Campbell Scientific TDRSDK Software Developement Kit - Manual (Page 25)

Appendix B. TDR100 Response Protocol
B-3
Acknowledge Response (Response to Type 1 and Type 3 Commands)
|$|CCCC|
$ ASCII ‘$’ to indicate Acknowledgment
C The Four ASCII command characters that followed the ‘:’
Value Response (Response to Type 2 Commands)
|#|CCCC|0xXXXX|data bytes up to 8192
# ASCII ‘#’ to indicate a value response
C The four ASCII command characters that followed the ‘:’
X data in 4 byte IEEE floating point in the Big-Endian format