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P4428



The classic Naval imager sold to navies worldwide including over 2000 to the US Navy where it was known as the ' NFTI ' (Navy fire-fighting thermal imager). Civil use was more limited, thermal camera were still often seen as specialist equipment, although as 'one per truck' became standard the older images were passed down to on vehicle use. These cameras can sometimes appear on sale through eBay etc.
Electrically similar to later builds of P4228 but smaller and lighter especially due to the separately housed battery and volage regulator allowing the battery weight to be taken directly on the body

Video Image from P4428
View into rear of P4428 showing battery LED's
Powered Handle Accessory



Data Table for P4428
   
Sensing Method Pyroelectric effect in TGS crystal material. Temperature changes from the scene cause charge to build up / decay on the inner face of the target material.
Sensor Type / Size EEV Pevicon P8092 and yoke MA509, 18mm circular target area. Normally a 'Soft' vacuum tube with slight helium pressure except in some variants as noted.
Lens Parameters 18mm f/0/7 giving 50° field of view. Fixed focus by moving tube & yoke assembly at build
Dynamic Range / Control 60°C with iris open. Automatic iris in lens allowing use in fires without damage or saturation
Display 38mm CRT with magnifier lens
Sensitivity (MDTD) <500mK, usually ~300mK in 'Pan' with a skilled operator
Power Source Internal carrier with 10 'AA' cells. Used LR6 alkaline, or optionally NiCd
Power System Battery regulated to 8.7V, camera ~4W
Video Output BNC, produced in 60Hz / 525 line and 50Hz / 625 line variants
Image Processing Normally 'chopped' with 1-field digital image store to give a constant image. Pan mode retained for training compatibility
Manufacturer Status Obsolete, no longer serviced
Number and Years Built High 1000's from 1985 - 1996
Export Status Not controlled
Publicity P4428 datasheet
P4428 brochure
Pevicon tube P8092 datasheet
Pevicon tube P8093 datasheet
Pevicon tube P8226 datasheet

Derivatives

The P4430 and P4431 were derivatives of the P4428 with a narrow field of view lens, manually focussed. See this page.
The P7099 was the same camera (in grey plastics) for a specific distributor.
The P4429 used a hard vacuum tube type P8093, but was otherwise to P4428 specification
The P7097 & P7098 were a medical / fixed imager with the voltage regulator inside. It has a 12V input and video output on the rear.
There were a number of 'one off' cameras essentially to support tube sales, for example a 'P4428' with Zinc Selenide tube and lens for mid-wave imaging. The tube was capable across quite a wide range, see P8226 datasheet above.

Hobby user information

Rechargeable batteries may be used in the 'AA' carrier, but the battery indicator is not accurate in this situation as the discharge curve of a NiCd / NiMH is not the same as for LR6 alkaline cells.

Camera is powered by 8.7V from the battery box which contains a linear regulator. The 4-core cable carries 0V, 8.7V, battery+ and screen. The battery voltage is only needed to drive the battery indicator.

Common faults are in the voltage regulator and also dealing with tube ageing that requires periodic setup. The cameras were supplied with a service manual so setup is possible with suitable equipment (video display, AVO and scope), see P4428 setup page for more details and scope photos

A late edition manual is available in 3 sections Front, PCBs, Rear and includes the 'new' PCB set.

Camera Chassis (later model) showing the scanning / high voltage PCB side of the camera.
Shutter and Lens. As the shutter rotated the edge of the blade moves up in front of the tube target following the scan. This, when locked to the camera field rate, ensured that each part of the tube (effectively a 'pixel') was exposed to the scene for one whole field and then covered for one whole field.
A phase locked loop varied the motor drive to align the blackened edge passing through a photosensor and the video frame sync.


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Heritage TICs EEV P4428 page 6 December 2020  All tradename © respective owners