SU580489A1 - Device for measuring humidity of moving webs - Google Patents

Description

The invention relates to the field of measurement technology and is intended for continuous automatic monitoring of the physical parameters of moving linen-like materials, for example, for measuring humidity, paper film thickness.

Devices are known with a one-way capacitive sensor comprising a series of electrodes, for example, moisture meters of paper web 1.

The known sensors have significant parasitic capacitances, which lead to a decrease in the relative sensitivity of devices according to the measured parameter.

The closest technical solution to the invention is a device for measuring the humidity of moving sheet-like materials, containing a capacitive one-sided scattered field sensor with electrodes, a high-frequency generator, a measuring transducer, thermostating elements and rollers of the position of the moving material 2. However, the known device has insufficient accuracy due to the occurrence of temperature errors.

To improve the measurement accuracy in the proposed device, the electrodes with a sensor capacitance are made on a foil-insulated dielectric, which is mounted

with a tension between two conical surfaces, for example, a supporting hollow cone and a conical ring with annular grooves, the taper of which is 3-5 ° more than the taper of the supporting cone, and the rollers of the position of the moving material are mounted on eccentric axes.

Making the base of a capacitive sensor of foil-coated dielectric film leads to a decrease in the parasitic capacitance and an increase in the quality factor of the sensor.

Installing a film sensor between a hollow cone and a conical ring with annular grooves ensures its preliminary tension exceeding the possible thermal deformations of the sensor, accurate spatial fixation of it in the device and high temperature stability of the initial capacity of the sensor. FIG. 1 shows a general view of the proposed device; in fig. 2 - film capacitive sensor scattered floor.

The device consists of a reference metal hollow cone 1, sensor 2 of the scattered floor, thermal insulating conical ring 3 with annular grooves, high-frequency generator 4, transducer meter 5 enclosed in screen 6, heating element 7, thermal insulating casing 8, housing 9, rollers-clamps 10,

mounted on eccentric axles x 11 and ball bearings 12 in housing 9.

The capacitive sensor 2 (Fig. 2) is an annular electrode 13, made on the foiled film dielectric 14.

Electrodes 13 are connected to a measuring transducer by 5 flexible leads 15 by soldering with low-melting solders or by gluing a conductor with wide glue. Gaskets 16 serve to adjust the axial clearance between the rollers 10 and axes 11. The radius of rounding of the surfaces of the metal hollow cone 1, equal to 3-5 thicknesses of the dielectric base of the capacitive sensor, provides a tight fit of the sensor 2 to the end surface of the support cone and a stable gap between the capacitive sensor 2 and the test material 17.

The device works as follows.

When moving the material under study 17 at a distance relative to the capacitive sensor 2, the increment of its capacitance will depend on the thickness and dielectric constant of the linen-like material 17. The dielectric constant of the linen-like material in turn will depend on the properties of the substance and its constituent components.

The increment of the capacitance of the sensor 2 in the measurement process is converted into an electrical signal in the measuring transducer 5, which is recorded from the high-frequency generator 4.

As a measuring transducer 5, for example, a bridge circuit with oscillatory circuits having inductive or capacitive coupling can be used. The output signal from the meter-converter 5 depends on the properties and thickness lolotnoobraznogo material 17.

To obtain high accuracy of measurement, the temperature and temporal stability of the initial capacity of the device must be sufficiently high, which is ensured by tensioning the film capacitive sensor 2 when it is installed between the hollow support cone 1 and its conical ring 3 with annular grooves.

The tension of sensor 2 at the same time exceeds its possible temperature deformations. and the sensor does not sag when the temperature changes. In addition, the device provides for temperature control of the sensor 2, the high-frequency generator 4 and the transmitter-meter 5. The thermistor and the switching circuit of the heating element 7 are placed in the meter-converter 5.

When the measured material 17 is moved, the rollers 10 rotate and, under the action of their own weight, the devices are pressed against the material, additionally pulling it. The eccentric axes 11 allow you to accurately set a fixed gap b between the capacitive sensor 2 and the material 17, and the lack of contact between them allows you to eliminate the wear of the sensor 2.

The implementation of a capacitive sensor of a scattered field of foil-coated dielectric film reduces the parasitic capacitance of the sensor by 10–20 times, increases the sensitivity of the device and increases the quality factor of the measuring sensor.

Claims (2)

1. The moisture meters of paper canvases by firm “Paul Lippke (Germany). 2. USSR author's certificate №273336 cl. G 01g 27/26,1970. sixteen F 17 10 V ; 7 2 FIG. one