Configuring the Quadrature Output (5600-0131-3 and 56-0131-50-1
models only)
Setting the Quadrature Scale Factor, Threshold, and Step Rate
The quadrature output tracks the pressure as returned by the M command. The units of pressure for
the M command are user configurable with the XUP command. Changing the units of pressure for
the M command with the XUP command also changes the units of pressure for the quadrature
output. The quadrature scale factor is the number of steps the quadrature output takes per unit of
change of the input pressure. As shipped from the factory the default units for the M command is
feet of water. The factory default scale value is 1000. This means that the quadrature output steps
1000 times for every change in the input pressure of one foot. This means that the resolution of the
quadrature output as shipped from the factory is 0.001 feet of water. This is the scale factor
necessary to produce one rotation of the output shaft of the Sutron 5600-0126-1 chart drive per foot
of input change. If the ACCUBUBBLE was being hooked up as a shaft encoder for a data logger,
the scale factor would usually be set to 100 since most incremental shaft encoders produce 100
steps per revolution.
The threshold level is utilized to minimize excess stepping by a chart drive and therefore conserve
power. If the difference between the measured pressure and the quadrature output is less than the
threshold level, the quadrature output is not changed. Once the difference between the measured
pressure and the quadrature output exceeds this threshold level, the quadrature output will be
stepped in order to eliminate this “error”. As shipped from the factory, the default value of the
threshold is 0.01. This means that once the measured pressure and the quadrature output differ by
0.01 feet of water, the output will be stepped to eliminate this error.
The interface to the Sutron 5600-0126-1 operates at the 0.001 foot level. This means that if the
threshold were set to zero then for every 0.001 foot of change detected by the AccuBubble, the
stepper would be stepped. This would cause excessive power consumption on the stepper side
because it would be attempting to track all the ripples in the water’s surface. To prevent this
excessive power consumption the threshold is set to the level of accuracy desired. This is usually
on the order of 0.01 feet. If a particular installation was using a stepper and was not interested in
any changes under 0.05 feet, then the threshold could be changed to 0.05 and a power saving would
result from the decreased stepping. If the quadrature output was run directly into a data logger
where there is not any penalty from the excessive stepping, then the threshold could be set to 0.
This command also supports setting the step rate for the quadrature output. The factory default for
the step rate is 100 steps per second. This corresponds to the maximum step rate for the Sutron
5600-0126-1 Chart Drive. This means that if the ACCUBUBBLE detected a one foot change, then
the output would be ramped at the rate of 0.1 foot per second for 10 seconds (1000 steps divided by
100 steps per second). If the ACCUBUBBLE was connected to the shaft encoder input of a data
logger the user might want to increase the step rate if the data logger could track a faster rate.
Likewise it can be decreased for slower devices. NOTE: Decreasing this number will result in
increased power consumption for the 5600-0126-1 Chart Drive, not lower power consumption.
The format for the command is:
aXQSstr!
where a is the address character, XQS is the extended command to set the
Quadrature Scale Factor s in steps per unit of change as returned by the M
command, the Quadrature Threshold t, and the Quadrature Step Rate r in
steps per second.
If a user wanted to setup an ACCUBUBBLE at address 3 to produce 1000 steps per foot (units of
pressure are 0 for feet of water), with a 0.01 foot threshold and a step rate of 100 steps per second,
the command would be:
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Summary of Contents for Accububble 56-0131-50-1
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