Before the development of modern data loggers in the 1960s, the only means of automatically recording measurements of the environment was on paper charts, either mechanically or on electrical strip-chart recorders with electrical sensors. It was the arrival of solid-state electronics, in particular its ability to operate digitally, that enabled computers and data loggers to be developed. Both have greatly enhanced the way in which the natural environment can be measured, indeed they have revolutionised it.

The construction of a data logger

The schematic of Fig. 11.1 shows each main section of a data logger. With the development of large-scale integration on one integrated circuit (IC) chip, and of the microprocessor, many of these functions are now carried out on a single IC, supported by a range of peripheral chips such as serial data communicators, memory access controllers, counters and clocks (Fig. 11.2), although even many of these are now on one single chip. However, to explain the functioning of a logger, it is useful to keep the boxes separate. Indeed they were, in reality, physically separate (until the development of the larger ICs in the 1980s), the first loggers using individual transistors, resistors and capacitors with wires interconnecting them. Today, a small number of ICs, mounted on printed circuit boards, perform all of the functions required – in a reduced space, at reduced cost, with increased reliability and with very low power requirements.