European standard for video surveillance systems.
EN 50132-2-1. This number hides the European standard for black and white video cameras for use in security systems. (Alarm systems — CCTV surveillance systems for use in security applications. Part 2-1: black and white cameras).
This is only one of the first parts of the large standard EN- 50132, dedicated to the use of video surveillance systems in security.
It was adopted in July 1997 and comes into force on February 1, 1998. More precisely, all members of the European Community must ratify this standard or adopt equivalent national standards by this date.
Russia is not a member of the EU, so we are not at risk of adopting a similar standard anytime soon. However, EN-50132 is very important, because it is the first international standard defining terminology and measurement methods in this area.
How did they sell fabrics in ancient times?
«I need 5 elbows of satin for a shirt!»
«Please… »
«But that's not even enough for one sleeve!»
«Well, that's the size of my elbow… «
A similar situation has existed in the CCTV industry up until now. For example, camera sensitivity was specified as God put it, just so the figure would look more impressive. «Our sensitivity is 1 lux!». «And ours is -0.01 lux!». «And our camera even works in the dark!». It is clear that it works, that it will break down, or what, in the dark?
And this was inevitable — even the most responsible companies are not able to provide a full description of the measurement procedure — it would require too much space. And even if they did — how can these parameters be compared with those provided by another company, whose entire testing methodology is built completely differently.
From now on, all leading equipment manufacturers will indicate parameters «according to EN 50132», otherwise their products will be banned from Europe.
Of course, even now you can find an opportunity to cheat a little, provide some one fantastic parameter and at the same time not focus on other parameters that turned out to be extremely bad.
However, at least the units of measurement are now the same for everyone (the standard meter instead of the subjective elbow).
In addition, the standard contains some limiting criteria — it specifies the maximum permissible values for some parameters. For example, the maximum permissible signal/noise value is specified.
The minimum required parameters for resistance to vibration, temperature, and other unpleasant environmental influences are specified.
The requirements are not too strict, but many small companies that have appeared on the video equipment market in recent years have apparently not even thought about this.
Large American companies are probably adapting most easily — their products have always been tested for compliance with many military requirements (MILSTD).
Obviously, large European companies that took an active part in the development of the standard will survive the innovations without any shocks.
But relatively small firms, especially those in the East, will have to fight for their existence again and again.
Now let's look at some sections of the standard in more detail.
Requirements for the parameters of black-and-white cameras
This section presents, firstly, the requirements that are mandatory for compatibility of products from different manufacturers (in fact, a repetition of the description of the low-frequency video signal from the CCIR standard) and, secondly, the requirements for the parameters provided in the descriptions. This part is of most interest to the domestic reader — understanding these parameters will allow you to correctly navigate in the sea of u200bu200bequipment.
Further, more or less literal excerpts from the standard are given in normal font, and my comments are in italics.
Sensitive element
The technology, size and (for sensitive elements with a matrix structure) the number of elements per row and per column in the active area must be indicated.
Most cameras produced today have a CCD matrix as a sensitive element, but sometimes you can also find vidicons or hybrid systems with an electron-optical converter.
They can have fantastic parameters, but are extremely inconvenient to work with — they have a very limited service life.
Please note that the size of the sensitive element is usually indicated in inches, indicating the diameter of the equivalent tube.
The standard fixes the following values:
1 » means the diagonal of the sensitive area is 16 mm.
2/3″ means the diagonal is 11 mm.
1/2″ — the diagonal is 8 mm.
1/3″ — 6 mm.
Electrical signal gain
The AGC (automatic gain control) range in dB and the gamma correction factor value must be specified. If the G-correction curve changes with gain changes, this must be specified.
Gamma correction is a nonlinear signal distortion that should compensate for the nonlinear transfer function of most modern monitors. At low signals, G-correction works like AGC — for example, at G=0.45, a -6 dB signal is provided at an illumination 5 times lower than that required for a full video signal.
The ALC (automatic light control) parameter should also be provided — it denotes the ratio of the minimum illumination at which the output signal is at -6 dB to the maximum at which the output signal does not exceed the permissible value (0.85 V from the level of the quenching pulses). It is provided as a ratio, for example, 1:10000.
This parameter (I do not know its official Russian name — for example, «permissible range of illumination») includes the operation of all mechanisms for adaptation to changes in illumination — AGC, automatic shutter speed and, possibly, auto iris, if the camera is equipped with a lens with an auto iris.
This parameter can have different values for different configurations.
For example, if a camera is designed to be used with either an auto-iris or non-auto-iris lens, two values should be given, especially if enabling the auto-iris disables the camera's automatic shutter speed control.
Sensitivity
Probably no other parameter has been juggled so actively and shamelessly by camera manufacturers (or rather, their marketing departments). The most, it would seem, generally understandable, visual parameter and at the same time providing the greatest arbitrariness in definition. Therefore, I will allow myself to quote verbatim the section devoted to the definition of the concept of sensitivity.
Sensitivity and signal-to-noise ratio are interdependent. For the correct interpretation of this quality parameter, the specifications must include three values:
sensitivity for a -6 dB signal at the output
sensitivity for a full video signal
signal-to-noise ratio.
Sensitivity at -6 dB for acceptable signal: The sensitivity of a camera is defined as the illuminance in lux at the sensing element (without lens) at which the camera delivers a signal of 0.35-1-0.05 V at the output under specified conditions.
Sensitivity for full video signal: The sensitivity of a camera is defined as the illuminance in lux at the sensing element (without lens) at which the camera delivers a full video signal at the output.
The signal-to-noise ratio at which this sensitivity is achieved must be stated next to the sensitivity value.
The signal-to-noise ratio at minimum gain of the AGC circuits should be specified along with the illumination of the sensitive element required to achieve this condition.
The signal-to-noise ratio specified in points 2 and 3 should be better than 40 dB (weighted).
First, the concept of «acceptable video signal level» is clearly defined — this is the level of -6 dB, that is, half the video signal, without taking into account the sync pulses.
Earlier, there were attempts to interpret even the concept of -6 dB in their own way.
For example, everyone knows that a normal video signal has a swing of 1 volt.
So they gave the sensitivity for a signal with a swing of 0.5 volts — although most of this swing is made up of sync pulses (300 mV), and the actual signal there is only 200 mV.
Taking into account the nonlinearity of the transfer characteristic (G-correction), this allowed us to absolutely honestly increase the sensitivity five times!
And if we ignore the widespread (but not mandatory!) criterion of -6 dB, then the limits of camera sensitivity were set only by the advertising manager's notions of conscience.
Secondly, the concept of «sensitivity for a full video signal» was introduced as a mandatory parameter.
Such a parameter does not depend on the selected value of the factor G, and most importantly, has a limitation on the signal-to-noise ratio.
The camera manufacturer has the right to build in an arbitrarily large AGC range, and thus pull out to the full video signal even an image completely drowned in noise, however, the sensitivity of the camera for the full video signal will be considered the illumination at which the noise remains at a reasonable level.
It is this sensitivity parameter that is recommended to be used as a basis for calculations when designing systems. Of course, when the illumination decreases, something will still be visible for a long time, but the specified probabilities of object recognition or the specified operator duty time until eye fatigue will no longer be ensured — this is an emergency mode for emergency situations.
It should also be noted that although the definition is given for illumination «on the sensitive element», the measurement procedure is described for measurements together with the lens, which also allows testing cameras with a built-in (non-removable) lens.
If the manufacturer quotes sensitivity in terms of illuminance «on target», it is recommended that it be quoted with an F/1.4 lens, a peak reflectance of 0.89 on target, a lens transmittance of 0.9, and illumination perpendicular to the subject.
In this case, sensitivity «on target» differs from sensitivity «on sensor» by exactly 10 times.
Not mentioned in the above passage, but clarified in the appendix: the definition of sensitivity is given for illumination by incandescent lamps with a color temperature of 2800 to 3200K.
Cameras intended for use in low-light conditions should have spectral sensitivity graphs in the range of 400-1000 nm, which will allow the system designer to adjust the data provided taking into account the spectrum of the lamps used.
Maximum Resolution
The maximum resolution of a video camera is defined as the maximum number of stripes (usually alternating black and white) that can be distinguished in a size equal to the height of the frame. Resolution is measured at an illumination level corresponding to the optimal signal-to-noise ratio (as described in point 3 of the previous section).
If the resolution deteriorates with decreasing illumination, it should also be specified for the conditions of point 1 of the previous section (video signal at -6 dB).
In addition, for values near the maximum resolution, the values of the modulation transfer function (contrast transfer function) — the depth of modulation of the video signal when displaying bands of a given spatial frequency — should be specified.
Please note: the maximum resolution is defined on the size of the screen height.
Given the standard 3:4 aspect ratio, this means that the horizontal resolution is measured over 3/4 of the screen width.
Since there is no 'band visibility' criterion, for CCD matrices this effectively fixes the 'limit resolution' parameter to 3/4 of the number of cells in a line, except in cases where the output signal bandwidth is severely limited (as is the case with composite color video).
A positive aspect is the recognition of the need to provide a transfer characteristic as the most objective way to describe the limitations imposed by the camera on the resulting resolution of the entire system.
Unfortunately, since this parameter is not yet widely used and tested in practice, no requirements are imposed on it.
General parameters
The weight, dimensions, supply voltage and power consumption must be indicated. In addition, the type of lens mount (for cameras with interchangeable lenses) and the method of mounting the camera itself must be indicated. For camera mounting, the «preferred» holes are 1/4″ threads with a pitch of 20 threads per inch, or 3/8″-16. And for lens mounting, the «C» or «CS» types are mandatory.
Parameters of resistance to external conditions
The group of parameters for protection against adverse external conditions has been worked out in great detail, but, unfortunately, it does not correspond to Russian conditions too much.
The temperature range of -25C .. +55C is called mandatory for «external» cameras. Of course, -25C is clearly not enough even for Moscow.
And for the Central Asian republics of the CIS, +55C is completely insufficient. However, other parameters may even seem overly strict — for example, resistance to saline solution for areas remote from the sea and from Moscow road services.
In the descriptions of the equipment (of the few new ones that I have already seen), manufacturers simply state «conforms to standard EN-501» 32 «, and provide specific parameters only if they exceed the requirements of the standard.
Therefore, I provide here in sufficient detail the «standard» requirements that are implied by the phrase «conforms to EN-50132 in relation to resistance to external conditions in class such-and-such».
The equipment is divided into 4 classes:
for use in office-type premises
for indoor use in general
for outdoor use under a roof
for outdoor use in general.
Class II chambers may be used outdoors in suitable enclosures that meet the requirements of Class IV and provide Class II conditions inside them.
Hereinafter I refer to the requirements for Classes II and IV as «indoor» and «outdoor» chambers, respectively.
There are two types of tests: for operability (under normal operating conditions) and for survival (under conditions exceeding normal permissible ones, to accelerate the manifestation of the effects of normal conditions).
In the first case, the camera's operability is checked before the test, constantly during the test, and after the test.
In the second case, the camera's operability is checked only before and after the test, and during the test it may not even be supplied with power.
Performance testing includes checking:
a) sensitivity
b) black level stability
c) maximum resolution
All these parameters must comply with those declared by the manufacturer.
Temperature tests are carried out for 16 hours separately for the upper and lower temperatures. The upper temperature is set at 55C for all cameras, the lower at -10C for internal cameras, and -25C for external cameras.
Resistance to high temperatures and humidity is tested separately— +40C at 93% humidity for 3 weeks (survival test).
In addition, external cameras are tested for survival — 6 heating-cooling cycles from 25C to 55C at 93% humidity at high temperature and condensation during cooling.
Water resistanceis specified only for classes III and IV. For class III, the requirements correspond to IPx2 — against water drops at an angle of up to 15 degrees from the vertical. For class IV — according to IPx4 — against jets from all sides with a flow of 10 liters/minute for 15 minutes. In this case, the chamber must not only continue to operate, but also no water is allowed to enter.
Sulfur dioxide resistance — survival test. In an atmosphere containing 25 ppm SO2, at a temperature of 25 °C and a humidity of 93%, the internal chambers must withstand 4 days, and the external ones — 21 days without loss of functionality and visible signs of rust.
Salt fog— Survival test. Only for external cameras. 4 cycles are carried out over 4 weeks — 2 hours in salt fog with a salt concentration of 5% at 35C, then 166 hours at +40C and 93% humidity. No decrease in parameters or signs of rust are allowed.
Impact — a sinusoidal half-wave with an amplitude of 300 in all directions, applied through the standard mounting point, should not cause even short-term image distortion.
Vibration— 0.5d in all directions in the frequency range 10-150 Hz for 12 minutes should not lead to a decrease in parameters during the tests, as well as after the tests under the influence of vibration for 6 hours.
Dust — the external chambers should withstand a flow with a high content of fine talc for 8 hours. Dust is not allowed to enter the interior.
Conclusion
The EN 50132 series of standards includes the following parts:
1 System requirements
2-1 Black and white cameras
2-2 Color cameras
2-3 Lenses
2-4 Auxiliary equipment
3 Control devices
4-1 Black and white monitors
4-2 Color monitors
4-3 Video recorders
4-4 Paper printers
4-5 Video motion detectors
5 Video transmission means
7 General provisions
At present, only Parts 7 and 2-1 have been published. As you can see, CENELEC and its Technical Committee 79 still have a lot of work ahead of them.
And even after the standards are adopted, they are not immediately implemented. Thus, production of products that began before the adoption of this standard can continue until 2003.
It is not at all necessary for Japanese and other Asian manufacturers to be guided by this standard.
As, incidentally, for Russian ones.
However, these first parts of the standard already provide a point of support for all those working in the security video surveillance industry.
And, I hope, the emergence of the European standard will accelerate the emergence of a domestic GOST.