Voltage Level of the Digital Output on the 734x and 735x Motion ControllersHardware: Motion Control>>Controllers>>PCI-7350
Problem: I am using the digital output on my 735x and 734x motion controller board. When I measure the voltage levels of the digital outputs from these two boards I notice a significant difference in the measured voltages. The output of 735x is around 3.3V while the output of the 734x is almost 5V. The manual for both of these boards states the output is 5V. Why is there such a discrepancy between these voltage levels? Solution: To answer your question, the 735x uses a newer technology that only drives to 3.3 volts, but is rated up to 5 Volts (thus the 5V specification in the manual). This board also has a pull-up resister connected to 5 volts on the output. While this output does not reach 5 volts, the 3.3 volt signal still matches the specifications of the 7344 in that the voltage will not drop below 2.4 volts when sourcing up to 24 mA. Also, we are dealing with TTL signals, so anything above 2 volts will be registered as a high signal. The 3.3 volt signal is well above this threshold. Looking at both boards, they both specify at least 2.4 volts and no more than 5 volts while supplying up to 24 mA. Both boards are compatible with 5 V TTL inputs so while the voltage levels are different, they should still behave exactly the same for any digital input or output. Related Links: National Instruments Motion Control Support Attachments:
Report Date: 10/08/2004 Last Updated: 10/11/2004 Document ID: 3E7GLDKD |
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