Instrumentation Monthly Test | Measurement | Control
DJB Instruments UK Ltd is once again proving they lead the way in developing unique products for extreme testing requirements. Their proven A33 water cooled range of tri-axial accelerometers have been available for many years and are popular in the Automotive and Aerospace industries for testing products with a surface temperature up to 800oC.
In 2011 the A33 was joined by the A133 integrated electronics version offering sensitivities at varying levels, 10mv/g, 31.6mv/g and 100mv/g, other higher outputs are possible though no requirements have been identified so far. Following long term successful field use by key customers the A133 is now available and providing a unique solution in a difficult testing environment up to 800oC. Particular applications have been for exhaust and turbo charger testing where high surface temperatures cause problems for standard accelerometer technology.
DJB’s Managing Director Neill Ovenden said of the A133 – ‘Many accelerometer users have wanted an integral electronics device that can withstand truly high temperatures for many years, with our A133 we have a proven solution that can withstand levels that have until now been unachievable whilst also offering the convenience of voltage output.’
Remarkably the A133 and A33 range don’t require any expensive pumping equipment to provide the necessary water supply to cool the accelerometer, Fabrice Breme MD of DJB Instruments SARL in France explained ‘The most common method of water supply has been via an automotive windscreen washer pump, this provides sufficient water flow, just 0.5 litre/minute to reduce the internal temperature to just 35oC even when operating at extreme’s of temperature’
A recent application in the USA utilised the A/133 IEPE version on live road tests. A major US Automotive OEM approached DJB Instruments via its US distributor for a triaxial accelerometer for use in testing exhaust vibration on vehicles in full operational conditions, i.e high temperature and road use. Their data acquisition and analysis system had the facility to provide the constant current supply to operate an IEPE accelerometer, so DJB specified the A/133 variant.
As the pictures below show the accelerometers were installed in a number of locations on a new exhaust development, with a single bolt mounting through the centre of the accelerometer body they are simple to install in what can be a confined space.
Supplied with cooling water via a windscreen washer pump the accelerometer cables and cooling pipes were protected by trunking to avoid damage under the vehicles during road tests, these were routed back to the instrumentation and pump/water supply within the vehicle. Cables were also supplied by DJB and were made to suit the customers’ installation requirements.
Neill continued… ‘The A33 and A133 have an important additional feature that many companies will appreciate, they are repairable, if one axis fails it can be repaired so the initial investment isn’t lost, this offers huge savings to users.’
Though the A33 and A133 are tri-axial devices DJB are also able to offer the same water cooled technology in single axis form.
For more information, please visit www.djbinstruments.com