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Setting a Measurement (Specific Set-up With User-Defined Parameters)
Voltage Measurement
The module has four analog ports to take analog voltage measurements. The voltage can be measured single-
ended (with respect to ground) or differential (between 2 channels or between a channel and Vref). The
measurement is done using a high precision delta-sigma, Analog-to-Digital (A/D) converter, which can be
programmed for following parameters:
Input Channels
Digital Filter for different data-output rate (averaging time) to get different line rejection frequencies
Buffered or Non-Buffered input
Input Gain of 1, 2, 4, 8, 16, 32, 64, or 128
In addition to this, you can specify
Slope: A multiplier to convert voltage reading to a different engineering unit
Offset: A constant value to be added to the result after adjusting it with Slope
Vref Warm-up Time: Time Vref should be turned on before taking a measurement
Switched Voltage: This can be set to 5volts or 12volts if sensor requires an external excitation
voltage
Switched Voltage Warm-up time: Time switched voltage should be present before taking a
measurement.
SDI-12 set-up command
To set-up a voltage measurement or change a parameter (other than default), you can use the SDI command
aXVm+p+n+s+o+t+v+w+x+i+g!
where,
a: SDI-address of module
m: Measurement number (M command number : 1…9)
p: Measurement channel (1:AN1, 2:AN2, 3:AN3 4:AN4 and V:Vref)
n: Reference channel. Default is ground
s: Slope. Default is 1.00
o: Offset. Default is 0.00
t: Averaging time (less than 0.09 for 15Hz, greater than 0.09 and less than 0.19 for 7.5Hz, greater than 0.19
for 3.75Hz). Default is 0.067.
v: Vref warm-up time. Default is 0.010,i.e. 10mS
w: Switched voltage during measurement ( = 0, 5 or 12). Default is 0
x: Switched voltage warm-up time in sec. Default is 0.1, i.e.100mS
i: U=Unbuffered, B=Buffered. Default is U
g: Gain = 0, 1, 2, 4, 8, 16, 32, 64, 128. Default is 0, which means auto-gain
You can do a quick set up by selecting channels only. For the omitted parameters, the module will retain the
previously specified value. To ensure that unspecified parameters are at factory defaults, suffix the
measurement channel with “+FD”.
