Universal CCTV Tester - TOMEK-8
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Tester of lens, cameras and monitors, and CCTV signal meter "Tomek 8" is universal device providing invaluable service while starting up new CCTV systems as well as maintaining and repairing them. Small size and comfy leather case make it especially handy in inaccessible places, just where cameras are usually mounted.
The tester has eight functions:
- Measurement of power voltage.
- Indication of improper polarity of supplying voltage.
- Measurement of ripples.
- Measurement of video signal.
- PAL generator.
- Control of lens ZOOM.
- Control of lens FOCUS.
- Opening and closing diaphragm in lens with automatic aperture control.
|Name||Tester Video TOMEK - 8|
|Supplying voltage||12V DC (Min 8V.Max 15V)|
|Current requirement||110 mA|
|ZOOM and FOCUS voltages||+/- 3V - terminals|
|Video measurement range||Max 5 Vpp - BNC input|
|Ripple measurement range||Max 10 Vpp|
|Working temperature||0-50 oC|
|Accessories||Leather case. manual|
The tester is equipped with measuring sockets and terminals to which the tested device is being connected.
Measurement of supplying voltage.
Testing a camera we should start from measurement of supplying voltage. Contrary to appearances, the 12V voltage can sometimes cause many problems, especially when we power cameras with long cables. Voltage loss caused by big resistance of long cable decreases the value at camera's terminals, disturbing proper operation. Cameras shouldn't be supplied with voltage lower than 11V. It's true that some can work at even 9V, but most cameras below 11V are becoming unstable (at about 10V) - they loose color or switch themselves off.
The power to the tester we connect to typical 5.5 mm socket or to screwed terminals. If we use the plug normally used for powering a camera and put it in the socket, then the terminals may be utilized for connecting the camera - via additional cable terminated with the same kind 5.5 mm plug. This way both the tester and camera are powered with the same source. So the socket and terminals are connected in parallel and marked in the figure below with brown color.
After power has been supplied, the tester by default is set in mode: voltage measurement - the LED "U" lights.
The display shows current voltage in Volts (two digits). Pressing down the "?" key we may gain the fractional part (the next two decimal places), having effectively 4-digit voltmeter.
In case of improper polarity the tester switches itself off, showing with ERR LED the fact of wrong connecting.
Measurement of ripples.
Usually, with stabilized supplies, the ripple level is very low and it is not taken into consideration as regards its impact on a system. The situation can change in case of broken down capacitors or excessive to nominal output current. If it occurs, it is mostly 100 Hz ripple, the second harmonic of mains frequency.
Typical sign of ripple is wide horizontal strips on a picture, slowly moving up or down. To assess the problem one might use an oscilloscope, or dedicated AC voltmeter.
Both methods need using additional equipment, whereas having one universal tool - the TOMEK 8 - one may immediately measure the value of ripple in supplying voltage. Only being sure that the supplying source has proper parameters, it is possible to continue further measurements and testing video paths.
We take measurement of ripple in this way:
With pressing [%u2194] key we make the [%u2206U] LED light up. This moment the display will show the value of ripple in volts, with 0.1V resolution. With properly working and loaded supplies the reading will simply be 0.0V.
Measurement of video signals.
Composite video signal we connect to BNC plug marked with [VIDEO IN].
Using this plug we are able to connect a camera directly with its output, and check the level of video signal. It is really handy solution for a man being up a ladder and manipulating a camera. Thus far, he would have to connect a cable and lead it to a monitor, in order to check the signal roughly. Now, he does not have to walk down and up again, but he may just measure the video signal to assess whether the camera is in running order. The same he can do with other video equipment like video splitters, separators, switches, routing switchers as well as cables and connectors. The quick test is effected by measuring input and output video signal just at examined piece of equipment.
In order to read a value of video signal, with pressing [%u2194] key we make [VID] LED light up. This moment the display shows value of peak-to-peak voltage in volts. A reading should be between 0.3 to 1.0 V. The more white areas in an image, the higher voltage will be noticed. It can be easily seen when covering lens with hand for a moment.
Having possibility of Vp-p measurement it is easy to test video amplifiers, passive and active devices dedicated for video transmission with twisted-pair, UTP or STP cables, separators and video transformers or even outputs of recorders.
PAL generator serves as a tool for checking monitors, recorders, video capture cards, and cabling. The device that should be tested needs to be connected to [PAL GEN] BNC socket.
Then with pressing [%u2194] key we make the [PAL] LED light up. The display will show a number of generated pattern e.g. P1. With the [+] and [-] keys we may change the pattern.
Sometimes it can be forgotten that a monitor, due to its screen's shape and settings may cut the coming from camera original image. The pattern in form of grate (6 x 8 squares) enables quick assessment of an area that is out of the displayed image. Looking at the outermost squares we see how much of them is cut off by the border of the screen.
The truncation of images is also met in e.g. video capture cards. During the process of switching cameras, the card needs some time to synchronize itself with coming new frame so that the result image is often a little smaller than the original one.
The P1 grate pattern allows to estimate monitor's linearity or, in other words, deformation of imaging. The P2 grate pattern enables to assess the level of reflection, if it occurs. Reflection is caused by mismatch of a receiver (the load) and the transmission line, and usually is noticeable with longer transmission lines. On a screen it can be seen on the right side of borders between light and dark objects (and vice versa).
The next pattern - vertical bars with graded level of luminance - enables to check and adjust proper levels of contrast and brightness in a monitor. All bars should be well distinguished. If some, mostly the outermost bars are seen as identical, it means that picture parameters are not suitably adjusted and need some correction. It is essential for proper observation of details in pictures from cameras.
The following test pictures - white and black backgrounds - permit to assess number of damaged pixels, especially with LCD monitors.
Gray background is suitable for above purpose, too, and may be used for testing the level of magnetization of color picture tubes.
The magnetization may be caused by any close devices generating strong magnetic fields, like mains transformers, electromagnets, loudspeakers. The effect is seen as no great tinges, mainly near the outer edge of a screen. The item used for demagnetizing, or degaussing, the aperture mask and metal-bell portion of a color picture tube is external air-core electromagnet - degaussing coil. In most common situations, when the level of magnetization is not high, it is sufficient to use the inner degaussing circuit, mostly present in color monitors. The gray background is also suitable for finding such effects like burnt areas on a screen, produced by constant, static pictures. Often it may be noticed e.g. in QUAD applications, where a dark cross comes into being in the center of a picture.
Using the PAL generator and a monitor, we can in a flash check faultlessness of such devices and equipment like: video splitters, image dividers, separators, amplifiers and cables, leading signal from cameras to mentioned items. No additional camera or device is needed.
Control of ZOOM and FOCUS of lens.
The picture below shows the way of connecting the tester to a camera and lens, in order to power all equipment with one supplier and ensure controlling ZOOM and FOCUS. Lenses are equipped with three or four terminals for ZOOM and FOCUS motors. In case of four terminals, two of them are connected to the ground, and the rest the same way as shown for three-terminal case, i.e. ZOOM to [Z] and FOCUS to [F].
With the [%u2194] key we choose the interesting function (adequately [Z] or [F] LED lights up). Next, with [+] or [-] key, we feed the chosen motor with +3 or -3 volts. The display shows the value of applied voltage.
Opening and closing diaphragm in lens with automatic aperture control.
It mostly happens that camera is adjusted during a day or even in the sun. But in the evening, it appears that images are of poor quality, they loose sharpness. The reason for that is change in depth of focus with weak light.
In full lighting the depth of focus is greater and the observed object may lie within its range, whereas during night-time, when the depth is shallow - the picture or object lies out of the zone and is blurred. The picture below shows the effect.
So far, the only method of "opening" a lens for focus adjustment was putting a gray optical filter. The filter diminished quantity of light coming into lens and made the diaphragm open wider.
Disadvantage of that solution is necessity of having numerous filters for different cameras and various lighting conditions.
The focus of a lens should be always set with fully opened diaphragm, that is with depth of focus settled in minimum position. To open diaphragm with the tester, we take out the cable from camera and connect it to the IRIS connector situated on the side of the device.
It should be remembered that the camera ought to be set into automatic shutter mode, otherwise picture will be overexposed. The tester is suitable for both DC and VIDEO lens.
With the [%u2194] key we light up the [I] LED (IRIS). Pressing the [+] or [-] key we change voltage on lens, opening or closing diaphragm. (For VIDEO lenses, the tester generates only two states: open or close).
After the focus has been adjusted, we put back the cable and turn off automatic shutter mode, and switch on the automatic aperture control.
The tester "Tomek-8" is a very useful tool for starting up CCTV systems, and in some cases e.g. with adjusting focus of lens with automatic aperture control is really irreplaceable! It is really handy solution for a man being up a ladder, often in hard conditions, giving convenient possibility of checking many parameters that influence quality of CCTV systems.
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Universal CCTV Tester - TOMEK-8
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