Coded data generation or conversion – Converter calibration or testing
Reexamination Certificate
2002-04-22
2003-11-18
Williams, Howard L. (Department: 2819)
Coded data generation or conversion
Converter calibration or testing
C341S145000, C324S607000
Reexamination Certificate
active
06650262
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an AD converter evaluation apparatus and in particular to a high-resolution AD converter evaluation apparatus for automatically measuring an AD converter to be measured using a computer, etc.
2. Description of the Related Art
FIG. 4
shows an AD converter evaluation apparatus in a related art. The AD converter evaluation apparatus will be discussed.
An AD converter evaluation apparatus
40
in the related art automatically measures an AD converter
50
to be measured using a computer
43
, etc. The AD converter evaluation apparatus
40
has a programmable power supply
41
, a controller
42
connected to the computer
43
by a PCI bus
45
, a buffer amplifier
49
, and the AD converter
50
, as shown in FIG.
4
.
The controller
42
has a GPIB interface
47
connected to the programmable power supply
41
by a GPIB cable
44
and an I/O interface
46
connected to the AD converter
50
by an AD converter conversion start signal line
48
.
Thus, output of the programmable power supply
41
is connected to the buffer amplifier
49
, an output signal of the buffer amplifier
49
is input to the AD converter
50
, and an AD converter conversion start signal is transmitted from the controller
42
for controlling and evaluating the AD converter
50
.
To evaluate the AD converter, the precision of the signal source need be higher precision about four bits than the number of output bits of the AD converter to be measured.
Thus, it is very difficult to provide a programmable power supply to evaluate an AD converter having a resolution of 12 bits or more.
For example, to measure an AD converter with output 0 to 5 V having a resolution of 16 bits, it becomes necessary to set a voltage finer than 4.75 &mgr;V.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide an AD converter evaluation apparatus that can produce programmable power supply having a high resolution required for measuring an AD converter to be measured.
According to the present invention, there is provided an AD converter evaluation apparatus for evaluating an AD converter, including:
a first programmable power supply for applying a first voltage;
a second programmable power supply for applying a second voltage;
an attenuator circuit for attenuating the second voltage output from the second programmable power supply to generate a third voltage;
an addition circuit for adding the third voltage of the attenuator circuit to the first voltage output from the first programmable power supply to generate a fourth voltage; and
a digital multimeter for measuring the first voltage of the first programmable power supply and the second voltage of the second programmable power supply,
wherein the fourth voltage of the addition circuit is input to the AD converter.
Accordingly, the output of one programmable power supply is attenuated by the attenuator circuit and the result and the output of the other programmable power supply are added together, whereby higher-resolution programmable power supply can be realized and the object can be accomplished.
The AD converter evaluation apparatus further includes:
a computer; and
a controller connected to the computer and connected through an interface section to the digital multimeter and the AD converter, the controller for controlling the AD converter.
Accordingly, the AD converter evaluation apparatus can be automatically controlled by the computer.
In the AD converter evaluation apparatus, the digital multimeter measures the fourth voltage of the addition circuit and outputs an actual measured voltage of the fourth voltage to the computer. The computer compares the actual measured voltage with an expected voltage of the fourth voltage programmed in the computer in advance to calculate a difference between the actual measured voltage and the expected voltage. The computer resets the first and second voltages of the first and second programmable power supplies, thereby to cancel out an error component thereof. The reset first and second voltages of the first and second programmable power supplies are input to the AD converter. The controller transmits an AD converter conversion start signal to start conversion operation of the AD converter.
Accordingly, the actual measurement value input to the digital multimeter is compared with the expected value programmed in the computer in advance, the difference between the actual measurement value and the expected value is found, and the values of the programmable power supplies are again set, whereby the measurement error can be canceled out and output voltage close to the precision of the digital multimeter can be provided.
REFERENCES:
patent: 3648175 (1972-03-01), Barnard et al.
patent: 5138267 (1992-08-01), Komagata et al.
patent: 5977774 (1999-11-01), Noble et al.
patent: 6131074 (2000-10-01), Kawai
patent: 6498507 (2002-12-01), Meany et al.
Ando Electric Co. Ltd.
Fish & Richardson P.C.
Williams Howard L.
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