Research On The Control System Of Low Frequency Current Comparator

With the development of science and technology,realizing an arbitrary proportion of current comparators plays an important role in precision electromagnetic measurement.DCC,CCC,and modulation current comparators can achieve output of any current ratio,but DCC is limited to DC,and the limitations make AC signals and low-frequency signals unusable.The CCC uses SQID,superconducting shields,and superconducting coils.The operating conditions of superconducting components are very stringent and require liquid helium to be used at a temperature of 4.2k.In terms of current technology,the liquid helium cost is quite high,and the equipment of the low-temperature current comparator is inconvenient to move.Now,the comparison experiment of the resistance of the low-temperature current comparator can only be performed in the China Institute of Metrology Science.Difficult to get a wide range of promotion.This makes it difficult to further promote the CCC.The disadvantage of the magnetic modulation current comparator is that the technology for monitoring the ampoule balance is not perfect and it is prone to magnetic leakage.It can be seen that how to solve the problem of accurate and convenient utilization has become a bottleneck in the development of electromagnetic measurement technology.The condition of the resistance comparator bridge of the current comparator is that the measurement resistance of the main loop is equal to the voltage drop from the resistance of the measurement loop,that is,the ratio of the resistance to the current is inversely proportional.Currently,common comparators such as Gaolian's comparators and MI's comparators are relatively strict in terms of material requirements,and the manufacturers who can produce the materials they need are very few.Therefore,this kind of equipment is very expensive and it is difficult to get a wide range of promotion.In addition,the DC signal may be affected by low noise interference,DC drift,and Peltier effect thermal effects.Based on the above situation,we put forward a new idea,using low frequency AC measurement technology to improve the resolution and accuracy.The design and manufacture of control system current at room temperature based on a low frequency(0-20 Hz)than the new resistance measurement of AC bridge.The current comparator in the electrostatic and magnetic shielding installed a tunable detection coil cover,by correcting the amplitude and phase tuning coil,in order to achieve the balance of the bridge resistance.This paper constructs 100:1 current comparator,were tested in 0Hz,1Hz,2Hz,5Hz,10 Hz,20Hz low frequency,standard resistor primary side and secondary side generates a difference voltage drop,through experiment and data confirmed the stability of the relative uncertainty of less than 10-5.These measured data is the national unit of measurement in the resistance ratio measurement breakthrough,but also a kind of new resistance bridge type,easy to carry and popularize.