SU1589164A1 - Apparatus for checking moisture content in food products - Google Patents

Abstract

The invention relates to the field of instrumentation for the food industry and is intended to automatically measure the moisture content of bulk products (such as meal, cake, pulp, food concentrates, etc.) in a stream, and can also be used to measure the moisture content of products under laboratory conditions. x The purpose of the invention is to improve the accuracy of moisture measurement. The device contains an optical path with separation of radiation reflected from the monitored product into two channels with measuring and reference wavelengths. Due to the presence of a simulator of zero humidity and two divider blocks with a variable division factor, the device can compensate for the drift of the parameters of the elements in each channel by adjusting the division factors of the divider blocks when periodically introducing the simulator of zero humidity into place of the monitored product. 2 Il.

Description

The invention relates to instrumentation for the food industry and is intended to automatically measure the moisture content of bulk products (for example, meal, cake, flour, food concentrates, etc.) in a stream, and can also be used to measure the moisture content of products under laboratory conditions. x

The invention is an increase in the accuracy of humidity measurements.

Fig. 1 shows a block diagram of the proposed device in the humidity measurement mode in Fig. 2, a block diagram of the optical part of the device in the calibration mode.

The device contains a light source 1, the radiation of which is the product 2 being examined and an optical interrupter 3, beam-splitting mirrors 4 and 5 forming two optical channels, light filters 6 and 7, blocks 8 and 9 of photo-receiving amplification, the outputs of which are electrically connected in each channel with the first inputs of blocks 10 and 11 dividers with a variable division factor, outputs

which are connected in pairs in each channel with the keys 12 and 13 and 14 n, 15, while the keys 13 and 14 connect in each channel the outputs of the blocks 10 and 11 of the dividers of the signals to the inputs of the gain blocks 16 and 17, the outputs of which are connected to the block 18 divisions associated with the scaling unit 19, the output of which is connected to the display unit 20, and the keys 12 and 15 connect the outputs of the signal separator units 10 and 11 to the first and second inputs of the comparison unit 21, which compares the input of the comparison unit 21 to the output of the unit 22 reference voltages, the first and second outputs are connected in each House channel, respectively, via keys 23 and 24 e by the de-energizing inputs of blocks 10 and 1-1 of signal splitters, control block 25, the outputs of which are connected to control inputs of keys 23 and 24, 12 and 13 and 14 and 15 and actuator 26 of simulator 27 of zero humidity .

The device works as follows.

In the measurement mode, keys 13 and 14 are open, and keys 23 and 24 and 12 and 15 are closed, as a result of which the zero humidity simulator 27 is in the OV position (Fig. 1), while light emission from light source 1 falls on product 2 and, having reflected, passes through an optical chopper 3, at the output of which a variable light signal is generated that carries information about humidity. The light beam mirror 4 divides the received light signal into two beams, one of which, reflected from mirror 5, passes through the light filter 6, and the second passes through the light filter 7. The signals passing through the light filters in each optical channel fall into blocks 8 and 9 a photoreceiver amplification consisting of photodetectors with preamplifiers, in which they are converted into electrical pulses, arriving at the first inputs of blocks 10 and 11 of signal splitters,

When choosing filters 6 and 7 with a maximum transmittance in the infrared region at wavelengths with the highest and lowest sensitivity to water absorption (1.95 µm and 1.84 µm), voltage, and and at the outputs of blocks 10 and 11 The lengths in each channel will be equal

and,,

and „e

- s, t,

(12)

where and (-, - and and Q2. are voltages in the channels at the outputs of blocks 10 and 11 of signal divisors, corresponding to zero moisture, equal to the ratio of the input voltages of the divider blocks, respectively, UqjQ, and if2. to the division factors of these blocks, equal to

responsibly K, and K

and.

 2 0 Ucpo (/ K (, Uo2. Ucpoz / K;

of i and oi 2. absorption coefficients

1 at selected wavelengths; m is the mass of moisture, the voltage values obtained, through public keys 13 and 14, as well as blocks 16 and 17 of amplification, go to block 18, at the output of which a signal appears that is exponentially dependent on the moisture content, equal to according to expressions (1) and (2):

and e

(oi, 2.-6Z,) m.

(3)

0

five

0

five

0

five

The signal is converted into units of humidity in scaling unit 19, with the measured moisture value in percent indicated in display unit 20.

Expression (3) is correct when the UQI U voltages are equal (, 2 in the channels corresponding to zero moisture. To do this, in the process of tuning, these voltages are preliminarily equalized with the help of blocks 8 and 9 of the photoreceiver amplification, substituting white for the product under study 2 standard plate.

However, under the influence of a number of factors (for example, a change in the ambient temperature, a general heating of the moisture meter elements), the sensitivity of blocks 8 and 9, the initial stresses UjpQ, and if2 change. in the channels at the outputs of the photo-amplification amplification blocks at zero humidity, they vary by

((accordingly, the signals at the outputs of the blocks 10 and 11 of the signal dividers, which will be respectively equal, iF01 ± Diff.

, - and

to.

 0

± yy,

if02. ± Dif1

- -Uoz- z. ()

In this case, taking into account (4), expression (3) takes the form

TI Tco ± & Ts1 {0 2-oil) t,

    ;

where + Di, and iAU2 are additional voltages corresponding to an increase with a positive sign or a decrease with a negative initial voltage in the channels.

From the expression (4) it follows that the slope of the calibration characteristics of the device changes, increasing the measurement error of humidity. To eliminate this phenomenon, a calibration mode is provided in the device, in which, following a command from the drive control unit 25, a zero-moisture simulator 27 is inserted into the optical channel, which is placed in the CA position (Fig. 2). As a result, the light emission from the light source 1 hits the simulator 27 and, having reflected, passes an optical path similar to the measurement mode, while the outputs of the blocks 10 and 11 of the signal splitters appear, for example, corresponding to a zero humidity value changes in the sensitivity of photodetectors equal to (,) and (U ± & U). At the same time, on command from the control unit 25, the keys 13 and 14 are closed, the keys 23 and 12 are opened, and the signal from block 10 of the signal divider goes through the key 12 to the first input of the comparison unit 21, in which a correction signal is produced as a result of the comparison with the reference voltage + Di The received signal from the output of the comparator unit 21 goes through the public key 23 to the de-inlet of the signal divider unit 10, thus changing the division factor K of the unit 10 to the value of K ", at which the voltage at the input of the divider unit is compared with the reference voltage et. those.

Have pho | + Bif | TO..

01

(6).

where K ,, is the new value of the division factor of the divider block 10, equal to the expression (6)

TO

to

 TO

(7)

In the next cycle, the keys 23 and 12 are closed, and the keys. 24 and 15 are opened and, in the second channel of the device, similar generation of the correction signal ± fckUg and automatic change of the division factor K occur to a value equal to

g-a

(eight)

Upon a command from the control unit 25, the keys 24 and 15 are closed, and the keys 13 and 14 are opened, with the result that the zero humidity simulator 27 returns to the OB position. This completes the calibration mode and the device enters the measurement mode. Thus, in the calibration mode, by changing the division factors of the blocks 10 and 11 of the signal dividers, the initial values of the voltages are set at their outputs, and the humidity measurement is performed using the expression (3)

Compared to the analogue, the use of the proposed device provides improved accuracy in measuring the moisture of the product, which allows narrowing the tolerance value of the humidity from the specified value and reducing the loss of raw materials, as well as improving product quality.

Claims (1)

Invention Formula A device for controlling the humidity of foodstuffs, containing a sequentially and optically coupled light source, an optical interrupter, beam-splitting mirrors that separate two optical channels, light filters in each channel and photoreceiver amplification units, whose outputs in each channel are electrically connected with amplification units of signals whose outputs are connected to a signal dividing unit whose output is connected to a scaling unit connected to an indication unit, characterized in that, in order to increase ochnosti humidity measurement, it is entered into the simulator nu Eve humidity equipped L actuator its input between the light source and an optical interrupter, a comparison unit, a reference voltage unit connected to the comparison unit, a control unit, dividers, with a variable division factor one per channel and six keys, with the inputs of the first and second keys connected respectively to the output DIA of the first and second divider blocks, the outputs of these keys are connected to the | inputs of the first and second signal amplification blocks, the inputs of the third and fourth keys are connected respectively to the outputs of the first and second divider blocks, and the outputs of these keys are connected us to first and second vhdam comparing unit that inputs n first and sixth keys are connected respectively to the first and second outputs of the comparison unit, and the outputs of these keys are connected to the trimming inputs of the first and second divider units, while the signal inputs of the latter are connected in each channel to the outputs of the photoreceiver amplifiers, and the outputs of the control unit are separated so that the first of them is connected to the zero-humidity simulator drive, the second to the control inputs of the fourth and sixth keys, the third to the control inputs of the third and fifth keys, the fourth to the control inputs Amy first and second keys. / I b-j 27 AT 1 t-, 9 1 from the scheme 26 GL 27 Z FIG. 2