Question

To achieve optimum performance and to enable the relationship of change in resistance with the volume of the cell to hold good, it is recommended that the ratio of the aperture length to the diameter of the aperture should be __________

(a) 75:1

(b) 0.75:100

(c) 0.75:1

(d) 0.5:10

This question was posed to me in a job interview.

I would like to ask this question from Electrocardiography topic in section Biomedical Recorders of Biomedical Instrumentation

Answer 1

Correct option is (c) 0.75:1

The best explanation: To achieve optimum performance and to enable the relationship of change in resistance with volume of the cell to hold good, it is recommended that the ratio of the aperture length to the diameter of the aperture should be 0.75:1, i.e. for an orifice of 100 m diameter the length should be 75 m. The instrument based on the Coulter principle works most satisfactorily when the average diameter of the particles ranges between 2 to 40% of the diameter of the measuring hole.