DGA-200 — Integrated Dissolved Hydrogen, Moisture & Oil Temperature Monitoring Unit
A wall-mounted on-line monitoring unit with rain cover, installed at the oil sampling valve of oil-filled electrical equipment. It monitors dissolved hydrogen, trace moisture and oil temperature continuously, and carries its own complete signal and communication section — RS-485 / Modbus RTU digital output, three 4–20 mA analog outputs, three relay outputs and three LED status indicators, with an optional LED panel for on-site reading. No extra transmitter or secondary instrument is needed to connect it to a substation monitoring system.
Wall-mount unit with rain cover — built-in RS-485 / Modbus RTU, three 4–20 mA channels and three relay outputs, with optional LED panel display
Key Features
Solid-State Palladium Alloy Thin-Film
Optimized Pd alloy doping and thin-film preparation give excellent long-term stability and sensitivity. The sensing chip sits directly in the transformer oil — no oil-gas separation is required, and measurement is unaffected by vacuum or positive pressure.
Hydrogen-Specific Coating
A specific coating lets the unit work reliably in backgrounds containing CO and CH compounds, so detection accuracy is not affected by other gases. C₂H₂ and other combustible gases do not interfere with the hydrogen measurement.
Hydrogen, Moisture and Oil Temperature in One Unit
Continuous monitoring of dissolved hydrogen, moisture (0 ~ 100 %RS) and oil temperature (−40 ~ 120 ℃, ±1 ℃) from a single device installed at the sampling valve.
Complete Outputs Built In
RS-485 / Modbus RTU digital output, three 4–20 mA analog outputs (load capacity ≤ 400 Ω), three NO/NC relay outputs and three LED status indicators — it connects straight to a station monitoring system without a secondary instrument.
No Degassing, No Periodic Maintenance
There is no oil-gas separation membrane, no sensor replacement and no carrier gas, so no periodic maintenance is required. Hydrogen concentration and generation rate are measured continuously for early warning of transformer faults.
Wall-Mount, Rain-Covered, IP66
The unit body is 120.2 mm wide and 300 mm high including its rain cover, rated IP66. It is designed for the oil sampling valve of distribution and industrial transformers.
Technical Specifications
Dissolved Hydrogen
| Detection Principle | Palladium alloy thin film |
| Measuring Range | 5 ~ 5000 ppm |
| Accuracy | ±15% reading or ±5 ppm (whichever is greater) |
| Repeatability | ±5% reading or ±5 ppm (whichever is greater) |
| Resolution | 1 ppm |
| Applicable Oil Temperature | −40 ~ 105 ℃ |
| Response Time τ90 | < 30 min (oil concentration above 100 ppm) |
Moisture (standard)
| Measuring Range | 0 ~ 100 %RS |
| Accuracy at 20 ℃ | 0 ~ 90 %RS: ±2 %RS 90 ~ 100 %RS: ±3 %RS |
| Response Time τ90 | < 10 min |
Oil Temperature
| Measuring Range | −40 ~ 120 ℃ |
| Accuracy at 20 ℃ | ±1 ℃ |
Electrical & Other
| Power Supply | 24 V DC ±10%, 0.5 A (max) |
| Digital Output | RS-485 |
| Communication Protocol | Modbus_RTU |
| Analog Output | 3 channels 4 ~ 20 mA (load capacity ≤ 400 Ω) |
| Relay Output | 3 channels NO/NC, 0.3 A @ 125 V AC; 1 A @ 30 V DC |
| Status Indication | 3 LED indicators |
| Panel Display | H₂ concentration, moisture and oil temperature (optional LED panel) |
| Ingress Protection | IP66 |
| Data Storage | Default interval 30 s (adjustable), 74,604 entries |
| Expected Life | 10 years |
| Weight | approx. 1.75 kg |
Outline Dimensions
| Unit Body Width | 120.2 mm (excluding rain cover) |
| Unit Body Height | 300 mm (including rain cover) |
| Probe Rod Overall Length | 253 ± 1 mm |
| Probe Insertion Depth | ≤ 100 mm |
| Probe Rod Diameter | φ19 mm |
| Process Connection | 3/4 in. two-ferrule tube fittings |
| Electrical Connector | 19-pin, type WF24K19ZMQ (mating plug WF24J19TE) |
Range Limit & Reference Standards
Range limit: the DGA-200 is specified for a dissolved hydrogen measuring range of 5 ~ 5000 ppm. Operation beyond the measuring range may cause irreversible damage to the sensor probe.
| Q/GDW 10536-2021 | Technical specification for on-line monitoring devices of dissolved gases in transformer oil |
| Q/GDW 12615-2025 | Technical specification for on-line monitoring devices of hydrogen in transformer oil |
| GB/T 191-2008 | Pictorial markings for handling of packages |
Ordering Information
| DGA-200 Basic | On-line monitoring unit for dissolved hydrogen, moisture and oil temperature, with analog, relay and digital outputs |
| DGA-200 with LED panel | Optional LED panel for local display of hydrogen concentration, moisture and oil temperature |
Each unit is supplied with a factory inspection report and a certificate of conformity. Check the accessories against the packing list before use; if anything is missing, contact your distributor or the manufacturer immediately.
Ideal Applications
Distribution Transformers
Grid distribution transformers are the target application — one valve-mounted unit adds hydrogen, moisture and oil-temperature trending at low cost.
Substation Monitoring
Built-in RS-485 / Modbus RTU, three 4–20 mA channels and three relay outputs connect directly to station monitoring, with no secondary instrument.
Transformer Fleets
Continuous hydrogen concentration and generation-rate trending gives early warning of incipient faults across a fleet, without periodic oil sampling.
Industrial & Commercial Power
Oil-filled rectifier, furnace and process transformers. IP66 wall-mount enclosure with rain cover for outdoor installation.
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