The device described here can store pH and temperature values during more as one month. An operator has to come on the site to download the data on a computer. The device is composed with a pH meter and a datalogger.
The pH meter Heito P310 measures the pH and the temperature. It has two 0-20 mA outputs for the temperature and the pH for connection of the datalogger.
We have used here the Gigalog datalogger. It has a 16 bits resolution A/D converter. The data are stored on a flash memory card, wich has a capacity of more millions of values. The data can be transfered diectly by inserting the card on card reader (text file) or over a RS232 interface (figure 1). All the components are fixed in a IP65 box.
We use the software Gigaterm to read the data over the RS232 interface or directly on the card. They can then be displayed as curves in fonction of time (figure 2).
Figure 2: Example of curves