DGA-300 — Embedded Dissolved Hydrogen Sensor for Multi-Gas DGA Systems
Designed for integration into multi-gas DGA on-line monitoring systems, where it serves as the hydrogen measurement element inside the host unit. Its chip uses a palladium alloy MOSFET structure combined with high-sensitivity Pd-alloy doping, thin-film processing and specific composite thin-film fabrication, giving a dissolved-hydrogen detection limit as low as 2 ppm over a 2 ~ 2000 ppm range. The chip is placed directly in transformer oil with no oil-gas separation.
Palladium Alloy MOSFET Hydrogen Sensing Chip — Direct Oil Immersion
Palladium Alloy MOSFET Sensing Chip
The DGA-300 chip combines a palladium alloy MOSFET (metal-oxide-semiconductor field-effect transistor) structure with high-sensitivity Pd-alloy doping, thin-film processing and specific composite thin-film fabrication.
Palladium Alloy MOSFET Chip
Structure: a palladium alloy MOSFET sensing element, fabricated with optimized Pd-alloy doping and thin-film preparation.
Result: a dissolved-hydrogen detection limit as low as 2 ppm, with excellent long-term stability and freedom from periodic maintenance.
Application: the hydrogen measurement element inside a multi-gas DGA on-line monitoring system.
Specific Composite Thin Film
Function: a specific composite thin film lets the sensor work reliably in backgrounds containing CO and CH compounds.
Result: the chip is placed directly in transformer oil with no oil-gas separation, and offers hydrogen specificity with no cross-response to other combustible gases.
Technical Specifications
Dissolved Hydrogen
| Detection Principle | Palladium alloy thin film |
| Measuring Range | 2 ~ 2000 ppm |
| Limit of Detection | 2 ppm |
| Accuracy | ±20% reading or ±2 ppm (whichever is greater) |
| Repeatability | ±10% reading or ±2 ppm (whichever is greater) |
| Resolution | 1 ppm |
| Applicable Oil Temperature | 0 ~ 60 ℃ |
| Response Time τ90 | < 10 min (oil concentration above 50 ppm) |
Moisture (optional)
| Measuring Range | 0 ~ 100 %RS |
| Accuracy at 20 ℃ | 0 ~ 90 %RS: ±2 %RS 90 ~ 100 %RS: ±3 %RS |
| Response Time τ90 | < 10 min |
Electrical & Other
| Power Supply | 24 V DC ±10%, 0.3 A (max) |
| Digital Output | RS-485 |
| Communication Protocol | Modbus_RTU |
| Ingress Protection | IP67 |
| Data Storage | Default interval 30 s (adjustable), 74,604 entries |
| Expected Life | 10 years |
| Weight | ≤ 350 g |
Type Configurations
| DGA-300 Base | Dissolved hydrogen sensor |
| DGA-300 with moisture | Dissolved hydrogen and moisture sensor |
Accuracy figures are measured at normal ambient temperature. Response time is concentration-dependent: the higher the hydrogen concentration, the faster the response.
Outline Dimensions
| Body Length | 116 mm |
| Probe Rod Length | 70 mm |
| Overall Length (incl. probe) | 186 mm |
| Overall Length (incl. fitting) | 201.5 mm |
| Probe Rod Diameter | φ12.7 mm |
| Process Connection | 1/2 in. two-ferrule tube fittings |
Range Limit
Range limit: the DGA-300 may only be used for hydrogen measurement in oil below 2000 ppm. Exceeding this range may cause the sensor chip to drift or even fail. Operation beyond the measuring range may cause irreversible damage to the sensor probe.
Calibration follows the product manual: save the current state with the DA command, take an oil sample near the probe for off-line DGA analysis per ASTM D3612, and if the deviation exceeds 15% calibrate to the actual value with the DB command. The DX command clears the calibration data and returns the unit to factory calibration.
OEM Integration
Hydrogen Measurement Element
The DGA-300 is designed to serve as the hydrogen measurement unit inside a multi-gas DGA on-line monitoring system, embedded in the host unit rather than installed as a standalone device.
RS-485 / Modbus RTU Interface
A standard MODBUS_RTU interface over RS-485 hardware (master-slave half-duplex), with function codes 0x03 read holding registers and 0x06 write single register.
Moisture Option
A moisture-sensing configuration is available for host systems that also need 0 ~ 100 %RS moisture measurement alongside dissolved hydrogen.
Factory Documentation
Each unit is supplied with a factory inspection report and a certificate of conformity. Check the accessories against the packing list before use.
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