Why Does the USB-4065 DMM Have 5 Input TerminalsHardware: Modular Instruments>>Digital Multimeters (DMM)>>USB-4065
Problem: I noticed that the USB-4065 DMM has 5 input terminals whereas other NI DMMs have 4. Why is this? Solution: The 5th input terminal on the USB-4065 does not add any new measurement features, but it does add more flexibility in taking voltage and current measurements together. By using the 5th connection you can connect a current measurement and it will provide a continuous path through the DMM even when switching to a different measurement mode. This allows you to measure voltage while current is still flowing through the current measurement leads as shown in the image below.  Without the 5th input terminal the external leads would need to be reconfigured or a switch would be required. All NI 407x and 4065 DMMs use the LO Input terminal for current measurements. The only difference is that DMMs with 4 terminals share the other current terminal with the HI Sense line, whereas the USB-4065 has a dedicated terminal for current which provides some additional flexibility as described above. If you are taking voltage measurements when a current is flowing through the DMM, a null offset should be taken to maximize measurement accuracy. This can be performed by shorting the voltage measurement terminals while current is flowing and then subtracting that voltage measurement from later measurements. For more details about the USB-4065, please refer to the NI Digital Multimeters Help File. Related Links: Products and Services: NI USB-4065 USB DMM Product Manuals: NI Digital Multimeters Help (October 2007) Attachments:
Report Date: 12/20/2007 Last Updated: 04/28/2008 Document ID: 4GJD4MMP |
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