Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Automated Rain Sampler for Real time pH and Conductivity Measurements   To monitor the acidity of rain water in real time, a rain water sampling
system was developed. The rain sampler detects the initial rain after a dry
spell and collects a water sample. Before performing the measurements, the pH
probe is calibrated using a standard buffer solution whereas the conductivity
probe is calibrated using deionized water. After calibrating the probes the pH
and the conductivity of the collected rain water sample are measured using the
pH and the conductivity probe. Weather parameters such as air temperature,
humidity and pressure are also recorded simultaneously. The pH and conductivity
measurement data including weather parameters are transmitted to central
station using a GSM modem for further analysis. The collected rain water sample
is preserved at the remote monitoring station for post chemical analysis. A
programmable logic controller controls the entire process.

37
The categories of this paper are: supr-con
36
The categories of this paper are: cmp-lg
14
The categories of this paper are: math-ph
28
The categories of this paper are: alg-geom
21
The categories of this paper are: adap-org
18
The categories of this paper are: econ
5
The categories of this paper are: gr-qc
15
The categories of this paper are: nucl-ex
26
The categories of this paper are: bayes-an
2
The categories of this paper are: math
24
The categories of this paper are: dg-ga
7
The categories of this paper are: hep-th
34
The categories of this paper are: chem-ph
32
The categories of this paper are: atom-ph
1
The categories of this paper are: cs
19
The categories of this paper are: eess