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 proper use, important notices, and safety precautions. To ensure maximum performance and accurate readings from this product, please read this user manual thoroughly before operation. Keep this manual in an easily accessible location for future reference.

Before using this instrument, perform simple tests to confirm its normal function.

2. Safety Warnings and Precautions

WARNING AND PRECAUTION:

Improper operation or use in unsuitable environments will reduce the performance and accuracy of this monitor. To ensure safe and effective use, please read the following operation procedures and use the instrument in suitable environmental conditions.

• Please read this instruction manual carefully before using the monitor.
• The gas sensor window and gas filter must be kept clean. If the window is blocked or the gas filter is dirty, it will cause the gas sensor reading to be lower than the actual measured concentration.
• Measuring combustible gas in an oxygen-deficient environment may result in a reading lower than the actual value.
• Measuring combustible gas in an oxygen-rich environment may result in a reading higher than the actual value.
• If the LEL concentration exceeds the over-range limit, the unit must be re-calibrated to guarantee the accuracy of the gas meter.
• Increased water vapor, silicon copper compounds, or other known miscellaneous substances may affect the normal operation of the LEL gas sensor, causing the reading value to be inaccurate.
• Sudden changes in atmospheric pressure may cause temporary fluctuation of the concentration reading.
• Charging the battery or repairing the unit must be performed in a safe environment.
• Charging the unit battery under a well-ventilated area is prohibited.
• Replacement of parts or sensors with non-recommended components is not advised, as it may cause serious safety problems.
• Repairs must be handled by an authorized person or agent. Using non-approved parts will cause malfunction or inaccurate measurements. Reading the user manual before repair is highly recommended.
• Notice: If the gas reading exceeds the highest unit and then suddenly drops or becomes unstable, it indicates that the tested gas is beyond the explosive range, which is a very dangerous situation.
• The operating temperature range for this unit is from -10 °C to 50 °C.
• All parts must not be changed or replaced with unauthorized components. It is highly recommended to ship the unit back to an authorized agent for repair. Do not connect the unit to other instruments.
• If a sample pump is required, use only our specifically designed sample pump for this unit.
• This unit must operate with the built-in lithium battery. Do not replace it with other lithium batteries. Do not disassemble the battery in an explosive environment.
• Before the battery fully discharges, charge it promptly to prevent shortening its lifespan.
• If the unit is not used for a long period, fully charge it before storage to prevent battery damage from deep discharge.

3. Product Overview

The SMART SENSOR ST8904 is a portable and handheld 4-in-1 gas monitor designed for industrial safety. It continuously monitors Carbon Monoxide (CO), Hydrogen Sulfide (H2S), Oxygen (O2), and Combustible Gas (LEL) concentrations in the surrounding environment. The device features a large color LCD display with backlight for easy reading, and provides sound, light, and vibration alarms when gas concentrations exceed preset levels.

Figure 1: SMART SENSOR ST8904 Gas Monitor and Included Accessories

3.1. Key Features

• Detects 4 kinds of gas: Carbon Monoxide (CO), Hydrogen Sulfide (H2S), Oxygen (O2), and Combustible Gas (LEL).
• Continuous monitoring of gas concentrations with professional and accurate measurement.
• Sound, light, and vibration alarms activate when gas concentrations reach alarm levels.
• Adjustable automatic shutdown time and alarm value concentration.
• Large color LCD display with backlight for clear reading.
• Option to connect to a sampling pump for operation in closed spaces.
• Widely applicable in shipping, mining, oil exploitation, chemical, gas pipeline, tunnel construction, coal, metallurgy, paper, fire, municipal, textile, and other industries.

3.2. Device Layout and Dimensions

Figure 2: Front View with Labeled Components

• LCD Display Screen: Shows gas concentrations, battery status, and alarm indicators.
• Light Alarm: Visual alarm indicator.
• Audible Alarm: Sound alarm indicator.
• Selection Key (Up/Down): Used for navigation and value adjustment.
• Confirm Key: Used to confirm selections.
• Power Button: Turns the device on/off.
• Charging Interface: USB port for charging.
• Air Pump Connection Port: For optional sampling pump.
• Sensor Window: Area where gas sensors are located.

Figure 3: Device Dimensions

• Dimensions: 70.9mm (Width) x 138mm (Height) x 48mm (Depth)

3.3. Packing List

The gift box should contain the following items. If any items are missing or pages of the instruction manual are missing, please contact your supplier.

• 1 x Multi-Gas Meter
• 1 x Instruction Manual
• 1 x USB Cable
• 1 x Cloth Bag
• 2 x Screws (for optional pump attachment)

Figure 4: Included Accessories

4. Specifications

4.1. Gas Hazard Information

Understanding the hazards associated with different gas concentrations is crucial for safety. The following tables provide reference information for Hydrogen Sulfide (H2S), Carbon Monoxide (CO), Oxygen (O2), and Combustible Gas (LEL).

*The above table is for reference only.

*The above table is for reference only.

*The above table is for reference only.

5. Operation Manual

5.1. Instrument Operation

Turning On the Instrument:

Depress and hold the Power button (red button) for over 2 seconds. The unit will turn on with a beep sound and vibration, then the LCD will light up all icons and segments. Then the LCD will display the software version code. After a 18-second countdown, the unit will enter normal gas monitoring mode.

Turning Off the Instrument:

Depress and hold the Power button for over 3 seconds, then the unit will power off after 3 beep sounds.

Automatic Power Off Function:

In normal gas monitor mode, depress the Down arrow key (▼) until the LCD displays "APO" and "ON" or "OFF".

• Press the Down arrow key (▼) again to select "ON" or "OFF".
• "ON" means the unit will turn off after 10 minutes if no button is activated during this period.
• "OFF" means no automatic power off function.
• Press the Confirm key (⏎) to confirm your selection. The unit will then return to normal gas monitor mode.

When the unit is set to auto power off mode, an "APO" icon will be shown on the LCD. If set to no auto power off, no "APO" icon will be displayed.

Figure 5: Auto Power Off Display

5.2. Gas Monitoring Modes

Normal Gas Monitoring Mode:

After turning on, the unit enters normal gas monitoring mode. It continuously monitors the four gases (O2, LEL, CO, H2S) and displays their updated values on the LCD.

View Peak Value Display Mode:

From normal gas monitor mode, depress the Up arrow key (▲) once to enter "Peak Value" display mode. The screen will show the peak concentration values for toxic and combustible gases, and the lowest concentration value for O2. Press the Confirm key (⏎) once to reset the peak values to normal monitoring.

View TWA Mode (Time Weighted Average):

Pressing the Up arrow key (▲) twice from normal gas monitor mode will put the unit in "View TWA" mode. The TWA screen will show the "TWA" icon and the Time Weighted Average value for the two toxic sensors. TWA values are reset every time the instrument is powered down, and the time base is set for 8 hours. TWA is only available for toxic sensors; if the instrument is not equipped with these sensors, this mode will not function.

View STEL Mode (Short Term Exposure Limit):

Pressing the Up arrow key (▲) three times from normal gas monitor mode will put the unit in "View STEL" mode. The STEL screen will show the "STEL" icon and the Short Term Exposure Limit value for the two toxic sensors. STEL values for the sensor are reset every time the instrument is powered down, and the time base for STEL is set for 15 minutes. STEL is only effective with toxic sensors; if the instrument does not have these sensors, this mode will not show.

5.3. Alarm Settings

The unit provides sound, light, and vibration alarms. When any gas concentration (CO, H2S, O2, LEL) exceeds the preset alarm levels (low, high, TWA, STEL), the corresponding alarm will activate.

Low Alarm Set Points:

From normal gas monitor mode, depress the Up arrow key (▲) for 2 seconds to enter the low alarm set points screen. The display will show "ALM. L" icon along with four low alarm set points.

• If no changes are needed, press the Up arrow key (▲) to move to the next screen.
• To adjust a value, press the Confirm key (⏎). The first low alarm value will flash.
• Use the Up arrow key (▲) and Down arrow key (▼) to change the desired digit.
• Press the Confirm key (⏎) to select the next low alarm value. Continue this process until all four low alarm set points are set.
• Pressing the Confirm key (⏎) will re-enter the mode to adjust values again. Pressing the Up arrow key (▲) will move to the High Alarm Set Points screen.
• Pressing the Confirm key (⏎) twice will return to the normal gas reading screen.
• The low alarm is a non-latching alarm.

High Alarm Set Points:

From the low alarm set points screen, press the Up arrow key (▲) to move to the high alarm set points screen. The display will show "ALM. H" icons along with four high alarm set points.

• If no changes are needed, press the Up arrow key (▲) to move to the next screen.
• To adjust a value, press the Confirm key (⏎). The first high alarm value will flash.
• Use the Up arrow key (▲) and Down arrow key (▼) to change the desired digit.
• Press the Confirm key (⏎) to select the next high alarm value. Continue this process until all four high alarm set points are set.
• Pressing the Confirm key (⏎) will re-enter the mode to adjust values again. Pressing the Up arrow key (▲) will move to the TWA Alarm Set Points screen.
• Pressing the Confirm key (⏎) twice will return to the normal gas reading screen.
• The high alarm is a non-latching alarm.

TWA Alarm Set Points:

From the high alarm set points screen, press the Up arrow key (▲) to move to the TWA alarm set points screen. The display will show "TWA ALM" icons along with the two TWA alarm set points.

• If no changes are needed, press the Up arrow key (▲) to move to the next screen.
• To adjust a value, press the Confirm key (⏎). The first TWA alarm value will flash.
• Use the Up arrow key (▲) and Down arrow key (▼) to change the desired digit.
• Press the Confirm key (⏎) to select the next TWA alarm value. Continue this process until both TWA alarm set points are set.
• Pressing the Confirm key (⏎) will re-enter the mode to adjust values again. Pressing the Up arrow key (▲) will move to the STEL Alarm Set Points screen.
• Pressing the Confirm key (⏎) twice will return to the normal gas reading screen.

STEL Alarm Set Points:

From the TWA alarm set points screen, press the Up arrow key (▲) to move to the STEL alarm set points screen. The display will show "STEL ALM" icons along with the two STEL alarm set points.

• If no changes are needed, press the Up arrow key (▲) to move to the next screen.
• To adjust a value, press the Confirm key (⏎). The first STEL alarm value will flash.
• Use the Up arrow key (▲) and Down arrow key (▼) to change the desired digit.
• Press the Confirm key (⏎) to select the next STEL alarm value. Continue this process until both STEL alarm set points are set.
• Pressing the Confirm key (⏎) will re-enter the mode to adjust values again. Pressing the Confirm key (⏎) twice will return to the normal gas reading screen.

5.4. Calibration

Security Code Setting Mode:

At the normal gas monitor mode, press the Up arrow key (▲) once to enter security code setting mode. The display will show "123" as the factory pre-set security code.

• To change the security code, press the Confirm key (⏎). The first digit will flash.
• Use the Up arrow key (▲) and Down arrow key (▼) to change the digit.
• Press the Confirm key (⏎) to confirm the digit and move to the next. Repeat for all three digits.
• Once completed, the display will show the new security code.
• If you press the Confirm key (⏎) while a digit is flashing, the unit will return to normal gas monitor mode without changing the code.
• Warm Hints: If you forget the security code, you can press the Down arrow key (▼), Confirm key (⏎), and Up arrow key (▲) simultaneously at the security screen to enter setup mode and set a new security code.

Setup Mode:

At the normal gas monitor mode, press the Up arrow key (▲) and Down arrow key (▼) simultaneously to enter setup mode. The display will show "123" as the factory pre-set security code.

• Use the Up arrow key (▲) and Down arrow key (▼) to input the correct security code.
• Press the Confirm key (⏎) to enter the gas calibration mode.
• At this time, the first digit of the security code will flash. Use the Up arrow key (▲) and Down arrow key (▼) to change the digit.
• Press the Confirm key (⏎) to confirm the digit and move to the next. Repeat for all three digits.
• Once completed, the display will show the new security code.

Gas Calibration Mode:

From the zero point calibration screen, press the Confirm key (⏎) to enter gas calibration mode. Press the Confirm key (⏎) once to enter Oxygen gas calibration mode. The screen will show as indicated in the manual. Once the digit on the screen becomes stable, press the Confirm key (⏎) to perform the calibration. If successful, a "P" icon will appear, and the unit will automatically jump to the next three gas calibration screens.

• Place the calibration cup firmly on top of the gas sensor.
• Connect the calibration cup with a silicone tube to the passive flow adjustment valve of the calibration gas cylinder.
• Adjust the flow valve to supply gas at 0.5 liters/minute to the gas sensor.
• Once the values for the three gases stabilize, press the Confirm key (⏎).
• If calibration is successful, a "P" icon will appear for all four gases. If "F" appears, calibration failed and needs to be re-calibrated.
• Press the Confirm key (⏎) to return to normal gas monitor mode.
• Oxygen calibration should be performed in a normal fresh air environment. The other three gases must be calibrated using a mixed calibration gas cylinder with the following concentrations: 25 µmol/mol (ppm) H2S, 100 µmol/mol (ppm) CO, 50% LEL Methane.
• Attention: CSA international rules require the calibration gas to be 50% Methane.
• Warning: If you do not have sufficient calibration equipment, do not enter this mode, as incorrect calibration may render the gas monitor inaccurate.

Zero Calibration Mode:

At the zero setup mode screen, press the Confirm key (⏎). The screen will show all values as "Zero" except Oxygen. Press the Confirm key (⏎) again to set the gases to zero point.

• If setup is successful, three "P" icons will appear at the related locations.
• If any "F" icon appears, calibration failed and needs to be repeated.
• Press the Up arrow key (▲) again to repeat the zero calibration.

LEL Over Range:

If the meter detects an LEL gas concentration beyond its range, the unit will enter an over-range state and continuously alarm. To cancel this alarm, turn off the unit and place it in a clean air environment.

After an over-range event, the unit must be re-calibrated to ensure the accuracy of the gas monitor.

ST 8930 Sampling Pump (Optional Parts):

The ST 8930 sampling pump can be used with this series gas monitoring meter. It cannot operate separately and receives power from the main unit via two contact pins located on the top side of the front panel. The gas flow is 0.5 SCFH (0.25 LPM), allowing gas sampling up to 50 feet with a suitable gas tube.

6. Maintenance

6.1. Cleaning:

• If necessary, wipe the outside surface of the unit with a soft, clean cloth.
• Never use any solvents or cleaning solutions.
• Ensure the rubber buttons are free of dirt.
• To clean the sensor opening, use a clean, soft cloth or soft brush.

6.2. Charging the Battery:

The lithium-ion battery should be fully charged before initial use.

• To charge the battery, plug the connecting lead wire of the battery charger into the charging port located on the right-hand side of the unit. The port is protected by a rubber flap, which needs to be released before charging.
• The battery should be fully charged within 6 hours.
• Once fully charged, the unit can operate for 6 hours (without alarm).
• The shaded area of the battery indicator shows full when the battery is fully charged.
• If only one bar of battery indicator is left, the battery needs to be charged immediately.
• When the battery is low, the unit might emit a periodic alarm sound to alert you to charge the unit.

Figure 6: Charging the Device

7. Troubleshooting

This section addresses common issues and their potential solutions. For more complex problems, refer to the warranty information or contact authorized service personnel.

• Inaccurate Readings: Ensure the gas sensor window and filter are clean. Blockages or dirt can cause inaccurate readings. Re-calibrate the unit if an LEL over-range event has occurred or if readings are consistently off.
• No Alarm or Incorrect Alarm: Verify alarm set points (Low, High, TWA, STEL) are configured correctly. Ensure the unit is not in an environment that would cause false alarms (e.g., sudden pressure changes).
• Battery Not Holding Charge: Ensure the battery is fully charged for 6 hours. If the unit is stored for long periods, ensure it is fully charged before storage to prevent deep discharge. Avoid disassembling the battery in hazardous environments.
• Unit Not Turning On/Off: Ensure the power button is pressed and held for the correct duration (2 seconds for on, 3 seconds for off). Check battery charge.

8. User Tips

• Always perform a quick functional check before each use to ensure the device is operating correctly.
• Keep the device and its accessories clean, especially the sensor area, to maintain accuracy.
• Familiarize yourself with the alarm thresholds for the gases you are monitoring to react appropriately in an emergency.
• Store the device in a cool, dry place away from direct sunlight and extreme temperatures.
• If using an optional sampling pump, ensure it is properly connected and that the gas tube is suitable for the sampling distance.

9. Warranty and Support

9.1. Quality Warranty

The SMART SENSOR ST8904 gas meter is warranted against defects in material and workmanship for a period of one year from the date of purchase. This warranty includes the sensor, battery pack, and optional gas sample pump. For products shipped out, the warranty period is 15 months.

SMART SENSOR Holding Co., Ltd. provides no other express or implied warranties, including any for sales promotion or special requirements.

If the product is found to be incompatible with the above quality warranty, the sole remedy for the customer and obligation of SMART SENSOR Holding Co., Ltd. is to replace or repair the incompatible product, or refund the purchase price.

SMART SENSOR Holding Co., Ltd. is not liable for any special, accidental, or consequential damages arising from the use of this product, including loss of time and money, whether based on contract or infringement.

The quality warranty is based on the following conditions:

• The customer must carefully check the product upon purchase to ensure it is perfect and undamaged.
• The product must be operated, maintained, and repaired precisely according to the user manual instructions.
• Maintenance or repair by unauthorized personnel, or the use of un-certified components or parts, will void this warranty.
• The user must be knowledgeable about the instrument's functions and limitations for correct and safe use.
• The user is responsible for ensuring the purchased product meets their specific requirements.

9.2. Copyright and Declaration

Our company reserves all copyright for this user manual and related content. No part of this manual may be plagiarized, reprinted, or copied by any means (including digital or electronic) without signed and approved documentation from "Smart Sensor Holding Co., Ltd."

All information in this manual is confidential and belongs to the owner. All related copyrights, business marks, business names, patents, and other intellectual property rights are exclusive to "Smart Sensor Holding Co., Ltd." (except where otherwise declared).

Any information (including data, graphics, instruction documents, software lists, signal, or target program code) may not be directly or indirectly disclosed to third parties without signed and approved documentation from "Smart Sensor Holding Co., Ltd."

All information and contents are confirmed for accuracy and trustworthiness.

Our company bears no liability for the user's use of this product in their own way.

Our company is not liable for any information in this manual that causes any charges and cost. No notice will be given for changes to this manual.

Declaration:

• As the end-user, you are legally bound (Battery ordinance) to return all used batteries and accumulators; disposal in household garbage is prohibited. You can hand over used batteries/accumulators at collection points in your community or wherever batteries/accumulators are sold. Follow valid legal stipulations for the disposal of the device at the end of its life cycle.
• Our company reserves the right to modify and update the content of this manual and design specifications without further notice.

10. Product Video

11. Additional Resources

A detailed user manual in PDF format is available for download. This document contains comprehensive information on the operation, maintenance, and specifications of the SMART SENSOR ST8904 Multi-Gas Monitor.

You can access the PDF manual here: SMART SENSOR ST8904 User Manual (PDF)