ENG-AFE-AETH-001 · Rev B · note B.2
Aetheris front end
Layer C · carbon / GNP sense grid. 1 m² flat coupon · ambient lab. This is the review copy for Citadel. Rev B.2 does not change parts. It changes how the gauge factor is read.
- Models
- GF 3, 5, 10
- Reference
- GF 20–30 only
- INA gain
- About 15
- ADC PGA
- 2 or 4
Build gate
Match or trim the dummy arm before the board is built. Resistor mismatch is the residual risk. At gauge factor 10 the front end clears its input range by about 0.06 V and overranges above about GF 13. Until R_COMP matches the coupon, gauge factor 10 is the top of the model set.
How to read the gauge factor
- GF 318.75 µV · 32.7 dB
- GF 531.25 µV · 37.1 dB
- GF 1062.5 µV · 43.2 dB
- GF 20–30 · reference125–187.5 µV · 49.2–52.7 dB
Figures are at 10 µε, 2.500 V excitation, at the bridge, before the instrumentation amplifier. SNR uses a bridge-referred noise floor of 0.435 µV. The first-pass 39.8 dB figure is withdrawn.
Signal path
No component changes from Rev B.
- 01ADR45252.500 V excitation
- 02Quarter-bridgeR0 1.000 kΩ · active + dummy
- 03AD8421Gain stays about 15
- 04Anti-alias2 kHz, before the converter
- 05ADS1256PGA 2 or 4 · 24-bit