JPH0318889Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a zero and span adjustment circuit for performing zero adjustment and sensitivity (span) adjustment in various analyzers, indicating controllers, and the like.

As schematically shown in Figure 6, this type of zero and span adjustment circuit basically uses input voltage
A zero-adjustment voltage adding means X is provided for zero-adjusting the input voltage E _IN by adding a zero-adjustment voltage _e1 to E _IN ;
The voltage that is the sum of E _IN and zero adjustment voltage e ₁ (E _IN + e ₁ )
(multiply by β: 0≦β≦1) to output a span-adjusted voltage E _OUT .

Therefore, as such a zero and span adjustment circuit,
Conventionally, there are known devices configured to perform zero and span adjustments in an analog manner and devices configured to perform digital adjustments.

That is, FIG. 7 shows a zero and span adjustment circuit using an analog method. In the figure, E ₁ and E ₂ are reference power supply voltages, R ₁ is a zero adjustment volume, and these are the zero adjustment voltage addition circuits. constitutes means X;
In addition, R ₂ is a span adjustment volume,
This constitutes the voltage compression means Y for span adjustment. Now, set the variable terminal position of the zero adjustment volume _R1 to α (0 to 1), and the span adjustment volume
If the position of the variable terminal of R ₂ is β (0 to 1), the relationship between the input voltage E _IN and the output voltage E _OUT is E _OUT =
It can be expressed as {E _IN +E ₁ −(E ₁ +E ₂ )α}×β...(1).

From this equation (1), we can see that zero adjustment can be performed by operating the zero adjustment volume R ₁ to change α, and that by operating the span adjustment volume R ₂ and changing β, the span can be adjusted. It will be readily appreciated that adjustments can be made.

However, in this analog-based zero and span adjustment circuit according to the conventional configuration, (a) the adjustment accuracy mainly depends on each volume R ₁ , R ₂
Because the linearity, resolution, and stability of _each volume depend on _the (c) When adjusting zero and span, it is necessary to mechanically rotate each volume R ₁ and R ₂ , so zero and span can be adjusted by external control signals. There are various disadvantages such as difficulty in making adjustments.

On the other hand, Fig. 8 shows the digital zero,
A span adjustment circuit is shown, in which E is a reference power supply voltage, DA ₁ is a zero adjustment digital/analog converter, which constitutes the zero adjustment voltage adding means X, and DA ₂ is a span adjustment circuit. A digital/analog converter for adjustment constitutes the voltage compression means Y for span adjustment.

That is, the reference power supply voltage E is digitally controlled by the zero adjustment digital/analog converter DA ₁ , and the zero adjustment voltage obtained by this control is added to the input voltage E _IN . , zero adjustment is performed. Furthermore, the sum voltage of the zero adjustment voltage output from the zero adjustment digital/analog converter DA ₁ and the input voltage E _IN is added to the span adjustment digital/analog converter DA _2.
The output voltage E OUT is digitally compressed and controlled by the E OUT to adjust the span of the output voltage E _OUT . In addition, in the figure,
V _DD , -V _DD are applied voltages, D _Z1 , ..., D _ZN are zero control digital signals, and D _S1 , ..., D _SN are span control digital signals.

However, even in this conventional digital zero and span adjustment circuit, (d) each digital/analog converter DA ₁ and DA ₂ includes an active element, so the input voltage E _IN
(e) Therefore, in order to improve the adjustment accuracy, the linearity and resolution of each digital/analog converter DA ₁ and DA ₂ should be improved. (f) Each digital/analog converter DA ₁ , DA ₂
Depending on the elements used, only one polarity may be obtained, in which case the adjustment range will be narrow. (g) A separate power supply is required for each digital/analog converter DA ₁ and DA ₂ . There are various drawbacks such as .

Therefore, an object of the present invention is to develop and provide a new and useful zero and span adjustment circuit that can eliminate the various drawbacks of the conventional devices as described above.

〔Example〕

Hereinafter, a specific embodiment of the zero and span adjustment circuit according to the present invention will be described with reference to the drawings (FIGS. 1 to 5).

In FIG. 1, X is the input voltage E _IN (e.g.
The zero adjustment voltage adding means X performs zero adjustment for the input voltage _EIN by adding the zero adjustment voltage _e1 to the output voltage from an amplifier provided for the sensor. Two reference power supplies 1 and 2 between which the voltage is set to 0 (in this example, they are the same voltage E, but different voltages are also possible), and the voltage +E at both ends of the reference power supplies 1 and 2, A first switching element 3 alternately switches -E at a relatively high frequency, and the pulsed voltage obtained through the first switching element 3 is averaged and the averaged voltage is used as the zero adjustment voltage e. ₁ and a first averaging circuit 4 (in this example, a smoothing circuit consisting of a resistor R ₁ and a capacitor C ₁ ) which outputs an output to be added to the input voltage E _IN as 1.

Further, Y is span adjusted by compressing the sum voltage (E _IN + e ₁ ) of the input voltage E _IN and the zero adjustment voltage e ₁ added by the zero adjustment voltage adding means X. The voltage compression means for span adjustment that outputs the voltage E _OUT is shown, and the sum voltage (E _IN
+e ₁ ) is alternately switched at a relatively high frequency, and the pulsed voltage obtained through the second switching element 5 is compressed by averaging and the compressed voltage is spanned. It is composed of a second averaging circuit 6 (in this example, it is composed of a smoothing circuit consisting of a resistor R ₂ and a capacitor C ₂ ) which outputs the adjusted voltage.

It is preferable to use semiconductor type switching elements 3 and 5 as the switching elements 3 and 5. For example, these switching elements 3 and 5 can be used together with the circuit shown in FIG.
Can be configured with MOSIC.

Now, the first switching element 3 is
When the voltage is input to the on side for t _Z1 seconds and to the off side for t _Z2 seconds out of T _Z seconds, the voltage input to the first averaging circuit 4 changes as shown by the solid line in Fig. 2. The voltage averaged and output by this first averaging circuit 4 (that is,
The zero adjustment voltage ( _e1 ) added to the input voltage _EIN is shown by a dotted line in FIG. In other words, the output voltage e ₁ is: e ₁ = t _Z1 / T _Z × ETt _Z2 / T _Z × (-E) = t _Z1 − t _Z2 / T _Z × E = T _Z −2t _Z2 / T _Z × E = (1-2t _Z2 /T _Z ) × E ...(2) Therefore, in this equation (2), if t _Z2 /T _Z is varied in the range of 0 to 1, the first averaging circuit 4
It is clear that the output voltage e ₁ from varies in the range +E to -E. Therefore, it can be seen that zero adjustment is possible by controlling the on/off time ratio (duty ratio) of the first switching element 3 and setting t _Z2 /T _Z to an appropriate value.

In addition, when the second switching element 5 is operated in the same way as the first switching element 3 to turn on for t _S1 seconds and turn off for t _S2 seconds out of a period of T _S seconds, the second switching element 5 turns on. The voltage input to the averaging circuit 6 changes as shown by the solid line in FIG. 3, but the voltage E _OUT averaged and output by the second averaging circuit 6 is This is shown by the dotted line in Figure 3. In other words, the output voltage E _OUT from the second averaging circuit 6 is E _OUT = (E _IN + e ₁ ) x t _S1 /T _S +0 x t _S2 / T _S = (E _IN + e ₁ ) x t _S1 / It is clear that T _S is expressed by (3), and from this equation (3),
It can be seen that the output voltage E _OUT from the second averaging circuit 6 is obtained by compressing the above-mentioned zero-adjusted voltage (E _IN +e ₁ ) times t _S1 / _TS . Therefore, the second
Span adjustment can be performed by controlling the on/off time ratio (duty ratio) of the switching element 5 to control t _S1 /T _S to an appropriate value.

Here, if the relational expression for zero and span adjustment in the circuit shown in Fig. 1 is expressed in one equation, by substituting the above equation (2) into the above equation (3), E _OUT = {E _IN + (1 -2α')E}×β'...(4) (However, α'=t _Z2 /T _Z , β'=t _S1 /T _S ).

The switching operations of the switching elements 3 and 5 can also be controlled using, for example, a one-shot circuit, but in that case, the control is analog-based and the accuracy is not very good. Therefore, it is desirable to use a digital control circuit as illustrated in FIG.

In this figure 4, 7 is an oscillator, 8 is an I/N
9 is a frequency divider, 9 is a preset counter, and 10 is a flip-flop. In this circuit, the oscillation signal of the oscillator 7 is divided by I/N by the frequency divider 8,
The rise of the frequency-divided signal causes the preset counter 9 to be preset and the flip-flop 10 to be set. When the preset is performed, the preset counter 9 starts counting the oscillation signal from the oscillator 7. When the count value reaches the maximum value (preset value) of the preset counter 9, a carry-out signal is generated and the flip-flop 10 is reset. That is, by appropriately adjusting the preset value, the timing at which the carry-out signal is issued can be arbitrarily controlled, and thereby the set and reset times of the flip-flop 10 can be controlled. Therefore, if the switching operation of the switching element 3 or 5 is controlled by the signal appearing at the output terminal Q of the flip-flop 10, the above (2),
α′(t _Z2 /T _Z ) or β′(=t _S1
/
T _S ) can be controlled digitally. In addition, the fifth
The figure shows signal waveforms at various parts in the circuit of FIG. 4.

As is clear from the detailed description above, the zero and span adjustment circuit according to the present invention includes a zero adjustment voltage adding means that performs zero adjustment to the input voltage by adding a zero adjustment voltage to the input voltage. , a first switching element that alternately switches the voltage of the reference power supply and the voltage of the reference power supply having the opposite polarity to the reference power supply at a relatively high frequency; and a pulse-like signal obtained through the first switching element. and a first averaging circuit that averages the voltage of the switching element and outputs the averaged voltage at that time to be added to the input voltage as the zero adjustment voltage, and the on/off time ratio of the first switching element At the same time, the span adjustment voltage compression means is adjusted to a voltage of the sum of the input voltage and the zero adjustment voltage applied by the zero adjustment voltage adding means, and a reference point voltage. A second switching element alternately switches the voltage at a relatively high frequency, and the pulsed voltage obtained through this second switching element is compressed by averaging, and the compressed voltage at that time is subjected to span adjustment. and a second averaging circuit that outputs a voltage of , As can be understood from equation (4), zero and span adjustment is possible only by adjusting the on/off time ratio of the switching element. Therefore, in order to improve the adjustment accuracy, it is necessary to control the switching element. All that is required is to increase the resolution of the circuit that performs the process, and it is possible to obtain high accuracy with relatively low-cost components. In addition, since the adjustment accuracy depends only on the on/off time ratio of the switching element, and the cycle does not affect accuracy unless it is extremely long, an inexpensive oscillator can be used in the circuit that controls the switching element. , which is also advantageous in terms of cost. The switching element can be operated, for example, by a signal from a circuit as illustrated in FIG. , zero, and span adjustment can be easily controlled from the outside.The switching element and its control circuit can also be configured with a low-power C-MOSIC, so it can be operated by battery power. can be done. In addition, in conventional circuits using D/A converters, which do not require a separate dedicated power supply, the on-resistance of the control switch for digital control may be a problem, but the present circuit As can be understood from equations (2), (3), and (4) above, the resistance of the switching element has little effect on accuracy, unlike conventional circuits using D/A converters. Since the devised circuit does not use active elements, it has good linearity even when the input voltage is low, and no offset occurs. By configuring the switching elements with semiconductors, the lifespan can be extended. It is possible to overcome the drawbacks of conventional devices, such as the above, and to achieve extremely excellent practical effects.

[Brief explanation of the drawing]

1 to 5 are for explaining one embodiment of the present invention, and FIG. 1 is a circuit diagram showing a zero and span adjustment circuit according to the present invention, and FIG.
3 and 3 are respectively explanatory diagrams of the operation of the main parts thereof, and FIG. 4 is a circuit diagram showing an example of a circuit for operating the switching element in the embodiment circuit of FIG. 1, and FIG. FIG. 5 shows waveform diagrams at various parts of the circuit of FIG. 4. And the sixth
8 to 8 are for explaining the technical background of the present invention and conventional problems, and FIG. 6 is a schematic diagram showing the basic configuration of a general zero and span adjustment circuit, and FIG. 8 and 8 respectively show zero and span adjustment circuits of conventional configurations. X... Voltage addition means for zero adjustment, E _IN ... Input voltage, e ₁ ... Voltage for zero adjustment, Y... Voltage compression means for span adjustment, E _OUT ... Output voltage, 1, 2...
Reference power supply, 3... First switching element, 4...
first averaging circuit, 5... second switching element,
6...Second averaging circuit.

Claims (1)

[Scope of utility model registration request] A zero adjustment voltage adding means for performing zero adjustment on the input voltage by adding a zero adjustment voltage to the input voltage, and a voltage that has been span adjusted by compressing the sum of the input voltage and the zero adjustment voltage. In a zero and span adjustment circuit comprising a voltage compressing means for outputting a span adjustment, the voltage adding means for zero adjustment compares a voltage of a reference power source with a voltage of a reference power source having a polarity opposite to that of the reference power source. A first switching element that alternately switches at a high frequency, and a pulsed voltage obtained through this first switching element is averaged, and the averaged voltage at that time is used as the zero adjustment voltage to set the input voltage. and a first averaging circuit that outputs an output to add to the input voltage, and performs zero adjustment by adjusting the on/off time ratio of the first switching element. a second switching element that alternately switches the sum of the voltage and the zero adjustment voltage applied by the zero adjustment voltage adding means and the reference point voltage at a relatively high frequency; a second averaging circuit that compresses the pulsed voltage obtained through the element by averaging it and outputs the compressed voltage at that time as a voltage after span adjustment; A zero and span adjustment circuit characterized in that span adjustment is performed by adjusting an on/off time ratio.