# Analog NH3 4-20mA Loop Transmitter ## Description Transmissor analógico 2 fios para sensor DD-Scientific GS+4NH3-100 com saída 4–20 mA loop-powered 24 V. ## Project Details - **Owner:** mikaelle - **Created:** 5/14/2026 - **Last Updated:** 5/19/2026 - **Visibility:** Public ## Key Components ### D1 — SMAJ33A - License: https://creativecommons.org/licenses/by/4.0/ - Role Details: 33V standoff TVS protects loop input against industrial transients while staying off at 30V nominal max. - Role: Protection - Manufacturer Name: Bourns Inc. - Manufacturer Part Number: SMAJ33A - Part Type: Diode - Datasheet URL: https://www.bourns.com/docs/Product-Datasheets/SMAJ.pdf **Pins:** - A [pin 2] - K [pin 1] ### D2 — SS14 - License: https://creativecommons.org/licenses/by/4.0/ - Role Details: Series Schottky prevents reverse-polarity damage on the 2-wire loop input. - Role: Reverse Polarity Protection - Manufacturer Part Number: SS14 - Manufacturer Name: Slkor(SLKORMICRO Elec.) - Part Type: Diode - Datasheet URL: https://datasheet.lcsc.com/lcsc/1912111437_Slkor-SLKORMICRO-Elec--SS14_C444721.pdf **Pins:** - Anode [pin A] - Cathode [pin C] ### FB1 — BLM18AG601SN1D - Datasheet URL: https://www.murata.com/en-us/products/productdata/8796738650142/ENFA0003.pdf - Manufacturer Part Number: BLM18AG601SN1D - Role Details: 600Ω@100MHz bead attenuates conducted RF noise before analog circuitry. - License: https://creativecommons.org/licenses/by/4.0/ - Manufacturer Name: Murata Electronics - Role: Choke (EMI Filter) - Part Type: Ferrite Bead **Pins:** - 1 [pin 1] - 2 [pin 2] ### J1 — WJ500V-5.08-2P - Manufacturer Part Number: WJ500V-5.08-2P - Connector Type: Terminal Blocks - Role: Industrial Loop Connector - Part Type: Connector - Role Details: Field 2-wire loop: LOOP+ and LOOP- carry both power and 4-20mA signal. - Datasheet URL: https://datasheet.lcsc.com/szlcsc/1912251636_Ningbo-Kangnex-Elec-WJ500V-5-08-2P_C8465.pdf - Manufacturer Name: Ningbo Kangnex **Pins:** - 1 [pin 1] - 2 [pin 2] ### J2 — Pin Header 01x04 2.54mm Vertical - License: https://creativecommons.org/licenses/by/4.0/ - Role Details: Provides WE, RE, CE socket connections; sensor datasheet says not to solder directly to sensor pins. - Role: Sensor Connector - Part Type: Connector **Pins:** - Pin_1 [pin 1] - Pin_2 [pin 2] - Pin_3 [pin 3] - Pin_4 [pin 4] ### Q1 — TSM170N06CP_ROG - Datasheet URL: https://www.snapeda.com/parts/TSM170N06CP%20ROG/Taiwan%20Semiconductor/datasheet/ - Role Details: Linear current-sink MOSFET; DPAK package selected for up to about 0.6W worst-case dissipation. - Manufacturer Part Number: TSM170N06CP_ROG - Part Type: Transistor - Role: Switching - Manufacturer Name: TSMC **Pins:** - D [pin 1] - G [pin 2] - S [pin 3] ### RV1 — 3224W-1-104E - Resistance: 100kΩ - Manufacturer Part Number: 3224W-1-104E - Part Type: Resistor - Datasheet URL: https://datasheet.lcsc.com/lcsc/1810271112_BOURNS-3224W-1-103E_C81348.pdf - Role: Feedback - Manufacturer Name: Bourns - Role Details: Span adjustment: trims TIA feedback to cover GS+4NH3 sensitivity tolerance of 100±30nA/ppm. **Pins:** - P1 - P2 - P3 ### RV2 — 35WR10KLFTR - Role: Voltage Division - License: https://creativecommons.org/licenses/by/4.0/ - Role Details: Zero trim adjusts command offset so clean air calibrates to 4.000mA. - Part Type: Potentiometer - Manufacturer Part Number: 35WR10KLFTR - Resistance: 10kΩ - Manufacturer Name: TT Electronics/BI - Datasheet URL: https://www.ttelectronics.com/TTElectronics/media/ProductFiles/Datasheet/35.pdf **Pins:** - 1 [pin 1] - 2 [pin 2] - 3 [pin 3] ### U1 — TPS7A1601DGNR - Manufacturer Part Number: TPS7A1601DGNR - Role Details: 3.3V analog LDO from 12-30V loop; TPS7A1601 supports up to 60V input and 5uA typical ground current. - Datasheet URL: https://www.ti.com/lit/ds/symlink/tps7a16.pdf - Role: Power Conversion - Manufacturer Name: Texas Instruments - Part Type: Integrated Circuit - License: https://creativecommons.org/licenses/by/4.0/ **Pins:** - DELAY [pin 7] - EN [pin 5] - FB/DNC [pin 2] - GND_1 [pin 4] - GND_2 [pin 9] - IN [pin 8] - NC [pin 6] - OUT [pin 1] - PG [pin 3] ### U2 — LMP7721MA/NOPB - Datasheet URL: https://www.ti.com/lit/ds/symlink/lmp7721.pdf - Role: Amplification - Manufacturer Part Number: LMP7721MA/NOPB - Part Type: Integrated Circuit - Manufacturer Name: Texas Instruments - Role Details: Femtoamp-input-bias transimpedance amplifier for 100nA/ppm NH3 sensor current. - License: https://creativecommons.org/licenses/by/4.0/ **Pins:** - IN- [pin 8] - IN+ [pin 1] - N/C_1 [pin 2] - N/C_2 [pin 5] - N/C_3 [pin 7] - V- [pin 3] - V+ [pin 6] - VOUT [pin 4] ### U3 — OPA2333AIDRBT - Manufacturer Name: Texas Instruments - Manufacturer Part Number: OPA2333AIDRBT - Role Details: Buffers VCM and drives CE so the non-biased sensor RE/WE stay near zero bias. - Part Type: Integrated Circuit - License: https://creativecommons.org/licenses/by/4.0/ - Role: Amplification - Datasheet URL: https://www.ti.com/general/docs/suppproductinfo.tsp?distId=10&gotoUrl=https%3A%2F%2Fwww.ti.com%2Flit%2Fgpn%2Fopa2333 **Pins:** - -IN_A [pin 2] - -IN_B [pin 6] - +IN_A [pin 3] - +IN_B [pin 5] - EP [pin 9] - OUT_A [pin 1] - OUT_B [pin 7] - V- [pin 4] - V+ [pin 8] ### U4 — OPA2333AIDRBT - Role Details: Analog signal-conditioning and loop-current control without MCU/ADC/DAC. - Manufacturer Part Number: OPA2333AIDRBT - Manufacturer Name: Texas Instruments - Role: Amplification - Datasheet URL: https://www.ti.com/general/docs/suppproductinfo.tsp?distId=10&gotoUrl=https%3A%2F%2Fwww.ti.com%2Flit%2Fgpn%2Fopa2333 - License: https://creativecommons.org/licenses/by/4.0/ - Part Type: Integrated Circuit **Pins:** - -IN_A [pin 2] - -IN_B [pin 6] - +IN_A [pin 3] - +IN_B [pin 5] - EP [pin 9] - OUT_A [pin 1] - OUT_B [pin 7] - V- [pin 4] - V+ [pin 8] ### U5 — LM4040C25IDBZR - Part Type: Integrated Circuit - Datasheet URL: https://rocelec.widen.net/view/pdf/z9hu7sya0n/slos456n.pdf - Role Details: Precision analog reference for calibration and current-loop scaling. - Manufacturer Name: Texas Instruments - Manufacturer Part Number: LM4040C25IDBZR - License: https://creativecommons.org/licenses/by/4.0/ - Role: Voltage Reference **Pins:** - A [pin 3] - K [pin 1] - REF [pin 2] *The full schematic, PCB layout, bill of materials, and interactive design are available at [https://www.flux.ai/mikaelle/analog-nh3-4-20ma-loop-transmitter~un](https://www.flux.ai/mikaelle/analog-nh3-4-20ma-loop-transmitter~un).* --- *Generated from [https://www.flux.ai/mikaelle/analog-nh3-4-20ma-loop-transmitter~un](https://www.flux.ai/mikaelle/analog-nh3-4-20ma-loop-transmitter~un)*