GB1369985A - Magnetic resonance apparatus - Google Patents

Abstract

1369985 Nuclear magnetic resonance spectrometer NEWPORT INSTRUMENTS Ltd 18 Oct 1971 [16 Oct 1970] 49265/70 Heading G1N [Also in Division G3] In a nuclear magnetic resonance spectrometer having a polarizing field which is repeatedly scanned under the control of a scanning oscillator 36, field/frequency stabilization is achieved by detecting the positions of a resonance line in successive scans and generating an error signal if they are not uniformly spaced in time. Fig. 1 shows a N.M.R. spectrometer for continuous on-line analysis of a flow line or conveyed samples 22. Resonance pulses from a relaxed water sample 10 (or from the analysis sample itself, if suitable) are fed to a level detector 34 which produces a sharp negative pulse for each resonance pulse. Line centre detector 52 produces alternately inverted pulses, whose areas are related to the time of occurrence of respective resonance pulses, and which are integrated at 60. A sample and hold circuit 64 provides a D.C. output to update the value of the magnetic field every other scan of the scan oscillator. The correction signal may be applied to the scan coils or to separate correction coils. A track and hold circuit 40 limits the scanning signal to within set limits. A supplementary modulation may be applied, if desired, by closing switch 80. On first switching on, a field search and lock circuit 70 is operative until resonance pulses are received. The spectrometer may also include an A.F.C. system, shown in Fig. 9, in which the beat frequency between oscillators 114 and 26 is detected and used to generate a D.C. error signal which is applied to voltagedependant capacitance diodes (144, 145), Fig. 10 (not shown) in the tuning circuit of oscillator 114. On first switching on an out-of-lock detector 138 triggers a slow sweep generator 140 until phase lock occurs. Circuit diagrams of most of the blocks in Figs. 1 and 9 are given.