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Often it’s useful to be able to record information over time.  Sometimes this is for regulatory reasons (e.g. food safety) sometimes fault-finding and sometimes just to review what’s happened.
This is the function of a logger.  In the instrumentation market, loggers capture measured parameters, processes the data and outputs either to its own software or to a spreadsheet such as Microsoft Excel.
Most commonly it’s temperature, but many other parameters such as pressure, process values (e.g. 4-20mA signals) or even brain or heart waves (the EEG or ECG) can be recorded.
Loggers might be handheld/portable, installed, within another instrument or integral in a PC.
Below are some examples of loggers:
Image 1
A wireless, logging digital pressure gauge
Image 2
A handheld temperature logger
Image 3 copy
NZ made food safety temperature loggers
Image 7
An aircraft flight recorder
Image 5
An 8 channel process input portable logger
Watlog 200

A highly customised portable or installed system which can have up to 256 channels
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An ECG showing parts of a heartbeat
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Antarctic Ice Cores:
Nature's own 40,000 year data logger



As mentioned above, temperature is the most commonly measured parameter, but it’s far from the only one measured.
Industrial transducers are very common and these might measure flow, pressure, level and other parameters, and if one purchases a process input logger, any of these parameters may be measured.
Tip: USB is the most common method for connecting a logger to a PC, but our experience is that the Windows approach to USB can be variable.  If one runs into trouble, check that the COM Port (device manager) matches the COM Port selected by the logger.  If your PC has a RS232 port, this is sometimes the best and easiest method for connecting your logger.

The “button logger” – a Cautionary tale

Dallas semiconductor came up with the concept of the “1-wire” button in the late eighties.  Something of a revolution they were used for loggers, for keyless access and a myriad other tasks. 

Eventually they became ‘generic’ and were manufactured in all parts of the world.  As one might expect, not all manufactures work to the same levels of quality and we have come across some button loggers that are waterproof and some that are not.
Image-10 200
The original "1-wire" temperature logger

The Chart Recorder

Originally chart recorders printed to paper.  Nowadays data-loggers may be paper based, or use other technologies to document.  In the food industry here in NZ they are often referred to as CATR’s. A digital or PC based system is also available but a printed log is still required by some processes.
PC based loggers have some appeal but for best performance, a standalone logger system is often advantageous.  If a PC based system is used, a dedicated computer is suggested to help avoid issues (think updates, restarts, viruses etc).
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Circular Chart Recorder
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Strip Chart Recorder
Image 11
Paperless/Video Recorder
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PC Based Datalogger
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Stand-alone Touchscreen logger


IANZ is the accrediting body in NZ for Metrology calibration labs. (read more about IANZ)
How accurate is your logger? 
If calibrated, how competent was the laboratory that calibrated it?
In one or two cases, the manufacturer of the logger may also be a calibration laboratory and may be able to apply corrections during manufacture.  This presents a major advantage in terms of accuracy and also cost; if regulations require one to have a logger certified, one done during manufacture will have a much lower total cost (logger plus certification).
For Accreditation, consideration is given to:
  • Laboratory accommodation and safety
  • Traceability of measurement
  • Laboratory equipment management and calibration
  • Computer-controlled calibration equipment
  • Laboratory staff
  • Laboratory test and calibration methods
  • Uncertainty of measurement
  • Certificates of calibration
  • Measurement audits
  • Management system maintenance and implementation
There are a multitude of options out there. If you need help deciding what is best for your process consult with the Homershams team on 03 358 8309.
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