AUTOMATIC LOGGING OF TEMPERATURE AND HUMIDITY DATA DURING VEGETABLE DRYING AND STORAGE EXPERIMENTS

The vegetable storage building at the N.V.R.S. contains six 20 m³ capacity bins which are used for drying and storage experiments with onions and other root crops in loose bulk. Thermocouples (Cu-Con) are placed in the crop and in psychrometer units (aspirated to give maximum wet-bulb depression) which are placed in the inlet and exhaust ducts of each bin. Temperatures measured by the thermocouples are recorded by a Solartron Compact Series 2 Data Logger. The logger at present has the facility to scan up to 200 channels in banks of 50 per head unit. The head units can be remote from the logger, as is the case in the vegetable storage building (230 m) where they and auxillary equipment are housed in an insulated trolley held at near-constant temperature. Each head unit has a built-in electronic reference unit used by the logger in producing the digital output, however, additional accuracy is obtained by monitoring variation in the electronic reference unit by reference to a central accurate hot junction. The computer programme corrects for any deviations detected by this system and the temperatures are recorded to 0.1°C and an overall accuracy in the recording equipment of better than 1° claimed. Data are recorded hourly on punched paper tape, with or without a strip print-out, and 24 h tapes are processed at Rothamsted by an ICL 4/70 Computer. The turn-round time for data is 4 to 5 days so experiments requiring immediate attention are monitored with the aid of the strip printer. The data retrieval programme