0-10V, 4-20mA conversion to 0-5V

MikeMl said:

I have never done it, but it looks like you could use an external reference of your choice, use it to produce the offset in the preamp, and then also use it inside the Atmega32 for the A/D by setting it up for an external reference. In that case, the choice of actual Vref is dictated by what the Atmega wants.

Click to expand...

I have never used SMD components.
Have you ever hand soldered surface mount resistors?
Been looking for high tolerance resistors for voltage divider and op-amp.

Found these Thin Film Resistors - SMD RN 0805 49R9
0.1% 10PPM - $0.41.
https://au.mouser.com/ProductDetail/TE-Connectivity-Holsworthy/RN73C2A49R9BTD/?qs=sGAEpiMZZMtlubZbdhIBIFho3SHfDXStxrXRNS3VAgQ=


Can you get better quality for cost in SMD, being so common now?
What do you think of these resistors for divider and bias circuit.
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For 5v Reference
I am not certain how % Initial Accuracy and PPM/C play out in real world use.
============
5v
1ppm = 0.000005
10ppm = 0.00005
-
10C to 50C = 40C differential Temp.
40C differential in temperature x 0.00005 = 0.002
-
0.02% = 4.999v to 5.001v
============
Suggests 0.02% Initial Accuracy would be similar to 5ppm over the 40C differential Temp range. 10ppm was just a component price break.

What would create the larger inaccuracy in the real world.
What %/Accuracy ppm/C ratings ratio would give the best real world Accuracy?
Wondering how much more Accuracy I get for the higher cost IC?
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MAX6126A21+
5v 0.02% Initial Accuracy
3 PPM / C
$5.99

This could do the op-amp bias ref and Arduino Aref pin.
I would like to find a more affordable ref if possible, but it is an option.

https://au.mouser.com/ProductDetail/Maxim-Integrated/MAX6126A21+/?qs=sGAEpiMZZMuBck1X%2b7j9fB2T4ftaG3guOyx5Ymmp6ys=
DataSheet: https://www.mouser.com/ds/2/256/MAX6126-88935.pdf

Or;
MAX6250ACSA+
5v 0.02% Initial Accuracy
2 PPM / C
$9.17

https://au.mouser.com/ProductDetail/Maxim-Integrated/MAX6250ACSA+/?qs=sGAEpiMZZMuBck1X%2b7j9fB2T4ftaG3guusM4a1A2rpc=
DataSheet: https://www.mouser.com/ds/2/256/MAX6225-MAX6250-87956.pdf