SU957182A1 - Device for adjusting heater temperature - Google Patents

Description

(54) DEVICE FOR REGULATING HEATER TEMPERATURE

one

The invention relates to a technique for controlling and controlling a roaring temperature and can be used in heating thermostats and other products in which it is necessary to ensure the constancy of a given heating temperature with a change in ambient temperature, and its measurement. Bridge circuits are known for measuring and controlling the heating temperature, operating using two temperature probes. One of them is included in a resistive balanced bridge, the other is made in the form of a thermocouple and is introduced in an appropriate manner 15 into the thermometry zone, for example, in the vicinity of the first 1.

In these devices, lowering the temperature of the first probe leads to switching on. heating on duty using a bridge 20 comparison circuit, and the temperature being controlled is controlled by a second probe.

The disadvantage of such devices is the low level of control;

It is captured both by introducing a second probe into the temperature metering zone, which distorts the temperature probe, and by influencing it. installation relative to the heated object.

Bridge devices for measuring and controlling the heating temperature are also known, operating using the same temperature probes 2 and 3.

The disadvantage of these devices is the presence of an error when the ambient temperature changes, more specifically, the error of the influence of the ambient temperature on the resistance of the supply wires for connecting a thermistor which is located in the heated region at a large distance from the device.

Claims (4)

Closest to the proposed technical solution is a device in which this disadvantage is eliminated by turning on a thermal resistor for .5-х; wired circuit 4. 3957 However, the error compensation in this device is provided only at one ambient temperature and is not provided in the temperature range. The circuit of the invention is an increase in control accuracy. The goal is achieved by the fact that a device for controlling the temperature of the heater containing a resistive bridge, one of the arms of which includes a thermistor located remotely relative to the bridge, in parallel with which a high-resistance voltmeter is connected, and a differential amplifier is included in the output diagonal of the pad. at the output of which a heater is installed, an amplifier with negative feedback is inserted into which a resistor of a bridge arm is connected adjacent to a thermo-dependent arm, and one of the outputs of the amplifier with feedback is connected to one output of the input diagonal of the bridge, and the other to the output Thermal resistivity of the torus associated with another output of the input diagonal of the bridge. The current stabilizer is designed as an amplifier with negative feedback, a link in which the circuit includes resistance of the bridge arm adjacent to the thermosetting arm. with him in one branch of the current. FIG. Figure 1 shows the scheme of the proposed device for measuring and controlling the heating temperature; in fig. 2 - its equivalent circuit. The device contains a resistive balanced bridge, the shoulders of which include a thermodependent resistance 1, (R) a sensor used as a temperature sensor, a regulating resistor 2 (}, which serves to set the required temperature value for non-constant resistors 3 and 4 (R, R). The bridge is made equally-armed, but it can also be made with symmetrical shoulders {R. The output diagonal of the bridge includes the inputs of the differential amplifier 5, the output of which has a heater power supply. 5 is loaded by an electric heater 6 introduced into a thermal link with a thermodependent resistance 1, in particular by mounting on it. Elements JL and 6 are placed in a heated thermometric region 7 located at a large distance from the device. 24 In the input diagonal of the bridge there is an on-current stabilizer flowing o through a thermistor resistor 1, for example, in the form of an amplifier 8 with deep negative feedback, in the test, which includes a resistor 4 of the arm of a bridge adjacent to a thermo-dependent arm with a resistor 1 and located with it in the same current branch. The magnitude of the current flowing through the indicated branch of the bridge does not depend on the magnitude of the resistances 1 and 9 (Fig. 2). Thermistor 1 is connected by a three-wire circuit with the help of lead wires 9-11 (Fig. 1). FIG. 2 equal resistance introduced by them is shown in the form of resistors 9 - ll (In this case, the condition Rg R, Q (. Parallel to the removed resistor 1 (Fig. 1) is included) the temperature indicator 12 is shown as a high-resistance voltmeter, the device works as follows The setting of the required temperature t, heating in the heated cloud 7 is carried out with the help of an adjustable resistor 2. With a corresponding change in the resistance of the resistor Rj, the switched on bridge circuit is balanced at to, when the temperature ig and It is shown on measuring device 12. Deviation (decrease) of temperature from tg results in an error signal in the output diagonal of the bridge, which is amplified by circuit 5 and fed to heater 6. The last, heating region 7 and thermistor 1, changes its resistance until equilibrium is restored. when the error is reduced to zero and the power supply to area 7 stops. The stabilized temperature i is indicated on the device 12. The use of a balanced bridge, in which the thermistor is switched on by three-wire circuits The temperature is measured with the bridge balance using a voltmeter connected to the external temperature-dependent resistance, eliminating the error of the readings from the influence of temperature i, the environment on the resistance of the supply wires 9-11 If Rq RQR (l), the same resistance of the bridge shoulders (or R + RI RIO, 63 ... (2) and stabilization of the current of thermodependent resistance ,,. (3). Condition (1) is fulfilled in the entire range of replacements i, condition (2) when the bridge is jealous, for example, at i working temperature. Conditions (1) and (2) are irrelevant when the thermistor is turned on in a three-wire circuit; additional mention of them is not necessary. The need to stabilize the current of the thermoresistor (condition 3) is due to the following. By switching on the thermistor of the bridge in a three-wire circuit, the error is compensated by the effect on the resistance of the supply wires and the balance of the bridge. When t changes, the balance of the bridge is not disturbed and the error does not occur. However, this changes the resistance of the bridge, and therefore the magnitudes of the currents in its branches x. As a result, while maintaining the equilibrium of the bridge, the readings of the voltmeter connected to the remote thermistor depend on the resistance of the supply wires. Stabilization of the current in the branch including the thermistor / eliminates this dependence and the error associated with it. Claims An apparatus for adjusting a heater temperature comprising a & A bridge, in one of the arms of which is on, is a thermistor located remotely relative to the bridge, parallel to which a high-resistance voltmeter is connected, and a differential amplifier is connected to the output diagonal of the bridge, at the output of which a heater is installed, in order to improve the accuracy of adjustment , a negative feedback amplifier is inserted into the device, into which a resistor of the bridge arm is connected adjacent to the thermo-dependent arm, one of the outputs of the amplifier with feedback 1 is connected to one the output of the input diagonal of the bridge, and the other to the output of the thermistor, associated with a different output of the input diagonal. Sources of informein taken into account in the examination of irprocceed-tn s ol the Lu & Wnie o {En rronmertqE Sciences.AhmeJE Techh-icaC MeeUn, l964, pp.6b-l-65. 2. The UK patent Ms 1290164, CL. q 05 D 23/24, published 1972. 3. The UK patent number 1442981. CL. q 05D 23/24, published 1976. 4.Ornatsky P.N. Automatic measurements and devices. Kiev, Vshtsa School, 1980, p. 176-177 (prototype). fe / g. (f / f.l