JPS5856815B2 - multi-pen recorder - Google Patents

Description

[Detailed description of the invention] This invention relates to a multi-pen recorder.

As is well known, in a multi-pen recorder, it is necessary to compensate for the difference in the position of each pen and record it on the recording paper, and for this purpose, the input signal given as an analog quantity is converted to a digital quantity, and this is converted into a digital quantity. A method is used to store the value, retrieve it with a time delay corresponding to the pen difference, and convert it back into an analog quantity.

According to this method, each input signal system must be electrically isolated from each other, and an isolation amplifier is usually used.

This type of isolation amplifier uses two operational amplifiers and achieves isolation using a photocoupler.

In this case, there is no problem if each photocoupler is physically identical, but in reality it is extremely rare for both photocouplers to exhibit the same characteristics, so generally the input signal and output signal of the isolation amplifier There will be a difference between the two.

This makes it impossible to accurately record the input signal applied to the recorder on the recording paper.

This invention makes it possible to accurately record each input signal on recording paper when using an isolation amplifier that uses a photocoupler to electrically isolate each input signal from each other. The purpose is to

This invention provides a known calibration signal between input signal measurement periods, calculates and stores the output from the isolation amplifier corresponding to this calibration signal using a microcomputer, and In this case, the applied input signal is determined from the output of the isolation amplifier by referring to the previously stored value.

To explain the above-mentioned calibration operation in more detail, suppose that when a known calibration signal ri is applied to an isolation amplifier according to an instruction from a microcomputer, an output pi is output from the isolation amplifier.

The characteristics of the insulation amplifier at this time are expressed by the relationship pi=f(ri).

The microcomputer stores pi for each r i IC.

Next, assume that an input signal xi of the recorder is given, and that this input signal causes an output yi to be output from the isolation amplifier.

This output yl is input to the microcomputer,
Calculate pi that matches the output yi.

Then, ri corresponding to the obtained pi is calculated.

This value ri is nothing but a calibration value of the human input signal xi.

This can be recorded on recording paper.

Note that the characteristics of the photocoupler used to achieve the insulation properties of the isolation amplifier change over time depending on humidity, etc., so if you repeatedly calibrate it between the measurement intervals (sampling intervals) of the input signal, it will always be calibrated. Accurate recording becomes possible.

According to this calibration method, not only photocouplers but also
It goes without saying that it is also possible to correct for drift in the operational amplifier.

Embodiments of the invention will be described with reference to the drawings.

1A to 1N are input terminals to which an input signal xixxn to be recorded is applied, 2A to 2N are insulation amplification systems including a calibration signal generator 3, 4 is a multiplexer, 5 is an AD converter,
6 is a microcomputer, I is a DA converter, 8A~8
N is a sample hold circuit 9A to 9N are output terminals, 10
．． 11 is an output port of the microcomputer 6.

Since the insulation amplification systems 2A to 2N all have the same configuration, the details will be explained for the insulation amplification system 1A.

This consists of a switching circuit 12, an isolation amplifier 13, and the above-mentioned calibration signal generation section 3, and this calibration signal generation section 3 includes a multiplexer 14 to which a calibration signal ri-rm is applied;
Microcomputer 6 for selectively generating calibration signals
Photocoupler 1 receives calibration level setting signal CR from
5.

A photocoupler 16 receives a command signal CH from the microcomputer 6 indicating whether the switching circuit 12 accepts an input signal or a calibration signal from the multiplexer 14.

FIG. 2 shows an example of the insulation amplifier 13.

In the figure, 21.22 is an operational amplifier, 23.24 is a photocoupler consisting of a light emitting element (for example, a light emitting diode) 25.26 and a light receiving element (for example, a photodiode or phototransistor) 27, 28, and 29 to 31 are resistors. It is.

Such a circuit is already well known, and the photocoupler 23
．． 24 provides electrical insulation between each input terminal.

Regarding the operational amplifier 21, since the input impedance is generally larger than the resistance value of the resistor 29, the current 1 caused by the input signal flows only to the light receiving element 27 of the photocoupler 23.

On the other hand, a current 2 is applied to the light emitting element 25 of the photocoupler 23 so that the input difference becomes zero due to the tank neutrality of the operational amplifier.
This controls the current of the light receiving element 27.

That is, the photocoupler 23 turns the operational amplifier 21 into a negative feedback circuit.

The current (2) flowing through the light emitting element 25 also flows through the light emitting element 26 of the photocoupler 24.

Therefore, a current of 1 is applied to the light receiving element 28 of the photocoupler 24.
' flows.

Here, if both photocouplers 23 and 24 are physically identical, the currents I, , 11' should be equal and the output signal y should be equal to the input signal Since the couplers 23, 24 are very rarely identical, the two types of flow will never be equal, although they will not be extremely different.

This point has already been mentioned. In this sense, it can be said that the insulation amplifier used here has slight nonlinearity.

In other words, an insulation amplifier using a photocoupler for insulation as shown in the figure inevitably has nonlinearity.

FIG. 3 shows an example of a characteristic curve related to human output of the insulation amplifier 13.

When a known calibration signal rl-rm is applied to the isolation amplifier 13, the output signals p1 to . PM appears.

Output signal pi-pm corresponding to each comparison signal rl-rm
is stored in the microcomputer 6.

For example, the configuration shown in FIG. 4 can be used to generate the calibration signal.

In the figure, 32 is an electronic switch element (for example, a transistor switch), 33 is an operational amplifier, 34 is a low-pass filter, 35 is an output terminal, and 36 and 3γ are input resistors and feedback resistors (both having the same resistance value). do.

).

Here, the DC component of a pulse train with a constant period and constant amplitude is
Utilizing the fact that it is proportional to the pulse width, a pulse train having a pulse width equal to the calibration level of the calibration signal to be selected from the microcomputer 6 (this becomes the above-mentioned calibration level setting signal CR).

) is generated and insulated by the photocoupler 15, and then a constant DC voltage ro is turned on and off by the electronic switch element 32, thereby being reproduced by the operational amplifier 33 of a separate power supply system.

After that, the DC component is detected by the low-pass filter 34,
This generates a selected calibration signal ri.

The generation of this calibration signal generates m calibration signals ri=rm between the measurement of one input signal X and the start of measurement of the next input signal X, and the input signal is continuously However, the measurement is performed by sampling by switching the switching circuit 12 at a frequency sufficiently higher than the frequency band of the input signal, and taking this sample through the switching circuit 12.

That is, when the switching circuit 12 receives an input signal in accordance with the command signal CH, measurement of the input signal is performed, and when the switching circuit 12 receives a calibration signal in accordance with the command signal CH, a calibration operation is performed.

In the above configuration, a switching signal CH is applied from the microcomputer 6 to the photocoupler 16 of each insulation amplification system 1A to 1N via the output port 10, and each switching circuit 12 is switched to receive or accept each input signal.

As a result, the input signal passes through the isolation amplifier 13 and the multiplexer 4 and enters the AD converter 5, where it is converted into a digital quantity and input into the microcomputer 6.

The digital value of the input signal taken in is calibrated as described later, and then converted into an analog value by the DA converter 7. Based on the sample-hold control signal from the output port 11, the digital value of each sample-and-hold circuit 8A to 8N is It is held in a corresponding one of the circuits and releases its bold value to a corresponding one of the output terminals 9A to 9N.

After one input signal measurement is performed as described above,
A switching signal CH is outputted from the microcomputer 6 via the output port 10, thereby switching the switching circuit 12 into a state in which it can accept or accept the calibration signal.

Further, a calibration level setting signal CR is outputted from the microcomputer 6 via an output port 10, and thereby a calibration signal ri-
rm is sequentially output from the multiplexer 14.

This signal passes through the switching circuit 12, enters the isolation amplifier 13, and is further introduced into the microcomputer 6 via the multiplexer 4/AD converter 5.

The microcomputer 6 stores the output pl=pm of each isolation amplifier corresponding to each calibration signal.

The above calibration work is completed before sample measurement of the next input signal is started.

When the next input signal is sampled by switching the switching circuit 12, the input signal at that time is input to the microcomputer 6 via the isolation amplifier 13 in the same manner as described above.

The microcomputer 6 compares this human power X1 with the output pi ''-'pm stored during the previous calibration work,
Select the output (for example, pi) that matches the input xi.

From this, calculate the calibration signal ri when pi is output.

This calibration signal ri is nothing but the input xi before being input to the isolation amplifier 13.

This calibration signal ri is applied to the sample and hold circuit as described above and is output to the output terminal.

Note that the number of calibration levels described above depends on the nonlinearity of the isolation amplifier, but since the nonlinearity is mild, a few points may be sufficient.

Also, the points between pl=pm may be determined by a linear interpolation input/output relationship.

In the above description, the input signal is sampled by switching the switching circuit 12. However, the input signal may be sampled manually before being inputted to the switching circuit 12. In other words, the sample signal of the input signal is sampled by the switching circuit 12. 12 may be given.

The microcomputer 6 is not used only for the above-mentioned storage and calibration, but may also be used for storage for pen difference correction and delay, as mentioned at the beginning.

As detailed above, according to the present invention, when an insulation amplifier is used to electrically insulate each channel in a multi-pen recorder, erroneous measurements due to variations in the characteristics of the insulation amplifier can be reliably prevented. It has the effect of preventing

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a circuit diagram of an isolation amplifier, Fig. 3 is a characteristic curve diagram showing the input/output relationship of the isolation amplifier, and Fig. 4 is a calibration diagram. FIG. 3 is a circuit diagram for signal generation. 1A to 1N...Input terminal, 3...Calibration signal generator, 6...Microcomputer, 1
3...Isolation amplifier.

Claims (1)

[Claims] 1 An isolation amplifier with nonlinearity using a photocoupler,
A calibration signal generation section that generates a plurality of calibration signals with different levels, and a switching circuit that alternately repeats the calibration signal and the input signal to be recorded and inputs it to the isolation amplifier, are connected to each channel of each pen. a microcomputer that calculates and stores the relationship between the calibration signal and the output of the isolation amplifier when the calibration signal is input; A multi-pen recorder that outputs, as an output signal, a calibration signal that produces an output equal to the output of an isolation amplifier.