CN2079320U - High precision controller constant temp. - Google Patents

Abstract

The utility model provides a high precision constant temperature controller, which is mainly composed of a constant temperature groove, a refrigeration system, a heating system and a temperature control circuit, wherein, the temperature control circuit uses a bridge type sensing line, a preselected setting line, a converting circuit and a photoelectric isolation circuit; preselected temperature and the temperature of the constant temperature groove are both displayed by a digital temperature display. Because the converting circuit of strong anti-interference and the photoelectric isolation circuit are used, temperature control precision reaches as high as positive and negative 0.025DEG. The range of controllable constant temperature is wide and can reach 5 DEG to 55DEG. Relatively, the utility model has the advantages of simple circuit and low cost.

Description

High precision controller constant temp.

The utility model relates to thermostatic bath or the constant temperature bath of liquid device that a kind of high precision constant temperature device, particularly High Accuracy Control make water or other neutral liquid.

The present high-accuracy and constant temperature control circuit that uses, what often use is PID control circuit mode.Two or three control circuit modes of employing often of the lower precision of control.The PID control circuit, because the integration rule, if an extraneous interference signal is arranged, output will rest on new position and non-homing, promptly the antijamming capability of PID circuit has weak point, and circuit itself, and the problem that interferes with each other is also arranged.The existence of these problems makes the PID circuit reach comparatively difficulty of very high control accuracy.For overcoming these difficulties, use more complicated and the higher circuit of cost with regard to need.Simultaneously, the parameter regulation of PID circuit is not at random, if make the temperature control scope very big, precision is high again, and is just very difficult.Though in order to make the randomization of PID circuit conditioning, can use microcomputer, the cost of PID control is improved greatly.Adopt two or three-position type adjusting, though circuit is comparatively simple, cost is lower, and it is impossible reaching high precision.

The purpose of this utility model just provides a kind of strong interference immunity, the control temperature range is very big, and control accuracy is very high, and compare price with existing high-accuracy and constant temperature control circuit low, the simple high-accuracy and constant temperature control device of circuit.Temperature-controlled precision of the present utility model is ± 0.025 ℃, and (in fact its temperature-controlled precision can be higher) temperature control scope is between 5～55 ℃, can have a high regard for meaning selected by the preliminary election fixation.

The utility model is achieved in that the semiconductor temperature sensor of selecting stability height, linearity, good reproducibility for use is as sensor element.Form bridge circuit by sensing element and resistance, setting apparatus (accurate electric wire is around electric position).Setting apparatus is by the setting value temperature of predetermined constant temperature and can be shown by the digital temperature display by the temperature value that a switch will set constant temperature.When if the temperature sensor measured temperature is design temperature numerical value just, bridge circuit is output as zero; When departing from constant temperature and set numerical value as measured temperature numerical value, then one of bridge circuit output and the linear signal voltage of temperature variation.This signal amplifies through differential amplifier circuit and two-stage direct current and enters a change-over circuit, through after the change-over circuit, output be exactly that a frequency is certain, rectangular pulse signal that pulse width and input signal are inversely proportional to.Use this rect.p. to go to control the complete conducting of silicon controlled or end fully by photoisolator.And controllable silicon is serially connected in the heated at constant temperature system.Thereby reach temperature controlling.Owing to use the temperature-sensing element and the bridge type magnetic sensor circuit of high stability, adopt antinoise, low drift, high input impedance (to reach 10 simultaneously ⁹The difference channel that field effect transistor Ω) is formed has been avoided the influence of control circuit to the bridge-type sense line.Take difference channel, bridge circuit to power, use accurate voltage stabilizer to supply with the bridge circuit power supply separately again, thereby suppressed power-supply fluctuation and room temperature changes the particularly influence of bridge circuit of prestage.These series of measures are crucial to guaranteeing that temperature-controlled precision has play a part.Change-over circuit then is that change-over circuit has some variations when bridge circuit, difference channel or direct current amplifier have the input of interference, in case but interference eliminated, change-over circuit can be got back to original position automatically, has therefore strengthened the antijamming capability of entire circuit.The photoisolator role is to have cut off the interference of temperature control heating system to temperature-adjusting circuit.Simultaneously, owing to make and use up every device, the controlled all-pass of controllable silicon is led or full cut-off, and the variation of admittance, off period is the temperature variation signal that provides according to temperature sensor and according to by the size of the big or small determined triangular wave frequency of the thermal inertia of temperature control device.Like this, just can enlarge the scope of controllable temperature greatly, and be applicable to the temperature control of different thermodynamic thermostat.The utility model temperature control scope reaches 5～55 ℃; In order to guarantee that calibration cell in work each point temperature unanimity, has adopted permanent steady conductor refrigeration cooling.

The high-accuracy and constant temperature control device that the utility model provides owing to adopted simply a series of but utmost point effective circuit, make temperature-controlled precision reach ± 0.025 ℃; Owing to adopted special change-over circuit and photoisolator, improved antijamming capability greatly, and made the temperature control scope very big, reach 5～55 ℃, can set the temperature control value at random.Prior art such as PID regulating circuit have reduced cost relatively, can satisfy some particular matters such as beer alcoholic strength fully and measure desired thermometric condition.

Below in conjunction with accompanying drawing and an embodiment the utility model is done more detailed narration.

Accompanying drawing 1 is a high-accuracy and constant temperature control device schematic appearance.

Accompanying drawing 2 is high-accuracy and constant temperature control device control circuit block schemes;

Accompanying drawing 3 is sensor bridge circuit circuit diagrams;

Accompanying drawing 4 is change-over circuit synoptic diagram and input and output waveform synoptic diagram;

Accompanying drawing 5 is that light is every device and heating system circuit and respective waveforms synoptic diagram;

Accompanying drawing 1 is a high-accuracy and constant temperature control device schematic appearance.1-cabinet wherein; The inside is equipped with wiring boards such as whole operation circuits, heating system; 2-calibration cell, the inside can be adorned water or other neutral liquid; 3-constant temperature notch, perfusion fluid or place the mouth of other measured objects in the groove has a lid it can be built; The 4-rack, stirring motor etc. is equipped with in the inside, and digital temperature display 6 is arranged on its panel, refrigeration heating combined switch 5; On the panel of cabinet 1, have: the coarse adjustment of 8-valuator; 7-valuator fine setting, with these two turn-knobs can the required constant temperature of definite value value, the numerical value of definite value is shown by digital temperature display (6).The 9-preselection switch; 10-warning turn-knob; The 12-temperature control shows.It is a two-way light emitting diode, whether shows temperature control; The 11-alarm indication is a light emitting diode.

Accompanying drawing 2 is control circuit block schemes of high-accuracy and constant temperature control device.The calibration cell of mentioning in the 2-accompanying drawing 1 wherein, the 13-semiconductor cooler is in order to make calibration cell in work each point temperature unanimity; The 14-heater strip has 4 groups; The 15-semiconductor temperature sensor; The 16-stirrer; 17-fixation device; The 18-difference channel; 19-digital temperature display; The 20-dc amplification circuit; The 21-change-over circuit; The two-way light emitting diode of 22-; The 23-photoisolator; The 24-controllable silicon; The 25-preselection switch;

As required, need at first to determine the numerical value of constant temperature, make numerical value by fixation device (17), the size of this numerical value can be shown by digital temperature display (19) by preselection switch (25).When the temperature of calibration cell (2) equates with the numerical value of fixation constant temperature,, there is not signal output by the bridge circuit that semiconductor transducer (15) etc. is formed; When the temperature of calibration cell (2) slightly changes, bridge circuit output just has small biasing, this signal passes through after differential amplifier (18) and the direct current amplifier (20), export a voltage Vx, this voltage is through Vx(H/T) change-over circuit (21) converts the rectangular wave pulse that a pulse width depends on the Vx size to.This pulsating wave is controlled reverse light emitting diode (22), and the light signal of light emitting diode (22) is controlled the conducting of controllable silicon (24) by photoisolator (23) or ended; The conducting of controllable silicon (24) just makes heater strip (14) have heating current to pass through, thereby to the calibration cell heating, the ON time of heater strip (14) is to be determined by the pulse width that change-over circuit (21) is exported.Like this, the conducting of heater strip or turn-off the temperature just can make calibration cell and to preset temperature consistent reaches the purpose of constant temperature.

Accompanying drawing 3,4,5 is the detailed descriptions to Key Circuit in the constant temperature control circuit.

Accompanying drawing 3 is sensor bridge circuit circuit diagrams.26-semiconductor transducer Rt wherein; 27-fixed resistance R ₁29-fixed resistance R ₂30-setting apparatus W ₁31-setting apparatus W ₂Semiconductor temperature sensor Rt(26) with fixed resistance R ₁(27), R ₂(29) and setting apparatus W ₁(30), W ₂(31) form bridge circuit.Setting apparatus W ₁, W ₂Be two accurate WW POT.Semiconductor transducer places calibration cell, and the linear voltage of its output can show the calibration cell temperature.The bridge circuit output signal is zero when constant temperature, and promptly preliminary election fixation device output voltage equals sensor output voltage.The output voltage of fixation device is to determine according to the temperature value of constant temperature.Preselection switch (25) can make digital temperature display (19) or show the thermostat temperature numerical value of preliminary election fixation, perhaps shows variation of temperature in the calibration cell groove.

Accompanying drawing 4 is change-over circuit synoptic diagram and input and output waveform synoptic diagram.33-triangular-wave generator among the figure; 32-open loop computing comparison amplifier.Change-over circuit is made up of triangular-wave generator (33) and open loop computing comparison amplifier (32).Triangular-wave generator (33) produces triangle wave voltage V _T, comparer will be compared from the voltage Vx that direct current amplifier comes, thus the counter-rotating of decision comparer.It is certain and pulsewidth (H) depends on the output square wave V of Vx so just to obtain one-period (T) _OThe utility model adopt when Vx=+1.5～-during 1.5V, the design of H/T=0～1, as can be known, the voltage Vx that the stacking factor H/T of output control pulse and direct current amplifier are exported is inversely proportional to.Vx is during greater than 1.5V, (H/T)=0; Vx is less than-1.5 o'clock, (H/T)=1, as Vx during at 1.5V～0, (H/T)=0～0.5, when Vx 0～-during 1.5V, (H/T)=0.5～1;

Accompanying drawing 5 is that light is every device and heating system circuit and respective waveforms synoptic diagram.Wherein 34, the reverse light emitting diode of 35-; 37-light is every circuit; The 38-bidirectional triode thyristor, 39-heater strip group; Capacitor C in the 40-heater circuit; Resistance R in the 41-heater circuit, capacitor C and resistance R provide a forward voltage signal to controllable silicon; 36-ground connection diode, its effect make the control diode whether show conducting, as the square wave V from change-over circuit output _OBe timing, red light is just sent in the light emitting diode energising in the optically coupled isolation circuit, and at this moment, with regard to conducting, the bidirectional triode thyristor (38) of its control was with regard to conducting when the light-operated triode in the photoelectric isolating circuit received ruddiness, and heater strip (39) just has electrical heating; Otherwise, if from the square wave V of change-over circuit output _OWhen negative, light emitting diode just outage does not work, and the triode in the photoelectric isolating circuit does not receive redness, just end, and the just outage of the bidirectional triode thyristor (38) of its control, heater strip (39) just stops heating.Therefore controlling the length of heat time heating time, is the signal that the bridge circuit according to temperature sensor and fixation device composition provides, thereby reaches the purpose of temperature control.The photoelectric isolating circuit has here been kept apart the 220V electricity of heating system effectively with control circuit, make the fluctuation of civil power 220V, and interference can not influence control circuit, has played vital role to improving temperature-controlled precision.

Claims (3)

1, it constitutes calibration cell a kind of high-accuracy and constant temperature control device, cabinet, rack, the fixation turn-knob is arranged on the cabinet panel, preselection switch, the warning turn-knob, alarm is equipped with the constant-temperature temperature-control wiring board in the cabinet, the heater strip group is housed in the calibration cell, stirrer, semiconductor cooler is equipped with the digital temperature display on the cabinet panel, the heating combined switch, it is characterized in that the stationary temperature value that the preliminary election initialization circuit presets is to show that by the digital temperature display change-over circuit is made up of a triangular-wave generator and an open loop computing comparison amplifier, between change-over circuit and controllable silicon heating system circuit a photoelectric isolating circuit is arranged.

2, thermostatically-controlled equipment as claimed in claim 1 is characterized in that the digital temperature display has the temperature value of the actual temperature control of calibration cell that a preselector switch measures by the direct displays temperature sensor of preselector switch.

3, thermostatically-controlled equipment as claimed in claim 1, it is characterized in that photoelectric isolating circuit is made up of a light emitting diode and a light-operated triode, light emitting diode links to each other with the output terminal of change-over circuit, and the output terminal of light-operated triode is connected on the control of bidirectional triode thyristor and extremely goes up.

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