Preliminary Results of Total Field Magnetometer Comparison Introduction During the XIVth IAGA Workshop (hereafter referred to as “the workshop”), several total field comparison measurements were conducted at the Changchun Magnetic Observatory (CNH). The purpose of these tests was to look for errors within the total field instruments which are considered “absolutes” instruments. The total field measurements is a critical component of the absolute measurement computation. Samples between two total field sensors, corresponding in time, were directly compared. Other methods for calibration exist for these sensors, including the use of frequency generators. Method The participants were Dr. Hans-Joachim Linthe from Germany, Haizhi Liu, Guihua Qi, Fuxi Yang and Suqin Zhang from China. Table 1 summarizes the testing specifications for each participant’s system. Participants Instruments make/model Date of test Start time (UTC) Duration of test(s) Sampling rate (Samples/Second) Number of samples H. J. Linthe, GermanyGSM19Sep 16, :29:571851/537 Suqin Zhang, ChinaG856AXSep 16, :25:381001/520 Haizhi Liu(26#), ChinaG856TSep 16, :12:201001/520 Haizhi Liu(27#), ChinaG856TSep 16, :19:241701/534 Table 1: Instruments and testing specifications Data collected by the test systems were directly compared to the corresponding samples collected by the GSM-90 Overhauser magnetometer at Changchun Observatory with 1Hz sampling rate. Data Table 2 presents the mean values and standard deviations for each system. Table 2: Pier difference (ΔF) results ParticipantsMean ΔFStandard Deviation ΔF H. J. Linthe, Germany2.77nT0.03nT Suqin Zhang, China2.77nT0.15nT Haizhi Liu(26#), China3.97nT0.15nT Haizhi Liu(27#), China3.10nT0.09nT Range in ΔF1.2nT NOFrequency/HzGSM19G856AXG856T(26#)G856T(27#) Average Table 7: Summary of Proton Magnetometer Frequency Test The pier difference (ΔF) was plotted for each system, see Figure 1. Figure 2: Second data curve of GSM-90 at Changchun Observatory in observation period Figure 1: Pie difference for each system Table 3: Proton Magnetometer Frequency Test of GSM19 Frequency Test #Frequency /HzNominal reading /nTReal reading /nTDerivation /nT 31, , , , , Average #Frequency /HzNominal reading /nTReal reading /nTDerivation /nT , , , , Average 0.31 #Frequency /HzNominal reading /nTReal reading /nTDerivation /nT 31, , , , , Average 0.33 #Frequency /HzNominal reading /nTReal reading /nTDerivation /nT 31, , , , , Average Table 4: Proton Magnetometer Frequency Test of G856AX Table 5: Proton Magnetometer Frequency Test of G856T(26#) Table 6: Proton Magnetometer Frequency Test of G856T(27#)