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| SYSTRON DONNER Model 1138...Nixie tubes....and, HEY; There's Dave Jones ! |
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| RJSV:
A recognizable face, as I browsed some history, of SYSTRON DONNER test equipment. Turns out Dave Jones did a Tear-Down (pls see #1138)! The thing has NIXIE TUBE displays, and is described as made in Australia ! Wow, (small world). My work time there was mid-70s, where I performed the various aircraft component 'Qual-Tests' in Sunnyvale, CA. It was the Safety Systems Division, West Berkeley industrial park, and they manufactured excellent and unique FIRE and Overheat detection systems. Infrared sensor technology wasn't strong yet, and the Safety Division systems used DC switches and 28 VDC powered relay and transistor units. The special aspect was the sensing element, consisting of, first, a helium filled tube that got snaked around inside aircraft engine cowlings and in some big trucks. With a bunch of (abnormal) HEAT present, this sensing tube and diaphragm switch would close the sensing circuit relay. That's the OVERHEAT function. But then also, in the same sensing tube would be an industrial 'oddity' which is a 'getter' material, which simply means a metal hydride wire, for absorbing relatively HUGE amounts of hydrogen atoms. Then, to release this hydrogen gas a spot-flame applied can cause a significant rise in pressure, for the system to monitor, in case of fire, or in case of overheat. Honestly, I don't remember how those two fire detection aspects were distinguished. In cases of a sensor element FAULT there was a fault pressure switch to alert the pilots that sensor pressure was lost. These switches were often a Molibdinum dome, approx 2 cm diameter. One benefit, of the moderate tech used, is that less semiconductor (switches) are used, in the often blistering HOT places; engines, elevator motor units off-road construction trucks and ginormous trucks used in mines, etc. Often, the electronics box housing had relays (28 VDC). It was a Cadillac priced deal back then. I suspect that most fire / overheat detection these days uses IR (infra-red) devices. Btw: A very similar method, of holding hydrogen gas, in the atomic in-between areas of a hydride metal is also the basis for some experimental HYDROGEN powered cars. |
| RJSV:
Oops, apologies, I meant to put the title as: EEVBLOG #1138 (not the freq counter model...) |
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