JPS61247922A - Small-sized portable measuring instrument - Google Patents

Abstract

PURPOSE:To check action of a total system including a reference signal by A/D converting output of the reference signal as input of a nonlinear circuit and obtaining digital output corresponding to the reference signal with a ratio of 1 to 1 and comparing it with a value corresponding to the initial reference signal. CONSTITUTION:A control circuit 105 sends a signal such as a multiplexer 102 selects a signal from a square circuit 107. As this result, the output squaring that from a reference signal circuit 103 as the input of an A/D converting circuit 104 is inputted and converted into a digital value and sent to the control circuit 105. The control circuit 105 calls the data corresponding to the initial reference signal stored in a storage circuit 108 and compares these with the digital value and decides, and in case the digital value is within a prescribed range of the data corresponding to the initial reference signal, a display of OK and in case the digital value is out of the prescribed range, the display of Error are displayed on a display device 106.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides an A/D converter for at least an analog quantity.
/Relates to a circuit system operation check in a small portable measuring instrument consisting of a D conversion circuit, a reference signal circuit, a storage circuit that stores data corresponding to an initial reference signal, a nonlinear circuit, and a control circuit that controls each part.

[Summary of the invention]

The present invention provides a small portable measuring instrument that includes at least an A/D conversion circuit, a reference signal circuit, a storage circuit that stores data corresponding to an initial reference signal, a nonlinear circuit, and a control circuit that controls each part. A/D converting the reference signal of the reference signal circuit or a signal proportional to the reference signal through a nonlinear circuit, and comparing the output with data corresponding to the initial reference signal stored in the storage circuit. By doing so,
This allows the operation of the entire system including the reference signal circuit to be checked.

[Prior art]

Conventionally, it has been common for measuring instruments to be periodically sent to the manufacturer for operational checks and calibration. Some measuring instruments have a self-diagnosis function and can be used to check operation independently, but the reference signal that serves as the basis for measurement must be checked using an external reference signal. .

FIG. 2 shows a block diagram of a conventional small portable measuring instrument. In the operation check state, this circuit operates as a reference signal circuit 1.
Reference signal from 03 (reference signal value: Vref)
is input to the A/D conversion circuit 104 and A/D converted, and the reference signal value Vre is displayed on the display device 106.
The value corresponding to f is displayed. Generally, in an A/D conversion circuit, if the input analog signal is Vin and the reference signal value is Vref *the conversion coefficient is 1 and the output is D, then
The output is expressed by the following formula.

1n D=□ ...-= (1-1) Vref Here, in the conventional circuit described above, in the operation check state, Vin = Vref, so from equation (1-1), D=. . The conversion coefficient is a constant determined by the constants of the components that make up the A/V conversion circuit, and if there is a change in the components for some reason, the conversion coefficient will also change, and this will appear as a change in the output. It becomes possible to check the circuit operation.

[Problems and objectives to be solved by the invention] However, in the conventional system, in equation (1-1), Vin = V
ref or Vin = @ Vref (m is a constant), then D = or D = km, and as can be seen from this relational expression, the term Vref disappears from the right side, so there is an abnormality in the reference signal circuit. ) Even if Vref changes, the output will be the normal value.

Therefore, the ability to check the operation with the conventional method is based on the normal operation of the reference signal circuit, and since it is not possible to check the operation of the reference signal, which is the most important element for a measuring instrument, it is not possible to check the operation using the operation check function. was insufficient.

Therefore, an object of the present invention is to provide a method that can check the operation of the entire system including the reference signal circuit.

[Means to solve the problem]

The output from the nonlinear circuit with the reference signal as input is A/
It is characterized by having a control circuit that performs D conversion and controls to compare it with a stored reference signal.

[Effect]

To describe the operation of the present invention, in the operation check state,
The reference signal is input to a nonlinear circuit, and its output is converted to A/D.
By converting, obtaining a digital output that corresponds one-to-one with the reference signal, and comparing it with a value corresponding to the initial reference signal, it is possible to check the operation of the entire system including the reference signal.

〔Example〕

FIG. 1 is a block diagram of a small portable measuring instrument according to an embodiment of the present invention. In this embodiment, a square circuit is used as a nonlinear circuit.

In a normal measurement state, the signal under test 101 is sent to the A/D conversion circuit 104 via the multiplexer 102, converted to a digital value based on the reference signal from the reference signal circuit 103, and displayed on the display device 106. Ru.

In the operation check state, the control circuit 105 outputs a signal that causes the 1 multiplexer 102 to select the signal from the 2 East circuit 107. As a result, the output from the reference signal circuit 103 is squared as an input to the A/D conversion circuit 104 and converted into a digital value.
Sent to 5.

The control circuit 105 calls the data corresponding to the initial reference signal stored in the storage circuit 108, compares it with the digital value described above, and determines whether the digital value is within a specified range of the data corresponding to the initial reference signal. If it is outside the OK1 specified range, an error message will be displayed on the display device 106.

Now, when the input is X, the output Y of the 2 East circuit 107 is:
When the conversion coefficient is A, it is expressed as y=Ax*. For example, if the reference signal value of the reference signal circuit 103 set by the manufacturer at the time of adjustment is Vref, and the conversion coefficient of the A/D conversion circuit 104 is k, then Equation (1-1) and 2 East circuit 107
Based on the conversion characteristics, the A/D conversion output Dref in the operation check state is expressed by the following equation.

Dref = kM = kAVref - (1-2
)Vref This Dref becomes data corresponding to the initial reference signal value Vref stored in the storage circuit 108.

Here, if we take the A/D conversion output when Vref increases by α for some reason, it will be displayed as ICrrOr if it is out of the specified range with respect to formula (1-2)%. The same applies to variations in the conversion coefficients, k, and h.

〔Effect of the invention〕

As explained above, according to the present invention, in the operation check state, after passing the reference signal through the squaring circuit, the A/D
The built-in reference signal circuit eliminates the need for an external reference signal and compares it with the reference signal value Vref at the time of adjustment by the manufacturer, which is stored in the memory circuit. It becomes possible to check the operation of the entire circuit.

In addition, in general, even the reference signal changes due to fluctuations in temperature and power supply voltage, but in the present invention, the memory circuit
Since it has data corresponding to the initial reference signal Vref, it is possible to easily correct the effects of temperature and power supply voltage fluctuations by taking the ratio with the current reference signal value Vref, making it possible to perform more accurate measurements. This has the effect of improving reliability and giving the user a sense of security.

[Brief explanation of the drawing]

Fig. 1...Block diagram of a system operation check circuit Fig. 2...Block diagram of a conventional system operation check circuit 101...Signal under test 102...・Multiplexer 105...Reference signal circuit 104...A/D conversion circuit 105...
...Control circuit 106...Display device 107...Square circuit 108...Memory circuit and above! 4◆31i・1ヱ111 Book l Figure 1/Bψnod 1! Figure 2

Claims (1)

[Claims] At least an A/D conversion circuit that A/D converts an analog quantity, a reference signal circuit that generates a reference signal for the A/D conversion circuit, a storage circuit that stores data corresponding to the reference signal, and a memory circuit that stores the reference signal. A small portable measurement device characterized by being composed of a nonlinear circuit as an input, a multiplexer that selects either the signal under test or the output from the nonlinear circuit, and a control circuit that controls each part and compares data. vessel.