DoseBadge Noise Dosemeter
Application details and FAQ’s
Sonomètres Pulsar 
Lärmmessgeräte Pulsar DoseBadge Application details and FAQ’s
How easy?
Because the method – especially the advanced database - is very powerful indeed, some safety staff who have not used such a system before may be tempted to think that POWERFUL = COMPLICATED. Nothing could be further from the truth. The ‘learning time’ – even for people who consider themselves ‘computer novices’ is usually far less than expected and most users manage to be in full command of the system very quickly. The whole system is geared up to people who may have a number of workers to monitor among many other duties and the process has been made very easy to learn. As well, any calculations required by National Regulations are done totally behind the scenes by the software; the user does not need to know how these are done if he does not wish to.
What is in the READER?
The READER contains the following functions
- An Infrared link to ‘talk’ to each badge
- An acoustical calibrator to make sure each badge is reading to full specification
- A large data store to hold the acquired data from about 99 badges
- An RS232 serial port to communicate with the PC
- A powerful internal cpu to calculate the noise metrics for the acquired data
- A display to allow each and every badge to have its data displayed quickly
- A configuration program to set up the badge (optional addition)
How does it work?
The principle is simple; a conventional “1990’s style” dosemeter has inside it an Integrating Sound Level Meter and a lot of processing power to computer the various metrics such as SEL and Leq plus LEP,d, and all manner of other integrating and averaging measures. Almost any current technology conventional dosemeter also has a data store as well as the RS232 transmission and display.
Each of these functions is in every conventional dosemeter and this is a very wasteful realization when several units are in use.
The doseBadge system is more logical. Each individual badge contains just enough circuitry to acquire the Sound Exposure very accurately and store it during the measurement time along with the actual measuring time. In a conventional dosemeter; this typically has about 25% of the circuitry of a ‘standard’ dosemeter.
In the doseBadge system, it is the READER that contains the remaining ¾ of the circuitry and thus for a single doseBadge and reader combination the complexity is much the same as a conventional unit. However, where more than one badge is in use, the cost and complexity of the system falls dramatically. Of course there is a very small overlap of circuitry that has to be in both the badge and the reader, but this is fairly insignificant. There is of course the additional infrared circuitry to allow the badge and reader to communicate with each other.
It follows that 4 badges and 1 reader have much the same circuit content as about TWO conventional dosimeters and the prices reflect this. In other words, a kit of 5 doseBadges will be about half the cost of 5 conventional dosemeters, even from the lowest cost supplier.
What is a dosemeter?
Today, the formal and correct name for a dosemeter - or dosimeter in American - is a Personal Sound Exposure Meter or PSEM and it has an International standard (IEC 61252) devoted entirely to it. This standard gives the technical requirements and the tolerances required of the dosemeter. The doseBadge complies with this standard. The acoustical accuracy of a PSEM meeting IEC 61252 is intended to be more or less the same as a conventional Type 2 meter meeting IEC 60651 and 60804.
The intent of any dosemeter is to measure the exposure of an individual worker to noise and not monitor the whole area and hope that ‘Everybody in the area is covered’. Some acoustic engineers have a very strong view that the use of a PSEM is not the best method “Because a sound level meter is more accurate”, while other are just as convinced that it is the only way “Because you measure at the correct point”. Both schools of thought have their reasons for their strong views, but now that PSEM have a proper IEC standard and the tiny doseBadge is available, many of the arguments against traditional dosemeters has disappeared. Indeed many regulatory bodies are now using the doseBadge for enforcement purposes.
Pulsar Instruments like many companies makes both noise dosimeters or PSEM as well as conventional sound level meters and if the user has very strong preferences for one or the other method both schools of thought are catered for. However, at Pulsar the dosemeter is available in the doseBadge form as well as in a conventional form.
Application pointers and FAQ
Overall problems
Because of the simplicity of the doseBadge system, there are very few significant problems, certainly far fewer than those posed by a conventional dosemeter. For example, when using a conventional dosemeter, it is not unknown for the user to set it up incorrectly and measure the wrong metric for the regulations in use. With the badge system, such errors are far harder to make and if the correct badge is purchased for ‘your’ country, the rest is taken care of by the badge itself.
Two of the most common questions from users is “Why does it have
to be charged overnight?” or “ Why is there no fast charge
option”. The answer is simple. To make the badge operate for the
design centre of 14 hours, every last coulomb is needed from the battery.
The capacity of the Ni-Cad cells used in the badge is used to the full
and anything that reduces the battery capacity must be avoided. Charging
is discussed in a paragraph below
Mounting
Mounting the badge is an important issue. As the noise at the workers ear is to be monitored, clearly the badge should be mounted as near as possible to the ear. If the worker is wearing a HARD HAT, this is very easy as helmet mounts are available. If however a hat is not being worn, the best location is the shoulder of the worker pointing slightly ahead of vertical and a mounting kit is provided for this position. In this location, the tiny size and lightweight do not impede the worker to any significant extent – or even at all in most cases.
Charging
The charge and discharge cycle of each badge is done under computer control by the intelligent charger. Once the badge has completed its day’s work and has been read, it is placed on the charger and totally discharged. A new charge cycle then starts that lasts for several hours and until this cycle is complete the badge cannot be used. A fast charge cycle could have been designed in, to allow the badge to be used after say 3 hours, but the process used has been designed for a long badge life and to ensure that the minimum 10 hour measuring usage is maintained. Re-chargeable batteries suffer from ‘charge memory’ and if the automatic discharge – charge cycle is not followed the badge may not operate for the full 10 hours (typically 14 hours for a new badge and 12 hours after 1 year’s operation). It was a feat of engineering to produce such a miniature instrument capable of measuring for so long; but only by being ‘kind’ to the batteries could this design be realised. In case a 12-hour battery life is felt to be low, it should be noted that many conventional sound level meters operate for less than 5 hours despite their being many times larger.
The Measurement
One of the most important features of any dosemeter or PSEM is the fact that if the worker moves from place to place his ACTUAL noise exposure is measured, not some arbitrary noise of a workshop. If the worker runs instead of walking, one minor problem is the wind noise he generates. While this is not significant in most cases, if he is outdoors and running into the wind, quite high spurious noise levels can be created. To avoid this problem, a windshield is available that clips over the badge and obviates the problem entirely – even if an Olympic athlete is being measured.
This windshield, while it obviously slightly affects the noise data, does not put the measurements outside the tolerance of the claimed standard. The windshield has a further use in what it protects the badge microphone from any possible damage if it is ‘banged’ into a very hard surface, or even perhaps dropped.
Sound Exposure Level
Sound Exposure level, Leq and ALL the other integrating sound level metrics are all computed inside the reader using as data the basic Sound Exposure and the measurement time. The technical glossary www.pulsarinstruments.com/ gives details of these mathematical conversions.
Annual Calibration
EVERY acoustic measuring instrument should be ‘calibrated’ at least every two years and ideally annually. This annual ‘calibration’ is properly called the ‘Routine Verification’ and as new International standards are being prepared such Routine Verification is becoming an integral part of the standard (for example IEC 61672 : part 3 Sound Level Meters.)
Because of the unique nature of the badge this annual verification is done by totally automatic means and at the same time the internal battery is checked for full function. It is therefore fairly important that the instrument is returned to the manufacturer – or his national representative – for such routine verification. There are however some National laboratories that are capable of doing the annual calibration, but as far as is known they do not have the facilities to check or change the battery. As well, National laboratories in general are far more expensive than commercial ones.