DIGITAL DYNAMOMETER DEVICES FOR CONTROL OF THE TENSION IN THREADLIKE MATERIALS G. N. Romanov, A. V. Shevelev, V. V. Revin, and I. N. Kiselev

UDC 621.318.44:531.7

Control of tensile forces in wires and threadlike and tape-type materials is an important direction of scientific and technological progress in refining production processes in electrical, radio, chemical, and textile engineering industries [1-3]. In this, strain gages, mechanotrons, and capacitance and other primary transducers are widely used as force transmitters [i, 4, 5]. Currently, the strain gage method of control of forces is being developed for the most part due to a number of merits which include flexibility, simplicity, high accuracy, and reliability. These features have predetermined the use of strain gages for measuring the tensile forces in wires. The traditional structural system of converters of the signal from the bridge strain-gage transmitters includes a preamplifier, analog-to-digital converter (ADC), indicator block, and matching and control devices. The preamplifier can be designed for a system of direct amplification of the direct signal or conversion from direct to alternating signal, its amplification, and reverse conversion to direct. The original circuits were, as a rule, simpler in design but less stable in operation. The ADC can also have various layouts and be made on different element bases. A digital dynamometer device was specially developed by using the series 176 microcircuits. The signal from the tensobridge was fed through matching resistors to the preamplifier inputs. Potentiometers were used for balancing and regulating the preamplifier amplification factor. The analog signal was fed from the amplifier output to the ADC consisting of a voltage-to-frequency converter assembled on two microcircuits and a transistor, and a counter. The transducer is constructed on the principle of a controlled voltage generator and consists of a voltage integrator, Smitt trigger, and a transistorized key. The pulse train, the repetition frequency of which is proportional to the signal of the bridge unbalance, was obtained at the collector of the key transistor. Assembled in microcircuits,the counter control device made it possible to organize the operation in three sequential modes which were set at fixed intervals, i.e., count of the pulse train, indications on the sevensegment indicators, and zero setting of the counters. Out of the analog-to-digital converters of integral design developed in the country (KRII08PPI, K572PVI, KR572PV2, and KIII3PVI), the KR572PV2 with the use of the double integration method of conversion of the transmitter signals provides for high noise-protection and the possibility of operating with considerable lines of communications [6, 7]. Considering the above reasons, we used the type KR572PV2A microcircuit D5. It presents the result of conversion of the input signal from the tensotransmitters Rtl ... Rt4 to the TABLE i .

.

.

.

.

.

.

i

System with System with ADC the ADC in the KR572PV2A series 176 (Fig. i). microcircuits.

Parameter Range of measured force, g Basic measurement error, % Time of heating the instrument before measurements, sec Time instability, g/h Power required, W

0---800 S 3O0

o,.--~o

•

•

3 6O

I0

Translated from Izmeritel'naya Tekhnika, No. 7, pp. 35-36, July, 1989.

680

0543-1972/89/3207-0680512.50

9 1990 Plenum Publishing Corporation

DS-

I I

#61

+

I Uref

.

BQI

I--I

"

,.L .

T__. o.

9

~I " ~ '

J

Fig. I type AL305A seven-segment indicators HGI ... HG4 (see Fig. 1 in which the circuit of the diBital dynamometer device with the type KR572PV2A ADC is given). The use of the KR572AV2A microcircuit makes it possible to automatically correct the zero and determine the input signal polarity. Inclusion of the quartz resonator BQI made it possible to stabilize the conversion interval. The reference voltage Ure f was formed from the transmitter voltage Esu p by means of the amplifiers D3, D4, and the matching cascade in the transistor VTI. The small temperature drift was achieved by means of the type KI4OUDI3 preamplifier a D1 which was constructed on the basis of a system in which there is conversion of a slowly varying input signal to an alternating voltage with its subsequent amplification and demodulation. A key modulator and demodulator in field transistors operating at 30 kHz frequency were used in the preamplifier. The amplification factor of the KI40UDI3 is i0 and the output voltage does not exceed • V. In order to form a signal with a high amplitude, the KI40UDI3 output was connected to the type KI40UDI7 precision amplifier D2 input. The demodulated and filtered signal of the bridge circuit unbalance is fed to the microcircuit D5. A conversion range of 0-I00 or 0 - 1 0 0 0 m V was selected by varying C5, RI6, and C7. The reference voltage supply (proportional to the supply voltage of the strain gages) to the ADC D5 input made it possible to measure the operating transmission coefficient of the strain-transducers. The extension dynamometer transducer with the seven-segment indicators contains a flat elastic beam of beryllium bronze fixed at one end. Wire-type strain gages are glued on to the beam surface. A roller is fixed at the other end of the beam. Another two rollers are fitted in the uprights near the first roller and are located at 120 ~ angle to it. A potentiometer is also fitted in the body of the transducer to balance the bridge (R3 in Fig. i). For control of the tension, the winding wire (or any other threadlike material) is wound between the rollers after the tensioning device. The coil-winding machine is then started. The reading of the wire tensioning force is obtained from the digital indicator. The principal technical characteristics of the examined digital dynamometer devices are given in Table i. As the comparative tests of the two systems of dynamometer devices showed, the system with the ADC on the KR572PV2A microcircuit is more stable in operation. Besides, its small overall dimensions make it possible to construct an independent, battery-supplied, and portable version.

LITERATURE CITED i.

E. ~. Vaks, Measurement of Thread Tension [in Russian], Legkaya Industriya, Moscow

2.

(1 96 6 ) . E. S. Ermakov and B. L. Z h o r z h o l i a n i , S e t t i n g up P r o d u c t i o n Machinery f o r Manufacture of RadioComponents [ i n R u s s i a n ] , Vysshaya Shkola, Moscow (1986). 681

3. 4. 5. 6. 7.

US Patent No. 4,577,512. I. A. Tsinskii et al., Inventor's Certificate No. 830,162 (USSR), Otkryt. Izobret., No. 18 (1981). A. G. Alekseenko et al., Inventor's Certificate No. 1,204,982 (USSR), Otkryt. Izobret., No. 2 (1986). M. M. Parfenov et al., Prib. Sist. Upr., No. 9, 17 (1985). B. G. Fedorkov et al., Microelectronic Digital-to-Analog and Analog-to-Digital Converters [in Russian], Radio i Svyaz', Moscow (1984).

CALCULATION FOR THE CONVERGING DEVICES OF FLOWMETERS BY A PROGRAMMED MICNOCALCULATOR UDC 681.121.001.24:681.3

S. B. Tyakhti

The necessity of bringing all currently operating flowmeter units (FU) with standard flow converging devices (CD) to conform to [I, 2] has led to considerable increase in the labor involved in metrological servicing of these devices. The rules [i] are different from [3] in that the possibility exists for using modern computing techniques, although these rules have been introduced without timely provision for standard programs for calculation for the CD. Development of programs independently is difficult, and, therefore, as was the case earlier, it is necessary to calculate and check the calculations for these devices manually. Under these circumstances, it is most advisable to use a programmed microcalculator (PMC) to calculate for the CD, thereby substantially cutting down on the labor consumption. Certain regularities were detected as a result of the analysis of [I, 2, 4] and also of the very process of the calculation for the CD (with a view to its optimization). Since the supplementary coefficients a and b (formula (21))* for determining ksh (henceforth, ash and bsh), and a, b, n (formula (22)) for determining k D (ap, bp, np) depend only on c = D/10 ~ (D is the pipe diameter), a supplementary table was compiled as follows for c ~ 0.3 (Table i). A table of the saturated vapor density was also compiled in accordance with appendix 6 of [i] by accounting for the average annual barometric pressures in Petrozavodsk (with steps of 0.05 MPa) and also a table of the water density (with steps of 0.05 MPa and I~ in accordance with appendix 8. The density is determined directly from these tables without any interpolation. For calculating for the CD (corner selection of the pressure gradient), the PMC programs were so composed that only the mathematical formulas which contain the most difficult-tocompute, interconnected, and variable quantities which depend on the relative diameter of the CD, such as formulas (20)-(22) and (59), are combined. TABLE 1 D

82 218.5 250 ~5o

T

ap

sh

a sh

b

0.0'2~666 t~.028484

1.000~)

1.011

0.01094~

4.250

I .t'~r1892

I .nlOq94

N.011056

4.250

q.fY2~.q312

I O001~,q5

I .N10q13

0.00833,2

1.00q~59 I.NOO1~

1,0~17 I .Oe~N.t?

0.011[62 0.00759~ n.rl.q5747

4.251 R.9~N tn.75~

I.~

IN

O.n05

14.P3~

q,flO53,~l

*All formulas without source reference are taken from [i]. Translated from Izmeritel'naya Tekhnika, No. 7, pp. 36-37, July, 1989.

682

0543-1972/89/3207-0682512.50

9 1990 Plenum Publishing Corporation