---

R_x 4- R_n

(1)

By measuring the unbalance voltage of the Wheatstone bridge, the relation between the unbalance voltage and the return factor is defined by Formula (2):

A ^f/2 r = 4 —— [/1

(2)

The return loss is given in Formula (3):

1
b_r = 20 log - (dB)
• r

(3)

6.3.4 Criterion for compliance

The input and output impedance for the transmission equipment shall be 75 Q and the return loss of > 20 dB in the frequency range between 0,1 MHz and 5 MHz.

6.4 DC voltage at the output

To define the DC voltage level of the black part of the video signal in the output of the transmission equipment.

A TV-signal generator providing a grey scale signal shall be connected to the terminated equipment input. The amplitude and the blanking reference voltage of the input and output signals shall be monitored on a DC-coupled waveform monitor.

The transmission equipment output shall be terminated in 75 Q ± 0,5 %.

The DC voltage level in the output shall be determined by measuring the voltage level of the reference black level in the test signal using a DC coupled waveform monitor.

The DC voltage level of the reference black level in the video signal at the output shall be 0 V ± 2 V.

To verify the waveform distortion with a short pulse signal.

Apply a test signal with elements B1 (2T pulse) and B3 (line time bar) as illustrated in Figure A.2.

Two measurements of distortion are made with the test signals. The first consists of expressing the amplitude of the pulse as a percentage of the line time bar.

The second consists of expressing the lobes, lagging and leading the pulse as a time weighted percentage of the received pulse. Refer also to the clauses related to short-time waveform distortion in CCIR Recommendation CMTT 567-3:1990, Parts В, C and D and Annex IV, Part C, Clause 1, 2.1 and 2.2.

T o define the pulse-to-bar ratio, first measure the pulse amplitude (P) and bar amplitude (B). See Formula (4):

(4)

Check the amplitude of the lobes of the 2T-pulse distortion using the mask (refer to Figure B.4) for the response to test signal B1. The indicated limits correspond to a K_(P/B) value of 3 %, other values can be found by linear interpolation.

The 2T pulse to bar ratio (A?_(P/B)) shall be < 5 %.

The 2T К-factor (A?_(2T)) shall be < 5 %.

To verify the waveform distortion with a square wave signal of the same order as one line. The waveform distortion is defined as the change in shape of the square wave at the output.

Apply a test signal with element B3 (Figure A.2).

Measure the maximum departure Fj of the bar top level from the level at the centre of the bar. The magnitude at the centre of the bar is V_c. The first and last 1 ps of the square wave are neglected in the measurements. The magnitude of the line time waveform distortion Z)_h is defined by Fj as a percentage of V_c as in Formula (5).

D

(5)

=21x100%

« У /о

The line time waveform distortion shall be < 5 %.

To verify the waveform distortion with a square wave signal of the same order as one field. The waveform distortion is defined as the change in shape of the square wave at the output.

Apply a field frequency square wave test signal (signal A of Figure A.1).

Measure the maximum departure of the bar top level from the level at the centre of the bar. The magnitude at the centre of the bar is V_c. The first and last 250 ps of the square wave are neglected in the measurements. The magnitude of the line time waveform distortion D₍, is defined by V_{ as a percentage of F_c as given in Formula (6).

_D

₍₆₎

_y.=2Z_x1Oo%

The field time waveform distortion shall be < 5 %.

To verify the ability of the transmission system to reproduce a sudden change from a low average picture level to a high one and from a high average picture level to a low one. The distortion may be in exponential form and in the form of damped very low-frequency oscillations causing distortion of the video and or synchronization signals.

Apply alternatively a (90 ± 10) % APL and a (10 ± 10) % APL picture to the input of the transmission system. The duration of the signal shall be at least five times the settling time of the damped low frequency oscillation. Refer to Figure B.3 for a detailed description of the signals.

Measure the output signal of the equipment with a DC-coupled oscilloscope.

Measure the variations at blanking level of the video signal at the output.

Also measure any form of clipping of the video or synchronization signal in the output of the equipment when the input signal is switched from (90 ±10) % to (10 ±10) % APL or from (10 ±10) % to (90 ±10) % APL.

The amplitude of the peak overshoot shall be less than 0,25 V and shall settle to less than 0,02 V within 5 s. Refer to Figure B.3.

Signal or synchronization clipping or compression during this test shall be less than 20 %.

To verify the change in amplitude and phase of the chrominance components relative to the luminance component of the video signal between the input and the output of the equipment.

Apply an input signal with F (Figure A.6). Measure the output signal of the system with an oscilloscope.

Measure the amplitude and phase relationship of the chrominance component with regard to the luminance component in the output signal. For an illustration of the different types of relationships, refer to Figure B.1.

Measure v_max, y-i and y₂, calculate the values — and ^У2 , and read the delay and gain .Утах Tmax

inequality values from the Rosman nomogram of Figure B.2.

The delay inequality shall be < 100 ns and the gain inequality shall be < 1 dB.

To verify the continuous random noise as the ratio, expressed in decibels, of the nominal amplitude of the nominal amplitude of the luminance signal to the r.m.s. amplitude of the noise measured after band limiting and weighting with a special network.

Apply a black signal to the input of the system. Connect a video noise meter with the band limiting and unified weighting filter as specified in CCIR Recommendation CMTT 567-3; 1990, Annex III, PartC (with 200 kHz high pass and 5 MHz low pass filters ) to the terminated output.

Measure the signal to noise ratio if the video noise meter is calibrated to do a direct measurement. If the video noise meter is calibrated to measure the r.m.s. noise voltage, calculate the signal to noise ratio from Formula (7):

S

(7)

/N ratio = 20 log (dB)

noise

The signal to noise ratio shall be > 46 dB.

To verify the operation of the video transmission system without interference from other signals, e.g. audio channels, data channels, other video channels, sharing the same physical transmission path or the same transmission system.

Apply grey scale signal D1 (Figure A.4) to the input of a representative video channel under test. Connect a video monitor to the terminated output.

One at a time, apply test signals to the additional channels as follows:

1. video channels: a multiburst video signal (signal C, see Figure A.3) to any of the other video channels;

2. audio channels: make a slow frequency sweep (approx. 10 s per decade) within the specified audio frequency range at the specified maximum amplitude;

3. data channels: the data signals for which the equipment has been designed.

Interference from these signals shall not be visible on the monitor screen at normal viewing distance and nominal monitor contrast.

To verify the ability of the transmission system to reproduce an output signal that is proportional to the applied input signal.

Apply a 5-riser staircase, test signal element D1 of Figure A.4, to the input. At the receiving end, the test signal is passed through a differentiating and shaping network whose effect is to transform the staircase into a train of 5 pulses. An example of such a filter is given in CCIR Recommendation CMTT 567-3:1990, Part C, Annex II.

Measure the difference between the largest I-_max and smallest K_min pulses. The value of the distortion is calculated from Formula (8):

'/max '/min
'/max

x100%

(8)

The luminance non linearity shall be < 10 %.

To verify the ability of the transmission system to reproduce the superimposed sub-carrier in the output signal at equal amplitudes as the luminance varies from blanking level the white level.

Apply a 5-riser staircase with superimposed sub-carrier, test signal element D2 of Figure A.5, to the input. At the receiving end, the sub-carrier is filtered from the rest of the test signal and its six sections are compared in amplitude using a waveform monitor.

Measure the difference between the largest Л_тах and smallest Л_тіп pulses. The amplitude of the sub­carrier at the blanking level is ^_o.The value of the distortion is calculated from Formula (9):

^max Anin
^/f0

x100%

0)

The differential gain error shall be < 10 %.

To verify the ability of the transmission system to reproduce the superimposed sub-carrier in the output signal at equal phase as the luminance varies from blanking level to the white level.

Apply a 5-riser staircase with superimposed sub-carrier, test signal element D2 of Figure A.5, to the input. At the receiving end test signal is fed to a vectorscope.

Measure the maximum phase difference of the sub-carrier on the all treads of the staircase.

The differential phase error shall be less than 10 °С.

7. Video signal transmission equipment environmental testing

   1. Introduction

In order to provide reproducible test methods and to avoid the proliferation of technically similar test methods, the test procedures have been chosen from EN 50130-5.

The purpose of environmental testing is to demonstrate that the equipment can operate correctly in its service environment and that it will continue to do so for a reasonable time.

However, equipment of CCTV systems for use in security applications are installed in many different environments and it would be impractical to test every aspect of the most extreme environmental conditions conceivable.

Therefore, the tests and severity are intended to provide a practical series of tests to determine the ability of the equipment to withstand the failure mechanisms most likely to be produced by the environment in which that type of equipment can be expected to be installed.

It should be noted therefore, that additional precautions may be necessary, in certain installations, where some aspects of the environment can be identified as being unusually severe.

The tests are divided into operational and endurance tests as follows:

1. Operational tests:

In these tests, the specimen is subjected to test conditions that correspond to the service environment. The object of these tests is to demonstrate the ability of the equipment to operate correctly in the normal service environment and/or to demonstrate the equipment’s immunity to certain aspects of that environment. The specimen is, therefore, operational, its condition is monitored and it may be functionally tested during the conditioning for these tests.

2. Endurance tests:

In these tests, the specimen may be subjected to conditions more severe than the normal service environment in order to accelerate the effects of the normal service environment. The object of these tests is to demonstrate the equipment’s ability to withstand the long-term effects of the service environment. Since the tests are intended to determine the residual rather than the immediate effects of the test conditioning, the specimen is not normally supplied with power or monitored during the conditioning period.

This European Standard specifies the tests and severity to be used for each of the following four environmental classes.

Classes I, II, III and IV are progressively more severe, and therefore class IV equipment may be used in class III applications, etc.

• Classi: indoor but restricted to residential / office environments;

• Class II: indoor in general;

Class III: outdoor but sheltered from direct rain and sunshine, or indoor with extreme environmental conditions;

Class IV: outdoor in general.

Environmental tests require that the equipment be examined before the test, during conditioning and after the test. This examination is carried out by applying a functional test for operational, and where applicable, for endurance tests. The output signal is also monitored on a video monitor during the functional test.

The functional test comprises the following tests:

1. insertion gain (see 4.3);

2. luminance non-linearity (see 4.7).

During the endurance tests, a deviation of maximum 10% from the required value is allowed. Furthermore, there shall not be visible interference visible on the monitor screen at normal viewing distance and normal monitor contrast.

The test and conditioning shall be in accordance with EN 50130-5:2011, Clause 8.

Before the conditioning, the specimen shall be subjected to and shall pass the functional test (see 7.2.2).

Mount the specimen as specified by the manufacturer, and connect it to a suitable power supply, monitoring and loading equipment. The specimen shall be in its normal operating condition.

Monitor the specimen during the conditioning period to detect any change in operating status.

During the last 30 min of the conditioning period, subject the specimen to the functional test (see 7.2.2).

After a recovery period of at least 1 h, subject the specimen to the functional test (see 7.2.2).

The test values resulting from the functional tests before and after conditioning shall stay within the limits specified by the manufacturer.

During conditioning, a 10 % degradation of the limits is allowed.

The test and conditioning shall be in accordance with EN 50130-5:2011, Clause 9.

Before the conditioning, the specimen shall be subjected to and shall pass the functional test (see 7.2.2).

Mount the specimen as specified by the manufacturer. The specimen shall not be supplied with power during the conditioning.

There are no measurements during conditioning.

After a recovery period of at least 1 h, subject the specimen to the functional test and visually inspect it both externally and internally for mechanical damage.

The test values resulting from the functional tests before and after conditioning shall stay within the limits specified by the manufacturer.

The test and conditioning shall be in accordance with EN 50130-5:2011, Clause 10.

Before the conditioning, the specimen shall be subjected to and shall pass the functional test (see 7.2.2).

Mount the specimen as specified by the manufacturer, and connect it to a suitable power supply, monitoring and loading equipment. The specimen shall be in its normal operating condition.

Monitor the specimen during the conditioning period to detect any change in status.

During the last 30 min of the conditioning period, subject the specimen to the functional test (see

7.2.2).