# AGRINOVO-GF-201: Fixed Hydrogen Sulfide (H₂S) Gas Detector

Agrinovo technical datasheet, revision 1.2 (October 2026).
PDF version: https://agrinovo.io/datasheets/sensors/AGRINOVO-GF-201_Datasheet.pdf

## 1. Overview

The AGRINOVO-GF-201 is a fixed-point hydrogen sulfide (H₂S) gas detector for continuous monitoring of toxic gas in industrial and agricultural environments. An electrochemical sensing cell with automatic temperature compensation and zero/span drift correction delivers stable readings, while a flameproof aluminium alloy enclosure (Ex d IIC T6) makes it suitable for hazardous areas. The on-board LCD shows live concentration and alarm status, and three independent output paths (4-20 mA, RS485 Modbus-RTU, and two relays) integrate the unit into a controller, PLC, or DCS.

### Key Features

- H₂S range: 0-100 ppm
- Resolution: 1 ppm
- Accuracy: ≤±3% FS
- Electrochemical cell, temperature compensated
- 4-20 mA + RS485 Modbus-RTU + two relays
- Two-stage alarm, freely configurable
- Flameproof Ex d IIC T6, IP65
- Wide supply: 12-30 VDC

### Applications

- Aquaculture and RAS (anaerobic sediment and biofilter off-gas)
- Wastewater treatment, pumping stations, and sewers
- Biogas, manure pits, and confined livestock housing
- Industrial process areas where H₂S may accumulate

## 2. Specifications

### Sensing and Performance

| Parameter | Specification |
|:----------|:--------------|
| **Target Gas** | Hydrogen Sulfide (H₂S) |
| **Measuring Range** | 0-100 ppm |
| **Resolution** | 1 ppm |
| **Accuracy** | ≤±3% FS |
| **Repeatability** | ≤±1% |
| **Sensing Principle** | Electrochemical |
| **Sampling Method** | Diffusion (pump-suction optional) |
| **Response Time** | ≤60 s (T90) |
| **Display** | LCD with backlight |
| **Temperature Compensation** | Automatic |

### Electrical and Outputs

| Parameter | Specification |
|:----------|:--------------|
| **Supply Voltage** | 24 VDC (12-30 VDC) |
| **Power Consumption** | ≤2 W |
| **Analog Output** | 4-20 mA, 3-wire (2-wire optional) |
| **Digital Output** | RS485, Modbus-RTU, 4-wire |
| **Alarm Output** | Two relays, normally open, AC 120 V 0.5 A / DC 24 V 1 A |

### Mechanical and Environmental

| Parameter | Specification |
|:----------|:--------------|
| **Mounting** | Wall mount or pipe flow-through |
| **Enclosure** | Aluminium alloy, flameproof |
| **Ex Rating** | Ex d IIC T6 |
| **Protection Rating** | IP65 |
| **Cable Entry** | M20×1.5 internal thread |
| **Operating Temperature** | -20 to 50°C |
| **Humidity** | 10-95% RH, non-condensing |
| **Pressure Range** | 86-106 kPa |
| **Dimensions** | 196 × 140 × 91 mm |
| **Weight** | 1.2 kg |

## 3. Wiring

Terminals are accessed by unscrewing the enclosure cover. Disconnect power before opening the housing in any area where gas may be present.

### Power and Analog Output (P2)

| Terminal | Function | Description |
|:---------|:---------|:------------|
| **24V+** | V+ | Power Supply (12-30 VDC) |
| **GND** | GND | Power ground / 4-20 mA return |
| **mA** | 4-20 mA | Analog current output (+) |

### RS485 (P3)

| Terminal | Function | Description |
|:---------|:---------|:------------|
| **A+** | RS485-A | Data+ |
| **B-** | RS485-B | Data- |

### Alarm Relays

| Terminal | Function | Contact |
|:---------|:---------|:--------|
| **P4 (AL)** | Low alarm relay | NO, dry contact |
| **P5 (AH)** | High alarm relay | NO, dry contact |

> Relay contacts are voltage-free (passive). Do not exceed the rated contact capacity (AC 120 V 0.5 A / DC 24 V 1 A) or the relay may be damaged. Connect the cable shield to the internal ground terminal.

## 4. Communication Settings

| Parameter | Value |
|:----------|:------|
| **Protocol** | Modbus-RTU |
| **Baud Rate** | 9600 bps |
| **Data Bits** | 8 |
| **Parity** | None |
| **Stop Bits** | 1 |
| **Default Address** | 0x01 |

RS485 is half-duplex. Use shielded twisted-pair cable, keep the bus below 1200 m, and terminate long runs as needed.

## 5. Register Map

### Measurement Registers (Function 0x03)

| Address (Hex) | Description | Data Type | Range | Scaling |
|:--------------|:------------|:----------|:------|:--------|
| 0x0000 | Gas Concentration | UINT16 | 0-65535 | Value ÷ 10^(decimals) |
| 0x0011 | Resolution (decimal places) | UINT16 | 0-3 | Direct |
| 0x0013 | Full-Scale Range | UINT16 | 0-65535 | Value ÷ 10^(decimals) |

On the 0-100 ppm / 1 ppm unit the decimal-places register (0x0011) reads `0`, so the concentration register (0x0000) reads directly in ppm and the range register (0x0013) reads `100`.

## 6. Reading Data

Read one register from 0x0000 to obtain the live concentration:

```
Request:  01 03 00 00 00 01 84 0A
Response: 01 03 02 XX XX [CRC]
```

**Decoding (decimals = 0):**

| Register | Hex | Decimal | Scaling | Result |
|:---------|:----|:--------|:--------|:-------|
| Concentration | 0x0020 | 32 | ÷ 1 | **32 ppm** |

To confirm scaling on any unit, read register 0x0011 for the number of decimal places and divide the raw concentration by 10 raised to that value.

## 7. Address Configuration

The device address is set from the front-panel menu (Settings → Device Address), not over the bus. Assign a unique address to each unit before wiring multiple detectors onto the same RS485 trunk. Example request frames reading concentration from successive addresses:

```
Address 1:  01 03 00 00 00 01 84 0A
Address 2:  02 03 00 00 00 01 84 39
Address 3:  03 03 00 00 00 01 85 E8
```

## 8. Calibration

Calibration is performed from the front-panel menu and must be carried out by trained personnel using certified gas. Recommended interval is at least once every six months.

### Zero Calibration

In clean air with no target gas present, open Calibration → Zero, wait for the reading to stabilise, then save.

### Span Calibration

1. Apply certified H₂S span gas (a value near 50% of full scale is recommended) to the sensor for 2-3 minutes.
2. Open Calibration → Span and confirm the standard-gas concentration matches the cylinder.
3. Wait for the reading to stabilise, then save.

A menu option restores factory calibration parameters if a setting is changed in error.

## 9. Installation Notes

**Placement**

- H₂S is heavier than air: mount 0.3-0.6 m above floor level
- Install close to likely release points, valves, and joints
- Keep clear of splashing water, oil, and mechanical impact
- Allow access space around the detector for service

**Maintenance**

- Keep the sensor gas inlet free of dust and deposits
- Recalibrate periodically with certified gas
- Verify alarm and output response after each calibration
- Replace the cell at end of life to maintain accuracy

## Ordering Information

| Part number | Description |
|:------------|:------------|
| AGRINOVO-GF-201 | Fixed Hydrogen Sulfide (H₂S) Gas Detector |

## Revision History

| Rev | Date | Changes |
|:----|:-----|:--------|
| 1.0 | June 2026 | Initial release |
| 1.1 | August 2026 | Layout revision |
| 1.2 | October 2026 | New layout |

## Contact

Agrinovo, https://agrinovo.io/products, contact@agrinovo.io, +972 54 688 8148 (direct / WhatsApp).
Specifications subject to change without notice.