Recalibration of compliance instrumentation is often an overlooked activity, but like any technical instrument, the accuracy degrades over time. Most people view recalibration as (at best!) an inconvenience – interrupting the normal workload. However, readings from any electronic measurement device drift over time, and if they drift too far, the accuracy of the output is severely compromised. So making sure your monitor is properly calibrated should be an important part of your monitoring and compliance program – unreliable data is not helpful for your operational requirements and won’t stand up in court (if you ever need it to do so!).
There are various standards which determine how regularly you should calibrate your equipment: For vibration and blast monitors, AS2187.2 – 2006 and the ISEE Performance Specifications for Blasting Seismographs 2017 both recommend annual recalibration. Consequently, Texcel also recommends annual recalibration of these monitors.
All calibration standards require that the calibration process be both fully traceable and documented.
So how does Texcel meet these requirements?
- The sensor (geophone or accelerometer) is calibrated by comparison with a reference sensor. The reference sensor itself is calibrated by the Australian Government’s National Measurement Institute whose laboratory is NATA accredited. This means that it meets the requirements of ISO/IEC 17025 and that results are traceable to Australian standards of measurement.
- The electronic circuitry is calibrated by using a calibrated multimeter. The multimeter itself is calibrated by an accredited NATA laboratory in accordance with ISO/IEC 17025 with results traceable to Australian standards of measurement.
Special challenges:
Monitors that can be returned to the factory for recalibration are easy to deal with. With fast turnarounds from Texcel, the biggest concern is the time taken to get the monitor to and from the factory.
However, if the monitor is under a Guardian or 360 contract, the unit cannot be returned to the factory. In these situations a field calibration is necessary. This will ensure that the unit will only be down for 1-2 hours.
“Types” of recalibration:
Texcel offers two “types” of recalibration:
- Factory recalibration – where the monitor is sent to Texcel
- Field recalibration – where a Texcel technician goes to site to perform the recalibration.
While both operations meet the same technical requirements discussed above, they are achieved in different ways.
With the factory recalibration, the sensors and the electronics are recalibrated in the Texcel calibration facility under laboratory conditions.
However, where the recalibration must be done in the field, the standard laboratory equipment cannot be utilised. This is because the equipment is both very heavy and very delicate and certainly not suited to field use.
In this case the Texcel technician utilises a modified technique using some pre-calibrated sensors as well as performing any necessary upgrades to software or firmware.
Texcel recalibration inclusions:
- The monitor and the sensors are recalibrated
- The full system is thoroughly tested
- The firmware is upgraded (if required)
- The software version is upgraded (if required)
- The equipment warranty is extended for another year.
In summary, regular recalibration of compliance instrumentation is essential to any data acquisition program.
