DO-6800 Dissolved Oxygen Analyzer – High Accuracy & RS485
DO-6800 Dissolved Oxygen Analyzer – High Accuracy & RS485
Oct . 22, 2025
Online DO Controller Field Notes: the DO-6800
If you’ve been tracking water quality automation, you know the story: tighter discharge permits, smarter aquaculture, and breweries that want oxygen on a leash. In that swirl, the DO-6800 has been popping up in integrator quotes more often than I expected—partly because it does the basics reliably, partly because it doesn’t fuss.
What it is (and why people pick it)
At heart, the DO-6800 is a micro-computerized online dissolved oxygen and temperature transmitting controller with a large LCD, an English menu that’s actually readable, and multi-parameter display (DO, temp, 4–20 mA output, alarm points). It auto-compensates temperature from 0–60°C, raises alarms on range overrun, and kicks an ON/OFF relay when thresholds are hit. Optional RS‑485 (MODBUS, partial compatibility) is there for SCADA. A small but handy touch: a notepad that stores ~50 measurements. Also: adjustable hysteresis to stop chattering relays, a watchdog so it doesn’t freeze, factory-restore, and a power-down memory spec of >10 years. Origin: No.188, Fengshou Road, Chang'an district, Shijiazhuang City, Hebei Province China 050041.
Quick specs (what most teams ask first)
| Measurement method | Electrochemical or optical probe (sensor-dependent) |
| DO range | Sensor-dependent; typical 0–20 mg/L (≈0–200% sat), real-world use may vary |
| Temperature compensation | Automatic 0–60°C |
| Display & UI | Large LCD, English menu, multi-parameter screen |
| Analog output | 4–20 mA, user-set mapping to DO |
| Digital comms | Optional RS‑485 (MODBUS partially compatible) |
| Alarms/relays | High/low with ON/OFF output; adjustable hysteresis |
| Data notes | Notepad stores ≈50 measurements |
| Protection | Watchdog; power-down memory >10 years; factory-restore |
Process flow, methods, and testing
- Materials: controller with foreign-brand core components, DO probe (galvanic/polarographic or optical), junction box, 24V loop or mains, SCADA if needed.
- Methods: two-point DO calibration is common—zero (sodium sulfite) and air-saturation; temperature is auto-compensated.
- Standards referenced: ISO 5814 (electrochemical DO), ASTM D888, APHA Standard Methods 4500-O—teams often align procedures to these.
- Verification: map 4–20 mA to process setpoints; check alarm hysteresis to avoid short-cycling blowers.
- Service life: electronics designed for multi‑year duty; probe maintenance interval depends on sensor type and fouling load.
- Industries: wastewater aeration control, aquaculture, craft brewing, environmental monitoring, power plant intake, pharma utilities (non-product contact).
Where it’s being used (and why)
Aeration control is the big-ticket item—several municipal plants report steadier blower turndown once hysteresis is set sensibly. Aquaculture folks like the notepad for quick spot checks; surprisingly handy during feeding peaks. Brewers? They’re cautious, but a few have used the DO-6800 on CIP return lines to keep oxygen pickup in check.
Vendor comparison (condensed)
| Model | Comms | Display/UI | Memory | Notes |
|---|---|---|---|---|
| DO-6800 (Watequipment) | 4–20 mA; optional RS‑485 (MODBUS ≈) | Large LCD, English menu | ≈50 logs | Hysteresis, watchdog, factory-restore |
| Competitor X (budget) | 4–20 mA only | Small LCD | No log | Basic alarms |
| Competitor Y (premium) | 4–20 mA + RS‑485/ETH | Color display | Extended logs | Advanced diagnostics; higher price |
Customization and integration
- Analog scaling: freely set 4–20 mA to your DO window (e.g., 0–10 mg/L).
- MODBUS registers: partial compatibility; map to SCADA tags after a quick poll test.
- Alarm strategy: set high/low setpoints and hysteresis to match process lag.
- Sensors: choose optical for low-maintenance or electrochemical for fast response.
Case snapshots
Wastewater aeration: A mid-size plant set DO at 1.8 mg/L with 0.3 mg/L hysteresis. Operators reported steadier blower VFDs and fewer nuisance alarms in the first month.
Aquaculture: Shrimp ponds used the DO-6800 to trigger paddlewheels at low DO. Farm manager told me the onboard notepad was “old-school but convenient” for midnight checks.
Certifications and test data (what to verify)
- Methods: Align calibration with ISO 5814 / ASTM D888 / APHA 4500-O where applicable.
- Data point mapping example: 0 mg/L → 4 mA; air-sat (≈8–9 mg/L at 20°C) → ~12–13 mA; high alarm at, say, 10 mg/L, with 0.2 mg/L hysteresis.
- Compliance: CE/EMC and RoHS are common in this class; ask the vendor for current declarations and IEC 61326 test reports.
References
- ISO 5814: Water quality—Determination of dissolved oxygen—Electrochemical probe method.
- ASTM D888: Standard Test Methods for Dissolved Oxygen in Water.
- APHA Standard Methods 4500-O: Dissolved Oxygen.
- MODBUS Application Protocol Specification, v1.1b3, Modbus.org.
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