CCpilot VA
1.2
Technical Manual
2017-03-13
www.maximatecc.com
24
voltages or currents are required or for interfacing open-drain (sink-only) drivers with inputs 1-4
which lack internal pull-ups.
Frequency measurement is implemented in a co-processor though timer captures at a time-base of 72
MHz (100 ppm). This time-base gives a theoretical frequency resolution of approximately 0.014 Hz at
1 kHz and 3.12 Hz at 15 kHz (better resolution at lower frequencies). A configurable
weighed
moving
averaging
algorithm can be enabled for increased resolution at high frequencies at the expense of
slower detection rate of frequency changes. Refer to the
CCAux API documentation
for details about
available configurations.
Note that input channels 1-4 can measure frequencies up to 100 kHz compared to 20 kHz for channels
5-8. They also give better accuracy (less deviation) than channels 5-8, especially at higher frequencies.
Consequently it is recommended to use input channels 1-4 for high accuracy frequency reading.
See
chapter 7.1
for electrical characteristics such as absolute maximum voltage, digital threshold
levels, pull-up/pull-down strength, frequency range and accuracy.
5.8.2.
Voltage measurement
Each input can be individually configured for measuring DC-voltages at ranges of:
0-5 V
0-10 V
0-32 V
In general, smaller voltage range gives better accuracy and higher input impedance. See
chapter 7.1
for
electrical characteristics such as impedances and accuracy for each range setting.
5.8.3.
Current measurement (4-20 mA)
Each input can be individually configured for interfacing 4-20 mA current-loop sensors commonly
used in industrial applications.
When enabled, a 100 Ω input shunt resistors is connected to ground for closing the current loop and
enabling current measurement. The 100 Ω shunt resistor is protected against over-load by
continuously monitoring the voltage drop and disabling (breaking the current-loop) in case of over-
voltage for more than 30-50 ms (typ). After being disabled by an overload condition, the current-loop
will automatically be reenabled after a time-out of approximately 1 second and the overload
monitoring is restarted. This protects the shunt resistor from destruction in case of short-circuit and
allows a current-loop sensor to stabilize after enabling/closing the loop.
See
chapter 7.1
for electrical characteristics such as effective range, accuracy and over-load threshold
voltage.
5.8.4.
Resistance measurement
Input channels 1-4 can be individually configured for resistance measurement in the 0-500 Ω or 0-5
kΩ range.
An internal high-precision current source is shared by all input channels configured for resistance
measurement. The current source is connected to one channel at the time in a sequence while
sampling the resultant voltage though A/D-conversion for calculating the external resistance.
See
chapter 7.1
for electrical characteristics such as effective ranges and accuracy.
