Analog-digital converter

Claim 2

An A-D conversion method using a V-F converter for converting an analog voltage signal into an output pulse signal having a frequency corresponding to the voltage level of the analog voltage signal, and a counter for counting the pulses of the output pulse signal from the V-F converter, said method comprising the steps of: supplying a reference analog voltage signal of a reference voltage level V R to the V-F converter for a first predetermined time period T 1 to generate a first output pulse signal having first output pulses of frequency F R to be counted by the counter, the counter storing a value N=F R ×T 1 at the end of said first predetermined time period; resetting the counter; supplying an analog voltage signal of an unknown voltage level V U to the V-F converter for a second predetermined time period T 2 to generate a second output pulse signal having second output pulses of frequency F U to be counted by the counter, the counter storing a value M=F U ×T 2 at the end of said second predetermined time period; wherein said second predetermined time period T 2 is so chosen as to satisfy the equation ##EQU12## so that the contents M of the counter, after said analog voltage signal of unknown voltage level has been supplied to the V-F converter for said second predetermined time period T 2 denotes a digital representation of the unknown voltage level V U of said analog voltage signal of an unknown voltage level: ##EQU13## where "n" denotes the number of converted pulses.

Claim 3

An A-D conversion method using a V-F converter for converting an analog voltage signal to an output pulse signal having a frequency corresponding to the voltage level of the analog voltage signal, and an up-down counter for counting the pulses of the output pulse signal from the V-F converter, said method comprising the steps of: supplying a first reference analog voltage signal of a first voltage level V R1 to the V-F converter for a first predetermined time period T 1 to generate a first output pulse signal having first output pulses of frequency F R1 to be counted in a first counting mode by the up-down counter; supplying a second reference analog voltage signal of a second voltage level V R2 to the V-F converter for said first predetermine time period T 1 to generate a second output pulse signal having second output pulses of frequency F R2 to be counted in a second counting mode by the up-down counter, the up-down counter storing a value N=(F R1 -F R2 ) xT 1 at the end of said second first predetermined time period; resetting the up-down counter; supplying said first reference analog voltage signal of the first voltage level V R1 to the V-F converter for a second predetermined time period T 2 to generate the first output pulse signal having first output pulses of frequency F R1 to be counted in the first counting mode by the up-down counter; and supplying an analog voltage signal of an unknown voltage level V U to the V-F converter for said second predetermined time period T 2 to generate a third output pulse signal having third output pulses of frequency F R3 to be counted in the second counting mode by the up-down counter, the up-down counter storing a value M=(F R1 -F RU )×T 2 at the end of said second predetermined time period; wherein said second predetermined time period T 2 is so chosen as to satisfy the equation ##EQU14## so that the contents M of the up-down counter, after said analog voltage signal of said unknown voltage level has been supplied to the V-F converter for said second predetermined time period T 2 comprises a digital representation of the voltage level V U of said unknown voltage level; where "n" denotes the number of converted pulses.

Claim 4

An A-D conversion method using a V-F converter for converting an analog voltage signal to an output pulse signal having a frequency corresponding to the voltage level of the analog voltage signal, and an up-down counter for counting the pulses of the output pulse signal from the V-F converter, said method comprising the steps of: supplying a first reference analog voltage signal of a first voltage level V R1 to the V-F converter for a first predetermined time period T 1 to generate a first output pulse signal having first output pulses of frequency F R1 to be counted in a first counting mode by the up-down counter; supplying a second reference analog voltage signal of a second voltage level V R2 to the V-F converter for said first predetermine time period T 1 to generate a second output pulse signal having second output pulses of frequency F R2 to be counted in a second counting mode by the up-down counter, the up-down counter storing a value N=(F R1 -F R2 ) xT 1 at the end of said second first predetermined time period; resetting the up-down counter; supplying said first reference analog voltage signal of the first voltage level V R1 to the V-F converter for a second predetermined time period T 2 to generate the first output pulse signal having first output pulses of frequency F R1 to be counted in the first counting mode by the up-down counter; and supplying an analog voltage signal of an unknown voltage level V U to the V-F converter for said second predetermined time period T 2 to generate a third output pulse signal having third output pulses of frequency F R3 to be counted in the second counting mode by the up-down counter, the up-down counter storing a value M=(F R1 -F RU )×T 2 at the end of said second predetermined time period; wherein said second predetermined time period T 2 is so chosen as to satisfy the equation ##EQU14## so that the contents M of the up-down counter, after said analog voltage signal of said unknown voltage level has been supplied to the V-F converter for said second predetermined time period T 2 comprises a digital representation of the voltage level V U of said unknown voltage level; where "n" denotes the number of converted pulses.

Claim 5

An A-D conversion method according to claim 2, wherein said first counting mode is a down counting mode and said second counting mode is an up counting mode.

Claim 6

An A-D conversion method according to claim 2, wherein said first counting mode is an up counting mode and said second counting mode is a down counting mode.