Xylem H-3553 - Manual (Page 24)

H-3553 Combo Bubbler setup menu sDI-12 Interface
B – Bubbler Settings Command: aXWPSnn!
: Response: a0061
Bubbler settings menu Command: aXRPS!
S – Purge Sustain: xx Response: a0021
Enter Purge Sustain (10 - 40) [ nn ] Command: aD0!
Response: a + nn
Table 4-16: Change the H-3553 Purge Sustain
SETUP & OPERATION
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4-20 Milliamp Output
The H-3553 has the ability to output the stage
value as a 4-20 milliamp signal. The 4-20
milliamp output is most commonly used in
industrial applications with PLC’s or SCADA
systems. The H-3553 controls the loop current
but does not power the loop. Therefore, the
loop must be externally powered. Figure
4-1 shows a basic wiring diagram for a 4-20
milliamp output loop with the H-3553. The
battery in the loop should be a +24VDC
power source. Figure 4-1: Typical H-3553 4-20 mA Output Setup
The H-3553 scales the current measured stage reading for the 4-20 milliamp output based on the 4-20
milliamp min and max stage values.
4-20 Milliamp Min Stage
The 4-20 milliamp min stage value should be the lowest the stage gets at the installed site. When the stage
equals this value or lower the 4-20 milliamp out put will be 4.0 milliamps, the min.
The H-3553 4-20 milliamp min stage default value is set to 4. There is no limit to this value, but keep in mind
that the smaller the overall range of the 4-20 stage scalar, which is the min to the max stage, the more accurate
the 4-20 milliamp output will be. To change the 4-20 milliamp min stage using the RS-232 main menu, press
the ‘P’ key to enter the “Advanced Options” menu and then press the ‘F’ key to enter the “4-20mA Output
Setup” menu. Then press the ‘N’ key in this menu and enter in the new “Min Stage” value and press the ‘Enter’
key.
To change the H-3553 4-20 milliamp min stage using the SDI-12 interface, send the “aXWILn.nn!” SDI-12
extended command. The response should be “a0021”, which means that it could take 2 seconds to complete
the command and then it will put 1 data value in the buffer. To check the new 4-20 milliamp min stage, send
“aXRIL!” command and wait the responded time. Then send the “aD0!” command to read back the new written
4-20 milliamp min stage. Note Table 4-17, the ‘a’ is the current SDI-12 address of the H-3553 and the ‘x.xx’ is
the current 4-20 milliamp min stage and the ‘n.nn’ is the desired 4-20 milliamp min stage.