SU1446489A1 - Multichannel temperature measuring device - Google Patents

Abstract

The invention relates to a measurement technique and makes it possible to increase the reliability and accuracy of temperature measurements in multichannel systems using direct current sensors connected with contact switches. The device contains a thermal converter 1 resistance and a thermoelectric converter connected to the inputs of the contact switch 5, shunted by capacitors 6.1 and 6.2, keys 7.1 and 7.2, AC source 8, isolation transformer 9, the primary winding 10 of which is connected to the output of source 8. First output of the switch 5 is connected via a serially connected secondary winding 11 of a transformer 9 and a resistor 12 to the first input of the ADC 13, the second input of which is connected directly to the second output of the switch 5, the first and second outputs of the ADC 13 are bounded by a capacitor 14, and the output of the ADC 13 is connected to the input of the data processing and recording unit 15, the outputs of which are connected to the control inputs of the switch 5 and the ADC 13. The conductivity of the contacts of the switches 7 of the switch 5 is restored and maintained directly during the measurement by passing an alternating current through them. An additional winding 16, connected in antiphase with the winding 11, the capacitor 17 and the resistor 18 provide at the output of the ADC 13 almost complete compensation of the alternating voltage. 1 hp f-ly, 1 ill. C /): & 2 00 co

Description

one

The invention relates to a measurement technique and is intended for use in multichannel data acquisition systems from direct current sensors with a low level of output signals, which are connected using contact switches (relays).

The aim of the invention is to increase the reliability and accuracy of temperature measurement by better restoring the conductivity of the contacts of the switches,

The drawing shows a functional block diagram of the proposed device.

The device contains thermal resistance pasoBa.Tejjb 1 included in the measuring bridge circuit

2 DC current, thermoelectric converter (thermocouple)

3c with block 4 for compensation of temperature changes at the free ends, contact switch 5, the inputs of which are bridged by capacitors 6.1 and 6.2, keys 7.1 and 7.2 of switch 5, source 8 of alternating current, separation transformer 9, the primary winding 10 of which is connected to the output of source 8 and its secondary winding 11 is connected in series

with a resistor 12 between the first output of the switch 5 and the first input of the analog-to-digital converter (ADC) 13, the second input of which is connected directly to the second output of the switch 5, a capacitor 14 connected between the inputs of the ADC 13, the processing and recording unit 15 whose input is connected to the output of the A / D converter 13, and its outputs are connected to the control inputs of the switch 5 and the A / D converter 13.

14

To further increase the measurement accuracy, the transformer 9 can be provided with an additional secondary winding 16, which is connected with one end through the additional capacitor 17 to the second input of the ts 13 ADC, and the other through an additional resistor 18 to the first input of the ADC 13, 40 In this case, the parameters of the additional winding 16, the capacitor 17 and the resistor 18 are selected to be identical to those of the winding 11, the capacitor b and the resistor 12, respectively, which

In the practical scheme of the device in 45, the input of the ADC 13 provides almost complete compensation for the alternating voltage of the source 8.

Claims (1)

Invention Formula 1, A multichannel temperature measuring device containing temperature transducers into voltage of a constant voltage source 8 and isolation transformer 9 can be used by an additional winding of the transformer of the power supply unit. The number of thermal converters connected to the inputs of the switch 5 is in principle unlimited and is determined by the required number of measuring channels. 50 The device operates as follows: 55, connected to the inputs of contact 5 ten 20 15 25 464Y92 Thermal converter is connected to the corresponding measurement channel. The alternating current of source 8 through isolation transformer 9 from winding 11 flows through the contacts of closed switches 7, resistor 12 and capacitors 6 and 14. Resistances of resistor 12 and capacitors 6 and 14 to alternating current and the voltage on winding 11 of transformer 9 are selected so that alternating the current flowing through the contacts of the keys 7 exceeded the minimum allowed value for this type of keys. The resistor 12, the capacitor 14 and tr the capacitor 6 form a U-shaped low-pass filter, greatly reducing the level of noise in the measuring channels. In this case, the resistor 12 and the capacitor 14 also form an RC filter, which reduces the variable component at the input of the ADC 13. Thus, the conductivity of the contact keys of the switch 7 of the switch 5 is restored and maintained directly during the measurement, which, given the significant reduction in the level of interference, increases the reliability and accuracy of the measurements. To further increase the measurement accuracy, the transformer 9 can be provided with an additional secondary winding 16, which is connected with one end through the additional capacitor 17 to the second input of the ts 13 ADC, and the other through an additional resistor 18 to the first input of the ADC 13, 40 In this case, the parameters of the additional winding 16, the capacitor 17 and the resistor 18 are selected to be identical to those of the winding 11, the capacitor b and the resistor 12, respectively, which thirty 45 provides at the input of the ADC 13 almost complete compensation of the alternating voltage of the source 8. 50 at once. The signal from block 15 closes one of a pair of keys 7 of the switch 5. At the same time, to the input of the ADC 13 I switch, the first output of which is connected directly to the first input of the analog-digital converter, the output of which is connected to the input of the data processing and recording unit, the outputs of which are connected to the control inputs of the switch and an analog-digital converter, characterized in that, in order to increase the reliability and accuracy of the measurements, a variable toKa source, an isolation transformer, a resistor , capacitors connected in parallel to the inputs of the switch, and a capacitor connected between the first and second inputs of the analog-digital converter. ten series-connected secondary winding of the isolation transformer and a resistor to the second input of the analog-digital converter. 2, The device according to claim 1, characterized in that an additional resistor, a capacitor and the secondary winding of the isolation transformer are introduced into it, which is turned on out of phase with the first secondary transformer. coil and connected by one of its output through an additional capacitor to the first input of the analog-digital moreover, the primary winding of the separator is a 15 converter, and another output of the transformer is connected to an additional resistor with an alternating current source, the second high-voltage input of the analog-to-digital switch is connected through a switch. series-connected secondary winding of the isolation transformer and a resistor to the second input of the analog-digital converter. 2, The device according to claim 1, characterized in that an additional resistor, a capacitor and the secondary winding of the isolation transformer are introduced into it, which is turned on out of phase with the first secondary transformer. coil and connected by one of its output through an additional capacitor to the first input of the analog-digital