Campbell-scientific Sentek EnviroSCAN EasyAG SDI-12 Manual v 3.4 Uživatelský manuál stáhnout pdf (Strana 12)

EnviroSMART & EasyAG SDI-12 Probe Manual

In this example shown in Figure 3, there is no inter-character gap sent by the SDI-12 probe interface.

The start bit for the second character follows immediately after the stop bit (marking) from the first

character.

Note: The EnviroSMART and EasyAG SDI-12 probe interface will permit up to 4 bit-times between

characters before rejecting the command.

Marking 8.4 mS

1 2 3 4 5 6 7 8 9 10

Intervals approx 0.8mS (1 bit time)

?=3F !=21

1 1 1 1 1 1 0 0 1 0 0 0 0 1 0 0

Break -

Min 12 mS

Marking Level

Spacing Level

Figure 3: Voltage levels on the SDI-12 line during an Acknowledge Active command (a!)

Following the terminating character (!) of the command, the controlling device must release the line

within 6.5mS. The EnviroSMART and EasyAG SDI-12 probe interface will hold the line at the

marking level for a minimum of 8.33mS before transmitting the first character of the response.

Addresses

The EnviroSMART and EasyAG SDI-12 probe interface accepts SDI-12 addresses in the range “0”

to “9”, “A” to “Z” and “a” to “z”. Setting the probe interface address can be done using the Change

Address command (aAb!) (see SDI-12 Commands Supported) or using the Intelligent Probe

Configuration Utility.

Note: If the new address is invalid, the current address will be kept.

Note: The probe interface will remain unresponsive for approximately 30 ms while the new address is

saved in non-volatile memory.

Note: The probe interface supports “?” (wildcard) as an address only for the Acknowledge Active

command (a!).

3.5V

1.0V

Bit Number:

Bit Value:

1 2 ... 7 8 9 10 11 12 13 14 15 16 17 ... 29 30

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Campbell-scientific Sentek EnviroSCAN EasyAG SDI-12 Manual v 3.4 Uživatelský manuál Strana 12