Shy of Retiring

Since I wrote my book "Slow Running", my running has got slower. Not surprising really, as I am now 60, and they say that no matter hard you train your running fitness is bound to decline from age 50 onwards. Since I no longer actually 'train', my personal experience doesn't serve as a robust test of this, but I use it as an excuse. I am still running reasonably regularly. Two things keep me running: a wife who is fit and enjoys running, and 'leading' a Run England run group. The latter I started almost three years ago, and with a few exceptions we have met each Saturday since. The run group came about through my interest in running for fun rather than for fitness, and my training with Run England as a Run Leader focused my mind on the particular concept of Slow Running. I stole it, actually, from the trainer - but she only mentioned it in passing and I already had the idea. What she said was, that when she met a group of new runners she would set them...

Sample and hold operations I am struck by how the term 'sample-and-hold' puts the two operations back-to-front. There are two steps to the conversion of an analog signal to digital form. The two are often confused, and the term "analog-to-digital conversion" is often (mistakenly) used to refer to both steps in the process. This confusion can hide important engineering choices. The idea of analog-to-digital conversion is to take a continually varying analog signal and convert that to a discrete set of samples taken (usually) at some regular time interval. The conversion is in fact a form of measurement, and for each sample will produce just one measured value. The problem here is, that the signal is continuously varying and so the (single) measurement will be some kind of average of the variation. Worse, the process of conversion to digital form can take some time and be done in stages - for example the method of "successive approximation" makes a fi...