NI WSN-3214 User Guide and Specifications
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Understanding Short Circuit Protection
The current that flows through the high side switch is continuously sensed. If a current above the trip
limit is detected, the current protection trips and turns off the high side switch. The protection latches in
the tripped state and only resets when the high side switch is given the command to turn off. High inrush
currents that exist for a short time do not trip the short-circuit protection. Refer to the
section for more information about the maximum continuous output current, short circuit behavior, and
short circuit trip time.
Preventing an Overcurrent Condition
Follow these recommendations to prevent an overcurrent condition:
•
Do not connect DIO PWR to ground.
•
Do not ground unused terminals.
•
Do not exceed the output current rating of the channel.
•
Do not exceed the voltage ratings of the channel.
Detecting an Overcurrent Condition
To check whether or not the short circuit protection is tripped, the logic state of the DIO pin can be read
when driving high using the digital input function. If DO is set to
and Low (Sinking and Sourcing)
modes and a digital value of 1 is written to the channel, a logical 1
should be read from the channel. If a logical 0 is read instead, then the current protection is tripped or a
fault is preventing the high side switch from driving the output high.
Resetting Channels After an Overcurrent Condition
To reset the short circuit protection turn off the high side switch by writing a digital value of 0 to the
channel. Then, check the wiring and remove any possible faults. The correct functionality of the circuit
should be confirmed by writing a digital value 1 to the channel and then reading a logical 1 from it.
Battery Considerations
NI WSN-3214 power consumption is different depending on whether or not you are using NI-WSN or
NI LabVIEW WSN.
NI-WSN
If you are using NI-WSN, you have control of the data using the following settings: waveform interval,
sample rate, number of samples per waveform, acquisition mode or bridge type. At each waveform
interval the NI WSN-3214 transmits the acquired data to the gateway. The size of the acquired data
varies along with the number of channels being measured and with the number of samples per
waveform. For each channel that is being measured a certain radio communication protocol is repeated,
meaning that the power required by the radio is directly proportional to the number of channels that are
being measured. As more samples per waveform are acquired, these are split into packages when sent,
which increases the amount of power required to send them.
The following timing diagram shows how the NI WSN-3214 acquires and sends data using NI-WSN.
