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Ophir 40w-oema-tr2

Cyparagon

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I saw this auction in the ebay deals thread and put a low bid on it. I won! $34 shipped. The external cable has red/black/white/green/drain and is a 5-pin connector. I took the back off (just two allen bolts). There's an op-amp, two local regulators (those TO-92's), and a bunch of passives. Only 4 of the 5 connector pins are used. I traced out the paths and found +, -, gnd, and output pretty easily.



Looking at the datasheets for the two regs, they're +/- 12V with 1.7V dropout at 40mA. So I suppose that means it wants +/- 15V in. Any lower and it's not in regulation. Any higher and the voltage gets dropped anyway. I hooked up a pair of bench supplies and checked the output which sat at 1.4mV. I pointed a beam at it - it's alive! I compared readings with my analog Gentec meter. They're within ~2% of each other with both a 280mW red and a 1.8W blue. The scale is 1mV/mW.

But my question is: is this a 40W sensor? The water lines suggest so, but the local 12V regulator and the mV/mW scaling suggest it only goes to 10V or so (10W). Google hasn't been helpful.

And what about those standard 20W ophir heads everyone gets? With a 9V supply, how can those go to 20V on the output? Surely I'm missing something simple.
 
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Flaminpyro

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I'm taking a stab in the dark here but since it's 12v negative and 12v positive that is a difference of 24 volts so wouldn't that be enough to cover 20W at 1mv=1mW :thinking:



But my question is: is this a 40W sensor? The water lines suggest so, but the local 12V regulator and the mV/mW scaling suggest it only goes to 10V or so (10W). Google hasn't been helpful.
 
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Cyparagon

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that is a difference of 24 volts so wouldn't that be enough to cover 20W at 1mv=1mW :thinking:
Does the output ever go negative?

To my knowledge, the output is read with respect to gound, not with respect to the negative rail. Otherwise my red is reading as 12.28W and my blue is reading as 13.8W.
 

Flaminpyro

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Like I said it was a shot in the dark, I have no real idea how these work as I have never had to operate on one.
 

sinner

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Looks fairly decent for a $30 sensor :na: Whoever was selling this, please sell more.
 

ARG

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And what about those standard 20W ophir heads everyone gets? With a 9V supply, how can those go to 20V on the output? Surely I'm missing something simple.
Those heads don't have regulators inside, the voltage feeds the op amps directly. They can't go to 20W at 9V, only about 7.5W. To get the full 0-20W range they need +/-22V. Depending on the 20C head the opamps rails will need 1V-2V more than the max output voltage.

I'm guessing the head has a custom voltage to power ratio as requested by the original customer, which only allows it to go to 10W despite being a 40W head.
 
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