Senquip ORB-X1-G, User Manual

Page: 72 / 136

and using the switched power output.
In digital mode, an alert can be generated when the input changes state. This may be useful, for instance
where monitoring an alarm system to see if it is activated or not. Each time the system is activated or
de-activated, an alert can be generated and transmitted
Input 1 has additional functionality that allows switch change of state detection whilst the ORB is in sleep
state. This allows the ORB to remain in a very low power sleep state, to wake on switch level change and
transmit the change of state. This functionality is not available on input 2.
Frequency mode
Input 1 has an additional mode that allows for the measurement of frequency. In frequency mode, on each
measurement interval, the frequency of a signal on the pin is measured. Primary applications are speed,
rpm and flow rate measurement.
In the diagram below, the ORB is configured to measure engine speed using an output from the P (pulse)
terminal on an alternator.
Note The noise suppressing low-pass-filter on pin 6 limits the frequency of pulses to 70Hz.
Figure 6.9. RPM measurement
Duty-Cycle mode
Input 1 has an additional mode that allows for the measurement of duty-cycle. In duty-cycle mode, on
each measurement interval, the duty-cycle of a signal on the pin is measured. Sensors regularly use duty
cycle to communicate percentage of full-scale; for instance, 0% duty cycle may represent 0% humidity and
100% duty-cycle may represent 100% humidity. In some sensors, 0% and 100% duty cycle represent error
conditions.
Calibration
In analog mode, frequency mode and duty-cycle mode, calibration can be applied so that the measurement
returned by the ORB is in the units of what is being measured. For instance, in analog mode, a voltage of 0
to 5V may represent 0% humidity to 100% humidity. The ORB can be calibrated to take a voltage
measurement and to convert the measurement to humidity in % and return that as the measured value.
In any system, the measurement instrument (the ORB), the sensor and possibly the measured value will
be subject to errors that may accumulate to reduce accuracy. In a system that uses the ORB to measure
fluid volume in a 100 litre tank using a 4-20mA sensor, the ORB and sensor may have offset errors such
that with zero liquid in the tank, the ORB is showing a small volume. The ORB and sensor may also not
be perfectly linear in that they may not measure 1 litre in exactly the same way when the tank is empty
ORB User Guide, Release 1.1
66 Chapter 6. External Sensors