The EEV P2238 ARGUS 1 Thermal Camera
Amongst my collection of thermal cameras I have several EEV ARGUS thermal cameras. These come up on ebay now and then so I thought I would provide an insight into one of them, the ARGUS 1 Fire fighters Camera.
I may provide similar for the ARGUS 2 (BST Detector) camera in future.
The ARGUS 1 was manufactured by the English Electric Valve Company (EEV). EEV were the first company to manufacture a hand portable uncooled thermal camera for the Military. This unit is based on their original military camera design named the P4428 and uses a Pyroelectric Vidicon tube. This is thermionic valve technology but it still performs well. Those familiar with Vidicon CCTV camera tubes will feel very at home working on the ARGUS 1 as she is similar in operating principle.
As stated, the ARGUS 1 is the successor to the original P4428 (aka “The Dustbin”) and it has the model designation P4438. The electronics were refined using more modern components but the optical block is little different.
A Germanium lens illuminates the thermally sensitive face of the Pyroelectric Vidicon (PE Vidicon). A mechanical iris in the lens assembly controls the energy passing out of it and acts to avoid overload situations. The PE Vidicon requires a chopper wheel to be placed between it and the lens assembly. In the ARGUS 1 the chopper wheel is constructed from very thin FR4. It is driven by a high quality coreless motor and synchronised to the video stage. The chopper wheel sets the frame rate and this is 30 frames per second in the ARGUS 1.
The PE Vidicon operates by having an electron beam scanned across the thermally sensitive surface by H and V deflection coils to form a Raster, as found in conventional Vidicon cameras and CRT televisions. The thermally sensitive surface is called the Target and its output is fed to a high impedance amplifier. The signal is then processed in a similar manner to the conventional Vidicon camera. I shall not go in to detail here as that will take too long. Google will supply plenty of information on the Vidicon camera operating principles.
The unit basically consists of the following sections:
1. Optical Block
2. PE Vidicon tube
3. H and V drive for PE Vidicon and CRT tubes
4. Chopper wheel Synchroniser
5. Video processing & AGC Block
6. Battery level meter & overlay circuit
7. Power Supply, HV & LV
8. CRT monitor assembly
I have the full service manual for the ARGUS 1 as it is not covered by ITAR. Regrettably I cannot share it as it was provided under a NDA that I would not wish to break. I am however including the adjustment point images of the PCB’s as that is not enough detail to break the NDA.
The camera has three PCB’s as shown in the attached images. They are simple to access and very easy to work on. Areas worthy of note on the PCB’s, The high impedance input amplifier from the Target output is contained inside a shielded can, as you would expect. The unit makes use of several ceramic substrate daughter boards that use DIL format connections to the PCB. An unusual design feature in such a camera, that is not found in its predecessor. The camera also contains an ‘hours run’ meter. I love to see those in equipment as it provides an idea of the run time on a unit.
It should be noted that the PE Vidicon tube in a thermal camera is a dynamic device in terms of the correct bias voltages applied to it. Over time the characteristics of the tube change and it requires the bias voltage to be adjusted to achieve the best possible image quality. The service manual provides full details of how to service and maintain these cameras. I love quality service manuals like this.
The camera is designed to survive in the hostile environment that Fire Fighters endure so its construction reflects this. The outer yellow shell is heat and flame resistant. Under this replaceable shell there is a special thermal blanket pre formed to fit the module that it protects within. Once the yellow shell and thermal blanket have been removed, the black camera module may be seen. This is a sealed unit that is designed to protect the electronics from immersion in water. The outer yellow shell is fitted with waterproof gaskets for this reason as well.
The black inner casing is easily opened to provide access to the electronics within. I have included another ARGUS 1 in the image to show it complete, the inner black module and the electronics. I own four of these cameras. They had a tough life but survive well. One of mine was used for training and is pristine. It never saw real smoke in its life, unlike the other example I have that still small of smoke and are a little marked as would be expected.
I found someone selling just the M509B Pyro-electric Vidicon tube on ebay so I am including those images here rather than dismantling the camera to duplicate what they show.
Ok to the pictures……. Enjoy ………
The PDF's of the PCB adjustment points is included under "Argman 3d" and "Argman 3e"
They will come in several posts due to their size and number.
Aurora
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