NI myDAQ User Guide | © National Instruments | 5
Analog outputs can be updated at up to 200 kS/s per channel, making them useful for waveform
generation. Analog outputs are used in the NI ELVISmx Function Generator, Arbitrary
Waveform Generator, and Bode Analyzer instruments.
Digital Input/Output (DIO)
There are eight DIO lines on NI myDAQ. Each line is a Programmable Function Interface (PFI),
meaning that it can be configured as a general-purpose software-timed digital input or output, or
it can act as a special function input or output for a digital counter. Refer to Digital I/O (DIO)
and Counters/Timers section for more information about the counter on NI myDAQ.
Note The digital I/O lines are 3.3 V LVTTL and are tolerant to 5 V inputs. The
digital output is not compatible with 5 V CMOS logic levels.
Power Supplies
There are three power supplies available for use on NI myDAQ. +15 V and -15 V can be used
to power analog components such as operational amplifiers and linear regulators. +5 V can be
used to power digital components such as logic devices.
The total power available for the power supplies, analog outputs, and digital outputs is limited
to 500 mW (typical)/100 mW (minimum). To calculate the total power consumption of the
power supplies, multiply the output voltage by the load current for each voltage rail and sum
them together. For digital output power consumption, multiply 3.3 V by the load current. For
analog output power consumption, multiply 15 V by the load current. Using audio output
subtracts 100 mW from the total power budget.
For example, if you use 50 mA on +5 V, 2 mA on +15 V, 1 mA on -15 V, use four DIO lines to
drive LEDs at 3 mA each, and have a 1 mA load on each AO channel, the total output power
consumption is:
5 V × 50 mA = 250 mW
|+15 V| × 2 mA = 30 mW
|-15 V| × 1 mA = 15 mW
3.3 V × 3 mA × 4 = 39.6 mW
15 V × 1 mA × 2 = 30 mW
Total output power consumption = 250 mW + 30 mW + 15 mW + 39.6 mW +
30 mW = 364.6 mW
Digital Multimeter (DMM)
The NI myDAQ DMM provides the functions for measuring voltage (DC and AC), current (DC
and AC), resistance, and diode voltage drop.
DMM measurements are software-timed, so update rates are affected by the load on the
computer and USB activity.
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