are a number of ways to select hearing protection including HML, C-A, Octave band analysis or just plain guesswork. What are the benefits of each method and what should I use?
  • Human vibration – an introduction to hand arm and whole body vibration measurement and the Physical Agents Directive:vibration
  • How to measure human vibration and how to devise a monitoring regime
  • Workplace monitoring for dust, VOC and gas: what do I have to measure for and how do I do it?
  • Heat stress and cold stress – what is it and how do you measure it?

 

For further information on the seminar please telephone 01234 639550

Noise Monitoring in Ports and Waterways

There are numerous noise sources in ports and waterways, including horns, whistles, signals, terminal operations, engines, construction and logistics. As well as ensuring compliance with environmental noise regulations, operators must minimise, mitigate or reduce noise from both essential processes and other sources.

As a result, monitoring the impact of sound levels on local communities can be a complex issue. Operators and contractors need to regularly monitor compliance with noise abatement procedures and regulatory requirements, plus investigate enquiries or complaints from members of the public.

An increasing number of port operators such as Felixstowe, Port of Tyne and Peterhead are choosing to install a permanent noise monitoring solution, which allows them to capture sound levels in real time and gain a better understanding of existing noise levels and also track changes over time.

Svantek’s SV200 outdoor noise monitoring station offers reliable, accurate and continuous operation in the harshest conditions. A fully integrated solution for unattended long or short-term noise monitoring applications, the weatherproof SV200 is small, lightweight and easy to install by a single person.

It has its own built-in web server that can continuously provide live, real time data, 24-hours a day, seven days a week, to a computer or hand held device. It will send an email or text message if the noise levels go above a pre-set limit and measures and stores results suitable for automatic reports and detailed information for advanced post processing analysis.

Standard measurement functionality includes multi-profile data logging, real time 1/1 and 1/3-octave logging, audio event recording and statistical analysis. Measuring capabilities can be extended with real time audio streaming and weather condition monitoring. All results are securely stored on the built-in 16GB microSD card.

The reference direction is user selectable in the instrument configuration and a highly efficient windscreen reduces noise, even at high wind speeds. It features special rain protection and weatherproof housing protects the SV200 noise monitoring station against extreme weather conditions while fulfilling IEC 61672 Class 1 accuracy.

Weather conditions have a significant influence on noise measurements so the SV200 is equipped with an interface for meteo sensors. With the optional SV205 weather station, the SV200 can measure wind speed, wind direction, temperature, humidity, ambient pressure and rain. Weather data is stored in parallel to the noise measurements.

Svantek’s SV200 features internal heating and rugged dual layer housing with natural airflow enabling it operate from -30°C up to +60°C and humidity up to 100% RH. It has a 2.45 Ah internal Li-Ion battery and interface for connecting solar panels. A waterproof mains adapter for charging the batter and powering the station is also included.

The SV200 features an ‘all-in-one’ design making it suitable for portable, mobile and permanent noise monitoring installations. This means it can also be moved from one location to another whilst still being able to provide information as often as required. A mounting tool for mast or stand is included in the standard package.

Nothing Shaky About Svantek Vibration Calibrators

Our extremely compact SV 110 hand-held vibration calibrator is designed for verification of machine sensors, as well as on-site checks of human vibration accelerometers, to ISO 8041. Faults caused by transverse vibrations are indicated by two LEDS on the calibrator’s housing. This unique solution ensures stability of both the calibration level and frequency, independent from the mass of the test object.

The small size of the SV 110 makes it perfect for calibration checks of both machine vibration accelerometers and hand-arm vibration meters including our SV103 and SV106 instruments. It can take loads up to 300 grams which makes it incredibly versatile. Depending on the selected frequency, the user can also choose to calibrate from 1 m/s2 to 10 m/s2. The SV 110 calibrator has built-in rechargeable batteries that will power it for 12 hours of continuous operation.

Our SV 111 is a state of the art calibrator designed for in-situ checks to ISO 8041. Intended for use in the field for pre and post calibration it is  ideal for quickly checking an instrument’s basic calibration and functionality.

New video

The SV104 and SV104IS are the most advanced noise dosimeters on the market by a mile. We thoughts we’d share with you why that is in this video. Just click this link to see what they can really do: SV104 video

Health & Safety North

Come and visit us on stand B28 at the Health & Safety North Show at the Bolton Arena on the 7th and 8th October. We’ll be showing our full range of H&S monitoring instrumnts including the SV104 personal noise dosimeter with octave band analysis and audio record and the SV103 personla HAV dosimeter.

We’ll also have the world’s best personal air sampling pumps from Gilian, heat stress monitors from LSI and thermal comfort monitors from e-instruments.

Technical paper on whole body vibration

We’re delighted to announce that Jacek Kuczynski from our head office in Poland will be presenting a technical paper titled “IMPROVED METHODS OF ASSESSMENT OF WHOLE-BODY VIBRATION RISK IN MOVING VEHICLES” at the “50th UK Conference on Human Responses to Vibration” at the Chilworth Manor Hotel in Southampton in September. For more details on this conference then click here.

To have a sneak preview of the paper then click here

IOHA London 2015

This year the IOHA and BOHS have a joint conference in central London which promises to be the most important of its kind in Europe this year. The conference runs at the London Hilton Metropole from the 27th to 30th April 2015 and there will be visitors from all over the world attending.

Of course Svantek will be there and we’ll be exhibiting our market leading SV104 and SV103 personal noise and vibration dosimeters. We’re also very proud to now be working with Sensidyne and their Gilian personal sampling pumps and LSI Lastem and their heat stress monitoring instrumentation.

Wind Turbine Noise Conference

We’ll be exhbiting at the INCE wind turbine noise conference in Glasgow on the 20th to 23rd April 2015 at the Radisson Blu Hotel in Glasgow.

Svantek has two instrumentst that are perfect for measuring wind turbine noise; the SV200 noise montiroign station and SVAN977 noise analyser. Come and see us at the show or give us a call to arrange a demonstration at your site.

IoA webinar – “Are you sure you’re calibrating your sound level meter correctly? Are you really sure?”

This webinar is presented by Richard Tyler, Chairman of the IoA’s Measurement & Instrumentation Group.

This presentation describes the role of the acoustic calibrator in obtaining the best possible calibration accuracy of a sound level meter, and therefore the best accuracy of measurement that the meter can achieve.

The correction factors that need to be considered when combining a given calibrator with any sound level meter will be covered in detail, and the method to achieve the correct setting for the sound level meter’s calibration routine demonstrated.

Some do’s and don’ts for this process will be highlighted.

To jon the webinar then follow these instructions