ET-S45
Isolated pH Probe Interface
Galvanically isolated 18-bit pH front end, BNC
AED 219.00
Out of stockOverview
Galvanically isolated 18-bit pH front end, BNC
The ET-S45 is built around the Lab-grade pH measurement from any combination pH electrode (BNC), galvanically isolated from the host. It connects over I²C 0x68 (MCP3421A0) and is powered from 5V on VIN only.
Two Qwiic / STEMMA QT connectors let you chain it with other boards without soldering, and the 2.54 mm header fits a breadboard.
Designed in Dubai by ElectroTrical — the full schematic, BOM and design notes are published below.
Good for
- Hydroponics and aquariums
- Pool and water-quality monitoring
- Lab pH logging
Key features
What makes it different
Function
Lab-grade pH measurement from any combination pH electrode (BNC), galvanically isolated from the host
Front end
TLV9061 unity-gain buffer (0.5pA bias) → MCP3421 18-bit ΔΣ, differential against a 1.65V reference that also biases the probe reference
Range
pH 0–14 = ±414mV around VMID; MCP3421 ±2.048V FS, 15.6µV/LSB at 18-bit → ~0.0003 pH resolution
Isolation
B0505S 1.5kVDC + ISO1540 2.5kVrms: no ground loops between probes in the same tank
Qwiic / STEMMA QT
Two JST-SH connectors plus a 2.54 mm header — 3.3 V and 5 V hosts.
Open documentation
Schematic, BOM and layout notes published for every board.
Specifications
Technical specifications
| Function | Lab-grade pH measurement from any combination pH electrode (BNC), galvanically isolated from the host |
|---|---|
| Front end | TLV9061 unity-gain buffer (0.5pA bias) → MCP3421 18-bit ΔΣ, differential against a 1.65V reference that also biases the probe reference |
| Range | pH 0–14 = ±414mV around VMID; MCP3421 ±2.048V FS, 15.6µV/LSB at 18-bit → ~0.0003 pH resolution |
| Isolation | B0505S 1.5kVDC + ISO1540 2.5kVrms: no ground loops between probes in the same tank |
| Interface | I2C 0x68 (MCP3421A0) |
| Supply | 5V on VIN only |
| Size | 50.8 × 25.4 mm |
|---|---|
| Mounting | 4 × M2.5 holes, 2.54 mm from each corner |
| Connectors | 2 × Qwiic / STEMMA QT (JST SH 4-pin) · 4-pin 2.54 mm header · BNC female R/A 50Ω PCB (THT) — pH probe BNC |
| Main IC | MCP3421A0T-E/CH (LCSC C29454) |
| Revision | Rev B |
| Libraries | Any MCP342x library (Adafruit/RobTillaart), pH conversion + 2/3-point calibration example (ElectroTrical) |
|---|
| JP1 (default Closed) | Cut to turn off the LED |
|---|---|
| JP2 (default Closed) | Cut to remove the host-side I2C pull-ups |
Performance
Why temperature matters
Pinout
Pin map and connections
| Pin | Name | Type | Function |
|---|---|---|---|
| 1 | VIN | Power | 5V required (B0505S input 4.5–5.5V) |
| 2 | GND | Ground | host ground |
| 3 | SCL | I²C | host level |
| 4 | SDA | I²C | host level |
Qwiic / STEMMA QT pins: GND, VIN, SDA, SCL (same on both connectors). I²C pull-ups (10 kΩ) are on the board; cut JP2 to remove them.
Mechanical
Dimensions and what's in the box
In the box
- 1 × ET-S45 Isolated pH Probe Interface (assembled)
- 1 × 4-pin 2.54 mm male header, unsoldered
Getting started
- Plug in a Qwiic / STEMMA QT cable, or solder the header and wire VIN, GND, SDA and SCL
- Libraries: Any MCP342x library (Adafruit/RobTillaart), pH conversion + 2/3-point calibration example (ElectroTrical)
- Run an I²C scanner to confirm the address: 0x68
Compare
Which water-quality board?
| Isolated pH Probe Interface (this board)This board | ET-S46 Isolated EC / TDS Interface | ET-S10 FDC1004 Capacitive Soil Moisture Probe | |
|---|---|---|---|
| What it does | Galvanically isolated 18-bit pH front end, BNC | Isolated conductivity front end (AD5933), BNC | Corrosion-proof capacitive soil probe with I²C |
| Interface | I²C 0x68 (MCP3421A0) | I²C 0x0D (fixed) | I²C fixed 0x50 |
| Best for | Hydroponics and aquariums | Hydroponic nutrient control | Plant and garden monitoring |
| Price | 219 AED | 219 AED | 23 AED |
Downloads
Documents and design files
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