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    Capacitors in Old I&C drawings

    @oneye14 Apologies, I made the simulation quickly and didn't think of presentation. I will check current consumption and let you know. This is an old I&C circuit from the 50's and I was confused as to the role of the 1uF capacitor. By current source do you mean it sources constant current...
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    Capacitors in Old I&C drawings

    This is their general definition/purpose. But they are used widely in all kinds of circuits, from filters to power supply stabilizers, timing and flashing circuits etc. They can also be used to block DC entirely sometimes. I simulated this circuit using Multisim earlier to see the differences...
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    Capacitors in Old I&C drawings

    That would be brilliant yet over kill I think. They did have timers and flashers back in the 50's. I do think your initial hypothesis was correct. PIA-1 is a pressure sensor with two high Impedance inputs (Like a comparator Op Amp, in fact it possible this device is just two comparator op amps...
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    Capacitors in Old I&C drawings

    Thank you Phil. What might be the purpose of the capacitor there? I understand the resistors limit current when HLP or LLP is trigger i.e the current patch will go through the PIA-1 sensor. Very interesting idea indeed.
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    Capacitors in Old I&C drawings

    Yes, I thought the same thing. The design however is from 1950's and I am assuming instrumentation and sensors worked quite differently back then. The supply is 120 VAC, 60 Hertz (Not 25 VDC). I am also assuming controllers either didn't exist or were fairly new back then. This is definitely...
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    Capacitors in Old I&C drawings

    Hi guys, thanks for your support. Just joined the world of Electrical & Industrial I&C. Was going through some old legacy drawings for work and found something interesting. HLP and LLP are relays. PIA-1 is a pressure sensor which is tied to an annunciator panel. I am having trouble understanding...
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