The magnetometer used in this field magnetic survey is EN-VI proton precession magnetometer produced by Sundali Company in Canada, which is relatively advanced in the world at present. The instrument has high sensitivity, no zero drift and is not affected by external temperature and pressure. It can read data directly from the LCD and automatically record the observed data. Data can be directly imported into the computer through the standard 232C interface.
The main features of this instrument are: instrument sensitivity: 0.1nt/word; Fully automatic coordination, range: 20000 ~1000000 nt; The vertical gradient of the magnetic field in the measurement area is less than or equal to 0.005 nt/m; Strong anti-interference ability and stable reading; Microcomputer control, mass memory; The instruments are connected by transmission lines, which can automatically correct the diurnal variation; Standard 232C interface, which can be directly connected with a computer for data playback and transmission.
(2) Instrument noise test
In the morning when the diurnal variation is relatively stable, choose the place with little interference to test the performance of the instrument, and choose the instrument with the best performance to observe the diurnal variation. The test method is as follows: firstly, select the test site that meets the requirements. According to the instrument hypothesis method of daily variation station, assume three instruments every 20m, automatically record data every 2s, and select 300s data for statistics. From the data mean square deviation, the performance of instrument 2232 is the best, and it is used to observe the daily variation.
Formula used for calculation:
When the number of observations for each point is twice,
Geophysical field and crustal evolution in northeast China
When each point is observed more than twice,
Geophysical field and crustal evolution in northeast China
Where: n is the number of points involved in error calculation (that is, the number of check points); M is the total observation times, which is equal to the sum of all observation times at each observation point; Δ i is the difference between the original observation value and the inspection value at point I; Vi is the difference between an observed value at point I (including all the figures involved in calculating the average value) and the average value of each observed value at that point.
(3) instrument consistency test
According to the requirements of Technical Specification for Ground High Precision Magnetic Survey, several magnetometers are put into production at the same time, so it is necessary to measure the consistency of the instruments, check their stability, accuracy and consistency, and ensure that the requirements of measurement accuracy are met. After the instrument noise test is completed, the data is directly played back in the instrument, and it is determined that the performance of the 2232 instrument is better. The instrument is used to observe the daily variation, with an interval of 2 s, to observe the consistency of instruments 523 1 and 2232. Within the qualified site, the interval is 10 1 point. In 2005, 35 points were selected and 52 points were selected for experiments in 2006, and each point was observed with various instruments. After Japan's reform, the statistics of data accuracy show that the mean square error observed by No.5231in 2005 is 0. 157nT, and that observed by No.2525 is 0.267nt.. The mean square error of the two instruments is 0.246 nt/kloc-0 in 2006/the mean square error of the instrument is 0.442nT, the mean square error of the 2232 instrument is 0.264nT, and the mean square error of the two instruments is 0.362nT, which fully meets the technical requirements.