Digital Sound Level Meter

1. Introduction

The SMART SENSOR ST9604 Digital Sound Level Meter is designed for measuring sound levels in various environments. It is widely used in noise engineering work, quality control, healthcare, and other environmental measurements. Applications include science and industry, as well as use in homes, offices, schools, businesses, and road construction.

Figure 1: Front view of the ST9604 Digital Sound Level Meter.

2. Features

This instrument is a high-precision sound level meter with an accuracy of up to ±1.5dB. Key features include:

• Measurement range: 30-130dB
• Frequency weighting: A weighting
• Maximum and Minimum value hold function
• Data Hold function
• Red backlight alarm and sound alarm
• Auto or manual power off function
• Temperature measurement function
• Temperature Unit (°C/°F) selection function
• Color Screen
• Low Battery Indication

Figure 2: Visual representation of key features.

3. Specifications

The device is certified with CE and FCC standards.

Figure 3: Product dimensions (5.94in x 2.0in x 1.05in).

4. Product Overview

The ST9604 Digital Sound Level Meter features a clear LCD display and intuitive controls. Key components include:

• ECM Microphone and Wind Shielding Ball: Located at the top of the device for sound capture.
• LCD Display Panel: Shows measurement readings, temperature, and various indicators.
• Power On/Off Key: Used to turn the device on and off.
• MODE Key: Used for data hold (Min/Max) and power off mode selection.
• SET Key: Used for alarm setup and saving settings.
• UNIT Key: Used for temperature unit selection (°C/°F) and adjusting alarm values.
• Battery Door: Located at the back of the unit.

The display features a black background with white numbers for clear readability.

5. Setup

5.1. Battery Installation

1. Locate the battery door on the back of the unit.
2. Open the battery door and insert three (3) 1.5V AAA batteries, ensuring correct polarity.
3. Close the battery door securely.
4. If the low battery indicator appears on the display, replace the batteries to ensure proper operation.

Figure 4: Battery compartment location.

5.2. Calibration Method

The unit is calibrated with a 94dB@1KHz calibrator. It is recommended to calibrate the unit once per year.

1. Turn on the unit. After it enters normal measurement mode, proceed with calibration.
2. Insert the 1/2-inch ECM microphone into the hole of the calibrator.
3. Turn on the power of the sound calibrator and set it to 94dB.
4. Insert a screwdriver into the calibration hole until it touches the trimmer. Adjust it until the screen displays 94.0 dB.

6. Operating Instructions

6.1. Power On/Off

• Power On: Depress the [Power On/Off] key. The LCD will show all segments for 1 second, then the unit will enter normal sound level measurement mode, displaying the current environmental sound pressure level.
• Power Off: In normal measurement mode, depress the [Power On/Off] key until the LCD screen turns off.

6.2. Data Hold (Minimum and Maximum Value)

• In normal measurement mode, depress the [MODE] key to cycle through Minimum, Maximum, and real-time values. The screen will show "HOLD" along with "MAX" or "MIN" icons.
• Depressing the [MODE] key again will release the hold function, and the "HOLD" icon will disappear.

6.3. Temperature Unit Selection (°C/°F)

• In normal measurement mode, depress the [UNIT] key to sequentially select between °C and °F.

6.4. High and Low SPL Alarm Setup

• In normal measurement mode, depress the [SET] key once to enter the low and high alarm setup mode.
• Use the [MODE] key to decrease the alarm value (long press for quick decrease).
• Use the [UNIT] key to increase the alarm value (long press for quick increase).
• After setting, depress the [SET] key again to save the values and return to normal measurement mode.
• Alarm Range:
  • Low Alarm (30dB~99.9dB): If the measured value exceeds the low alarm setting, the red backlight will illuminate.
  • High Alarm (100~130dB): If the measured value exceeds the high alarm setting, the red backlight will illuminate, and a voice alarm will sound.

Figure 5: Example of alarm display with red backlight and sound indicator.

6.5. Auto or Manual Power Off Setup

• In normal measurement mode, depress the [MODE] key for more than 3 seconds to enter the "Auto" or "Manual" power off screen.
• Use the [Power On/Off] key to select "Auto" OFF or "Manual" OFF mode.
• Depress the [MODE] key for more than 3 seconds to save the setting and return to normal measurement mode.
• If "Auto" OFF is selected, the unit will power off after 5 minutes of inactivity. The LCD will show a specific icon.
• If "Manual" OFF is selected, the unit must be turned off manually using the [Power On/Off] key. No specific icon will be shown for this mode.

6.6. Alarm ON/OFF

• In normal measurement mode, depress the [SET] key for a while to toggle the alarm function ON or OFF.
• When the alarm is ON, "Alarm" will be shown on the LCD. If the alarm is OFF, no "Alarm" icon will be displayed.

7. Maintenance

• Storage: Do not store the device in high temperature or high humidity environments. Avoid environments with high concentrations of salt or sulfur.
• Battery Care: If the instrument will not be used for a long period, remove the batteries to prevent leakage and potential damage.
• Outdoor Use: When measuring sound pressure levels outdoors, always cover the ECM microphone with the wind shielding ball to ensure accurate readings.
• Operating Environment: The recommended measurement environmental temperature range is 0°C to 40°C, and humidity range is <80% RH.

8. Troubleshooting

• Inaccurate Readings: If readings appear inconsistent or unusually high in quiet environments, ensure the device is properly calibrated. Refer to the "Calibration Method" section. Environmental factors like strong air currents or vibrations can also affect readings.
• No Display/Power Issues: Check battery installation and ensure batteries are not depleted. Replace batteries if the low battery indicator is shown or if the device does not power on.
• Alarm Not Functioning: Verify that the alarm function is enabled (check for "Alarm" icon on LCD) and that the alarm thresholds are set correctly.

9. User Tips

• Calibration: While the device is factory calibrated, annual calibration is recommended for maintaining accuracy.
• Display: The display features a black background with white numbers for optimal visibility.
• Weighting: This device uses A-weighting for sound level measurements and does not support C-weighting.
• Data Recording: The device features a data hold function for Min/Max values but does not have a continuous data recording function.

10. Warranty and Support

Our company reserves the right to change the design and the user manual without prior notice to the end user.

For detailed information and diagrams, please refer to the official user manual PDF available at: SMART SENSOR ST9604 User Manual (PDF).