SMART SENSOR ST8904 Multi-Gas Monitor User Manual

1. Introduction

Thank you for purchasing the SMART SENSOR ST8904 Multi-Gas Monitor. This instruction manual provides essential information for safe and effective use, including operational procedures, important notices, and maintenance guidelines. To ensure optimal performance and longevity of your device, please read this manual thoroughly before use and keep it in an easily accessible location for future reference.

The ST8904 Multi-Gas Meter is a portable, handheld instrument designed for continuous monitoring of four different gases: Oxygen (O2), Combustible Gas (LEL), Carbon Monoxide (CO), and Hydrogen Sulfide (H2S). The device displays real-time concentrations on its LCD screen and features configurable high and low alarms, as well as Short-Term Exposure Limit (STEL) and Time-Weighted Average (TWA) alarm functions. For user safety, the unit provides audio, vibration, and visual alarms when gas concentrations exceed set limits.

2. Safety Information, Warnings, and Precautions

Failure to follow these safety instructions may result in injury, damage to the instrument, or inaccurate readings.

Environmental Conditions: Operate the monitor in suitable environments. Extreme conditions can reduce performance and accuracy.
Sensor Maintenance: Keep the gas sensor window and gas filter clean. Blocked or dirty filters can lead to readings lower than actual concentrations.
Oxygen Levels and LEL Readings: Measuring combustible gas (LEL) in an oxygen-deficient environment may result in readings lower than actual values. Conversely, a high-oxygen environment may cause higher readings.
Over-Range Events: If LEL concentration exceeds its range, the unit must be re-calibrated to ensure accuracy.
Chemical Interference: Water vapor, silicon copper compounds, or other known contaminants can affect LEL sensor operation, leading to inaccurate readings.
Atmospheric Pressure: Sudden changes in atmospheric pressure may cause temporary fluctuations in concentration readings.
Battery Safety: Charge or replace the battery only in a safe environment. Do not charge the battery in a confined space. Use only the built-in lithium battery; do not replace it with other types. Do not disassemble the battery in an explosive environment.
Unauthorized Repairs/Parts: Do not use unauthorized replacement parts or sensors. Repairs must be handled by authorized personnel or agents. Using non-approved parts can cause malfunction, inaccurate measurements, and serious safety issues.
Explosion Hazard: If gas readings exceed the highest unit and then drop suddenly or become unstable, it indicates the tested gas is beyond the explosive range, which is extremely dangerous.
Operating Temperature: The unit's operating range is -10°C to 50°C.
Battery Charging and Storage: Charge the battery before it fully discharges to prevent shortening its lifespan. If storing the unit for a long period, fully charge it beforehand to prevent deep discharge.
Cabinet Access: Do not open the cabinet in a dangerous environment.
Alarm Function: The alarm function does not have a hold feature; it will stop automatically once gas concentration returns to normal.
Accuracy Check: Before each use, verify the unit's accuracy with 25% LEL or 50% LEL using Pentane or Methane calibration gas.
Protection: When measured values are outside preset alarm levels, take immediate action to protect lives and property from potential explosion.

3. Packing List and Included Accessories

Please check the contents of your package upon receipt. If any items are missing or damaged, contact your supplier immediately.

3.1 Packing List

Multi-Gas Meter: 1 pcs
Instruction Manual: 1 pcs
USB Cable: 1 pcs
Screw: 2 pcs

3.2 Included Accessories (as shown)

Contents of SMART SENSOR ST8904 product package

Figure 2: Package Contents (Gas Monitor, Carrying Case, Manual, Charging Cable, Calibration Cover)

Carrying Case/Bag
Gas Calibration Cover

4. Setup

4.1 Device Overview

The ST8904 features an LCD display, control buttons, alarm indicators, and sensor windows. Familiarize yourself with the layout:

LCD Display Panel: Shows gas concentrations, battery status, and mode indicators.
Alarm Light: Visual alarm indicator.
Alarm Sound: Audible alarm indicator.
Down Key (▼): Used for navigation and value adjustment.
Up Key (▲): Used for navigation and value adjustment.
Confirm Key (↵): Used to confirm selections and enter settings.
Power On/Off Key (⏻): Used to power the device on and off.
Charge Inlet (USB): USB port for charging.
Gas Sensor Windows: Where gas samples are drawn for analysis.

4.2 Battery Charging

Figure 3: Charging the 3.7V 1800mAh Rechargeable Battery

The unit is powered by a built-in lithium-ion battery. It is recommended to fully charge the battery before first use.

Locate the charging port on the right side of the unit, protected by a rubber flap.
Plug the USB charging cable into the unit's charging port and connect the other end to a suitable USB power adapter.
The battery should be fully charged within approximately 6 hours.
The battery indicator on the LCD will show full when charging is complete.
When the battery is low (only one bar left), the unit may emit a periodic alarm sound, indicating it needs to be charged.

4.3 Power On/Off

To Turn On: Depress and hold the Power On/Off key (⏻) for over 2 seconds. The unit will emit a beep sound and vibrate, the LCD will light up, display the software version code, and then begin an 18-second countdown. After the countdown, the unit will enter normal gas monitoring mode.
To Turn Off: Depress and hold the Power On/Off key (⏻) for over 3 seconds. The unit will power off after 3 beep sounds.

5. Operating Instructions

5.1 Gas Monitoring Mode

After powering on and completing the countdown, the unit automatically enters normal gas monitoring mode. In this mode, it continuously monitors and displays the real-time concentrations of O2, LEL, CO, and H2S on the LCD.

5.2 View Peak Value Mode

From normal gas monitoring mode, press the Up Key (▲) once. The display will switch to