Sampling type measuring device

• US 5,170,115 A
• Filed: 05/06/1991
• Issued: 12/08/1992
• Est. Priority Date: 08/23/1990
• Status: Expired due to Fees

• Current Assignee: Yokogawa Electric Corporation
• Original Assignee: Yokogawa Electric Corporation
• Inventors: Goto, Eiichi, Hiraishi, Yukiyoshi, Kashiwabara, Yukio
• Primary Examiner(s): Karlsen, Ernest F.
• Application Number:
  US07/696,393
• Time in Patent Office: 582 Days
• Field of Search: 324/142, 324/141, 324/111, 364/483
• US Class Current: 324/142
• CPC Class Codes: G01R 21/133 by using digital technique

Abstract

A sampling type measuring device wherein an analog signal is measured by sampling the analog signal, converting each value obtained by sampling into digital form, and then processing the digital values. Exponential averaging calculation is performed directly on the digital values. Thus, no provision or time is needed to regulate the sampling period, thereby shortening the time required to perform measurement.

Claims

1. A sampling type measuring device for measuring an analog input signal by sampling the analog input signal at a certain timing, converting each value picked up by sampling into digital form, and processing the digital values, said device comprising

first analog to digital converter means for sampling an analog input voltage at said certain timing and coverting each value so sampled into digital form;

second analog to digital converter means for sampling an analog input current at said certain timing and converting each value so sampled into digital form;

multiplier means for multiplying together the output value of the first analog to digital converter means and the corresponding output value of the second analog to digital converter means to provide an instantaneous power value b(n), wherein the value b(n) corresponds to the n-th sampling; and

averaging means for providing a present mean value of power P(n) covering n samplings, said averaging means comprising

arithmetic means, and

memory means, wherein

said arithmetic means receives from said multiplier means the instantaneous power value b(n), and from said memory means a last mean value of power P(n-1), and calculates the present mean value of power P(n) from the two received values of b(n) and P(n-1) using the following equation

space="preserve" listing-type="equation">P(n)=P(n-1)+(1/G)·

{b(n)-P(n-1)},

wherein G is a present constant and 1/G>

>

1, and wherein said arithmetic means calculates the last mean value of power P(n-1) which covers the n-1 samplings and supplies it to said memory means.