MEMS sensors for flow measurement in harsh environments
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    /4 Appendix/4.2 Details on the developed CTA circuit for SiC sensors

    #4.2 Details on the developed CTA circuit for SiC sensors

    SVG Image created as cta.svg date 2026/08/20 12:22:22 Image generated by Eeschema-SVG 1 1 2 2 3 3 RV2 RV2 R_Potentiometer R_Potentiometer C2 C2 C C VPP VPP GND GND HWA1 HWA1 R R GND GND GND GND GND GND R1 R1 100 100 OUTA OUTA 1 1 -INA -INA 2 2 +INA +INA 3 3 V- V- 4 4 +INB +INB 5 5 -INB -INB 6 6 OUTB OUTB 7 7 V+ V+ 8 8 U1 U1 ADA4522-2ARZ-RL ADA4522-2ARZ-RL 1 1 2 2 J3 J3 A OUT A OUT GND GND GND GND GND GND 1 1 2 2 BRIDGEA1 BRIDGEA1 Bridge A Bridge A R10 R10 100K 100K GND GND VPP VPP GND GND 1 1 2 2 J2 J2 Offset CTA A Offset CTA A GND GND R2 R2 100 100 1 1 2 2 3 3 RV1 RV1 R_Potentiometer R_Potentiometer HWB1 HWB1 R R GND GND VPP VPP GND GND GND GND VPP VPP 1 1 2 2 J1 J1 Power Power VPP VPP GND GND R1B1 R1B1 100 100 GND GND Rg Rg 1 1 - - 2 2 + + 3 3 V- V- 4 4 Ref Ref 5 5 6 6 V+ V+ 7 7 Rg Rg 8 8 U3 U3 INA128 INA128 R3 R3 1k 1k GND GND Rg Rg 1 1 - - 2 2 + + 3 3 V- V- 4 4 Ref Ref 5 5 6 6 V+ V+ 7 7 Rg Rg 8 8 U2 U2 INA128 INA128 GND GND GND GND C6 C6 C C VPP VPP GND GND C3 C3 C C C C B B E E Q1 Q1 NPN NPN R4 R4 R R C C B B E E Q1B1 Q1B1 NPN NPN R3B1 R3B1 1k 1k 1 1 2 2 J4B1 J4B1 Bridge B Bridge B 1 1 2 2 3 3 RV2B1 RV2B1 R_Potentiometer R_Potentiometer R2B1 R2B1 100 100 1 1 2 2 3 3 RV1B1 RV1B1 R_Potentiometer R_Potentiometer GND GND R4B1 R4B1 R R GND GND GND GND GND GND Rg Rg 1 1 - - 2 2 + + 3 3 V- V- 4 4 Ref Ref 5 5 6 6 V+ V+ 7 7 Rg Rg 8 8 U2B1 U2B1 INA128 INA128 C4 C4 C C VPP VPP VPP VPP GND GND GND GND GND GND GND GND C1 C1 C C VPP VPP C7 C7 C C OUTA OUTA 1 1 -INA -INA 2 2 +INA +INA 3 3 V- V- 4 4 +INB +INB 5 5 -INB -INB 6 6 OUTB OUTB 7 7 V+ V+ 8 8 U9 U9 ADA4522-2ARZ-RL ADA4522-2ARZ-RL GND GND GND GND GND GND VPP VPP GND GND R9 R9 100K 100K GND GND GND GND C8 C8 C C GND GND GND GND 1 1 2 2 J2B1 J2B1 Offset CTA B Offset CTA B Rg Rg 1 1 - - 2 2 + + 3 3 V- V- 4 4 Ref Ref 5 5 6 6 V+ V+ 7 7 Rg Rg 8 8 U3B1 U3B1 INA128 INA128 1 1 2 2 J3B1 J3B1 B OUT B OUT C5 C5 C C VPP VPP GND GND R6 R6 R R R5 R5 R R GND GND GND GND C9 C9 C C VPP VPP Rg Rg 1 1 - - 2 2 + + 3 3 V- V- 4 4 Ref Ref 5 5 6 6 V+ V+ 7 7 Rg Rg 8 8 U5 U5 INA128 INA128 GND GND GND GND C10 C10 C C VPP VPP Rg Rg 1 1 - - 2 2 + + 3 3 V- V- 4 4 Ref Ref 5 5 6 6 V+ V+ 7 7 Rg Rg 8 8 U6 U6 INA128 INA128 GND GND GND GND VPP VPP GND GND 1 1 2 2 J12 J12 Conn_Coaxial Conn_Coaxial GND GND 1 1 2 2 J13 J13 Conn_Coaxial Conn_Coaxial Rg Rg 1 1 - - 2 2 + + 3 3 V- V- 4 4 Ref Ref 5 5 6 6 V+ V+ 7 7 Rg Rg 8 8 U7 U7 INA128 INA128 GND GND GND GND GND GND C12 C12 C C GND GND VPP VPP 1 1 2 2 J15 J15 Conn_Coaxial Conn_Coaxial R7 R7 R R GND GND GND GND C11 C11 C C 1 1 2 2 J14 J14 Conn_Coaxial Conn_Coaxial R8 R8 R R Rg Rg 1 1 - - 2 2 + + 3 3 V- V- 4 4 Ref Ref 5 5 6 6 V+ V+ 7 7 Rg Rg 8 8 U8 U8 INA128 INA128 GND GND GND GND 1 1 2 2 J8 J8 Conn_01x02_Pin Conn_01x02_Pin 1 1 2 2 J9 J9 Conn_01x02_Pin Conn_01x02_Pin 1 1 2 2 J11 J11 Conn_01x02_Pin Conn_01x02_Pin 1 1 2 2 J10 J10 Conn_01x02_Pin Conn_01x02_Pin S S 6 6 1 1 8 8 U4A U4A REF200AU REF200AU GND GND VPP VPP C13 C13 C C 1 1 10 10 11 11 12 12 13 13 14 14 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 J7 J7 Conn_01x14_Pin Conn_01x14_Pin HW1 HW1 HW2 HW2 HW1 HW1 HW2 HW2 GND GND U2 U2 INA128 INA128 Rg Rg 1 1 - - 2 2 + + 3 3 V- V- 4 4 Ref Ref 5 5 6 6 V+ V+ 7 7 Rg Rg 8 8 GND GND GND GND C6 C6 C C VPP VPP GND GND U2B1 U2B1 INA128 INA128 Rg Rg 1 1 - - 2 2 + + 3 3 V- V- 4 4 Ref Ref 5 5 6 6 V+ V+ 7 7 Rg Rg 8 8 C4 C4 C C VPP VPP GND GND GND GND C1 C1 C C VPP VPP C2 C2 C C VPP VPP GND GND GND GND GND GND BRIDGEA1 BRIDGEA1 Bridge A Bridge A 1 1 2 2 VPP VPP GND GND VPP VPP J1 J1 Power Power 1 1 2 2 R3 R3 1k 1k Q1 Q1 NPN NPN C C B B E E GND GND Q1B1 Q1B1 NPN NPN C C B B E E R3B1 R3B1 1k 1k J4B1 J4B1 Bridge B Bridge B 1 1 2 2 R4B1 R4B1 R R GND GND GND GND R10 R10 100K 100K GND GND GND GND J2 J2 Offset CTA A Offset CTA A 1 1 2 2 GND GND U3 U3 INA128 INA128 Rg Rg 1 1 - - 2 2 + + 3 3 V- V- 4 4 Ref Ref 5 5 6 6 V+ V+ 7 7 Rg Rg 8 8 C3 C3 C C VPP VPP GND GND J3 J3 A OUT A OUT 1 1 2 2 GND GND VPP VPP GND GND GND GND GND GND GND GND U1 U1 ADA4522-2ARZ-RL ADA4522-2ARZ-RL OUTA OUTA 1 1 -INA -INA 2 2 +INA +INA 3 3 V- V- 4 4 +INB +INB 5 5 -INB -INB 6 6 OUTB OUTB 7 7 V+ V+ 8 8 C7 C7 C C U9 U9 ADA4522-2ARZ-RL ADA4522-2ARZ-RL OUTA OUTA 1 1 -INA -INA 2 2 +INA +INA 3 3 V- V- 4 4 +INB +INB 5 5 -INB -INB 6 6 OUTB OUTB 7 7 V+ V+ 8 8 GND GND GND GND GND GND VPP VPP GND GND R9 R9 100K 100K GND GND GND GND C8 C8 C C GND GND GND GND J2B1 J2B1 Offset CTA B Offset CTA B 1 1 2 2 U3B1 U3B1 INA128 INA128 Rg Rg 1 1 - - 2 2 + + 3 3 V- V- 4 4 Ref Ref 5 5 6 6 V+ V+ 7 7 Rg Rg 8 8 J3B1 J3B1 B OUT B OUT 1 1 2 2 C5 C5 C C VPP VPP GND GND R6 R6 R R R5 R5 R R GND GND GND GND C9 C9 C C VPP VPP U5 U5 INA128 INA128 Rg Rg 1 1 - - 2 2 + + 3 3 V- V- 4 4 Ref Ref 5 5 6 6 V+ V+ 7 7 Rg Rg 8 8 GND GND GND GND C10 C10 C C VPP VPP U6 U6 INA128 INA128 Rg Rg 1 1 - - 2 2 + + 3 3 V- V- 4 4 Ref Ref 5 5 6 6 V+ V+ 7 7 Rg Rg 8 8 GND GND GND GND VPP VPP GND GND J12 J12 Conn_Coaxial Conn_Coaxial 1 1 2 2 GND GND J13 J13 Conn_Coaxial Conn_Coaxial 1 1 2 2 U7 U7 INA128 INA128 Rg Rg 1 1 - - 2 2 + + 3 3 V- V- 4 4 Ref Ref 5 5 6 6 V+ V+ 7 7 Rg Rg 8 8 GND GND GND GND GND GND C12 C12 C C GND GND VPP VPP J15 J15 Conn_Coaxial Conn_Coaxial 1 1 2 2 R7 R7 R R GND GND C11 C11 C C J14 J14 Conn_Coaxial Conn_Coaxial 1 1 2 2 R8 R8 R R U8 U8 INA128 INA128 Rg Rg 1 1 - - 2 2 + + 3 3 V- V- 4 4 Ref Ref 5 5 6 6 V+ V+ 7 7 Rg Rg 8 8 GND GND GND GND GND GND U4A U4A REF200AU REF200AU S S 6 6 1 1 8 8 GND GND VPP VPP C13 C13 C C J7 J7 Conn_01x14_Pin Conn_01x14_Pin 1 1 10 10 11 11 12 12 13 13 14 14 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 GND GND GND GND
    Figure 4.7.
    Circuit board schematic. The complete design includes 2 independent CTA controllers (left), and a constant current measurement circuit (right), made to operate two calorimetric sensors simultaneoulsy.

    Figure 4.8.
    Routing of the CTA circuit on the PCB layout.

    SVG Image created as cta-F_Cu.svg date 2026/08/19 13:54:38 Image generated by PCBNEW

    (a) Front copper traces.
    SVG Image created as cta-B_Cu.svg date 2026/08/19 13:54:38 Image generated by PCBNEW

    (b) Back copper traces.
    Table 4.1.
    Component list
    Component Manufacturer Quantity
    Active components
    INA128 instrumentation amplifier Texas Instruments 8
    ADA1522-2 differential amplifier Analog Devices 2
    REF200AU 100 µA current source Analog Devices 1
    Passive components
    100 Ω precision, low-TCR SMD resistor 6
    100 kΩ TH resistor 2
    1 kΩ TH resistor 8
    2N2222A NPN TH transistor ST Microelectronics 2
    100 nF SMD capacitor 8
    Potentiometer 4
    Connectors
    031-5540 BNC connector Amphenol 11
    22-28-4140 1×14 pin header Molex 1