|Frequency range||31.5Hz - 8kHz|
|Measurement range (A)||30dB - 130dB|
|Frequency weighting||A, C, Flat|
|Time weighting||F, S|
|Standards||IEC 651 Type 2, ANSI 1.4 Type 2|
The Colead SL5868P is a sound level meter with RS232 connectivity.
It has live (Lp), equivalent continuous (Leq), and threshold-based (Ln) measurement modes. It can also trigger alarm conditions based on a configured level, and drive a relay accordingly.
It is rebranded under many names, but appears to generally have the SL-5868P model designation. It's available for under $100.
The serial port is set to 2400bps, 8 bits, no parity, 1 stop bit (2400/8n1).
The meter sends two measurements per second. When a new measurement is ready, the device sends
0x10. The PC responds with
0x20, which causes the device to transmit a 10-byte structure containing configuration and measurement.
When the user presses the
Read key on the keypad, the device sends all its stored measurements out via the serial port. This is preceded by two bogus measurement records as a marker, where all the digits are set to
0x0a and byte 2 contains
0x09 in the first record, and
0x08 in the second record. The stored measurement records then follow; the entire sequence is typically repeated twice, including the marker.
When the user switches back to live measurement mode, another two bogus measurement records are sent. To mark the return to live mode, the second bogus record this time contains
0x07. All following records are then live.
|0x10||Device -> PC||Measurement ready|
|0x20||PC -> Device||Send measurement|
|2||Configuration. The low nibble has the following meaning:|
|0000||Lp, Weighting A, Fast|
|0001||Lp, Weighting A, Slow|
|0010||Lp, Weighting C, Fast|
|0011||Lp, Weighting C, Slow|
|0100||Lp, Flat, Fast|
|0101||Lp, Flat, Slow|
|0110||Ln, Weighting A, Fast|
|0111||Ln, Weighting A, Slow|
|1000||Leq, Weighting A, Fast (10-second mean)|
|1001||Leq, Weighting A, Fast (mean over minutes)|
|1010||Leq, Weighting A, Slow (10-second mean)|
|1011||Leq, Weighting A, Slow (mean over minutes)|
|1100||Internal calibration mode, Fast|
|1101||Internal calibration mode, Slow|
|The high nibble has the following meaning:|
|0010||Max hold mode|
|3-7||BCD-encoded value, one byte per digit 0x00-0x09. 0x0a means ignored digit. The last digit represents the decimal.|
|9||Checksum: sum of bytes 0-8|