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Old 5th November 2010, 06:29 PM   #1
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Default A better formula for Silonex LDR's

I plugged in about 100 data points for Current (x) and ON-Resistance (y) for the Silonex NSL32SR3 Attenuator -- the errors for the very low currents are close to zero --

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This is much better than the results using the Silonex equations.

Here's the equation - ymmv:

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Old 5th November 2010, 06:46 PM   #2
AndrewT is offline AndrewT  Scotland
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Can I assume that e5 = 10^5?
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Old 5th November 2010, 06:48 PM   #3
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Can I assume that e5 = 10^5?
Yep, that is the notational custom - as I know it at least
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Old 5th November 2010, 06:55 PM   #4
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I liked it because there is no exponentiation, and only a few terms. The equations with multiple terms offer no improvement in accuracy. A stepwise approximation can probably resolve the low ohms error.
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Old 5th November 2010, 07:38 PM   #5
udailey is offline udailey  United States
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How many different LDRs is this based on John? One with 100 measurements or several with several measurements? Yeah, their datasheet is nothing close to real use.
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Old 5th November 2010, 09:07 PM   #6
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Nice one Jack...btw, x=current in uA. Actual testing/matching is still the way to go but it can serve as cross reference.
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Old 5th November 2010, 09:17 PM   #7
Blues is offline Blues  United States
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On second thought...your formula is pegged down at 47R...it certainly can go lower
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Old 8th November 2010, 02:03 AM   #8
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On second thought...your formula is pegged down at 47R...it certainly can go lower
the very low resistance points are the insertion loss.

do the math for a 0.5dB 100K+100K attenuator -- you need accuracy in the tens of picoamps in the part of the range where we do most of our listening.
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Old 8th November 2010, 06:08 AM   #9
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Quote:
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On second thought...your formula is pegged down at 47R...it certainly can go lower
And can also go much higher, I might add, and controllable too.

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the very low resistance points are the insertion loss.

do the math for a 0.5dB 100K+100K attenuator -- you need accuracy in the tens of picoamps in the part of the range where we do most of our listening.
Not quite...with a more precise power delivery "engine" . Listening range is mostly in 10s of uA to 100s of uA. With this design working range is from <1uA thru 10s of mA.

I'll probably start a thread...
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Old 12th November 2010, 04:19 PM   #10
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Several forms of equations will work -- but I have to say that the Silonex devices are all over the place!

Here's my setup -- using an LTC or ADI difference amp allows stable current in the picoAmperes:

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