Colead SL-5868P

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Colead SL-5868P.jpg

The Colead SL5868P is an inexpensive sound level meter with RS232 capability. It has Lp and Leq measurement modes, and can trigger alarm conditions based on a configured level.

It is rebranded under many names, but appears to generally have the SL-5868P model designation. It's available for under $100.

Hardware

Photos

Protocol

TODO: serialcomm

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.

Commands

Command Direction Description
0x10 Device -> PC Measurement ready
0x20 PC -> Device Send measurement

Data structure

Byte Value Description
0 Always 0x08
1 Always 0x04
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
1110 Unused
1111 Unused
The high nibble has the following meaning:
0001 Normal measurement
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.
8 Measurement status
0 Invalid
1 Valid
9 Checksum: sum of bytes 0-8