JPH0455275B2 - - Google Patents

Description

[Detailed Description of the Invention] A. ``Object of the Invention'' [Industrial Application Field] The present invention relates to a time measuring device.
More specifically, the present invention relates to a time measuring device that can accurately measure even so-called fractional hours that are less than the period of a reference clock signal.

[Conventional technology]

Universal counters are widely used as devices for measuring the frequency, period, etc. of signals. In addition, not only counters like this, but also counters such as
Devices such as LSI testers use devices that measure the time from a certain point to a certain point in a signal to be measured.

Generally, the following principle is adopted to measure time with high precision. A clock signal with a period T ₀ is passed through a gate that is open during the measured time width Tx, and the number N of the clocks passing through is counted. And, NT ₀ is the time width. Although this method improves resolution as the clock frequency increases, there is actually a limit to the speed of the circuit elements. That is, this means cannot measure with a resolution greater than the clock period.

Strictly speaking, in the above method, Tx does not equal NT ₀ , but TxNT ₀ . This is typically Tx
This is because T ₀ is not divisible and there are small fractional times. This is shown in FIG. In FIG. 6, ΔT ₁ is the fractional time from the rising edge of Tx to the clock C ₀ that occurs immediately thereafter;
ΔT ₂ is the fractional time from the falling edge of Tx to the immediately following clock Cn. Then, the gate is opened during the period between clock signals _C0 and Cn (see d in FIG. 6), and the number of clocks passing through is counted. Assuming that the number of clocks in that period is N, the time width Tx is expressed by equation (1).

Tx=NT ₀ +ΔT ₁ −ΔT ₂ (1) Therefore, if we measure the fractional times ΔT ₁ and ΔT ₂ , we get
It can be seen from equation (1) that the time width Tx can be measured with a resolution greater than the clock period _T0 .

As a known means for measuring this fractional time ΔT, there is a time expansion method shown in FIG. This method uses an integrator to expand the fractional time using the charge or voltage stored in the capacitor as an intermediary, and measures it using a clock. FIG. 7 is a diagram showing a case where voltage is used as an intermediary. This uses two integrators, one of which charges the capacitor C ₁ with a current I ₁ during ΔT,
This output voltage is then held. Then the other integrator starts working and charges the capacitor C ₂ with the current I ₂ . If ΔT _E is taken as shown in Figure 7, ΔT _E = ・ΔT (2), and the expansion ratio is given by.

[Problem that the invention seeks to solve]

However, in the above-mentioned means, in order to eliminate the influence of the bias current and offset voltage of the integrator when measuring fractional times, it is necessary to introduce a reference clock and perform correction calculations. Furthermore,
In order to separately measure the fractional time at the start and stop of time width measurement, two sets of fractional time measuring circuits are required, which increases the cost of the apparatus. In addition, it takes a lot of time in principle to measure by enlarging the fractional time, and it also takes a considerable amount of time in total to perform correction calculations for each fractional time and calculate the period using these results. Become. Therefore, since it takes too much time to measure fractional times, there is a problem that high-speed repeated measurements or real-time measurements cannot be performed.

An object of the present invention is to provide a time measuring device that can perform high-speed repetitive measurements, real-time measurements, and high-resolution measurements.

B "Structure of the Invention" [Means for Solving the Problems] In order to solve the above problems, the present invention introduces a signal corresponding to the time width to be measured and a clock signal, and measures the time width corresponding to the so-called fractional time. The control circuit is equipped with a control circuit capable of outputting a fractional time pulse signal of the pulse width and a gating clock signal, a counter that counts the gating clock signal, and a processor that performs arithmetic processing. A device that measures a measured time width from a fractional time includes a time-voltage converter that introduces a pulse signal and outputs a signal whose voltage changes according to the pulse width of the signal; An AD converter that converts the output into a digital signal, and the control of the processor ensure that the initial value when measuring the stop fractional time pulse width is the same and opposite to the voltage when measuring the previous start fractional time pulse width. Generates a polar voltage with a time-voltage converter and outputs an analog signal to the time-voltage converter
It is equipped with a DA converter and a fractional time measuring circuit consisting of.

〔Example〕

Hereinafter, the present invention will be explained in detail using the drawings.

FIGS. 1 to 3 are diagrams showing configuration examples of a fractional time measuring circuit, which is a main part of the present invention. Further, FIG. 4 shows a block diagram of a time measuring device according to the present invention, and FIG. 5 is a time chart.

First, the entire timepiece measuring device according to the present invention will be explained using FIG. In the figure, reference numeral 10 denotes an input amplifier, which shapes the waveform of a signal having a time width to be measured introduced from the input terminal p1 into a rectangular wave as shown in FIG. 5(1). 20 is a control circuit, which includes an input amplifier 10 having a time width Tx to be measured;
Introducing the signal s1 and the clock signal s2 from
It is possible to output a fraction time pulse signal s3 having a pulse width corresponding to a so-called fraction time, and a gating clock signal s4. A counter 30 measures the number of times the gating clock signal s4 introduced from the control circuit 20 crosses a certain level. A clock generator 40 generates a clock signal s2 serving as a time reference with a period _t0 . Reference numeral 50 denotes a fractional time measuring circuit which has the function of introducing a signal having the same period as the fractional time pulse signal and the clock signal, and outputting a signal that is the basis for calculating the fractional time. The configuration of this fractional time measuring circuit 50 is illustrated in detail in FIGS. 1 to 3. 60
is a processor (for example, a microprocessor) which inputs signals from the counter 30 and the fractional time measuring circuit 50 and performs calculations to calculate the time width.

In FIG. 1, 1 is a time-voltage converter, which outputs a signal whose voltage changes corresponding to the pulse width of the introduced signal s3. Specifically, it consists of something like an integrator (not shown), and charges or discharges an integrating capacitor (not shown) with a constant current during the period of the applied pulse width signal, and calculates the pulse width. It can output a voltage signal proportional to (time).

3 is a buffer circuit that transmits the output voltage of the time-voltage converter 1 to the next stage.

5 is an AD converter that converts the output of the time-voltage converter 1 introduced via the buffer 3 into a digital signal. Since this AD converter 5 is required to be high-speed in the field related to the present invention, a flash type (fully parallel type) AD converter is usually used. The output s6 of the AD converter 5 is applied to the processor 60 as the output of the fractional time measuring circuit 50.

7 is a DA converter that generates an analog signal based on the signal s7 from the processor 60.

9 is a switch that applies the output signal of the DA converter 7 to the time-voltage converter 1 at an appropriate timing.

The operation of the circuits of FIGS. 1 and 4 configured as described above will be explained.

The signal having the time width to be measured, which is applied to the input terminal p1 in FIG. . The control circuit 20 generates a start fractional time pulse (pulse width ΔT ₁ ) and a stop fractional time pulse (pulse) at the rising edge and falling edge of the signal shown in FIG. width ΔT ₂ ).
The control circuit 20 also introduces the clock signal s2 from the clock generator 40, and as explained in FIG. 6, the clock signal C generated after the rising edge and falling edge of the signal under test (FIG. 6A) ₀
Gate circuit that is open during the period of and Cn (not shown)
The gating clock signal s4 passing through this gate circuit is output to the counter 30.

This gating clock signal s4 is counted by the counter 30 (count number N), and then processed by the processor 60 to calculate NT ₀ as shown in equation (1).

On the other hand, in the fraction time measuring circuit 50, as shown in FIG.
The fraction time pulse shown in > is introduced, and a signal proportional to the difference between the fraction times ΔT ₁ and ΔT ₂ is output by the following operation.

It is assumed that the voltage value of the time-voltage converter 1 is OV before the start fractional time pulse is applied, as shown in FIG. When the start fractional time pulse is applied, for example, an integration operation is performed during the period of the pulse width (ΔT ₁ ), and the voltage value at the end of the pulse becomes −ν ₁ .

Next, this voltage (-v ₁ ) is converted into a digital value by the AD converter 5 and read into the processor 60 as a signal s6. The processor 60 converts the signal s7 into DA so that a voltage (-v _{1 ) corresponding to the start fractional time pulse width (ΔT 1 )} and a voltage (v ₁ ) of opposite polarity are generated at the output of the time-voltage converter 1. Output to converter 7. As a result, (v ₁ ) generated in the DA converter 7 is applied to the time-voltage converter 1 via the switch 9. Therefore, time-voltage converter 1
Now, change the output to a voltage (-) as shown in Figure 5.
ν ₁ ) to (ν ₁ ).

In this state, a stop fractional time pulse is then applied to terminal p1. Time-voltage converter 1
Then, for example, the integrating capacitor is discharged with a constant current I, and a voltage ν ₁ −ν ₂ =νx proportional to the difference (ΔT ₁ −ΔT ₂ ) between two fractional times is obtained.

After these processes, the control circuit 20 generates a pulse having a pulse width of 2t ₀ , t 0 with a period of clock period t ₀ as a reference pulse, and applies it to the fractional time measuring circuit ₅₀ in FIG. Similar processing is performed, and the voltages ν ₁ , νx, νy are converted into digital values by the AD converter 5, read into the processor 60, and subjected to the following calculations.

ν ₁ = 1/C∫〓 ^T1 ₀ (I-i _B ) dt + Δν ₀ = 1/C (I-i _B ) ΔT ₁ + Δν ₀ (3) i _B : Bias current Δν ₀ : Offset voltage Therefore, νx= ν ₁ −ν ₂ =1/C(I−i _B )ΔT ₁ +Δν ₀ −{1/C(I−i _B )ΔT ₂ +Δν ₀ } =1/C(I−i _B )(ΔT ₁ −ΔT ₂ ) (4) Similarly, νy=1/C(I-i _B )(2t ₀ −t ₀ ) =1/C(I-i _B )t ₀ (5) νx/νy=ΔT ₁ −ΔT ₂ / Since t ₀ , ΔT ₁ −ΔT ₂ =t ₀ ·νx/νy (6) In this way, the term (ΔT ₁ −ΔT ₂ ) in equation (1) can be found. Further, the processor 60 can calculate the measured time width Tx by performing the calculation shown in equation (1) together with the signal from the counter 30. As described above, according to the configuration of the present invention, the influence of the bias current i _B , offset voltage Δν ₀ , integral constant current I, and integral capacitor C can be removed.

Note that when generating the voltage (v ₁ ) using the DA converter 7 and the switch 9, if this value is not accurately obtained, it will cause an error. Therefore, the offset value can be known and corrected by outputting it to the DA converter 7 at the start of processing, converting the value to a digital signal again by the AD converter 5, and reading the value.

FIG. 2 shows another example of the configuration of the fractional time measuring circuit 50, which is the essential part of the present invention. This figure differs from FIG. 1 in that a RAM 8 is newly provided and the procedure for generating voltage (v ₁ ) in this RAM 8 is stored in a table. That is, in FIG. 2, by creating a table including the above-mentioned correction processing and storing it, the voltage (ν ₁ ) can be generated and the conversion processing can be speeded up.

FIG. 3 shows another example of the configuration of the fractional time measuring circuit 50 which is the essential part of the present invention. In this figure, the difference from FIG. This converts the data into digital values using a successive approximation method. With this configuration, although AD conversion takes time, it becomes an inexpensive configuration.

C. “Effects of the Present Invention” As described above, according to the present invention, the following effects can be obtained.

Conventional devices require expansion time. Even if the operating speed of the AD converter becomes faster in the future than it is now, this time is a theoretically necessary time and there is no room for improvement.

On the other hand, in the device according to the present invention, fractional time is converted into voltage, which is directly AD converted, and then calculated by a processor etc.
At present, there are very high-speed AD converters such as flash type AD converters, and for this reason, the present invention can operate at higher speeds than conventional means in principle. Therefore, the time width can be measured at high speed and in real time.

In the present invention, by using the voltage corresponding to the start fractional time as the initial value for the next stop fractional time measurement, conventionally two sets of fractional time measuring circuits were required, but in the present invention, one set of fractional time measuring circuits is required. This can be done with a time measurement circuit.

In the past, fractional times (ΔT ₁ and ΔT ₂ ) were calculated separately to obtain ΔT ₁ −ΔT ₂ , but in the present invention, this can be done in one process as shown in equation (4), which is faster. processing can be performed. Also,
The influence of offset voltage can also be removed as shown in equation (6).

[Brief explanation of the drawing]

1 to 3 are diagrams showing an example of the configuration of a fractional time measuring circuit which is a main part of the present invention, FIG. 4 is a block diagram of a time measuring device according to the present invention, and FIG. 5 is a time chart. FIG. 6 is a diagram showing the general principle of measuring time width, and FIG. 7 is a diagram for explaining the operation of the time expansion method. 1... Time-voltage converter, 4... Comparator, 5... AD converter, 7... DA converter, 8...
...RAM, 9...Switch, 10...Input amplifier, 20...Control circuit, 30...Counter, 40
... Clock generator, 50 ... Fractional time measuring circuit, 60 ... Processor.

Claims (1)

[Claims] 1. Control capable of introducing a signal corresponding to the time width to be measured and a clock signal, and outputting a fraction time pulse signal with a pulse width corresponding to a so-called fraction time and a gating clock signal. In a device that includes a circuit, a counter that counts this gating clock signal, and a processor that performs arithmetic processing, and that measures the time width to be measured from the output of the counter and the so-called fractional time, a pulse signal is introduced, and this signal is A time-voltage converter that outputs a signal whose voltage changes according to the pulse width of the signal, an AD converter that converts the output of the time-voltage converter into a digital signal, and a stop fractional time pulse that is controlled by the processor. Outputs an analog signal to the time-voltage converter that causes the time-voltage converter to generate a voltage whose initial value when measuring the width is the same value as the voltage when measuring the previous start fractional time pulse width, and whose polarity is opposite. do
A time measuring device characterized by comprising a DA converter and a fractional time measuring circuit consisting of. 2. The time-voltage converter obtains a voltage value corresponding to the period of the clock signal, and this value is used to correct the bias current of the voltage value corresponding to the fractional time. The time measuring device according to item 1.