JPH0219777A - Instrument for measuring linearity error of a/d converter - Google Patents

Abstract

PURPOSE:To remove an influence of a reference voltage drift by connecting a voltmeter between an input terminal in an A/D converter and each junction of resistors in a reference resistors-string having equivalent resistance values to designed values for the reference voltage by changing-over. CONSTITUTION:In the A/D converter 1, the resistors-string 13 designed to divide the reference voltage for quantizing is provided between the reference voltage terminals 3 and 4. The reference resistors-string 2 having an equivalent constitution and resistors to the resistors-string 13 is provided between the above terminals 3, 4 separately from the converter 1, and the voltmeter 6 capable to be connected by changing-over is provided between an analog input terminal 5 of the converter 1 and each terminal of the resistors. Then, the same fluctuation in a voltage comparator 8 generated by voltage drifts of reference voltage sources 9, 10 for low and high potentials, e.g. in a voltage 7 of the x-th stage, is also appeared in an outside voltage 15 of the x-th stage on the resistors-string 2. So, the influence of the drift is not appeared in the potential to be measured between the terminal 5 in a changing point of an output monitor part 17 and the resistor junction terminal corresponding to the voltage 15.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an A-D converter linearity error measuring device.

[Conventional technology]

The conventional A-D converter linearity error measuring device has a variable input voltage source 14 at the analog input terminal 5, and a quantized analog input voltage at the reference voltage terminals 3 and 4, as shown in the block diagram of FIG. Low potential and high potential reference voltage sources 9.10 are connected, respectively, for setting the upper and lower limits of the step. The voltmeter 19 has a plurality of digital output terminals 11.0, t configured to measure the input voltage between the analog input terminal 5 and ground potential. For each clock terminal 12, an output monitor section 17. A clock section 18 is connected. On the other hand, the analog signal and the reference voltage value of each step divided by the resistor array 13 are input into the A-D converter l, and a detection signal is output when the voltage of the analog signal reaches the reference voltage. and a digital converter 16 that judges the detection outputs of the plurality of voltage comparators 8 and outputs an encoded digital signal to an output monitor section 17. The linearity error of the A-D converter was calculated from the input voltage value measured by the voltmeter 19 at the point where the output sign changes and the design reference voltage value of the corresponding X-stage voltage 7.

[Problem to be solved by the invention]

In the conventional A-D converter linearity error measuring device described above, there is no relationship between the input voltage and the reference voltage, and the input voltage and the reference voltage are supplied from completely independent power sources. Therefore, if a drift occurs in the reference voltage source during measurement and the reference voltage to each voltage comparator 8 fluctuates, the measured input voltage will have an error equal to the change in the reference voltage, resulting in inaccurate measurement results. There is a drawback that it cannot be obtained. Particularly when measuring a high-precision A-D converter, this measurement error may make it impossible to measure the inherent error of the A-D converter. On the other hand, conventionally, as a means for performing accurate measurements, there is a method of suppressing the drift of the reference voltage to a value that can be ignored with respect to measurement accuracy, but there are limits to its implementation. In addition, in order to accurately measure whether the analog input voltage being measured is within the design tolerance, a precision voltmeter with a sufficiently large number of significant digits is required, which requires an expensive measuring device. There are also problems.

SUMMARY OF THE INVENTION An object of the present invention is to provide an A-D converter linearity error measuring device that can perform accurate measurements even when there are fluctuations in the reference power source and does not require an expensive precision voltmeter.

[Means to solve the problem]

The A-D converter linearity error measuring device of the present invention measures the linearity of an output digital signal with respect to changes in input voltage.
- In the D converter linearity error measuring device, a resistor string that is connected between reference voltage terminals of the A-D converter to be measured and that generates a reference voltage for quantization in the A-D converter. a reference resistor string having a resistance value equal to the design value of the reference resistor string; and a voltmeter connected alternately between each resistance connection point of the reference resistance string and the input terminal of the A-D converter; The potential difference between the input voltage at the time when the output digital signal of the A-reverse converter changes and the voltage at the corresponding resistor connection point generated by the reference resistor string is measured.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention.

In this embodiment, the A-D converter 1 is connected between the reference voltage terminals 3 and 4.
Connect the reference resistor array 2 with the same configuration as the resistor array 13 with the resistance value designed to divide the reference voltage in order to determine the quantized voltage, and connect the analog input terminal 5 and each resistor terminal of the reference resistor array 2. A voltmeter 6 is connected between them. In addition, the reference resistance string 2
The measurement point can be moved as appropriate. In addition, the conventional voltmeter 19
A voltmeter 6 is used instead. The configuration other than the above is the same as the conventional example. In the measuring device according to this embodiment, the reference voltage of the voltage comparator 8 caused by the voltage drift of the low potential and high potential reference voltage sources 9 and 10, for example,
The same fluctuation as that of the X-th stage voltage 7 appears in the X-th stage external voltage 15 of the external reference resistor array 2. Therefore, the potential to be measured between the analog input terminal 5 at the change point of the output monitor section 17 and the resistance connection terminal corresponding to the X-stage external voltage 15 is not affected by the drift of the reference voltage. Here, the measured value indicated by the voltmeter 6 at the X-th stage directly represents the deviation from the design voltage value at the X-th stage, which does not include fluctuations in the reference voltage source, that is, the error.

In this way, if there is only a deviation from the design value of each step voltage that generates the quantized voltage in the A-D converter, there is no need for the voltmeter 19 that measures the input voltage as in the past, and the design A-D without performing calculations between values and input measurements.
The linearity error of the converter can be directly measured.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to remove the influence of the drift of the reference voltage on the input voltage to be measured, and the measurement accuracy can be improved. In addition, since it measures the linearity error voltage compared to the conventional input voltmeter that measures between ground and ground, the value is much smaller, and it can be measured with a voltmeter with a small number of effective digits, making it possible to configure the measuring device at a low cost. It's also effective.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an embodiment of the present invention, and FIG. 2 is a diagram of a conventional A.
- It is a block diagram of a D converter linearity error measuring device. DESCRIPTION OF SYMBOLS 1...A-D converter, 2...Reference resistance string, 3.4.
...Reference voltage terminal, 5...Analog input terminal, 6...
・Voltmeter, 7... X-stage voltage, 8... Voltage comparator, 9... Low potential reference voltage source, 10... High potential reference voltage source, 11... Digital output terminal, 12...Tarlock terminal, 13...Resistance example, 14...Input power supply, 1
5...X-stage external voltage, 16...Digital converter, 17...Output monitor section, 18...Clock section,
1...voltmeter, 20...power supply.

Claims (1)

[Claims] In an A-D converter linearity error measuring device that measures the linearity of an output digital signal with respect to changes in input voltage, the device is connected between reference voltage terminals of the A-D converter to be measured. , a reference resistance string having a resistance value equal to the design value of a resistance string that generates a reference voltage for quantization in the A-D converter, and each resistance connection point of the reference resistance string and the A-D converter. a voltmeter connected to the input terminal of the A-D converter, the input voltage at the time when the output digital signal of the A-D converter changes and the corresponding resistance connection point generated by the reference resistor string; An A-D converter linearity error measuring device, characterized in that it measures a potential difference between voltages.