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CHY 650 Sound Level Meter


This instrument is a portable easy use 3 digit, compact- sized digital sound level meter designed for simple one hand operation, and can be mounted on a tripod for long-term measurement. Meter with A and C frequency weighting of the RMS signal, F and S time weighting and maximum level indication.

Safety Information

It is recommended that you read the safety and operation instructions before using the sound level meter.
  • The sound level meter must be protected from shocks and vibration as it is a precision instrument.
  • The microphone in particular must be protected from exposure to water or dust. The unit should also not be stored in locations with high temperatures or humidity.
  • Dust or contamination can alter the performance characteristics of the unit. Always replace the unit in its carrying case when not in use.
  • The microphone cover at the tip of the unit is not designed to be removed. Do not try to disengage the cover. Cleaning the microphone is not advisable.
Operating Instructions
  • 1. Setting the measurement range :
    Slide switch O (power-off) / Lo (35-9OdB) / Hi (75- 130dB).
    The meter has 2 sound pressure level (SPL) measurement ranges each with a dynamic range of 55dB. The sound pressure level indication is updated every one second. If OVER or UNDER is continuously shown, change the setting of the power-range slide switch to a suitable range.
  • 2. Setting the Time Weighting :
    Slide switch: S (SLOW) / F (FAST)
    The time weightiness available is shown below:
    S (SLOW) : for normal measurements
    F (FAST) : for checking average levels of fluctuating noise.
  • 3. Setting the Frequency Weighting :
    Slide switch: A / C
    The available frequency weightiness of the RMS signal is shown below:
    A: for general sound level measurement
    C: for checking the low-frequency content of a noise (If the C-weighted level is much higher than the A- weighed level, then there is a large amount of low- frequency noise.)
  • 4. Setting the Maximum Level Hold :
    Slide switch: MAX / RESET
    The MAX Hold is used to measure the maximum level of sounds. The maximum measured level is indicated continuously.
    To reset the maximum level indication and enter the new measurement, set the slide switch to RESET position.
  • 5. Using the AC and DC Output Jack :
    AC Output: Serves to supplie AC signals (approx. 1 .0Vrms at the top of the selected measurement range) to external equipment.
    DC Output: Serves to supplie DC signals (approx. lOmV/dB) to external equipment.
  • 6. Using the Tripod Mounting Screw :
    For long-term measurements, the meter can be mounted on a tripod.
    • 1. Remove the screw from the back of the meter.
    • 2. Replace the screw with the tripod mounting Screw-nut.
    • 3. Use the tripod mounting screw fixed to the tripod Screw-nut.
  • 7. Calibrating :
    • 1. Set the meter slide switch to the Hi-range (75-130dB), A-weighting ,F (FAST)-time weighting and RESET positions.
    • 2. Fit the sound level calibrator carefully onto the meter and rest the meter on a table or other flat surface. Ensure that the calibrator fits snugly on the microphone.
    • 3. Set calibrator at 94dB and 1KHz.
    • 4. Switch on the calibrator. The calibrator emits a 1KHz calibration signal.
    • 5. Remove the 94dB CAL label from the front of the meter.
    • 6. Adjust the calibration control to obtain a reading of 94.0dB.
Measurement Considerations
  • 1. Background Noise :
    If the level difference between the absence and presence of the sound to be measured is 10dB or more, the influence of background noise may be disregarded.
    If the difference is less, a compensation as shown below should be applied.
    Level Difference dB 4 5 6 7 8 9 10
    Compensation value dB -2.2 -1.7 -1.3 -1 -.08 -.07 0
  • 2. Refection :
    The microphone should be placed well away from reflective surfaces such as walls or the floor, in order to eliminate errors due to reflections. When making sound measurements, hold the meter at arms length. This will help to avoid both reflections from your body and also blocking of sound from some directions.
  • 3. Obstruction :
    Make sure that nothing obstructs the noise source.
  • 4. Readings :
    Be careful not to accept readings. If the meter is under loaded and overloaded.
Battery Replacement
Power is supplied by four 1 .5V (AAA size) batteries. The 'Battery' sign appears on the LCD display when replacement is needed. To replace the batteries, remove the screw from the back of the meter and lift off the battery cover case. Remove the batteries from battery contacts.
Periodically wipe the case with a damp cloth and detergent, do not use abrasives or solvents.
Display 3 digit liquid crystal display (LCD) with maximum reading of 1999
Low battery indication The 'battery' sign is displayed when battery voltage drops below the operating level
Operating Enviromnent -10C to 50C at < 90% relative humidity
Storage Temperature -20C to 60C, 0 to 80% R.H. with battery removed from meter
Battery 4 pcs 1 .5V (AAA size) UM-4 R03 Battery Life: 50 hours
Dimensions 217mm(H) x 44mm(W) x 4Omm(D)
Weight 168g including batteries Accessories: Windscreen xl, Battery x4, Plug xl, Tripod mounting screw-nut xl, Carrying case xl


Applicable Standard IEC 651-1979 Type 2
ANSI S1.4-1983 Type 2
JIS C 1502
Measurement Range Lo - range 35-90 dB
Hi-range 75-130dB
Resolution 0.1 dB
Frequency Weighting A and C accordng to IEC 651 Type 2
Frequency Range 31.5 Hz to 8000 Hz
Detector True-RMS with independent frequency weightiness
Dynamic Range 55 dB
Maximum Hold decay time < ldB / 3 minute with Reset switch
Time Weighting S (SLOW) and F (FAST) according to IEC 651 Type 2
Microphone " electret (prepolarized) condenser microphone
DC Output Output - 10 mV/dB
Output Impedance - 50Ω approx
AC Output Output - 1.0V RMS corresponding to the top of the selected measurement range.
Output Impedance - 600Ω approx
Warm up < 5s
Calibration Conditions Reference Frequency: 1000 Hz
Reference SPL: 94 dB
Reference Temperature: 20C
Reference RH: 65%
Reference Range: 75-130dB
Reference Direction of incidence: Frontal
Effect of Temperature < 0.5dB (-10C to 50C)
Effect of Humidity < 0.5dB for 30% < RH < 90% (at 40C , 1KHz)

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Copyright ? 2001 JaySafe Systems. Last modified: 22 July 2016.
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