JPH02262719A - A/d converter with offset control function - Google Patents

Abstract

PURPOSE:To prevent an offset from being remarkably broken down even when an ambient environment changes and an offset quantity changes by always performing offset control when a device is not operated. CONSTITUTION:Since an external variable power source 1 is separated judging from a circuit standpoint when an operation command OP is cut, the input of an amplifier 4 is set at O<v> via a dummy resistor 3. The output of the amplifier 4 goes to the offset value of the amplifier itself, and the output of an A/D converter 5 goes to the sum of the offset of the amplifier 4 and that of the A/D converter 5. The output of the A/D converter 5 is stored in an offset quantity preserving file 7 by a closed switch 6. Hereafter, a preserved value is used as the offset quantity.

Description

Detailed Description of the Invention [Industrial Application Field] This invention is applicable to A where offset is a problem, such as a speed command circuit of a speed control device where commands are given in analog quantities.
/D conversion device.

[Conventional technology]

The offset adjustment of the conventional A/D converter is performed by, for example, the second
This is done using the circuit shown in the figure.

That is, in the offset adjustment mode during a test run of the device, the output voltage of the external variable voltage (input analog voltage) source 1 is fixed at Ov, the input of the amplifier 4 is set to Ov, and the amplifier 4 is set to Ov.
The output is input to the A/D converter 5 and A/D converted. The output of the A/D converter 5 at that time is the sum of the amplifier offset and the offset of the A/D converter 5, and this value is saved in the offset file 7 as the offset amount of the A/D converter. This value is then used as the offset until the offset adjustment mode is entered again.

[Problem to be solved by the invention]

In the conventional offset adjustment of an A/D converter, there is a problem in that it is necessary to perform offset adjustment as an offset adjustment mode during a test run, and it has to be incorporated into the process as a special operation during the test run. In addition, the offset adjustment is only performed during the trial run and is not updated thereafter, so if the usage environment of the equipment differs from that during the trial run, for example, the ambient temperature of the equipment changes, the amplifier and A/D
Even if the offset amount changes due to temperature drift of the converter, the offset amount at the time of trial run is used, so the final A
There is also the problem that the /D conversion data has an offset.

[Means for solving the problem] An A/D conversion means that converts an input analog voltage amount into a predetermined voltage value and converts it into a corresponding digital amount, and when the input voltage of this A/D conversion means is zero. memory means for storing the output value of as an offset amount; and subtraction means for subtracting this offset amount from the output of the A/D conversion means;
In the A/D converter device with an offset adjustment function, the input side of the A/D conversion means includes a first switch means that is turned on and off depending on the presence or absence of an operation command for the device; A holding means is provided for holding the input of the A/D converting means at a reference voltage including zero when the switch means is off, and an operation command for the apparatus is provided between the A/D converting means and the memory means. The second switch is turned on and off depending on the presence or absence of
A switch means is provided so that off-safety flag l-ff1 can be updated every time the operation is stopped.

[Effect]

1st. Since the second switch means is linked to the operation signal of the device, when the device is not in operation (at rest), the A/
The input side of the D conversion means can be set to a reference voltage including zero, and the output of the A/D conversion means at that time can be stored in the memory means.

〔Example〕

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

Here, the externally variable type R1 is connected to a switch 2 linked to the operation command OP, and the output of the switch 2 is connected to a dummy resistor 3 and an amplifier 4 whose reference potential is Ov. Note that a reference voltage source may be used instead of the dummy resistor. The output of the amplifier 4 is connected to the A/D converter 5, the output of the A/D converter 50) is connected to a switch connected to the operation command OP, and the output of the switch 6 is connected to the offset amount storage file 7. Ru. On the other hand, the output of the A/D converter 5 is subtracted from the value of the offset amount storage file 7 by a subtracter 8, and becomes final data.

When the operation command OP is on, the switch 2 is closed, so the voltage of the external variable power supply 1 is converted into a digital quantity through the amplifier 4 and the A/D converter 5, and the contents of the offset quantity storage file 7 are calculated from that value. is subtracted by subtractor 8,
Create final data.

At this time, switch 6 is open, so it is off.

The contents of the amount storage file 7 are not updated.

On the other hand, when the operation command OP is turned off, the external variable power supply 1 is disconnected from the circuit by the switch 2.
The input of the amplifier 4 is set to Ov through the dummy resistor 3. The output of amplifier 4 becomes the offset value of the amplifier itself, and A/
The output of the D converter 5 is the sum of the offset of the amplifier 4 and the offset of the A/D converter 5. The output of the A/D converter 5 is stored in the offset amount storage file 7 through the closed switch 1. Thereafter, the saved value will be used as the offset amount.

〔Effect of the invention〕

According to this invention, offset adjustment is always performed when the device is not operating, so there is no need for a special mode during trial operation, and even if the surrounding environment changes and the offset amount changes, the offset adjustment is always performed. Since the offset adjustment is updated when the vehicle is stopped, it is possible to eliminate the possibility that the offset will be significantly distorted.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing a conventional example of an A/D converter device with an offset adjustment function. Code explanation 1 -- External variable power supply, 2, 6... Switch, 3...
- Dummy resistor, 4... Amplifier, 5... A/D converter, 7... Offset amount storage file, 8... Subtractor. Agent Patent Attorney Akio Namiki

Claims (1)

[Claims] 1) A/D conversion means for converting an input analog voltage amount into a predetermined voltage value and a corresponding digital amount; An A/D conversion device with an offset adjustment function, comprising: a memory means for storing an output value as an offset amount; and a subtraction means for subtracting the offset amount from the output of the A/D conversion means. The input side of the means includes a first switch means that is turned on and off depending on the presence or absence of an operation command for the device, and a reference voltage including zero that controls the input of the A/D conversion means when the first switch means is off. and a holding means for holding the device at the same time, and a second switch means is provided between the A/D conversion means and the memory means to turn on and off depending on the presence or absence of an operation command of the device, so that the operation is stopped. An A/D conversion device with an offset adjustment function, characterized in that the offset amount is updated every time the offset is adjusted.