Abstract:
Proton magnetometers are the oldest scalar magnetometers. The first commercial
units were produced in early 1960s as portable instruments. In continuation airborne instruments
appeared with optimized speed of readings and sensitivity, large sensors etc. Later development
of Overhauser and optically pumped magnetometers has eliminated Proton magnetometers from
airborne surveys. However they remain very popular in various ground surveys and observatories.
With this primary purpose of generating the ground based magnetic data, the Indian Institute
of Geomagnetism (IIG) for the last 3 decades have been developing low cost Proton Precession
Magnetometers (PPM). Beginning with the 1 nT PPM which has undergone several changes in
design, the successor PM7 the advanced version has been successfully developed by the institute
and is installed at various observatories of the institute. PM7 records the total field ‘F’ with accuracy
of 0.1 nT and a sampling rate of 10 seconds/sample. This article briefly discusses the design and
development of this IIG make PM7 and compares the data recorded by this instrument with one
of the commercially available Overhauser magnetometer in the world market. The quality of data
recorded by PM7 is in excellent agreement with the Overhauser. With the available quality of
data generated by this instrument, PM7 is an affordable PPM for scientific institutions, schools and
colleges intending to carry out geomagnetic studies. The commercial cost of PM7 is 20% of the
cost of Overhauser available in market.
