JPH0654594A - Measuring instrument with stepper motor - Google Patents

Abstract

PURPOSE:To reduce a rise-up time at starting when the instrument is used again, by providing a sleep mode for supplying a current enough for holding a rotational position in a measuring instrument, in which a home-position initialization step is carried out at the moment of power-on. CONSTITUTION:In a microcomputer spectral photometer, a pulse (step) motor (PM) is used for changing positions of a shifting element like a switching mirror while a spectroscope scans the wavelength. At the moment of power-on for the instrument, the pulse motor(PM) is rotated and a home-position initialization step for the pulse motor(PM) is carried out by using a home-position detecting mechanism. The spectral photometer includes a sleep mode in addition to a normal operation mode. The sleep mode is selected while the keyboard is operated or any operation is not carried out after the measurement. Moreover, a current enough for holding the rotational position is applied to the pulse motor(PM) so that the rotation of the pulse motor(PM) is checked.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring device such as a spectrophotometer which uses a step motor as a driving source for accurately controlling the position of a driven object.

[0002]

2. Description of the Related Art As an example of such a measuring apparatus, the structure and operation of a microcomputer-controlled spectrophotometer will be described with reference to FIG. The basic function of the spectrophotometer is to irradiate the sample in the transparent sample cell 17 with monochromatic light emitted from the spectroscope 11 and measure its absorbance with a photodetector 18 (photomul, etc.), The sample is analyzed by changing (scanning) the wavelength of the irradiated monochromatic light by the spectroscope 11 and detecting the absorbance for each wavelength. In order to generate the monochromatic light whose wavelength changes in this way, the spectrophotometer body is constructed as follows. A spectroscope 11 having a dispersive element 14 such as a diffraction grating in the center has a light source L1 for visible region, a light source L2 for ultraviolet region, a switching mirror 12 and an entrance slit 13 at the entrance side (left side in the drawing). An exit slit 15, a high-order light cut filter 16, a sample cell 17, and a photodetector 18 are arranged in this order on the exit side. The wavelength of the monochromatic light generated by the spectroscope 11 is basically scanned by changing the angle of the dispersion element 14. When the generated wavelength is in a wide range from the visible region to the ultraviolet region, it is not possible to deal with it with only one light source. Therefore, the switching mirror 12 allows the light from either the visible region light source L1 or the ultraviolet region light source L2 to enter the slit. The angle of the switching mirror 12 has to be switched so that it reflects on 13. When a diffraction grating is used as the dispersive element 14, the emitted light contains higher-order diffracted light of the second order or higher, so a filter 16 for cutting them is required on the exit side of the spectroscope 11. At present, there is no filter that covers the entire wavelength range, so it is necessary to use several types of filters depending on the wavelength. Therefore, the high-order light cut filter 16 also needs to be moved according to the generation wavelength. Further, in order to change the bandwidth of the monochromatic light emitted from the spectroscope 11, the entrance and exit slits 13 and 15 are provided.
Are prepared respectively, and any one of them is selected and inserted into the optical path.

When the spectroscope 11 scans the wavelength, the positions (angles) of these moving elements (the switching mirror 12, the dispersive element 14, and the high-order light cut filter 16) must be changed in relation to each other. Therefore, the driving of each of these moving elements is performed by pulse (step) motors 26, 28, 29 capable of controlling the rotational position, and together with the pulse motor 27 for switching the inlet and outlet slits 13, 15, all by a microcomputer. It is controlled uniformly. The microcomputer is CPU 34, ROM 35, RAM 3
6, a keyboard 38, a display 39, etc., and other pulse motors 26, 27, 28, 29.
A control unit I / O 31 serving as an interface with the operating unit, an operation unit I / O 37 serving as an interface with the keyboard 38, and a bus line 33 connecting these elements. The detection signal of the photodetector 18 is the amplifier 25 and A
The sample is analyzed by inputting it to the microcomputer via the / D converter 32 and analyzing the relationship between the scan wavelength and the absorbance.

[0004]

As described above, in order to perform accurate analysis with a spectrophotometer, it is necessary for each moving element to change while maintaining a fixed positional relationship, but a pulse motor for driving them is required. Although it is possible to control the relative rotational position, it does not originally have the origin of rotation, and the absolute rotational position immediately after the power is turned on is indefinite. Therefore, in order to operate the spectrophotometer correctly, the origin of the moving (rotating) position of each moving element is determined in advance, and each moving element (driven object) is placed at the origin position immediately after the power is turned on. It is necessary to perform absolute positioning of the pulse motor. Positioning of the pulse motor is performed, for example, by the method shown in FIG. Rotating shaft 51 of pulse motor PM
The light-shielding plate 52 extending in the lateral direction is fixed to the
A detector 53 is provided which is fixed to the main body side of the device and in which a light emitting portion and a light receiving portion are arranged so as to face each other. In such an arrangement,
The origin of the rotational position of the pulse motor PM is defined as the time point at which one end of the light shielding plate 52 starts blocking light between the light emitting portion and the light receiving portion of the detector 53. When the pulse motor PM is energized, the rotational positions of the rotary shaft 51 and the light shielding plate 52 are indefinite, so the CPU controlling the pulse motor PM first rotates the pulse motor PM in either direction, and the light shielding plate 5 is rotated.
The pulse motor PM is stopped when one end of 2 starts blocking light between the light emitting portion and the light receiving portion of the detector 53.
This is the initialization operation for detecting the origin of the pulse motor PM.

There is a problem that such an initialization operation for detecting the origin takes time as the accuracy of the origin position determination becomes higher. In particular, when high-precision positioning is required as in the dispersive element 14 of the spectrophotometer, a temporary origin is set with coarse accuracy, and then the origin is set with higher accuracy in the vicinity thereof (for example, ultraviolet light). There is also a case where a double origin positioning is performed, in which the bright line spectrum position of the region light source L2 is used as a high precision origin. In such a case, the initialization operation requires more time. For example, in the case of a spectrophotometer, it takes less than 1 minute to measure one sample (that is, to scan a wavelength within a predetermined range). On the other hand, an inversion phenomenon occurs in which the initialization operation takes several minutes.

The present invention has been made in order to solve such a problem, and it is possible to obtain the same power-saving effect as when the power source is completely cut off, and moreover, at the time of resuming the operation of the apparatus, such a time is required. A measuring device provided with a sleep mode which does not require such an initialization operation.

[0007]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention uses a step motor as a drive source for controlling the position of a driven object, and rotates the step motor when the power is turned on. In a measuring device that performs an initialization operation for detecting the origin of the rotational position of the step motor by the origin detection mechanism, a) a switch for switching between a normal operation mode and a sleep mode, and b) a drive in the normal operation mode in the sleep mode. The step motor drive circuit supplies a step motor with a current smaller than the current and sufficient for maintaining the rotational position.

[0008]

When the operator switches to the sleep mode with the switch a, the step motor drive circuit b supplies only a smaller amount of drive current to the step motor than in the normal operation mode. Therefore, power saving is achieved during the sleep mode in a measuring device that uses a large number of stepper motors. On the other hand, since the current for generating the torque sufficient to hold the rotational position is supplied, the rotational position of the step motor does not change during the sleep mode. Therefore, when using the measuring device again,
The initialization operation of the step motor is unnecessary, and the measurement can be started immediately. In sleep mode,
By not only reducing the drive current of the step motor, but also reducing or completely shutting off the power to other parts, the effect of power saving can be further enhanced.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A microcomputer-controlled spectrophotometer according to an embodiment of the present invention will be described with reference to FIGS. The basic configuration and operation of the spectrophotometer of this embodiment are the same as those of the conventional device (FIG. 3) described above, and therefore their description is omitted, and the control of each unit by the microcomputer will be described in detail with reference to FIG. In the spectrophotometer of this embodiment, the pulse motors 26,
In addition to 27, 28, and 29, lighting and extinction of both the light sources L1 and L2 for the visible range and the ultraviolet range are also controlled by the CPU 34 of the microcomputer via the control unit I / O 31. In this embodiment, each pulse motor 26, 27, 28, 29 (1 in FIG.
A commercially available pulse motor driver chip 41 is used to drive each pulse motor PM), and control pulse signals φ1 to φ4 from the control unit I / O 31 are given to the pulse motor driver 41. The pulse motor driver 41 supplies the drive current from the power source (+ V) to the pulse motor PM based on the control pulse signal from the control unit I / O 31.
Is supplied to each of the phases φ1 to φ4 to rotate by a predetermined number of steps (that is, a predetermined angle). The pulse motor PM is supplied with a drive current in order to maintain its rotational position (angle) not only during rotation but also during stop. In addition to the pulse motor driver 41 PD
A terminal is provided, and the drive current to the pulse motor PM is halved by setting this terminal to L (low) level.

An ON / OFF signal from the control unit I / O 31 for turning on / off the light sources L1 and L2 (of which only the visible light source L1 is shown in FIG. 1) is transmitted via the AND gate 42 to a transistor. Given to Tr1. A relay 43 is connected to the transistor Tr1 and AND
Relay 4 when the output of gate 42 becomes H (high)
3 operates to turn on the light sources L1 and L2.

The spectrophotometer of this embodiment is provided with a sleep mode in addition to the normal operation mode, and the operator performs a predetermined key operation on the keyboard 38 of the microcomputer or a predetermined program. (For example, when no operation is performed for a predetermined time after the measurement is completed), the spectrophotometer enters the sleep mode. At this time, the CPU 34 of the microcomputer is the SL of the control unit I / O 31.
Set the EEP terminal to L. The SLEEP terminal is directly connected to the PD (power down) terminal of the pulse motor driver 41, and in the sleep mode, the pulse motor PM is supplied with only half the current as in the normal operation. However, although the current is half, the pulse motor PM continues to be supplied with current, so the pulse motor PM is not completely free and its rotational position is maintained. That is, sufficient holding torque is provided to counter the torque that attempts to rotate the rotation shaft of the pulse motor PM. Therefore, while the spectrophotometer of this embodiment is in the sleep mode, the pulse motor PM
(26, 27, 28, 29) does not change its rotational position, and each moving element 12, 13, 1 driven by them is
The positions of 4, 15, and 16 also do not change.

The SLEEP signal of the control unit I / O 31 is also given to the AND gate 42. Therefore, in sleep mode
When the SLEEP terminal becomes L, the output of the AND gate 42 becomes L, and the light sources L1 and L2 are turned off by the relay 43.

In this embodiment, the SLEEP signal is further given to the transistor Tr2 via the inverter 45. The transistor Tr2 turns on the power supply to the light emitting diode 44.
In the sleep mode, the light emitting diode 44 is turned on to indicate that the power supply of the device is not completely cut off, but that the device is in the sleep mode.

When the operator wants to restart the measurement, the operator operates the keyboard 38 to perform an appropriate key operation (or the program is set to restart after a predetermined time), and the sleep mode is resumed. Return to normal operation mode. At this time, the CPU 34 controls the controller I / O.
The SLEEP terminal of 31 is set to H. As a result, the pulse motor PM is supplied with a normal amount of current (double that in the sleep mode), and each moving element is surely moved (rotated) by a predetermined amount (angle) according to the control pulse signals φ1 to φ4. Torque is applied to cause it. In addition, the light source L by the relay 43
1 and L2 are also turned on. As described above, since the rotational position (angle) of each pulse motor PM does not change during the sleep mode, the initialization operation for detecting the origin of the pulse motor PM after restart is unnecessary, and the normal operation from the sleep mode is not necessary. The measurement can be started immediately after switching to the mode. The light emitting diode 44 indicating the sleep mode is turned off.

Although the dedicated driver chip 41 is used for controlling the pulse motor PM in the above embodiment, the controller I / O
The circuit that halves the drive current according to the signal from 31 can be realized by various methods without using a dedicated chip. Further, only the light sources L1 and L2 are shown as the elements for which the power supply is cut off in the sleep mode, but in addition, the display 39 (stopping the power supply to the CRT, or turning off the backlight in the case of liquid crystal) is The power supply can be stopped to improve the power saving effect. For example, as shown in FIG. 4, in the case of a double beam type spectrophotometer in which chopping mirrors 19 and 21 are provided before and after the sample cell 17, the motor 30 for rotating the chopping mirror should be stopped in the sleep mode. It should be set to.

[0016]

In the device according to the present invention, when the device is not used for the time being, although it is planned to be reused after a relatively short time, the step motor is set to the sleep mode according to the present invention and the other main parts are transferred. By stopping the supply of the power source, the power consumption of the entire apparatus can be reduced while the rotational position of the step motor is fixed. When the apparatus is used again, the step motor is switched from the sleep mode according to the present invention to the normal operation mode and the power supply to other main parts is restarted. At this time,
Since the step motor does not perform the initialization operation for positioning the origin like when the power is turned on, the apparatus can be immediately used as usual. The present invention is particularly effective in a measuring device such as a spectrophotometer, which requires a long time for the initialization operation because high accuracy is required for positioning the driven object, but is similarly applied to other measuring devices. can do.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a control system of a microcomputer-controlled spectrophotometer that is an embodiment of the present invention.

FIG. 2 is a perspective view of a step motor having an origin detection mechanism.

FIG. 3 is a block diagram showing the configuration of a microcomputer-controlled spectrophotometer that is an embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a double beam type spectrophotometer.

[Explanation of symbols]

11 ... Spectrometer 12 ... Light source switching mirror L1 ... Visible light source L2 ... Ultraviolet light source 13 ... Entrance slit 14 ... Dispersion element 15 ... Exit slit 16 ... Higher-order light cut filter 17 ... Sample cell 18 ... Photodetector 26, 27 , 28, 29, PM ... Pulse (step) motor 31 ... Control unit I / O 41 ... Pulse motor driver chip 42 ... AND gate 43 ... Relay 44 ... Sleep mode display light emitting diode

Claims (1)

[Claims] 1. An initialization operation of using a step motor as a drive source for controlling the position of a driven object, rotating the step motor when the power is turned on, and detecting the origin of the rotational position of the step motor by an origin detection mechanism. A) a switch for switching between a normal operation mode and a sleep mode, and b) a step in which a current smaller than the drive current in the normal operation mode and sufficient for holding a rotational position is stepped in the sleep mode. A stepping motor drive circuit for supplying to a motor.