User guide

5-14 SDI-12 Command and Response Protocol H-3521
5.13 Extended Read Power_Mode and Write Power_Mode
The quadrature, 0-5V, and 4-20mA outputs are updated whenever a measurement is made. For
industrial applications such as 4-20mA where the H-3521 is connected to a SCADA or PLC
system and low-power is not of concern, the H-3521 can be programmed to make continuous
measurements. This command is used to change the power mode. The H-3521 comes from the
factory with the power mode set to the Sleep mode. Once a new value is written, a copy is sent to
the sensor data buffer for verification. This data can be viewed by using a subsequent "aD0"
command. To read or verify the value any other time, use the "XRPM" command.
Command Response Description
"aXRPM!" “a0011<cr><lf>" Read Power_Mode
"aXWPMn!" “a0011<cr><lf>" Write Power_Mode
Where:
a is the sensor address ("0-9", "A-Z", "a-z", "*", "?").
XRPM are upper case characters.
XWPM are upper case characters.
n is the new setting (0, 3 or 4):
0 = Sleep between measurements
1 = Sleep with sensor bias On (reserved for factory use)
2 = Sleep with sensor bias and reference On (reserved for factory use)
3 = Make measurements and update all outputs based on measure rate
4 = Power profile for Modbus
This command takes 001 seconds to complete and places 1 value in the data buffer. Use the
“aD0" command to collect and view the current value.
Example of a H-3521 Extended "Read Power_Mode" command:
Command Response Time Values Description
"aXRPM!" "a0011<cr><lf>" 1 sec 1 Read Power_Mode
Command Response Description
"aD0!" "a+0<cr><lf>" Mode = Sleep
Example of a H-3521 Extended "Write Power_Mode" command:
Command Response Time Values Description
"aXWPM3!" "a0011<cr><lf>" 1 sec 1 Write Power_Mode
Command Response Description
"aD0!" "a+3<cr><lf>" Mode 3 = Continuous mode