Appendix a: hdt power-on sequence, timing diagram, Appendices page 19 – COSA Xentaur Xentaur HDT User Manual
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Appendices
page 19
Appendix A: HDT power-on sequence, timing diagram
Decision tree and Timing diagram of HDT current loop during power on startup
Loop Current (mA)
Time (sec)
0
4
8
1
21
62
02
42
83
2
0
4
20
10
If the HDT is in Normal Addressing Mode (this is the
factory default), then the current loop is tested for
voltage and impedance to verify sufficient capability to
have at least 5VDC across transmitter when pulling
20mA.
Normal Addressing Mode
Current corresponds to
measurement
Polling Mode (stay at 4mA)
Loop Voltage too low (stay at 3.8mA)
EEPROM Checksum Fault (stay at ~3.8mA)
4.0mA for 8 sec
4.5mA for 8 sec
~3.5mA
for 4 sec
~15mA/sec
90% of final reading
100% of final reading
If the HDT is in Polling Mode, then the loop test is
bypassed the HDT begins measuring and loop goes
to 4mA within 5 seconds of powerup. Data is obtainable
only through the HART digital interface.