SU928242A2 - Calorimetric watt-meter with direct reading - Google Patents

Description

The invention relates to measuring equipment, namely to directly countable calorimetric wattmeters, and can be used to measure $ absorbed power of continuous and average values of pulse-modulated electromagnetic oscillations.

By main auto No. 815657 from a jq news, a directly countable calorimetric wattmeter containing a calorimetric load connected between the first and second temperature sensors connected respectively to the inputs of the temperature difference meter, a flow meter of the calorimetric liquid, the output of which is connected to the first input of the multiplication unit, to the output of which a measuring device is connected __, an adder, a subtraction unit and a delay line, the output of which is connected to one of the inputs of the subtraction unit, the other input of which and the input of the delay line are connected with the output of the first temperature sensor, the output of the subtraction unit 25 and the output of the temperature difference meter are connected respectively to the inputs of the adder, the output of which is connected to the second input of the multiplication unit '1Ί. . thirty

However, the known device is characterized ² * 'ized by insufficient precision of measurement due to fluid temperature instability.

The purpose of the invention is to improve the accuracy of measurement.

This goal is achieved by the fact that in a directly countable calorimetric wattmeter containing a calorimetric load connected between the first and second temperature sensors connected respectively to the inputs of the temperature difference meter, the flow meter of the calorimetric liquid, the output of which is connected to the first input of the multiplication unit, to the output of which the measuring device is connected , adder, subtraction unit and delay line, the output of which is connected to one of the inputs of the subtraction unit, the other input of which and the input of the line the holders are connected to the output of the first temperature sensor, the output of the subtraction unit and the output of the temperature difference meter are connected respectively to the output-1 of the adder, the output of which is connected to the second input of the multiplication unit, a compensation device and a scale converter are connected in series, the output of which is connected to one of the inputs of the adder, and the input of the compensation device is connected to the output of the first temperature sensor.

The drawing shows a block diagram of a straight-line calorimeter wattmeter.

The wattmeter contains a calorimetric load 1, temperature sensors 2 and 3 connected to the inputs of the temperature difference meter 4, a calorimetric liquid flow meter 5, an adder 6, a delay line 7, a subtraction unit 8, a multiplication unit 9, a measuring device 10, a compensation device 11, a scale converter 12.

The power meter works as follows.

The signal of the temperature sensor 2, proportional to the temperature of the liquid, is supplied to the compensation device 11, t used to set the zero of the wattmeter produced after zero-balancing the temperature difference meter 4, during which the corresponding input of the adder 6 is disconnected from the output of the scale converter 12. Zero indication carried out by measuring device 10. Thus, at the output of the compensation device 12 receive a signal proportional to the difference between the current value of the temperature of the liquid and its value in the moment nt zero-balancing meter 4 temperature differences.

The signal from the measuring instrument 4, the temperature difference is proportional to the algebraic sum of useful yTr and parasitic _n dT fluid temperature difference at the location of temperature sensors λΤρ-accident Tr- * q ^ <Dt) - y / & .Ί (Τ) * jrti <X) · GL>_; where db (1) is the difference between the current value of the fluid temperature and its value at the moment of zero-balancing of the temperature difference meter, 50

At ¹ (t) is the time derivative of d t (X);

K is the static coefficient of heat transfer of fluid from the section between the thermo, sensors to the environment - ¹³ environment (air);

G ₃ is the effective part of the heat capacity of the section between the temperature sensors washed by the calorimetric liquid (effective heat capacity of the load);

W is the water equivalent of the calorimetric fluid in the load; 65

Q is the transport delay time of the liquid during the passage of the section between the temperature sensors.

The signal is fed to the input of the scale converter 12, which serves to form the transmission coefficient of the correction circuit, consisting of a temperature sensor 2, a compensation device 11, a scale converter 12, and an adder b, in accordance with the ——— ratio.

W

When the measured power is supplied to the load 1, the sum of the signal is formed at the output of the adder 6, which is proportional to the temperature difference coming from the output of the meter 4 and the signal proportional to dT _p coming from the output of the subtraction units and the scale converter 12, so that the resulting signal arriving from the output of the adder b to the input of the multiplication unit 9, it is proportional only to the useful temperature difference A Tr.

The blocks included in the correction circuit can be performed in various ways, depending on the construction. 4 temperature difference meter. For example, if adder b is made on the basis of the well-known scheme of a nonequilibrium AC bridge, then as an compensation device 11, conveniently combined with a cold temperature sensor, and isolated from the temperature difference meter 4, an unbalanced bridge circuit at a constant e, in one of the arms of which a cold temperature sensor 2 is switched on. To convert the output signal from such a circuit into a proportional signal of an alternating current of a fundamental frequency, a power supply of a reference voltage generator common chopper that allows easy to carry out the desired phasing correction signal with the signal from the temperature differential meter 4.

The delay time of line 7 is chosen equal to the sum of the transit time of the calorimetric liquid from cold to hot temperature sensor and time · equal to the quotient of dividing the effective heat capacity of the load by the corresponding liquid (water) equivalent.

Claims (1)

1. USSR author's certificate 815657, 03.08,79.