A comparative study of emissive probe techniques for vacuum space potential measurements

The major emissive probe techniques for the measurement of vacuum space potentials are compared to find the best emissive probe method in a vacuum. An overview of the inflection point method, the floating point method, and the vacuum current bias method is given, addressing how each method works in a vacuum. A comparison of the experimental data measured in a vacuum shows that the improved inflection point method has a best accuracy of 0.1 V in vacuum space potential measurements, while the original inflection point method can yield about half of a volt below the real space potential due to the inappropriate linear fitting in the method. Although the floating point method and the vacuum current bias method are convenient and rapid measurement techniques, the floating point method can only measure the vacuum potentials more than 1 V, and the space charge effect is not considered in the vacuum current bias method.