JPS60188860A - Effective value meter - Google Patents

Abstract

PURPOSE:To obtain an effective value meter that can measure the effective value of an AC distorted wave in a short time by converting directly a measured signal to numerical value data, and determining the effective value by making aritmetic processing. CONSTITUTION:Principal part of the meter is constituted of an A/D converter 13, CPU14 that reads, stores and operates the numerical value data, etc. After starting measurement, the CPU14 makes initial setting, then sets frequency sweep data Dvi successively from i=1 to (n) and outputs. In the course of sweeping, the pulse signal of a maximum value detecting circuit 8 is detected, and when the pulse signal is present, corresponding sweep data are recorded successively in a memory. The sweep data recorded in the memory are taken out successively, set and outputted. Then, sample holding 11 is made twice continuously, and numerical value data DOi obtained by A/D conversion are recorded successively in a memory. An effective value Vrms for each frequency Fi is calculated from the numerical value data DOi recorded in the memory. The result is added, and the gain etc. of an amplifier 9 is corrected to obtain the effective value Vrms of the measured signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] [Background of the Invention] Traditional RMS meter times covering video installations have been long. The response time of commercially available products is 1.5 to 7 seconds (Model 340
0A: YHP, Model 93: Punto was long and inappropriate.

[Object of the invention J The purpose of the present invention is to reduce the effective value of AC strain waves in a short time [Summary of the invention]

[Embodiment of the invention] The ADC 114 that converts the output voltage value 2K·V (t i ) into numerical data: DIi is the DAC 3
, local maximum detection circuit 8, AMP9, pulse generator 10 and ADC13, and has an interface with the DAC3.
A function to provide sweep data to the maximum value detection circuit, a function to detect the pulse signal from okara, a function to provide gain data to the AMP 9 and determine the amplification degree of the AMP, a function to control CLK generation and stop of the pulse generator 10. , numerical data from the ADC 13. It is now assumed that each frequency component represents the effective value of the signal under measurement consisting of Fp+Fq and Fr.

After starting the measurement at time Ts, C1) U is the tape at #1.

Next, in #2, sweep data: Dri from 1 = = l to DAC3
converts the sweep data=D to voltage:ri and applies it to the VCO4. The VCO 4 generates an oscillation frequency fi proportional to the voltage Fi and applies it to the mixer 5. These relationships are shown in FIG.

On the other hand, after passing through LPF 2, test object No. 18 passes through mixer 5.
, and undergoes amplitude modulation by the output signal of the VCO 4, the output signal of the mixer 5 has a frequency distribution as shown in FIG. Therefore, if the intermediate frequency = lI゛0 is set equal to fi, the VCO 4 oscillation frequency is 8. By sweeping from fl to fn, the frequency components of the signal under measurement from DC to (fn-, fl) are converted to an intermediate frequency: FO and obtained as the output signal of the IP filter 6. When the offset signal component is converted into an intermediate frequency during the sweeping process, the Il'' filter 6
Since the output square amplitude temporarily increases, the detection circuit 7 and local maximum value detection circuit 8 can detect this moment. #3 is a routine for detecting the local maximum horizontal circuit 8 pulse signal for the above purpose.

In this embodiment, this is at times Tp, Tq, and rl+r, that is, when the sweep data is Dyp, 1) rq, and Drr. If there is no pulse signal in #3, jump to #5, and if there is a pulse signal, record the corresponding sweep data in Memo+JAi sequentially. In this embodiment, in #4, the sweep data: Dyp, Dyq and 1)? r are recorded in memories AI, A2 and A3, respectively.

#5 is a routine that determines the end of the sweep, and #5 is executed during the sweep.
Loop control is performed in steps 2 to #5. Immediately after time Te, the process exits to #6 at the end of the sweep. #6 is a routine provided to process pigeon lofts in which the signal component to be measured could not be detected during the sweep cycle.

As described above, each frequency component constituting the signal under test was analyzed in #1 to #6 and recorded in Memo 1JAi.

In #7, the sweep data recorded in the memo 1JAi in #4 is sequentially taken out, and set and output in the same manner as in #2. First, set and output the sweep data: Dyp at time Thl, and output the frequency component: Fp as the IF filter 6 output signal: V(t
). V (t) is multiplied by AMP9 and becomes 8/
) 111. #8 has s/H11 and AMP9
Al cage pressure value: After fixing K-V (t), ADC
Numerical data obtained by analog-to-digital conversion in step 13'
:Sequentially record DOi in memo 1JBi.

In this embodiment, sampling and holding are performed at times T1 and T2, and analog-to-digital conversion is performed at times Tll and 1゛21, respectively, and numerical data is stored in memos IJBI and B2:
1) Record 011 and DO21 and finish processing for frequency component: Fp. #9 is a routine for determining the end of the sweep, and during the sweep, a loop jttl'' is controlled in steps #7 to #9. Frequency component: 4 corresponding to 1 for Fq and Fr When the processing of #7 to 4 and 8 is completed, the process exits to #10.

#10 is the numerical data recorded in Memo 1JHi: DOi
Therefore, the effective value for each frequency component: r rms(F
i) appears for the first time. In #11, the effective value v rms (Fi) for each frequency component is added to obtain the effective value of the signal under measurement. Finally, in #12, corrections for the mixer 5 and the others of the AMP 9 are performed at the same time, and the final effective value of the signal under measurement: V nns is obtained.

This example targets the measurement of video band (DC to 6 MHz) signals, and has a CO oscillation frequency sweep range of 820 to 30 MHz.
MH211F filter passing frequency ef was set to 20MHz.

It is now possible to make cPU-led timing decisions when output signals are being read, making it possible to simplify, downsize, and lower the cost of the circuit. By adjusting the advantage of AMP9, we were able to effectively utilize the maximum human power range of ADC, 8.

〔Effect of the invention〕

According to the present invention, the signal to be measured is directly converted into numerical data using an ADC, and the effective value is calculated through arithmetic processing, so the sub-assembly time can be reduced compared to the conventional effective value calculation method using heat transfer. Monkey.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the embodiment, Figure 2 is a flowchart, Figure 3 is a time chart, Figure 4 is an explanatory diagram of the correspondence between sweep data and CO oscillation frequency, and Figure 5 is a diagram of the signal under measurement. FIG. 4 is an explanatory diagram of the frequency component f4 of the mixer output signal. 1... Signal to be measured 4... VCO 501, mixer 6... I k' filter 8... Maximum value detection circuit 9... AMPio -°° pulse generator 13... ADC14...・CPU $2 figure 3 figure (of

Claims (1)

[Claims] 1. A sweep signal generator that sweeps the oscillation frequency over a wide band;
A mixer that mixes the output No. 4B and the signal under test and converts each frequency component constituting the signal under test into an intermediate frequency, and a narrow band pass filter that selectively passes the intermediate frequency in the mixer output signal. and a maximum value detection circuit that detects when the DC conversion value of the IP filter output signal takes a maximum value and outputs a maximum value detection number, and a period that is twice the intermediate frequency (N22: integer) as described above. A pulse generator that oscillates at , sweep signal generation/stop control, maximum value detection circuit detection, analog/digital conversion start/stop control, converter output data reading, etc. The arithmetic processing shown in equation (1) is performed on the continuous numerical data Drl and DV2 obtained by continuous AD conversion of the IP filter output signal when the local maximum detection signal is turned on. The effective value of the corresponding medium In3 frequency: s
r rms i, 2π, =゛(However, N22: integer, i≧1: integer Furthermore, the signal under test obtained by one round of frequency sweep is Jm
Effective intermediate frequency value corresponding to each frequency component: t
' rms i, where m is a positive integer and m is the effective value of the signal to be measured: V rms It is characterized by being composed of a program and a computer with built-in hardware. Patented value meter.