A ground vibration monitor sometimes also known as a seismograph has two separate uses.

  1. To monitor ground-borne vibration from quarry blasting, when it is often known as a blast monitor. A blast monitor has an air over-pressure sensor to measure the peak air blast in decibels (dBzpeak)as well as velocity sensors to record ground ground-borne vibration in three axes:- vertical, radial (or longitudinal) and transverse.
  2. To monitor ground-borne vibration arising from civil engineering activities such as piling, compaction, and demolition.

Note: In the UK there are several British Standards that provide guidance on making measurements using a vibration meter (blast monitor or seismograph) and these include:

BS:7385-2:1993 Evaluation & Measurement for Vibration in Buildings

Part 1 – Guide for Measurement of Vibrations & Their Effects on Buildings

Part 2 – Guide to Damage Levels from Ground-borne Vibration.

BS:5228-2:2009+A1:2014 Code of Practice for Noise & Vibration Control on Construction and Open Sites – Part 2: Vibration.

BS:6472-1:2008 Evaluation of Human Exposure to Vibration in Buildings.

Note: BS:7385 and BS:5228 are concerned with levels of vibration that may cause damage, whereas BS:6472 is a guide for nuisance levels. The latest revision of BS:5228, BS:5228-2:2009+A1:2014 now contains an addendum,

Table 9.4: Guidance on Effects of Vibration Levels.

 

A ground vibration monitor typically has a frequency range from 1Hz to 100Hz and is not used for measuring earthquakes where a much larger sensor measures frequencies below 1Hz.

Should I rent a vibration meter?

  1. When there is a need to measure ground vibration for a short period of time, such as a construction project then rental will very likely be the best option.
  2. A hired vibration meter will be delivered to site with a certificate of calibration, typically of 12 months duration. If the project exceeds the calibration certificate’s validity then the rental company will supply another unit.
  3. A rented vibration meter will be relatively new, modern and reliable.
  4. Renting a vibration meter will not be a company asset and so not add to a company’s tax burden.
  5. The cost of hiring a vibration meter may be tax deductible.

Should I buy a vibration meter?

  1. If a user has a long term project or a continuous need to use a ground vibration meter then purchase rather than rental is often preferable. For example, a quarry where blasting regularly takes place will normally own one or more vibration monitors or for a long term construction project of more than six months.
  2. Ownership of a vibration monitor enables the user to become fully familiar with its operation, characteristics and the application software.
  3. There will be no waiting time whilst ordering or waiting for delivery.
  4. Generally ownership will prove to be a lower cost option than rental after about six months.
  5. Universities and colleges often buy ground vibration meters for use on their civil engineering courses.

Whether buying or hiring, it is important to choose a ground vibration monitor that is accurate and will comply with British and or International Standards. The vibration meter should be supplied with a certificate of calibration. There is at least one manufacturer that issues its own calibration certificates and claims that their meters will measure in compliance with Standards but in reality, when checked by independent calibration laboratories, their seismographs are found to be completely inaccurate below 20Hz. As an example with a 10mm/s reference and a reference frequency of 4Hz the response of one manufacturer’s units was 4.52mm/s. This inaccuracy was found to be due to very poor design and a lack of any correction of the geophone’s response, making any reading with a frequency under 8Hz to be well below what it should be. Accuracy at these low frequencies is crucial when monitoring structural vibration.

In conclusion, whether rented or purchased, Accudata offers some of the most accurate ground vibration meters available.