SU883671A1 - Multi-channel device for measuring temperature - Google Patents

Description

one

The invention relates to a measuring technique, in particular, to devices for measuring temperature using resistance sensors.

A device for measuring temperature is known with a resistive sensor connected in one arm of a bridge circuit and in another, adjacent to the sensor. Regarding the diagonal of the bridge supply, a reference resistor is switched on, the value of which corresponds to the initial measurement level can exceed the measured range.

An advantage of the bridge measurement circuit is the increased sensitivity of the measurement by suppressing the initial scale level and elevation, thereby measuring accuracy 1.

The drawback of the device is a non-linear transfer function and complexity in operation, requiring balancing of the bridge and the subsequent measuring circuit.

. A multichannel device for temperature measurement is known, which contains resistive sensors connected via keys to a reference resistor and current source, a measuring unit with potential and common

inputs that are connected to the output of a dip switch, the input terminals of which are connected to the terminals of the reference resistor in the first position and to the sensor leads through a pair of keys in the second position, as well as two circuits for controlling the dip switch and keys. According to the signal from the control circuit, the sensors are connected in series to the current source through the keys and the reference resistor, and through a pair of keys and a two-position switch in the second position to the unit

15, to which the reference resistor is connected in the first position of the switch, resulting in a push-pull mode of operation used to obtain measurement information in the form of voltage differences created by the current of the power source at the sensor and reference resistor counterparts.

Thus, the known device also, due to the suppression of the initial part of the scale, possesses up to the bridge cxe№i, but is free from its disadvantages, since the transfer function is linear, and

30 measuring unit does not require balancing circuit. In addition, due to the push-pull mode of operation, and the measurement result, slow fluctuations of the power source and measurement units are eliminated, which increases the accuracy of measurement 2.

The drawback of the device is excessive power consumption due to the excess time spent by the sensor and the reference resistor under current, since the measurement information is taken from them alternately.

The purpose of the invention is to reduce power consumption and increase device reliability. ..

The goal is achieved by the fact that a multichannel temperature measuring device containing a reference resistor, a current source, a measurement unit with potential and common inputs, a resistive sensor and three keys in each channel, one of which is in the power supply circuit and two in the measurement circuit, and the second of them is connected to the first output of the resistive sensor, and the second output of the resistive sensor to the common input of the measuring unit via a wire, as well as two control circuits, the first to one output, the second to several, by the number of channels, Interrator, reference resistors by the number of channels minus one, an additional switch to each channel and two logical circuitry AND, one of whose inputs is connected to the corresponding outputs of the second control circuit, another input of the first logic circuit is connected to the output of the first control circuit, and the other input of the second logic circuits - with the output of the first control circuit through the inverter, while the first output of the resistive sensor, through the additionally inputted key, is connected to the first pole of the current source, and its second pole - to the common input a measuring unit, a second terminal of resistive sensor provod.i through the second reference resistor is connected to a first pole of the current source and the measuring potential input unit through the first keys respectively.

The drawing shows the functional scheme of the proposed multi-channel measuring device. temperature.

The device contains resistive sensors 1 with three connecting wires 2, 3 and 4, supporting resistors 5, current source b, measuring unit 7 with potential 8 and common 9 inputs, two logical circuits 10 and 11 and four keys in each channel 12 and 13 in the supply circuit, and 14 and 15c of the measurement circuit, two control circuits 16 and 17 and an inverter 18, the input of which is connected to the output of the circuit 16

The principle of operation of the device is as follows.

In circuits 10,11,16,17 and 18, key control signals are generated, with the aid of which a sequential connection of channels in a push-pull mode is ensured.

As a result, in the first measurement cycle, a circuit consisting of two connecting wires 3 and 4 and a reference resistor 5 is connected to the power source 6 and the measuring unit 7 via keys 12 and 14, and the keys 13 and 15 respectively are connected to the second bar from two connecting wires 2 and 4 and sensor 1, i.e. the sensor and the reference resistor are connected to the current source alternately, simultaneously with the connection to the measurement unit.

In this case, the measurement result will have the following expression;

Uj. i (Ro + 2r), Uji i (Ro + 2r), dO Ug –Uj, 5 where U is the measured voltage in

1 tact;

U is the measurement of the thermal stress in the AND 2 cycle;

di - voltage measuring information;

D

RQ is the resistance of the reference resistor;

Rg sensor resistance; g - resistance of the connecting wire.

The resulting gain in energy consumption compared with the known device will have the following meaning:

- V Pm- 4V / hs

where p. - power consumption of the known device;

five

- power consumption of the proposed device;

y is the measurement time of one

tact

When formula (1) will have the following form:

Puv-4 RT; p ,, - iXK-l i. the power consumption of the proposed device is 4 times less than the known, which is a significant economic effect.

Also in this device,

compared to the known, increased measurement accuracy: due to a decrease in the error due to the Cc1MORheating of the sensor as a result of the elimination of the excess residence time

Claims (2)

its under current; and also due to increased noise immunity, due to the elimination of spurious communication circuits by combining the common poles of the current source and the measuring unit. It should be noted also the additional economic effect of the proposed device due to the introduction of a three-wire sensor switch-on circuit, instead of the four-wire one that took place in a known device, as well as an increase in the efficiency of its use, due to the possibility of simultaneous measurement at different levels of the initial portion of the measuring scale, unlike devices where this feature is limited to one level. Multi-channel device for temperature ruling, including a reference resistor, current source, a measuring unit with potential and common inputs, a resistive sensor and three switches in each channel, one of which is in the power supply circuit and two in the measuring circuit, and through of them, the first output of the resistive sensor is connected to the potential input of the measuring unit, and the second output of the resistive sensor is connected to the common input of the measuring unit via the first wire, as well as two cxetm. control, the first with one output, the second - with several Kimi, by the number of channels, characterized in that, in order to reduce power consumption and increase the reliability of the device, an inverter is inserted into it, reference resistors by the number of channels minus one, an additional key to each channel and two logical circuits AND, one of the inputs of which is connected to the corresponding outputs of the second control circuit, jopyrofi the input of the first logic cxettn is connected to the output of the first control circuit directly, and the other input of the second logic circuit is connected to the output of the first circuit control through the inverter, with the first output of the resistive sensor through the additionally introduced key connected to the first pole of the current source, and its second pole to the common input of the measuring unit, the second output of the resistive sensor via the second wire and the reference resistor connected to the first pole of the current source and potential input of the measurement unit through the first keys, respectively. Sources of information taken into account in the examination 1.Turichin A.M. Wire converters and schemes for their use. M., 1962. 2. The patent of Germany 1573257, cl. G 01 K 7/20, published. 1974 (prototype).