Measuring system

• US 4,240,149 A
• Filed: 02/16/1979
• Issued: 12/16/1980
• Est. Priority Date: 02/16/1979
• Status: Expired due to Term

• Current Assignee: Leeds & Northrup Co.
• Original Assignee: Leeds & Northrup Co.
• Inventors: Fletcher, David L., Stadlin, Walter O.
• Primary Examiner(s): Wise, Edward J.
• Application Number:
  US06/012,632
• Time in Patent Office: 669 Days
• Field of Search: 364/483, 324/94
• US Class Current: 702/60
• CPC Class Codes: G01R 19/02 Measuring effective values, i.e. root-mean-square values
• CPC Class Codes: G01R 21/133 by using digital technique

Abstract

There is provided a method for measuring a parameter whose value is calculable as an integral with time of a function of at least one variable so as to make possible the use of a microprocessor when measurements of such variables are desired. The variable is sampled periodically at a frequency asynchronous with the wave form which the variable follows and then there is periodically calculated the value of the function by summing the values for the function determined by the samples taken during the time between the calculations, thus determining the desired integral.

Claims

1. The method for measuring a parameter whose value is calculable as the integral with time of a function of at least one variable which has a value following a periodic wave form, comprising the steps of:

sampling the value of said variable periodically at a frequency asynchronous with said wave form; and

periodically calculating the value of the integral of the function in accordance with the sum of the values for the function determined in accordance with the values of all of the samples taken during the time between said calculations.

2. The method set forth in claim 1 in which the parameter is RMS voltage, the variable is the instantaneous voltage e for each sample, and the function of the variable is e².

3. The method set forth in claim 1 in which the parameter is RMS current, the variable is the instantaneous current i for each sample, and the function of the variable is i².

4. The method set forth in claim 1 in which the parameter is average power, the variables are e and i for each sample, and the function of the variables is ei.

5. The method set forth in claim 1 in which the parameter is energy for a period T, the variables are e and i for each sample, and the function of those variables is ei.