Mark began with a survey of members to find how many, the type and age of their meters after he said his presentation would detail multimeter types and uses, vintage examples from his collection, taking readings and understanding the uncertainty, ending with making and using precision references which he had brought to display.
Mark showed a few meters and how they should be used, followed with photos of several vintage models, dating from the nineteen twenties, including the fascinating ‘Pocket Watch’ model. He also showed photos of advertisements from the British Vintage Wireless Society and gave comparisons prices in today’s money which indicated they certainly were not inexpensive.
It was explained that even with today’s modern meters, it was necessary to understand the uncertainty of the readings. The list of parameters to assure the ‘goodness’ of readings included: Error, Validity, Reliability, Repeatability, Accuracy, Precision, and Resolution. Mark explained just what these terms meant. The first being: “In all measurements there is a certain degree of error present. An error is the deviation between the actual value of a measurand and the indicated value produced by a sensor or instrument used to measure the value. Error is inherent and is not the fault of the person making the measurement. Error is not the same as a mistake! Measurement error can be minimised by procedural methods.” (Joseph J Carr – Practical RF Test and Measurements: A Technicians Handbook)
Each of the remaining parameters was explained with the same thoroughness. Mark ended by detailing the precision references available commercially or to build and the members then had a chance to test their own meters.
This was the last meeting before the summer break. Regular meetings will resume on 13 September.