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Voltage ratio with compensation

VDC ppm/°C Ω 1 Ω Ω ppm/°C ppm/°C Ω 1 Ω Ω 0.99 VDC 0.99 ppm/°C R_DMM Ω 99.9999 pA Target Vout: VDC Vout w/o compensation: VDC ppm/°C
Cells marked as light green are for your inputs, determined by your early measurements
Cells marked as purple are the results calculated
Cells marked as pink need you input for desired targets
Cells marked as blue are final design results

Usage workflow

1. Design your PCB, assemble and short Ra, Rc1, Rb, Rc2 first
2. Measure you system for voltage and tempco, enter the values on the light green cells
3. If you don't know the exact value R1 and R2, make adjustments till measurement matches Vout w/o compensation value
4. If you don't know you tempco of R1, R2 and you 7VREF, make up something as close as possible so that cell Vout w/o compensation TC is equal to the tempco you have measured.
5. Ra or Rb calculated automatically, matching target Voutput and used resistors R1/R2
6. Suggested value for R_C1 or R_C2 are marked in pink, or use your own type in the corresponding green cell
7. If output tempco not close to zero, adjust R_C1 or R_C2 for better value once more

Credits go to lymex (EEVBlog member)!