Building Low-Cost Data-Logging Systems with the NI PXI-4065 Digital Multimeter (DMM)
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The new low-cost NI PXI-4065 DMM offers 6½-digits of resolution at up to 10 readings per second and up to 3,000 readings per second at lower resolutions. With ±300 VDC/Vrms of isolation, current measurements up to 3 A and 2- or 4-wire resistance measurements, NI 4065 DMMs offer a complete multimeter solution for basic 6½-digit measurement needs. Furthermore, the low cost of the NI PXI-4065 DMM along with its 6½-digit performance offers a new entry point for reliable, high-channel-count automated measurement systems. This paper will explore the various ways in which engineers can combine this new DMM with in order to create low-cost multichannel systems.
Table of Contents
Lowering the cost of PXI
PXI now meets more low-cost, high-performance application needs by applying the cost benefits of commercial technologies such as cabled PCI Express. The new PXI-1033 chassis offers five peripheral slots and an integrated MXI-Express remote controller with host card to connect to the host PC. The PXI-1033 chassis is available in two host interface versions – a PCI Express interface to connect to a desktop PC and an ExpressCard interface to connect to a laptop. With the PXI-1033 chassis, you can start a PXI system with a chassis and controller for $999 USD.
Learn more about PXI, or visit the PXIAdvisor to configure your own system.
System Integration with the NI PXI-4065 6½-digit DMM
Combining the new low-cost PXI-1033 chassis with the NI PXI-4065 DMM, engineers can create a PXI based 6½-digit measurement system starting at under $2,300 USD. Then, NI PXI switches can be added to increase system channel count all the way to 784 channels using the 4 remaining slots of the PXI-1033 chassis. For systems that require higher channel counts, NI offers 18-slot PXI chassis that can accommodate more than 3000 multiplexed channels each.
In this section of the paper, we will look at 2 example configurations. With over 150 available PXI switch topologies and over 1,000 available modules in the PXI form factor, these are just 2 of the many data-logging systems that can built using PXI.
The PXI-4065 Low-Cost 6½-Digit DMM
Example Configuration 1: 64-Channel Multiplexer System
Using a single PXI-2527 armature multiplexer along with the TB-2627 terminal block, engineers can create either a 64-channel 1-wire data-logging system or a 32-channel 2-wire data-logging system. With a maximum scan rate of 140 cycles/second, and a carry current of up to 2A, this low-cost multiplexing system has the ability to accommodate a variety of applications. Furthermore, this configuration leaves 3 extra PXI slots which can be filled with any other PXI modular instruments, such as Digital I/O modules or High-Speed Digitizers.
Configure this system in the PXI Advisor
Example Configuration 2: 784-Channel Multiplexer System
Using 4 PXI-2575 high-density switch modules, engineers can create data-logging systems with 784 channels (1-wire) or 392 channels (2-wire). With thermal EMF of less than 3uV and path resistances of less than 1 Ohm, this configuration is ideal for high-channel count precision measurement systems. The connectivity option chosen in this particular configuration breaks all channels out to bare wire so that they can be interfaced with custom hardware. For other connectivity options, visit the How to Connect Signals to the PXI-2575 tutorial.
- PXI-1033 Integrated Chassis and Controller
- PXI-4065 6½-Digit DMM
- 4 PXI-2575 196-Channel Multiplexers
- 4 LFH200 to Bare Wire Switch Cables
Configure this system in the PXI Advisor
Data-Logging Software
There are a variety of options for software to control a PXI data-logging system, including the LabVIEW graphical programming environment as well as C++ or other text based languages. For the configurations mentioned above, a great software option that lets users quickly configure data-logging applications interactively is the LabVIEW SignalExpress environment. Built with data-logging in mind, LabVIEW SignalExpress provides a broad set of features for completing common data-logging tasks including basic data analysis, alarming and customizable graphs and displays to present your data.
Figure 2. Quickly configure data-logging applications without programming in LabVIEW SignalExpress.
There is a free version of LabVIEW SignalExpress that ships with the NI PXI-4065, which offers basic data-logging capability. For more information on the benefits of LabVIEW and LabVIEW SignalExpress for data-logging applications visit the SignalExpress Data-Logging Tutorial.
The DMM/Switch Express VI
Available in both the LabVIEW and LabVIEW SignalExpress environments, the new NI DMM/Switch Express VI allows users to create custom scan lists within minutes by adding support for multipoint DMM operations and synchronization with any NI multiplexer switch module. While most synchronized DMM/switch systems require extensive programming to route trigger signals between modules, the DMM/Switch Express VI abstracts this complexity from the user for high-level options such as synchronous mode, full-hardware handshaking and internal or external trigger-signal route configurations. The DMM/Switch Express VI combines the most common setup and module configuration steps into one simple dialog box.
View the webcast that demonstrates how to program a LabVIEW application with the DMM/Switch Express VI.
Conclusion
Using the NI PXI-4065 6½-Digit DMM along with the NI PXI-1033 integrated chassis and controller, engineers can create high-channel count data-logging systems with a new low-cost entry point. These systems can make use of more than 150 supported topologies offered by NI PXI Switches, and can be easily configured using the NI DMM/Switch Express VI in both the LabVIEW and LabVIEW SignalExpress environments.
For more information on NI hardware products discussed in this paper, visit the following links:
For more information on the NI data-logging software discussed in this paper, visit the following links:
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