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aXPm+FD!
Where,
a: SDI-address of module
m: Measurement number (M command number : 1…9)
For example, 1XP4+FD! will configure the M4 command in the module at SDI-12 address “1” to measure the
period of the signal on the DIN channel with the factory defaults of: slope=1.00, offset=0 , without any pull-
up or pull-down, de-bounce-time=0mS, no switched voltage on SWD port.
Quadrature Shaft Encoder Measurement
To set up a Quadrature Shaft Encoder measurement on channel DIN and AN4, issue the following SDI-12
command:
aXQm+FD!
Where,
a: SDI-12 -address of module
m: Measurement number (M command number : 1…9)
For example, 1XQ9+FD! will configure the M9 command in the module at SDI-12 address “1” to measure a
Quadrature Shaft Encoder with the factory defaults of feet (assuming a wheel with a 1-foot circumference and
100 counts per rotation) and to set the current-level as the reference(zero). Issuing a 1M9! followed by a 1D0!
will then return two values, the first one will be current level in feet and the second value will be a status byte
that will be one of the following:
0:
Okay
64:
Level has never been Set
128: Shaft Over-speed detected
192: Level has never been set and Shaft Over-speed has been detected
Notes on Handar 436 Quadrature Ecoder (any switch closure output encoders)
The Handar 436 encoder has open collector / switch closure outputs. Since it does not drive its
outputs high, an external pull-up resistor is required. While the DIN port in the module provides an
internal pull-up for tipping buckets, the shared AN4 input can not have any pull-ups when used for
analog readings.
To configure the module to read the encoder, follow these steps:
1.
Configure a measurement command as described above.
2.
Connect two 10 K ohm (20%, 1/4 watt or better) resistors between the {sw'd} voltage
and {DIN} and {AN4}.
3.
Set the sw'd voltage to a co5 volts, using the aXW+5! command.
4.
Connect the encoder outputs to the {DIN} and {AN4} inputs.
5.
Connect the encoder power to to SDI-12 {+12} and {GND} connections.
To test that the module can now read the encoder, issue the measurement command (to what ever
command number above was used), and then issue the aD0! command to read the current level. Then
rotate the encoder and measure the encoder again to see that the reading changed (i.e for a 1 foot
wheel, verify one rotation returns 1 foot of change).
